Natural Features

Natural Features

 

The geographic position of the USSR gives rise to an extraordinary diversity of natural conditions. Most of the European part of the USSR is occupied by the East European (or Russian) Plain. The northern part of Asia rises eastward, toward the Pacific Ocean, in a series of steps—the Western Siberian Plain, the Central Siberian Plateau, the Verkhoiansk Range, the Cherskii Range, and the mountains of the Far East. The western part of Middle Asia is occupied by the Turan Plain (or Turan Lowland). Immense mountain systems stretch in the southwest and south, the most important being the Carpathians, the Caucasus, the Pamirs, the Tien-Shan, and the mountains of Southern Siberia. The relief of the ocean and sea floors is equally complex, particularly in the east, where deep basins, trenches, and underwater ridges that often form island arcs occur near Soviet shores.

The general characteristics of the climate are determined by the country’s being located predominantly in the temperate zone; the climate ranges from the cold arctic climate in the north to the subtropical and desert climates in the south and from the marine climate in the northwest to the sharply continental climate of Siberia and the monsoonal climate of the Pacific coast.

The vastness of Soviet territory, the complexity of the relief, and the diversity of climate and the soil and vegetation cover are expressed in the natural zonality. Most of the country is occupied by the forest, forest-steppe, steppe, semidesert, and desert zones. The northern regions are included in the arctic and subarctic zones (tundra and forest-tundra zones), while part of the south lies in the subtropical zone.

The largest structural elements of the earth’s crust in the USSR are the Eastern European and Siberian platforms and the folded geosynclinal belts that separate them: the Ural-Mongolian geosynclinal belt, which separates the Eastern European Platform from the Siberian Platform and bends around the latter from the south; the Mediterranean geosynclinal belt, which borders the Eastern European Platform on the south and southwest; the Pacific geosynclinal belt, which forms the margin of the Asian continent; and part of the Arctic geosynclinal belt, including the northern coast of the Chukchi Peninsula. Distinguished within the folded geosynclinal belts are the following: young regions that have not as yet completed geosynclinal development—the active modern geosynclines (the peripheral part of the Pacific belt); regions that have completed geosynclinal development in the Cenozoic (the southern USSR, which belongs to the Alpide geosynclinal folded region); and the more ancient regions, which make up the basement of the young platforms. Depending on when the processes of geosynclinal development, folding, and metamorphism of sedimentary strata concluded, the more ancient regions are subdivided into folded regions of different ages: Late Proterozoic (Baikal), Middle Paleozoic (Caledonian), Late Paleozoic (Hercynian, or Variscan), and Mesozoic (Cimmerian). The geosynclinal type of crustal structure arises at earlier stages of development. Later, the geosynclinal regions develop into the basement of platforms, which in subsided sections is then overlain by a mantle of platform sediments (platform plates). In this way, in the course of the crust’s development, the geosynclinal stage is supplanted by the platform stage, with the double-tiered structure typical of platforms. In the course of the formation of platform basements, the oceanic crust of the geosynclinal belts is transformed into a continental crust, with a thick granitic-metamorphic layer. The age of the platforms conforms to the age of the basement. The basements of ancient (Precambrian) platforms were largely formed by the beginning of the Riphean (Late Proterozoic). Among the young platforms, a distinction is made between epi-Baikalian (Upper Proterozoic rocks are present in the basement structure and Paleozoic, Mesozoic, and Cenozoic rocks are developed in the mantle), epi-Paleozoic (the basement formed in the Paleozoic and the mantle during the Mesozoic and Cenozoic), and epi-Mesozoic (Mesozoic rocks are present in the structure of the basement).

The parts of the ancient platforms and geosynclinal belts that were transformed into young platforms were again caught up by subsequent orogeny (epiplatform orogeny), which occurred numerous times in Siberia (the Stanovoi Range, western Transbaikalia, and the Saian, Altai, Gissar-Alai, and Tien-Shan mountains).

The structural regions of dry land are directly continued on the floor of the shelf seas that border the USSR on the north, east, and, partially, northwest.

Ancient platforms. EASTERN EUROPEAN PLATFORM. The Eastern European Platform includes two basement outcrops—the Baltic Shield and the Ukrainian Crystalline Massif—and the vast Russian Platform, where the basement is sunken and overlain by a sedimentary mantle. Archean, Lower Proterozoic, and Middle Proterozoic strata are present in the basement structure. The Archean rocks form numerous massifs, within which two rock complexes differing in composition and age are identified. The more ancient rocks, which are more than 3 billion years old, form the lower horizons of the Kola Series on the Kola Peninsula (biotite and amphibole gneisses and amphibolites), and in the Dnieper section of the Ukrainian Massif, between Zaporozh’e and Krivoi Rog, they form the rocks of the Konka-Verkhovtseva Series, which are similar in composition. In the Podol’e Upland and the Bug River basin, the oldest rocks are pyroxene and plagioclase garnet gneisses and charnockites. The younger Archean complex, which is between 2.6 and 3 billion years old, consists of thick series of biotite, dimicaceous and amphibole gneisses, amphibolites, schists, quartzites, and marbles. A typical example of this complex occurs along the shores of the White Sea (the White Sea Series). The processes of metamorphism undergone by the rocks of the White Sea complex in the Early Proterozoic were accompanied by the formation of granitic massifs and migmatites.

The Archean massifs are separated by bands of Lower Proterozoic (1.9 to 2.6 billion years old) folded structures, composed of gneisses, schists, quartzites, and diabases, which had undergone strong folding and granitization at the end of the Early Proterozoic and repeated (superimposed) metamorphism in the Middle and, in some places, Late Proterozoic (1.75–1.6 billion and 1.5–1.35 billion years ago).

The Middle Proterozoic rocks of the Baltic Shield and Ukrainian Massif occur unconformably and are represented by quartzites, phyllites, diabases, and dolomite marbles (the Jatulian Series of Karelia, the Jotnian Series of Finland, and the Ovruch Series of the Ukraine). These strata are characterized by the products of metamorphism of kaolinic weathering crusts, which could have formed under conditions of slight tectonic activity. They are beds of the oldest Middle Proterozoic mantle, after whose accumulation large massifs of porphyroid rapakivi were intruded (1.67–1.61 billion years ago), the youngest granitic intrusions in the basement.

The depth at which the basement of the Russian Platform occurs varies from a few hundred meters in uplifted areas to several thousand meters in depressions. The major uplifts are the Voronezh, Byelorussian, and Volga-Ural anteclises. The tectonic depressions include the Moscow, Baltic, and Caspian syneclises. The deeper parts of the platform adjacent to the Urals, the Timan Ridge, and the Carpathians correspond to pericratonic depressions (the Timan, Kama-Ufa, and Dnestr pericratonic depressions). Aulacogens constitute a special type of structure, often forming a single system. The largest system of aulacogens is the Middle Russian Aulacogen, stretching from the Valdai Hills to the Timan Region. The Orsha-Kresttsy, Moscow, Ladoga, and Dvina aulacogens have been identified in the northern, western, and central parts of the Russian Platform and the Pachelma, Kazhim, and Upper Kama, among others, in the eastern part. The largest aulacogen of the Eastern European Platform is the Pripiat’-Dnieper-Donets Aulacogen. The aulacogens and pericratonic troughs are the most ancient depressions of the Russian Platform. The former are filled with Riphean deposits, while the latter are filled with Riphean and Wendian deposits.

The eastern part of the Pripiat’-Dnieper-Donets Aulacogen formed during the Riphean but became a distinct structure only in the Devonian. The Carboniferous and Permian deposits in its eastern part (the Donets Coal Basin) are crushed into folds.

The rocks that fill the syneclises range in age from the Wendian to the Cenozoic and form the upper parts of the structures of the Russian Platform. The largest syneclise, the Moscow Syneclise, separates the basement outcrop of the Baltic Shield in the north from the Voronezh and Volga-Ural anteclises in the south and southeast. Triassic and Jurassic rocks are developed in its axial part, while Permian and Carboniferous rocks occur on the limbs. In the central part, the basement lies at a depth of 3–4 km. The horizontal bedding of the mantle on the limbs is complicated by flexures, the deepest of which is the Caspian Depression in the southeastern part of the platform, where the thickness of the sedimentary mantle exceeds 20 km and the structure of the basement and lower horizons of the mantle is unknown; according to geophysical findings, the basement rocks in the center of the depression have a high density, close to that of basalt, and the structure of the mantle is complicated by numerous Permian salt domes.

Wendian and Cambrian deposits are developed in the Moscow and Baltic syneclises and in the pericratonic troughs, for example, in the Dnestr Region. They are represented by clays with pockets of sandstones and occasional tuffs. Ordovician and Silurian deposits are found in the western part of the Eastern European Platform (limestones, argillaceous shales containing graptolites). Kukersite, a type of oil shale, is of Ordovician age. Devonian deposits, including clay-carbonate, gypsum-bearing, and salt-bearing deposits, are developed throughout the Russian Platform, with volcanic tuffs and diabases occurring along faults. Bituminous limestones are widespread in the east. Carboniferous deposits are represented primarily by limestones and dolomites. The coal-bearing suite is associated with the Lower Carboniferous. In the Donets Basin, the Carboniferous forms a series up to 18 km thick consisting of sandstones, limestones, and clays alternating with coal strata. Permian and Triassic deposits, including detrital rocks, dolomites, and gypsums, are widespread in the syneclises. Large reserves of rock salt are associated with Lower Permian beds. The Jurassic and Lower Cretaceous deposits in the central parts of the Eastern European Platform are represented by characteristic dark clays and glauconitic sands containing phosphorites. Marls and chalk occur in the cross section of the extensive Upper Cretaceous deposits of the southern regions; in the north there are many argillaceous and siliceous rocks. Cenozoic beds of marine sands and clays occur in the southern part of the Russian Platform.

SIBERIAN PLATFORM. The Siberian Platform has an ancient, largely Archean, basement, whose highly metamorphosed rocks (gneisses, schists, marbles, and quartzites) are exposed in two areas—the Anabar Mountain Mass (Anabar Massif) and the Aldan Shield. The Archean rocks are subdivided into Lower Archean rocks (Iengrian Series and others), which make up several large massifs, and the younger Upper Archean rocks, which bound the ancient massifs, for example, the Timptonian and Dzheltulinian series. The basement rocks of the Aldan Shield and Stanovoi Uplift contain intrusions of Precambrian, Paleozoic, and Mesozoic granites and syenites. The Lower Archean complexes form domelike folded structures, whereas the Upper Archean complexes form large systems of linear folds with a northwesterly strike. Aeromagnetic surveying has established buried ancient massifs (Tunguska and Tiung massifs) beneath the sedimentary mantle of the Central Siberian Plateau; these massifs are bounded by the folded systems of the Upper Archean.

There are several platform troughs and uplifts in areas where the sedimentary mantle occurs. The northwestern part of the platform is occupied by the Paleozoic Tunguska (or Tungus) Syneclise. In the east is the Mesozoic Viliui Syneclise, which opens into the deep Upper Jurassic and Cretaceous Verkhoiansk Trough, which separates the Siberian Platform from the Verkhoiano-Chukotka region of Mesozoic folding. The Mesozoic Khatanga and Lena-Anabar tectonic depressions stretch along the northern margin of the platform. The complex Anabar Anteclise, with outcrops of Proterozoic and Cambrian beds, forms a relatively uplifted block between the two aforementioned troughs. In the southern part of the Siberian Platform, along the upper Lena River, stretches the elongated, shallow Angara-Lena Trough, filled with Cambrian (including a stratum of rock salt), Ordovician, and Silurian deposits. A system of ridgelike folds and faults is characteristic of the trough’s southeastern margin; in the north the trough is separated from the Tunguska depression by the Katanga Uplift. A series of depressions with Jurassic coal-bearing deposits occur along the southern edge of the Siberian Platform: the Kan and Irkutsk depressions along the northern spurs of the Vostochnyi Saian Mountains and the Chul’man, Tokko, and other depressions in the southern part of the Aldan Shield.

The mantle of the Siberian Platform comprises Upper Proterozoic, Paleozoic, Mesozoic, and Cenozoic deposits. There are thick strata of sandstones and algal limestones in the Upper Proterozoic beds. Cambrian deposits occur everywhere except the shields. Ordovician and Silurian deposits occur in the western and central parts. The Devonian and Lower Carboniferous are represented by marine carbonate-terrigenous strata in the north and east and by continental deposits in the south; basic tuffs and lavas occur in the Viliui River basin.

Middle and Upper Carboniferous and Permian continental coal-bearing deposits, as well as thick Triassic tuffaceous and lava series (the Siberian traps), fill the Tunguska Syneclise. Multiple intrusions of trap are developed along the margins of the syneclise, on the slopes of the Anabar Anteclise, and in the south of the Siberian Platform, forming linear zones along the faults that cut across the basement and mantle beds. In addition to the Upper Paleozoic trap intrusions and the age-related diatremes containing kimberlites, similar Devonian and Jurassic magmatic bodies are known. The Jurassic and Cretaceous Viliui Syneclise overlies the Paleozoic aulacogens. Mesozoic beds are represented by detrital rocks interbedded with brown coal and, in the north, limestone. At the end of the Proterozoic and beginning of the Paleozoic, the Siberian Platform, unlike the Eastern European Platform, was entirely submerged beneath the sea and was characterized by the universal accumulation of marine, primarily carbonate, deposits. In the second half of the Paleozoic and during the Mesozoic and Cenozoic, it was relatively uplifted and most of the accumulated deposits were continental. The Siberian Platform is distinguished by a high degree of tectonic activity. The sedimentary mantle is broken by numerous faults and is characterized by many flexures and extensive basic and alkaline magmatism.

Folded geosynclinal belts. URAL-MONGOLIAN BELT. By the beginning of the Mesozoic, the Ural-Mongolian belt had acquired the structure of a platform, whose basement in different sections was formed by folded systems of different ages: the Baikal, Salair, Caledonian, and Hercynian systems. In the Baikalides and Salairides the sedimentary mantle is composed of Paleozoic, Mesozoic, and Cenozoic deposits, but only Mesozoic and Cenozoic deposits occur in the Hercynides. Paleozoic and Precambrian rocks crop out to form such modern mountain ranges as the Urals, the Tien-Shan, Central and Eastern Kazakhstan, the Altai and Saian mountains, Transbaikalia, and the Taimyr Peninsula. A sedimentary mantle overlies the basement within the platforms—the Timan-Pechora and Western Siberian platforms and the northern parts of the Turan Plate and Bureia Platform.

The structures of the zone of Baikal folding form an arc that bends around the Siberian Platform from the northwest and southwest and is exposed in the northern part of the Taimyr Peninsula, in the Enisei Ridge, in the Vostochnyi Saian Mountains, and in the Baikal Region. Baikal structures extend along the left bank of the Enisei River beneath the mantle of the eastern margin of the Western Siberian Platform. Also included in the Baikal Region are the Bureia Massif in the basins of the Amur, Zeia, and Bureia rivers, which is partially covered by a sedimentary mantle, and the region extending along the northeastern margin of the Eastern European Platform (the Timan Ridge and the basement of the Pechora Syneclise). Thick Precambrian, in particular Upper Proterozoic, strata compressed into intricate linear folds predominate in the regions of Baikal folding. They are represented by various sedimentary and mixed sedimentary and volcanic geosynclinal formations. Upper Riphean and, in some places, Wendian detrital accumulations are classified as molasses. Large massifs of Late Riphean and Wendian granitoids are widespread, but younger alkaline intrusions from the Devonian, Jurassic, and Cretaceous periods are also encountered.

To the west and east of the Baikalides of the Vostochnyi Saian Mountains are structures of Early Caledonian, or Sálair, folding, in which thick marine and volcanic geosynclinal strata of the Upper Proterozoic and Lower and Middle Cambrian predominate, forming linear folds. The molasse complex of the Salairides begins with the Upper Cambrian, which is represented by red detrital accumulations. Salair folding and intrusive granitoid magmatism also play a significant part in regions attributed earlier to Baikal folding (for example, the Baikal-Vitim Highland). Areas of Caledonian folding encompass part of the Altai Mountains and Tuva, as well as the Northern Tien-Shan Mountains and Central Kazakhstan. Cambrian and Ordovician sedimentary and mixed sedimentary and volcanic rocks compressed into linear folds are widespread in the Caledonides. Precambrian beds are exposed at the surface in the nuclei of anticlinoriums, in the massifs. Silurian and younger deposits are usually represented by molasses and surface vulcanites. In some places, such as the Northern Tien-Shan Mountains, Caledonian structures have been fused by enormous massifs of Lower Paleozoic (Ordovician) granitoids.

Large intermontane basins, such as the Minusinsk, Rybinsk, Tuva, Dzhezkazgan, and Teniz basins, filled with marine and continental, frequently molasse, formations of the Devonian, Carboniferous, and Permian, are typical of regions of Baikal, Salair, and Caledonian folding. The basins are superimposed structures, but some, such as the Tuva Basin, follow major deep faults.

Classified as Hercynian folded regions are the Urals, with the Cisural Foredeep, the Gissar-Alai Mountains, some parts of the Tien-Shan (the Turkestan, Zeravshan, Alai, Gissar, and Kokshaltau ranges), the region of Central Kazakhstan near Lake Balkhash, the Zaisan Lake region, the Rudnyi Altai, and a narrow strip of eastern Transbaikalai between the margin of the Siberian Platform and the Bureia Massif (the Mongol-Okhotsk folded system). The Hercynian folded structures were formed primarily by Lower Paleozoic, Devonian, and Lower Carboniferous marine geosynclinal sedimentary and volcanic formations, grouped into linear folds and frequently forming vast overthrust faults. Precambrian metamorphic rocks within these regions are exposed at the surface in the nuclei of anticlinoriums. In certain intermontane basins, they are overlain by Upper Carboniferous and Permian continental molasses. Sedimentary and volcanic rocks in Hercynian regions are intruded by large masses of Upper Carboniferous and Permian granites. Late Paleozoic (Hercynian) intrusions are also developed in regions that had undergone folding in earlier times.

Within the vast area of the platforms of the Ural-Mongolian belt, the basement is composed of the same folded systems as the basement in the mountain regions, but it is overlain by a sedimentary mantle. Distinct Late Proterozoic (Baikalian) massifs are identified in the basement, surrounded by younger Caledonian and Hercynian systems of structures. Jurassic, Cretaceous, Paleogenic, Neogenic, and Anthropogenic rocks, represented by both marine and continental sedimentary rocks, predominate in the mantle of the platforms. Triassic and Lower Jurassic continental, volcanic, and coal-bearing deposits fill certain grabens, such as the Cheliabinsk Graben. A complete cross section of the mantle of the Western Siberian Platform has Lower and Middle Jurassic continental coal-bearing deposits on the bottom, then Upper Jurassic and Lower Cretaceous marine clay and sandstone strata, Lower Cretaceous continental strata, Upper Cretaceous and Eocene marine clay and silica strata, and Oligocene marine clays. The Neogenic and Anthropogenic deposits are usually continental. The Mesozoic and Cenozoic sedimentary mantle lies almost horizontally, forming distinct arches and downwarps; flexures and faults are observed in some places.

Within the Ural-Mongolian belt there is evidence of Neogenic processes of epiplatform orogeny, as a result of which the basement is often deformed and broken up into distinct blocks of different heights. These processes occurred most intensively in the Gissar-Alai, Tien-Shan, Altai, and Saian mountains and in the Baikal and Transbaikal regions.

MEDITERRANEAN BELT. The Mediterranean geosynclinal belt is located southwest and south of the Eastern European Platform. Its structures adjoin the structures of the Ural-Mongolian belt along the deep Gissar-Mangyshlak Fault. In the USSR, the Mediterranean belt comprises an outer zone and an inner zone. The outer zone, which encompasses the Scythian Platform, the southern part of the Turan Plate, the Tadzhik Depression, and the northern Pamirs, is a young platform, within which Mesozoic and Cenozoic deposits form a gently bedded platform mantle on a folded, metamorphosed base with Paleozoic and Precambrian intrusions. Orogenic processes occurred in the Tadzhik Depression and the northern Pamirs in the Neogene and Anthropogene, as a result of which the Mesozoic and Cenozoic beds of the platform mantle are compressed into folds.

The Scythian Platform, which includes the plains of the Crimea and Ciscaucasia, has a basement in which blocks of Upper Proterozoic rocks (fragments of Baikalian structures) fused with the folded geosynclinal Paleozoic are identified. A mantle of gently bedded Paleozoic deposits with Late Paleozoic intrusions occurs on the Baikalian massifs. Everywhere in the platform mantle there are deposits from the Cretaceous to the Anthropogene. The lower horizons of the mantle (Triassic and Jurassic) are not universally developed, often occurring in grabens. In places they are dislocated and contain intrusions (the Kanev-Berezan’ folds of the Northern Caucasus and the Tarkhankut folds of the Crimea). Lower Cretaceous and Paleogenic strata of clays and sands and Upper Cretaceous strata of marls and chalks are developed in the mantle, forming a series of depressions and uplifts, of which the largest are the Stavropol’ Arch, the Simferopol’ Uplift, and the Kuma and Azov depressions. The depth of the base of the mantle is 500 m in uplifted areas and as much as 3,000–4,000 m in downwarps.

The basement in the southern part of the Turan Plate consists of a series of Precambrian massifs (for example, the Central Karakum, Kara-Bogaz, and Northern Afghanistan massifs) overlain by a mantle of Carboniferous, Permian, and Triassic rocks containing Late Paleozoic intrusions. The massifs are separated by Paleozoic folded systems (Tuarkyr, Mangyshlak, Nuratau). The large graben-like depressions of the basement are filled with dislocated Triassic marine terrigenous and volcanic deposits (Mangyshlak, Tuarkyr, Karabil’). The mantle of the platform as a whole consists of a series of beds ranging in age from the Jurassic to the Anthropogene. It is thickest in the southeast, in the Murgab and Amu Darya depressions. There is a major uplift, the Karakum Arch, in the central part of the platform; other uplifted zones, the Turarkyr Meganticlinorium and the Kara-Bogaz Arch, are located to the west. The Mangyshlak system of uplifts stretches along the northern boundary from the Caspian Sea to the Aral Sea. The folded structures observed in the mantle are caused by faults in the basement.

The Mesozoic and Cenozoic deposits in the inner zone of the Mediterranean belt, including the Carpathians, the Crimean Mountains, the Caucasus, the Kopetdag, and the Middle and southern Pamirs, are represented by geosynclinal-type formations. The separation of the inner and outer zones began in the Late Triassic or in the Jurassic.

The Ukrainian Carpathians are part of the Carpathian-Balkan Arch. In the USSR, they are primarily composed of Cretaceous and Paleogenic flysch series. Uplifts of the base of the geosynclinal complexes of the Lower Mesozoic, Paleozoic, and Precambrian play a lesser role. The Carpathians are characterized by an intricate folded structure with numerous thrust faults. The eastern Carpathians are separated from the Eastern European Platform by the deep Ciscarpathian Foredeep onto which they are thrust.

The Crimean Mountains are a distinct anticlinal structure, whose southern limb is submerged beneath the Black Sea. Upper Triassic, Jurassic, and partially Lower Cretaceous sand-clay, carbonate, and volcanic geosynclinal-type deposits are exposed at the surface in the nucleus of the Crimean anticlinal uplift. The northern limb is composed of gently dipping platform-type Cretaceous and Paleogenic rocks. The chief manifestations of intrusive and effusive magmatism are from the Middle Jurassic, represented by diorites, granodiorites, gabbro, spilites, and keratophyres.

The intricate folded structure of the meganticlinorium of the Greater Caucasus was formed by Paleozoic, Mesozoic, and Paleogenic geosynclinal complexes of different composition, broken by numerous faults and intrusions of different age. Upper Precambrian metamorphic rocks are exposed at the surface in the nuclei of the most uplifted structures. Precambrian and Paleozoic rocks make up the pre-Alpine base, while Mesozoic and Paleogenic rocks make up the Alpide geosynclinal complex, which reaches maximum thickness along the southern slope of the Greater Caucasus. The meganticlinorium has an asymmetric structure. The Jurassic, Cretaceous, and Paleogenic sands, clays, and carbonate rocks on its northern limb mostly have gently sloping, monoclinal bedding; on the southern limb they lie at steep angles and are compressed into folds and are complicated by thrust faults. The Upper Jurassic and Paleogenic beds of the western and eastern parts of the southern limb are represented by flysch series. The Neogenic Indolo-Kuban’ and Terek-Caspian foredeeps lie to the north of the Greater Caucasus, while the Rioni-Kura zone of intermontane basins, which separates the meganticlinoriums of the Greater and Lesser Caucasus, lies to the south. Jurassic, Cretaceous, and Paleogenic mixed sedimentary and volcanic formations, including ophiolite complexes, predominate in the Lesser Caucasus, which has a block-type structure, large areas of which are overlain by thick, gently sloping Neogenic and Anthropogenic strata of lava.

The Kopetdag is a comparatively simple folded structure, consisting at the surface of Cretaceous and Paleogenic mixed carbonate and clay complexes with folds overturned in a northerly direction, toward the Ciskopetdag Depression, which separates the Kopetdag from the Turan Plate. Northwest of the Kopetdag, along the continuation of the Kopetdag deep marginal fault, stretches a meganticline—Bol’shoi Balkhan—with outcrops in the nucleus of the geosynclinal Jurassic rock complex. The limbs of the meganticline are composed of platform-type Cretaceous and Paleogene deposits. Paleozoic and Mesozoic sedimentary geosynclinal complexes crushed into complex folds complicated by thrust faults are developed in the central Pamirs, while Precambrian metamorphic rocks and large massifs of granites of various age occur in the southern Pamirs.

PACIFIC BELT. The Pacific geosynclinal belt encompasses the region east of the Siberian Platform and the Bureia Massif. Its eastern boundary is the Kuril-Kamchatka and Aleutian system of deep-sea trenches. Oriented nearly meridionally, the Pacific belt includes Mesozoic folded regions (the Verkhoiano-Chukotka and Sihote-Alin’ regions) and structures of a more recent geosynclinal region—geoanticlinal uplifts (Kamchatka, Sakhalin, and the Kuril Islands)—as well as the basins of the marginal seas—the Sea of Japan, the Sea of Okhotsk, and the Bering Sea.

The Verkhoiano-Chukotka folded region occupies the northeastern part of the USSR. Within its boundaries, Permian, Triassic, and Jurassic beds are most extensively developed on the surface, forming several anticlinal and synclinal zones. The geosynclinal complex (Middle Carboniferous to Upper Jurassic) is composed of a thick series of marine mixed clay and sandstone deposits, in which volcanic rocks occupy a subordinate place. The largest positive structures of the region are the Verkhoiansk Meganticlinorium and the Sette-Daban, Aniui, Chukchi, Tas-Khaiakhtakh, Moma, and Polousnyi anticlinoriums. In the last three anticlinoriums, the late Mesozoic (Mesozoide) complex of the base plays an important part. The most important negative structure is the Iana-Indigirka (Iana-Kolyma) synclinorium zone, composed of Triassic and Jurassic deposits at the surface. An Upper Jurassic and Lower Cretaceous molasse orogenic complex, in large part coal-bearing, fills the Verkhoiansk Foredeep, as well as several large interior inherited troughs and intermontane basins (Ol’dzho and Moma-Zyrianka). An important role in the structure of the region is played by uplifts of the base, in places covered by a mantle of Paleozoic and Mesozoic deposits (the Kolyma, Okhotsk, Omolon, Chukchi, and other massifs). Late Jurassic-Early Cretaceous and Late Cretaceous-Paleogenic granitoids form batholiths along the deep fault zones. The Upper Cretaceous and Cenozoic (postgeosynclinal) complex is of limited development and is composed primarily of continental coal-bearing and volcanic series. In the lower courses of the lana, Indigirka, and Kolyma rivers, Cenozoic rocks are overlain by geosynclinal and orogenic structures forming the platform mantle that underlies the shelves of the Laptev and East Siberian seas.

The Sihote-Alin’ folded region differs from the Verkhoiano-Chukotka region by the extensive distribution of Middle and Upper Paleozoic and Mesozoic mixed volcanic and silica strata and by the later completion of geosynclinal sediment accumulation (second half of the Late Cretaceous). Orogeny, accompanied by the accumulation of detrital and volcanic rocks, occurred in the Sikhote-Alin’ region in the Late Cretaceous and in the Cenozoic.

The Mesozoic structures are separated from the modern geosynclinal region located to the east by a system of deep faults, which controlled volcanic eruptions, and by various intrusions, which occurred throughout the Late Cretaceous and the Cenozoic. The Okhotsk-Chukchi and Eastern Sihote-Alin’ marginal volcanic belts, zones where Cretaceous and Paleogenic effusive rocks developed, correspond to the position of the faults.

The modern geosynclinal region includes the Koriak Highland, the Kamchatka Peninsula, the Kuril and Komandorskie (or Commander) islands, the island of Sakhalin, and the floor of the adjacent Bering Sea, Sea of Okhotsk, and Sea of Japan. Its eastern boundary is the Kuril-Kamchatka Trench, which separates the modern geosynclinal region from the Pacific Ocean basin. The exposure of the zone of deep-focus earthquakes (Zavaritskii-Benioff zone), which is associated with the largest deep faults in the earth’s crust and upper mantle, corresponds to the position of the trench.

The island chains are considered positive geosynclinal structures (geanticlines). The abyssal plains (Bering Sea and Southern Kuril) and deep trenches (Kuril-Kamchatka and Aleutian) are negative structures (geosynclinal troughs) lacking a “granitic” layer in their crustal cross section. Part of the floor of the seas of Okhotsk and Japan consists of submerged rigid median massifs amid linearly extended geosynclinal troughs and geanticlinal uplifts. Most of the modern geosyncline of the Far East is a region of sediment accumulation characterized by intensive seismic and volcanic activity (the volcanoes of Kamchatka and the Kuril Islands). The geological structure of the region is dominated by thick Cretaceous, Paleogenic, and Neogenic sedimentary and mixed volcanic and sedimentary complexes and Anthropogenic deposits crushed into systems of folded structures. The more ancient rocks are of Triassic and Jurassic age. Paleozoic and Mesozoic metamorphic complexes are developed on Kamchatka. The most ancient rocks on the Kuril Islands are Upper Cretaceous volcanites and beds of sands and clays.

M. V. MURATOV, V. M. TSEISLER, E. S. CHERNOVA, and E. A. USPENSKAIA

The history of the geological development of the area occupied by the USSR can be subdivided into two major stages: the Archean through the Middle Proterozoic, lasting more than 3 billion years, and the Upper Proterozoic through the Cenozoic, lasting about 1.5 billion years. The basements of the Eastern European and Siberian platforms developed during the first stage and the mantles of the platforms and the tectonic structures of the folded geosynclinal belts during the second. Because the Archean-Middle Proterozoic deposits underwent profound alterations as a result of intensive subsequent heating and partial remelting, the history of their accumulation cannot be completely reconstructed. The Late Proterozoic history of the ancient platforms is better known, and beginning with the Paleozoic, it is possible to trace the main changes in the paleogeography of the USSR.

In the early stage of its formation, the earth’s crust was composed of basalt; volcanic rocks brought up from the interior accumulated on its surface. This stage is sometimes called the lunar stage. Subsequently, the water shell appeared, and volcanic rocks and the initial products of their decomposition accumulated under conditions resembling contemporary oceanic conditions. In later stages of the Archean, carbonate, terrigenous, and mixed sedimentary and volcanic strata, often enriched with iron, accumulated in the vast marine basins in a relatively weakly differentiated tectonic situation. At the end of the Archean, about 2.6 billion years ago, fold-forming movements associated with intensive granitization and metamorphism occurred. Large nuclei of continental crust with a granite-metamorphic layer bounded by deep faults formed in Eastern Siberia. The Archean crust was probably quite mobile and fairly hot.

PROTEROZOIC. In the Early Proterozoic the already uplifted blocks of the continental crust and the troughs separating them, many with an oceanic-type crust, became differentiated. Argillaceous-carbonate, silica, and terrigenous deposits, including basic effusive and iron-containing rocks, accumulated in trough-like downwarps, bounded by deep faults (such troughs are known in the Baltic Shield, the Ukrainian Massif, and the Aldan Shield). The early Karelian folding, which occurred about 2 billion years ago, led to the complex deformation of the trough sediments and the expansion of crustal segments with the granite-metamorphic layer. The folding was accompanied by the intrusion of enormous masses of acidic magma and the formation of large anorthosite complexes. The general character of sediment accumulation, influenced by earlier tectonic structures, continued in the Middle Proterozoic.

The late Karelian processes of folding and granitization, which occurred 1.7–1.6 billion years ago, led to the final shaping of the modern structure of the basements of the Eastern European and Siberian platforms. Their original dimensions were greater than contemporary ones because at later times the platform margins were broken up and drawn into geosynclinal development.

Beginning in the Late Proterozoic, the geological development of the USSR was determined by the existence of two major blocks of continental crust—the Eastern European and Siberian platforms, surrounded by belts of oceanic (“nongranitic”) crust: the Ural-Mongolian, the Mediterranean, and Pacific belts. The geosynclinal belts, for a long time and until they were transformed into folded regions and young platforms, resembled modern oceans and marginal seas with island archipelagoes. During the period of general submergence, the platforms were occupied by vast shelf seas, which in orogenic periods were transformed into major areas of dry land with a continental crust and often rugged mountain relief.

RIPHEAN. Significant segments of the Eastern European Platform were uplifted in the Riphean, and the margins of the platform and the linear graben-like troughs, such as the Pachelma, Kresttsy-Valdai, and Middle Russian troughs, were invaded by shallow seas, in which gray and red terrigenous sedimentary strata accumulated. In the pericratonic troughs and over the entire Siberian Platform, considerable algal limestone is found in the Riphean cross section. Series of various rocks accumulated in the Ural-Mongolian, Mediterranean, and Pacific belts, ranging from deep-water, silica-clay, silica-carbonate, and volcanic rocks in the downwarps to coarse elastic continental rocks in the uplifts. From the end of the Early Riphean to the Late Riphean foldlike movements accompanied by intrusions of masses of acidic magma occurred in the Urals, the Tien-Shan, and Southern Siberia. Evidence of the mountain-building movements of the Riphean is seen in the rhythmic character of the beds, expressed in the alternation of large pockets of coarse fragmental red rocks of continental origin and marine carbonate deposits. The end of the Late Proterozoic (Wendian) on the Precambrian platforms was characterized by the accumulation of marine deposits that formed the lower horizons of the platform mantle. The Wendian deposits are always laid down transgressively with respect to the Riphean deposits, forming large syneclises. Mountain-building movements occurred in certain parts of the geosynclinal regions accompanied by folding and acidic magmatism (Baikalian orogeny), resulting in the formation there of the basements of the young platforms (for example, the Timan-Pechora platform, part of the Western Siberian Platform, and the Enisei Ridge). The Wendian beds in these regions are represented by molasses. Tillites are found in the Wendian deposits on the ancient platforms and in many other regions, attesting to the existence of a cold climate.

CAMBRIAN. The paleogeography of the beginning of the Cambrian differs little from that of the Wendian. The Siberian Platform was almost completely occupied by a marine basin, filled with carbonate deposits and deepening eastward. The Archaeocyatha reef structures of the Early Cambrian appear to have blocked off the southwestern part of the platform, where salt-bearing deposits were accumulating. The northern and central parts of the Eastern European Platform were covered by the sea only in the first half of the Cambrian; at this time, sand and clay sediments accumulated, which experienced little secondary alterations. At the same time, differentiated movements and powerful submarine basaltic volcanism were occurring in the geosynclinal belts, in Kazakhstan, the eastern Saians, and elsewhere. Certain segments were uplifted, forming chains of islands with numerous volcanoes. Terrigenous and carbonate strata accumulated in the shallow areas. In the Late Cambrian vast areas of the geosynclinal belts were engulfed by the mountain-building movements of the Salair orogeny, accompanied by granitic magmatism in Transbaikalia, the Saians, Tuva, the Kuznetskii Alatau, the Transcaucasus, and the Far East. The Salair orogeny led to the expansion of the young platforms and enlargement of the area of the geanticlinal zones in the geosynclinal regions. The relief of the platforms was also rejuvenated in the Late Cambrian, and continental strata accumulated in places, for example, Southern Siberia.

ORDOVICIAN AND SILURIAN. A new phase of sediment accumulation began in the Early Ordovician on the platforms and in the geosynclinal regions and continued in the Silurian. During the Ordovician and Silurian, marine basins occupied the western part of the Eastern European platform and virtually the entire Siberian Platform. Carbonate sediments accumulated in the western part of the Eastern European Platform; large coral reefs formed in the Silurian sea to the south of the Baltic Shield. Carbonate terrigenous sediments are numerous on the Siberian Platform, as are red terrigenous sediments in the south. Active underwater volcanism occurred in areas now occupied by the Urals, Kazakhstan, and the Tien-Shan and Altai mountains, and flysch series accumulated in some places, such as Kazakhstan and the Tien-Shan. Particularly intensive volcanism developed in the Urals during the Silurian. Large coral-reef structures on the rises of the sea floor were also typical. Terrigenous and carbonate terrigenous sediments were deposited in the marine basins of Southeast Asia, and graptolite shales became extensively distributed.

Mountain building (Caledonian, orogeny) accompanied by powerful granitic magmatism began in the Late Ordovician in the Northern Tien-Shan and in the Silurian in Central Kazakhstan and the Altai and Saian mountains and other regions. Enormous masses of acidic magma were intruded into the upper parts of the crust, forming large batholiths (Northern Tien-Shan). The accumulated sedimentary layers underwent folding and metamorphism.

The Caledonian orogeny concluded the Early Paleozoic stage of the formation of the continental crust. Where the blocks of continental crust joined, rocks of the ophiolite series—oceanic crust of the geological past including blocks of the mantle—were extruded onto the surface along faults. By the end of the Early Paleozoic, the area of the block of continental crust in Siberia had been considerably enlarged through the addition of Caledonian folded structures. A major continental massif formed in what is now Central Kazakhstan and the Northern Tien-Shan. Many segments of dry land emerged in the areas now occupied by the Urals, Altai Mountains, Kazakhstan, Kirghizia, the Saians, Tuva, and Transbaikalia.

DEVONIAN. The next phase of general submergence began in the Middle Devonian and was associated with the formation of new and renovation of formerly existing systems of geosynclinal troughs in the Urals, the Altai Mountains, the Caucasus, Tien-Shan, Transbaikalia, and the Far East. The vast oceanic basins of the Ural-Mongolian, Mediterranean, and Pacific belts were deeply submerged, and only individual ridges of islands in the zones of Early Paleozoic folding were located above sea level. On the platforms, the principal modern downwarps (syneclises) and upwarps (anteclises) began forming, and the primarily marine terrigenous-carbonate, carbonate, and salt-bearing deposits of the Middle and Upper Devonian accumulated. The formation of structures was accompanied by intrusions of basic and alkaline magma along the faults. Active basaltic magmatism occurred in numerous regions. Large superimposed basins and inherited downwarps formed in the mountain regions of Kazakhstan, Southern Siberia, and Northeast Asia (in certain parts of the platforms, Baikalides, Salairides, and Caledonides) and filled with the products of weathering of the mountain ranges—detrital red volcanic and molasses (the Minusinsk, Rybinsk, Tuva, and other basins). The formation of the intermontane basins and the uplift of the ranges separating them was accompanied by the effusion of acidic and basic magma of increased alkalinity. Devonian alkaline intrusions also occur on the Eastern European and Siberian platforms and in the regions of Baikal, Salair, and Caledonian folding. Volcanic rocks accumulated in many Devonian geosynclinal troughs. Saltbearing and multicolored terrigenous strata, attesting to arid conditions, are widespread in the cross section of Devonian beds on the platforms and in the depressions.

CARBONIFEROUS. In the early Carboniferous period the structural elements that had formed in the Devonian continued to develop. However, the climate was becoming increasingly more humid, evidenced by the coal-bearing series distributed over vast areas of the Eastern European Platform, the Urals, and Kazakhstan.

A large part of the Siberian Platform (the Tunguska Syneclise) was occupied by a plain with many lakes and swamps; such conditions, which prevailed until the end of the Permian period, led to the formation of enormous reserves of coal in the Upper Paleozoic beds of the Siberian Platform. Volcanic eruptions began there in the Late Paleozoic. Marine conditions continued on the Eastern European Platform, and white limestones and dolomites accumulated. Detrital strata appeared along the margins of the platform in the Cisural Region and Donets Basin.

PERMIAN. During the Permian period the seas covering the platform gradually retreated. Gypsums, dolomites, rock salt, and variegated clays and sandstones became widespread owing to arid climatic conditions. Further uplifts at the end of the Permian period led to the replacement of chemogenic sediments by detrital red sediments. Detrital material appeared on the platform from the adjacent geosynclinal belts (the Ural-Mongolian and Mediterranean belts), which experienced a general uplift at this time. Intrusions of large granitoid massifs occurred in the Urals, the Caucasus, the Tien-Shan, Kazakhstan, the Altai Mountains, and elsewhere. Within the geosynclinal regions and along the outer margins, large intermontane and submontane basins developed and became filled with very thick coal-bearing strata (for example, the Cisural Trough and the Karaganda and Kuznets basins). At the same time, a special type of platform depression formed, deeply downwarped with steep margins and a flat bottom (the Tunguska and Caspian depressions).

At the end of the Paleozoic, the ocean basins of the Ural-Mongolian belt closed. Traces of the basins have been preserved in the form of zones with blocks of oceanic crust, called ophiolite zones, squeezed into faults in the Urals, Eastern Kazakhstan, the Southern Tien-Shan, and elsewhere. Separate blocks of continental crust in various parts of contemporary Eastern Europe, Siberia, Kazakhstan, and Kirghizia merged into a single continental mass. A latitudinal continental margin volcanic belt developed along its southern border, along the boundary with Paleotethys. At this time, the Caledonides, Salairides, and Baikalides experienced secondary mountain building as a result of renewed tectonic activity; depressions with Middle Carboniferous-Permian molasses developed in these regions. Many Late Paleozoic depressions occupied the same position as Devonian depressions. Marine conditions predominated in the geosynclinal regions of the Pacific belt from the Middle Carboniferous through the Permian. Small segments were uplifted during the Permian period.

TRIASSIC. At the beginning of the Triassic, much of what is now the USSR was dry land. Characteristic of the Early and Middle Triassic was widespread volcanic activity on the Siberian Platform, in the Kuznets and Pechora basins, on the Western Siberian Platform, and elsewhere, leading to the formation of the Siberian traps. Red continental strata accumulated on the Eastern European Platform (the Moscow and Caspian syneclises and the Dnieper-Donets Depression). Marine basins occupied Ciscaucasia, the southern part of the Caspian Syneclise, the western part of the Turan Plate, and the northeastern parts of the continent (Taimyr Peninsula, Verkhoiansk region, and the Chukchi Peninsula). A new stage of subsidence began in the Late Triassic, resulting in the formation of the geosynclinal troughs in the Crimean and Caucasian regions and the reemergence of the downwarps in the Sikhote-Alin’ and Pamir mountains. General downwarping began on the platforms.

JURASSIC AND CRETACEOUS. In the Jurassic and Cretaceous periods, several new depressions, superimposed on more ancient Paleozoic downwarps and uplifts, formed on the Eastern European Platform. Relatively stable marine conditions continued in the southern regions, occupied by the Tethys Sea; the northern regions of the modern European part of the country were below sea level in the Late Jurassic. The Cretaceous period was marked by several transgressions of the boreal sea into the Moscow Syneclise and the Pechora Basin. In the Jurassic and Cretaceous periods, the Western Siberian Platform was occupied by an enormous bay of the boreal sea, in which mixed sand and clay and mixed clay and silica strata accumulated. The external shelf seas of the Tethys Sea flooded the Scythian Platform and Turan Plate, where Upper Jurassic and Upper Cretaceous carbonate sediments are widely distributed, along with terrigenous sediments. The southern part of the Turan Plate experienced the greatest submergence, while the northern parts east of the Aral Sea developed under land conditions in the Jurassic and Early Cretaceous. Only the late Cretaceous transgression, the most extensive one, flooded the northeastern part of the Turan Plate and established a connection between the northern and southern basins through the Turgai Strait. The northeastern and eastern regions of the USSR were occupied at that time by boreal seas, with the accumulation of beds of sands and clays. The northeastern margin of the Siberian Platform was invaded by the sea as far as the Viliui Syneclise. The southern and central parts of the platform and the folded regions of Southern Siberia, the Altai Mountains, Kazakhstan, the Tien-Shan, and Transbaikalia were areas of dry land, in certain basins of which Jurassic coal-bearing strata formed. In some places, such as Chul’man, Irkutsk, and Kan, the strata reach enormous thickness and contain major coal reserves. Mountain building accompanied by acidic intrusive magmatism occurred at the boundary between the Jurassic and Cretaceous periods in the northeastern part of the USSR and in Transbaikalia, on the Aldan Shield, and in the Pamirs. At the end of the Late Jurassic and in the Early Cretaceous, the continental block expanded significantly in northern Eurasia as a result of the closing of the geosynclinal troughs in Northeast Asia and the attachment of major median massifs, such as the Okhotsk, Omolon, and Kolyma massifs, to the Siberian Platform. The Cisverkhoiansk Trough, filled with a coal-bearing molasse, formed along the front of the rising late Mesozoic complex (Mesozoides). Many intermontane basins with coal-bearing strata formed within the late Mesozoic complex. After the general uplifts at the end of the Early Cretaceous, the areas now occupied by Kamchatka, the Koriak Highland, and Sakhalin were flooded by the seas. The eastern margin of the former continent remained uplifted, and in the zones of the largest deep faults, active outpourings of andesite magma and acidic intrusions along the Okhotsk-Chukchi continental margin volcanic belt occurred.

PALEOGENIC. The Paleogenic period in the USSR was characterized by relatively little tectonic activity. Marine sediment accumulation continued in the southern parts of the Eastern European Platform and on the Scythian Platform, on the Turan Plate, and in the Alpide geosynclinal region. The Western Siberian Platform was occupied by the sea. The accumulation of marine sediments under conditions of geosynclinal structures was characteristic of the marginal eastern regions of the Pacific belt (Kamchatka, Sakhalin, and the Kuril Islands). In the geosynclinal regions, marine sediment accumulation was accompanied by volcanism; active Paleogenic volcanism occurred in the Lesser Caucasus, where there was a system of downwarps separated by cordilleras. Volcanic activity occurred along the margins of the downwarps. Flysch series accumulated in many downwarps in the Caucasus. The zones of flysch accumulation surrounded the block of continental crust of the Eastern European and Scythian platforms on the south (Caucasus) and west (Carpathians). The land relief of the platform regions was probably fairly level, as seen from surviving Paleogenic weathering crusts.

NEOGENIC. The end of the Paleogenic period is characterized by the uplifts caused by the Alpine orogeny, which reached greatest activity during the Neogenic and Anthropogenic periods. Mountain building occurred not only in the geosynclinal regions (Carpathians, Crimea, Caucasus, and Kopetdag) but also in regions whose tectonic regime was similar to typical platform conditions throughout the Mesozoic and Paleogene (Tien-Shan, the mountains of Southern Siberia, and the southern part of the Siberian Platform). The mountain systems that arose in regions that had completed geosynclinal development long before the Neogene greatly surpass in area the mountain systems that formed in place of the Alpide geosynclines. The Alpine mountain building was accompanied by the formation of large interior depressions occupied by marine basins (Black Sea and the southern part of the Caspian) and lakes (Aral Sea, Lake Balkhash, and Lake Baikal). Some of the depressions are typical rift structures. Significant areas of the marginal seas—the Sea of Japan, Bering Sea, and Sea of Okhotsk—are also new formations. Geosynclinal development associated with active volcanism is presently continuing in the eastern parts of the Pacific belt (the Kuril Islands and Kamchatka); thick series of Anthropogenic andesite lavas form a solid shell that covers the Paleogenic and Neogenic structures of Kamchatka. Volcanic activity occurred in chains along the fault zones.

V. M. TSEISLER

Paleogeography of the Anthropogenic period. The Anthropogenic (or Quaternary) period has been characterized by renewed tectonic activity and by the cooling and greater continentality of the climate. The uplifting of the continents, formation of rejuvenated epiplatform mountains, and the closing of the geosynclines of the Mediterranean belt resulted in the isolation of the polar basin and greater latitudinal differentiation of climate and was accompanied by the appearance of latitudinal zonality close to that of the present day. In addition, one other characteristic has been identified in the Late Cenozoic, namely, rhythmic (oscillatory) changes of climate. Such changes have been observed in cross sections of Cenozoic beds even before the beginning of the Anthropogene, being well expressed as far back as the Eopleistocene, but only in the Pleistocene proper did they reach a magnitude sufficient to cause the continental glaciation that spread over the flat areas of the USSR during epochs of cooling and receded during the warm, interglacial, epochs.

Three major waves of cooling, separated by epochs of warming, are characteristic of the plains during the Pleistocene. The most ancient reliably established glaciation—the Oka Glaciation—has been identified in the Early Pleistocene. In the European part it spread south to 52°–54° N lat.; in Siberia, where it is called the Dem’ian Glaciation, its boundaries have not been established. The subsequent Likhvin interglacial period was characterized by a climate warmer than the present one and the widespread distribution of broad-leaved forests. Soils close to subtropical soils predominated in the southern half of the Eastern European Plain.

The Middle Pleistocene was characterized by the greatest development of glaciation. The source area of the European ice sheet was located on the Scandinavian Peninsula, outside the USSR. During the glacial maximum—the Dnieper Glaciation—the ice advanced far south along the valleys of the Dnieper and the Don, its thickness reaching 2–2.5 km.

Ice also advanced great distances from the islands of Novaia Zemlia (Novaia Zemlia source area), reaching the Pechora River and the northern coast of the Kola Peninsula. Glaciers in Siberia also reached their maximum extent during the Middle Pleistocene, although they did not advance as far south as those of the European part of the USSR. The boundary of the Samarovo Glaciation in Western Siberia passed somewhat south of the mouth of the Irtysh River but shifted farther north east of the Ob’. Several source areas of glacial radiation have been identified in the regions of the Ural and Siberian ice sheets: the polar Urals, the Putorana and Byrranga mountains, Severnaia Zemlia, and the Anabar Shield. The thickness of the Siberian glaciers did not exceed 1 km. A distinguishing feature of the Middle Pleistocene glacial epoch in Western Siberia was its coincidence in time with the transgression of the sea as a result of local tectonic down-warping.

Two waves of cooling, separated by a warm interval, are clearly identified in the Middle Pleistocene. The second advance of ice in the Middle Pleistocene is known as the Moscow Glaciation in the European part and the Taz Glaciation in Western Siberia. It was less extensive than the first. On the Eastern European Plain the boundary of the glacier was slightly to the north and west of Moscow.

The Mikulino, or Mgin, interglacial period that followed the Middle Pleistocene differed from the modern epoch by higher temperatures and greater precipitation, but it was not as warm as the preceding Likhvin interglacial. The Mikulino interglacial was marked by a transgression of relatively warm seas into the level northern parts of the USSR, known as the boreal transgression. The resulting deposits are found in the northern part of the Eastern European Plain at elevations of 80–100 m above the current sea level.

The Late Pleistocene was also marked by glaciation, known in the European part where its boundary coincided with the Valdai Hills as the Valdai Glaciation and in Siberia as the Zyrianka Glaciation. The extent of this glaciation was significantly less than the extent of the Middle Pleistocene glaciation, although the climatic conditions of the Valdai epoch were extremely harsh, giving us cause to consider it the chief climatic minimum of the Pleistocene.

Two periods of cooling, separated by a warm period, are identified in the Late Pleistocene. The last cooling and advance of ice in the European part occurred 20,000 years ago, after which the ice on the plains retreated, completely disappearing about 10,000 years ago.

The patterns of glacial development in the mountain regions of the eastern and southern USSR differed. Throughout the Pleistocene, the most typical type of glaciation in the northeastern USSR was mountain-valley glaciation; during periods of greatest extent, the glaciers reached the margins of the plains, forming piedmont glaciers (the western foothills of the Verkhoiansk Range). The traces of Late Pleistocene glaciation are most clearly expressed, particularly the concluding stage, known as the Sartanian, which occurred 12,000–14,000 years ago. Tectonic and climatic factors influenced the development of glaciation in the mountain belt along the southern boundaries of the USSR. Glaciation so far south became possible owing to the tectonic uplift of the regions and encompassed most of the mountain regions throughout the entire Pleistocene. Variations in the extent of the ice cover were primarily related to climatic changes.

The effects of the glacial epochs, and in particular of the glaciers themselves, on the modern topography varied. The glaciers left traces in the relief in the form of clearly expressed terminal moraines (where the glaciers thawed) and a solid sheet of glacial formations north of the boundaries of thawing (the region of swell and swale topography), as well as in the form of special types of land surfaces near the source areas of glacial radiation, for example, on the Kola Peninsula, where the enormous mass of moving ice removed the more ancient loose beds and scoured the surface of the exposed bedrock. The glacier meltwaters ran off through low-lying parts of the relief, often along river valleys carved out in preglacial time. In low-lying areas, the meandering meltwater streams redeposited the material transported by the glaciers, creating flat flooded outwash plains. In places where the relief prevented water from running off, vast glacial basins formed (for example, the Western Siberian Plain).

Fluctuations of the level of the world ocean were related to the formation of ice sheets. The level dropped significantly in the glacial epochs, primarily because the formation of ice sheets required vast amounts of water, which thus were removed from the water cycle for extended periods. For this reason, the glacial eustatic drop in the Late Pleistocene glacial epoch was about 100–110 m; when the glaciers melted during the interglacial periods, the level of the ocean rose again.

Changes in atmospheric circulation related to the emergence of ice sheets and variations in the rate of evaporation from the surface of bodies of water caused significant changes in the moisture content of nonglaciated areas. Specifically, epochs of somewhat greater moisture, known as pluvial and approximately contemporaneous with the glaciation of the plains, have been clearly established in Middle Asia. The transgressive phases of the Caspian Basin generally correspond to periods of climatic cooling.

The alternation of transgressive and regressive phases accompanied by variation in salinity has also been clearly identified in the Pleistocene history of the Black Sea. In periods of transgression, the sea’s level was 10–20 m higher than at present, and water ran off through the Bosphorus and Dardanelles into the Mediterranean Sea. The periods of cooling, accompanied by glaciation, influenced the entire course of natural processes in areas distant from the areas of glaciation. One example was the formation of the permafrost zone, whose expansion during the cold epochs of the Pleistocene significantly influenced the entire course of exogenic processes and led to the expansion of the area of cryogenic morphosculpture, relicts of which are observed far to the south of the current distribution of permafrost rocks.

The continentality of the climate, which increased sharply during epochs of cooling and caused an expansion of the permafrost zone, led to a revision of the structure of the natural zonality characteristic of the interglacial epochs. Over most of the modern temperate zone, vast open spaces with significant development of xerophytic elements in the vegetation cover predominated. Intensive accumulation of loess deposits occurred in these areas. These conditions existed on the Eastern European Plain until the beginning of the Holocene and possibly even somewhat later. The last stage in the development of the environment, the Holocene, was characterized by a period of warming accompanied by a northward retreat of the boundary of the permafrost zone. For a relatively short time interval, about 5,000–6,000 years ago, climatic conditions were warmer and more humid than the presentday climate, constituting the climatic optimum of the Holocene. As a result, trees made significant northward advances.

I. I. SPASSKAIA

Bibliography

General works
Mil’kov, F. N., and N. A. Gvozdetskii. Fizicheskaia geografiia SSSR, 4th ed. Moscow, 1976.
Mil’kov, F. N., N. A. Gvozdetskii, and N. I. Mikhailov. Fizicheskaia geografiia SSSR, vols. 1–2. Moscow, 1969–70.
Fiziko-geograficheskoe raionirovanie SSSR. Moscow, 1968.
Prirodnye usloviia i estestvennye resursy SSSR, vols. 1–15. Moscow, 1963–72.
Sovetskii Soiuz: Geograficheskoe opisanie, vols. 1–22. Moscow, 1966–72.
Geological structure
Geologicheskoestroenie SSSR, vols. 1–5. Moscow, 1968–69.
Laz’ko, E. M. Regional’naia geologiia SSSR, vols. 1–2. Moscow, 1975.
Tektonika Evrazii (Ob”iasnitel’naia zapiska k tektonicheskoi karte Evrazii; masshtab 1:5,000,000). Moscow, 1966.
Muratov, M. V. “Glavneishie strukturnye elementy materikov, ikh vzaimootnosheniia i vozrast.” In the book Tektonika. Moscow, 1972.
Markov, K. K., G. I. Lazukov, and V. A. Nikolaev. Chetvertichnyi period, vols. 1–2. Moscow, 1965.
Pleistotsen. Moscow, 1968.
Velichko, A. A. Prirodnyiprotsess v pleistotsene. Moscow, 1973.
Atlas litologo-paleogeograficheskikh kart SSSR. Moscow, 1967–69.
Muratov, M. V. Proiskhozhdenie materikov i okeanicheskikh vpadin. Moscow, 1975.

The USSR has the world’s largest explored reserves of iron and manganese ores and asbestos. It is the world’s leading producer of iron and manganese ores, asbestos, petroleum, coal, and potassium salts. Its reserves of natural gas are the largest in the world, and the USSR is the world’s second largest producer of natural gas. It also leads the world in proven reserves and extraction of numerous nonferrous metals, phosphate fertilizers, chromite, and other useful minerals.

Fuel and energy resources. PETROLEUM AND GAS. In Russia, petroleum deposits were known to exist in the area of Baku, Groznyi, and Maikop in the Caucasus, at Cheleken and Nebit-Dag in Western Turkmenia, in the Fergana Valley in Middle Asia, and in the Emba region in Kazakhstan. On the eve of World War I (1914–18), the major petroleum deposits of the Apsheron Peninsula, near the city of Baku, accounted for more than 75 percent of Russia’s total annual petroleum production. No industrial deposits of gas were known. Geological explorations, which expanded considerably after the Great Patriotic War (1941–45), have revealed new petroleum deposits and have discovered gas deposits.

In 1950 petroleum and gas accounted for 19.7 percent of the total fuel extraction, whereas in 1970 they accounted for 60 percent, and in 1975 for 66 percent. In addition to supplying domestic needs, the USSR also exports petroleum and gas, primarily to the members of the socialist community.

The discovery of petroleum and gas deposits in the region lying between the Volga River and the Ural Mountains, in the northern part of the European USSR (the Komi ASSR), in the Western Siberian Lowland, and in Middle Asia and Kazakhstan fundamentally shifted the center of the petroleum and gas industry. Petroleum and gas deposits have also been found beneath the waters of the internal and marginal seas.

The principal petroleum and gas regions of the USSR are characterized as follows. The Azerbaijan Petroleum and Gas Region encompasses the southeastern part of the Glavnyi Range of the Caucasus, the Apsheron Peninsula, and the floor of the Caspian Sea adjacent to the peninsula and extends into the Kura Lowland and partially into the foothills of the Lesser Caucasus. Its main deposits are located both on land (Balakhany-Sabunchi-Romana, Surakhany, Karadag, Bibi-Eibat, and Kiursangia) and in the Caspian Sea (Neftianye Kamni, Zhiloi Island, Banka Darvina, Giurgiany, and Peschanyi Island). All the deposits are of Neogene age. The petroleum from these deposits has a low sulfur content and a high percentage of gasoline fractions. Since the 1950’s, petroleum has been extracted in the Caspian Sea dozens of kilometers from shore, where sea depths are usually 30–40 m, sometimes reaching more than 60 m.

The petroleum and gas deposits of the Northern Caucasus—in the Dagestan ASSR, the Chechen-Ingush ASSR, and Stavropol’ and Krasnodar krais—are associated with Mesozoic and Cenozoic beds. The country’s oldest petroleum deposits, Maikop and Groznyi, are located in the Northern Caucasus, as are large deposits of natural gas, discovered and developed in Soviet times, including the North Stavropol’, Leningradskaia, Anastasievo-Troitskoe, Maikop, Starominskaia, and Berezan’ deposits.

The petroleum regions of the Ukraine are confined to the Dnieper-Donets Depression and the Ciscarpathian Foredeep. The largest gas and petroleum deposits are associated with Paleozoic beds and, to a lesser extent, Mesozoic beds. Among the deposits of greatest industrial importance are the Shebelino, Efremovka, and Zapadnye Kresttsy gas deposits and the Gnedintsevo, Glinsko-Rozbyshevskoe, Radchenkovo, and Zachepilovka petroleum deposits. Gas deposits have also been found in the Black Sea and the Sea of Azov.

In Byelorussia the Rechitsa, Ostashkov, and other petroleum deposits are associated with the Paleozoic (Devonian) beds of the Pripiat’ Depression. Small deposits of petroleum have been discovered in Kaliningrad Oblast and the western part of the Lithuanian SSR. There may also be petroleum-bearing deposits in the Baltic Sea. In the European part of the USSR petroleum and gas deposits are concentrated in the area between the Volga and the Urals and along the northern extension of the Urals into the Ukhta and Pechora regions.

For many years after the Great Patriotic War, the Volga-Ural Oil and Gas Region was the principal producer of petroleum and gas in the USSR. The first promising areas were discovered in the Tatar, Bashkir, and Udmurt ASSR’s and in Perm’, Kuibyshev, Saratov, Volgograd, and Orenburg oblasts. Geologically, this petroleum and gas province is located in the southeastern part of the Eastern European Platform and in the Cisural Foredeep. All the industrial deposits of petroleum and gas are associated with Devonian, Carboniferous, and Permian beds and are particularly concentrated in Devonian and Lower Carboniferous beds. Of the several hundred deposits discovered in the Volga-Ural Oil and Gas Region, the Romashkino petroleum deposit in the Tatar ASSR and the Orenburg gas and gas-condensate deposit are the largest. Other major petroleum deposits include the Bavly deposit in the Tatar ASSR, the Tuimazy, Shkapovo, and Arlan deposits in the Bashkir ASSR, and the Iarino-Kamennolozhskoe deposit in Perm’ Oblast. An important feature of the deposits is that the petroleum and gas strata occur at comparatively shallow depths, ranging from 1.5 to 2.5 km; deposits in Transcaucasia, the Northern Caucasus, and the Ukraine occur at depths of 3–4.5 km and more.

Petroleum and gas reserves have been found in the Timan-Pechora Oil and Gas Basin, which is located in the Komi ASSR, the Nenets Autonomous Okrug (formerly Nenets National Okrug), and the northeastern part of Arkhangel’sk Oblast. The petroleum and gas are confined to Paleozoic beds, namely, beds of Silurian through Permian age. The most important deposit is the Vuktyl gas deposit.

The Western Siberian Oil and Gas Basin, located between the Ural Mountains and the Enisei River, is, geologically, an enormous platform, whose Paleozoic basement is overlain by a thick mantle of Mesozoic and Cenozoic deposits. The productive petroleum and gas horizons occur in the Mesozoic beds, primarily Jurassic and Cretaceous beds. The most numerous petroleum and gas deposits are located in Tiumen’ Oblast, particularly along the middle Ob’ River and in the northern part of the oblast as far as the Iamal Peninsula. Numerous deposits have been found in Tomsk Oblast. Major deposits in the Western Siberian Oil and Gas Basin are the Urengoi, Iamburg, Medvezh’e, and Zapoliarnoe gas deposits and the Samotlor, Mamontovka, Fedorovskoe, and Ust’-Balyk petroleum deposits.

A region that appears to be promising is the Caspian Petroleum and Gas Province, which is bounded by the Volga River in the west and the foothills of the Southern Urals in the north and which occupies the coast of the Caspian Sea in the east (Western Kazakhstan). The petroleum deposits of the Ural-Emba region were known even before the Revolution. A notable characteristic of the geological structure of the Caspian Syneclise is the existence of a thick Lower Permian salt-bearing stratum, which divides the sedimentary beds into two structural levels, one above and one below the salt stratum. The petroleum and gas deposits in the Caspian Depression occur primarily in Paleozoic beds, at depths of 4–7 km and more beneath the salt-bearing strata. In the 1960’s, deposits of petroleum and gas (at Zhetybai and Uzen’) were discovered and explored on the Mangyshlak Peninsula.

There are also deposits of petroleum and gas in Middle Asia, particularly in Turkmenia and Uzbekistan. The productive horizons are confined to Mesozoic beds, primarily Jurassic and Cretaceous beds. The geological structure of the deposits in Western Turkmenia is very similar to that of the deposits of the Apsheron Peninsula. The petroleum deposits of the Fergana Valley have been exploited since prerevolutionary times. Large gas deposits have been explored in Bukhara Oblast (Gazli and Kandym deposits) and in Chardzhou Oblast (Bagadzhinskoe, Naip, and Kirpichly deposits). The Shatlyk gas deposit, the largest gas deposit in Middle Asia, is located in the region between the Murgab (Murghab) River and the Tedzhen (Harirud) River in Mary Oblast.

In Eastern Siberia extensive geophysical investigation and prospecting was begun in the early 1970’s in Krasnoiarsk Krai, Irkutsk Oblast, and the Yakut ASSR, where the petroleum and gas bodies are associated with Mesozoic and Paleozoic beds. A series of large gas deposits has been explored in the central part of the Yakut ASSR. In the Far East industrial deposits of petroleum and gas have been explored on the island of Sakhalin.

COAL, OIL SHALE, AND PEAT. In 1913 the total estimated geological reserves of coal in Russia amounted to 231 billion tons. In the mid-1970’s the total estimated geological reserves of coal in the USSR amounted to 6.8 trillion tons, two-thirds of it hard coal, and the rest, brown coal. The USSR is the world’s leading producer of coal. Major basins of hard and brown coals, mostly of Carboniferous, Permian, and Jurassic age, have been discovered and explored in the USSR. The largest coal basins are the Donets, Pechora, Moscow, Dnieper, and L’vov-Volyn’ coal basins in the European part of the USSR, the Kizel and Cheliabinsk basins in the Urals, the Karaganda, Ekibastuz, Maikuben, and Ubagan basins in Kazakhstan, the Angren and Uzgen basins in Middle Asia, and the Kuznetsk, Kansk-Achinsk, Irkutsk, Tunguska, Lena, South Yakutia, Partizansk, and Bureia basins in Siberia and the Far East. In 1975 the total coal extraction in the USSR included 701 million tons.

The Donets Coal Basin is the largest basin in the European part of the USSR. Its coal is of the most valuable industrial grade, and is distinguished by high quality; for example, the calorific value of the coal is 32.4–36.0 megajoules (mJ), or 7,700–8,600 kilocalories (kcal). The coal seams, whose average thickness is 0.75–1 m, occur at depths ranging from 200–500 m in the outlying parts of the basin to 1,500 m in the central parts.

The Pechora Coal Basin has significant reserves of coking and energy hard coals. The calorific value of these coals is 16.8–32 mJ (4,000–7,600 kcal).

The Kuznetsk Coal Basin is one of the largest basins in the USSR and leads the world in reserves and the thickness of the coal seams and coal quality. The calorific value of the coal is more than 29.2–35.6 mJ (7,000–8,500 kcal), with an ash content of not more than 4–16 percent and a negligible sulfur content. The thickness of the productive coal seams is 6–14 m, occasionally reaching 20–25 m.

The Kansk-Achinsk Basin of brown coal, one of the largest in the USSR, is located in the southern part of Eastern Siberia. The coal-bearing Jurassic beds, which contain productive coal seams up to 70 m thick, extend in a latitudinal direction along the Siberian Railroad for more than 700 km. The coal lies at shallow depths, which makes possible open-pit mining operations. The net cost of extracting coal in the Kansk-Achinsk Basin is three to four times lower than the average cost for the USSR’s entire coal industry. The largest explored deposits are the Itatskoe, Berezovkskoe, Bogotol’skoe, Nazarovskoe, and Irsha-Borodinskoe deposits. The calorific value of the coal is 11.9–19.1 mJ (2,800–4,600 kcal), with an ash content of 8–16 percent. The brown coal of the Irkutsk, or Cheremkhovo, Basin is similar in composition to the brown coal of the Kansk-Achinsk Basin. The South Yakutia Basin, which has significant reserves of hard coking coals, is a promising area for development.

The Karaganda Coal Basin, with total estimated geological reserves of hard coal of 51 billion tons, is located in the central part of Kazakhstan. The coal seams, which are 0.7–8 m thick, are dominated by the presence of hard low-sulfur coal suitable for obtaining high-quality coke. The Ekibastuz Basin of hard coal, located near the Karaganda Basin, is now being exploited. Although its coal has a high ash content, 35–50 percent, it also has considerable calorific value, up to 32.2 mJ (7,700 kcal). The coal seams are being worked using large open-pit mines.

The principal oil-shale basins and deposits are located in the European part of the USSR. Industrially, the Baltic Shale Basin is most important; its productive beds occur in the northern part of the Estonian SSR and the western part of Leningrad Oblast. The oil shales are of high quality, providing not only energy but also valuable chemical raw material.

The USSR accounts for more than 60 percent of the world’s total peat reserves. The total area of inventoried peat bogs is 71.5 million hectares, and estimated geological reserves amount to 162.5 billion tons of air-dried peat. Western Siberia, the northern part of the European SSR, and Eastern Siberia have the largest reserves of peat. Virtually all of the peat extraction is concentrated in the European part of the country.

Ore for ferrous and nonferrous metallurgy. IRON ORES. In prerevolutionary Russia, the only comparatively large known iron-ore deposits were at Krivoi Rog in the Ukraine and in the Urals. According to calculations made in 1910, of the world’s total ironore reserves of 22.4 billion tons, Russia accounted for only 800 million, that is, less than 4 percent. Today, the USSR contains the world’s largest reserves of iron ore and leads the world in iron-ore production. It has more than 300 iron-ore deposits. Most of the explored ore reserves are concentrated in the Ukraine, the Kursk Magnetic Anomaly, the Urals, and Kazakhstan. Significant reserves have been explored in Western and Eastern Siberia and in certain parts of the Kola Peninsula and Karelia. The USSR has magmatic, contact-metasomatic, hydrothermal, sedimentary, sedimentary-metamorphosed, weathering crust, and other types of deposits containing various iron ores, including titanomagnetite, magnetite, hematite, siderite, limonite, ferruginous quartzites, and silicate iron-chrome-nickel ores.

The iron-ore deposits of the Ukraine contain the largest explored reserves of iron ore in the USSR and are the chief source of iron-ore production. The Krivoi Rog Iron-ore Basin, located in the Ukraine, is one of the largest in the USSR; rich magnetite ores are mined by underground methods, and ferruginous quartzites are extracted in large open-pit mines. There is a major basin of oolitic limonites on the Kerch’ Peninsula.

The deposits of the Kursk Magnetic Anomaly, located in the central part of the European USSR, contain large reserves of rich magnetite ores and ferruginous quartzites. The martite ores of the Iakovlevskoe, Gostishchevskoe, and other deposits in Belgorod Oblast, which occur at depths of more than 400–500 m, are characterized by a particularly high iron content, more than 60 percent. Deposits suitable for open-pit mining are being developed first, including the Lebedinskoe and Stoilenskoe deposits in Belgorod Oblast and the Mikhailovskoe deposit in Kursk Oblast.

The Olenegorskoe and Imeni Kirova deposits of ferruginous quartzites and the Kovdor deposit of complex apatite-magnetite ores have been explored on the Kola Peninsula. The Kostomukshskii deposit of ferruginous quartzite and the Pudozhgorskii deposit of titanomagnetite have been identified in Karelia. The Dashkesan deposit of magnetite ores is presently being exploited in the Caucasus. The oldest and one of the most important iron-ore regions in the USSR is the Urals, where the Mount Blagodat’, Mount Vysokaia, and Mount Magnitnaia skarn-magnetite deposits and the Bakal deposit of siderite and limonite ores, among others, have been exploited for many years. The Urals have especially large reserves of titanomagnetite ores (the Kachkanar and Gusevogorskoe deposits), which are low in iron but can be easily beneficiated.

There are major iron-ore reserves in Kazakhstan. The Sokolovskaia, Sarbai, and Kacharsk deposits of magnetite ores in Kustanai Oblast do not require beneficiation or are easily beneficiated and provide the ore raw material for the Magnitogorsk Combine and other Ural metallurgical enterprises. In addition to magnetite ores, large deposits of sedimentary-type limonites have also been explored in Kustanai Oblast, including the Aiat and Lisakovsk deposits, which are suitable for open-pit mining. The Karazhal, Bol’shoi Ktai, Ken’tiubetogai, and other deposits that supply iron ore to the Karaganda Metallurgical Plant are being exploited in central Kazakhstan.

The principal iron-ore deposits in Southern Siberia, primarily magnetite ores, are located in Gornaia Shoriia, the Kuznetskii Alatau, and Khakassia. The Kuznetsk Metallurgical Combine uses ores from these deposits—the Sheregesh, Tashtagol, Shalym, Kaz, Abakan, Teiskii, and other deposits. Significant ironore deposits have been discovered in Eastern Siberia, including Krasnoiarsk Krai and Irkutsk and Chita oblasts. Deposits of the Angara-Ilim region, such as the Korshunova and Rudnogorsk deposits, are of the greatest industrial importance. The Tagarskii and Neriundinskii deposits in Irkutsk Oblast have been explored. There are relatively large deposits of hematite ores in the Angara-Pit region in Krasnoiarsk Krai, as well as the Berezovaia deposit of limonites and siderites in Chita Oblast.

The Aldan iron-ore region in South Yakutia, where the Taezhnoe, Pionerskoe, and other deposits of magnetite ores have been explored, appears to be promising. Thick beds of ferruginous quartzites have been identified in the Charo-Tokkinskii ore region, on the boundary of Chita Oblast and the Yakut ASSR. The proximity of the South Yakutia Basin’s deposits of coking coals to the Baikal-Amur Railroad, now under construction, has made it possible to establish a major base for a new metallurgical plant in the eastern part of the USSR. The largest iron-ore deposits in the Far East are the Garin and Kimkan deposits.

MANGANESE ORES. The USSR leads the world in explored reserves and the production of manganese ores. Most of the reserves are concentrated in the Chiatura (Georgian SSR) and Nikopol’ (Ukrainian SSR) manganese-ore basins. The rich oxide and oxidized ores of Chiatura are of especially high quality. The Bol’shoi Tokmak deposit of carbonate manganese ores, similar to the Nikopol’ ores, has been explored in Zaporozh’e Oblast. Small deposits of manganese ores have been found in the Urals, Kazakhstan, Western Siberia, and the Far East.

CHROMITE ORES. Deposits of chromite ores have been discovered in Western Kazakhstan, where the Southern Kempirs group of deposits of chromites, used in the metallurgical and chemical industries, has been explored. The Sarany deposit of chromites, used primarily to produce refractory materials, is located in the Central Urals.

TITANIUM ORES. Deposits of titanium ores occur in the form of sedimentary rutile-ilmenite placers (for example, in the Ukraine and the littoral areas of the Baltic Sea), ilmenite-containing metamorphosed sandstones (the Iarega deposit in the Komi ASSR), and magmatic titanomagnetite ores, which have been identified in significant quantities, for example, in the Urals.

ALUMINUM ORES. The largest deposits of high-grade bauxites have been explored in the Northern Urals—the Krasnaia Shapochka, Kal’ia, and Cheremukhovo deposits—which supply ore raw material for the Ural aluminum plants. The Pavlodar Aluminum Plant operates on the basis of the bauxite deposits in Western Kazakhstan. In the European part of the USSR, the most significant bauxite deposits are in Arkhangel’sk Oblast (the North Onega bauxite-bearing region), in the Komi ASSR (the South Timan bauxite-bearing region), and in the vicinity of the Kursk Magnetic Anomaly, where bauxites occur in the weathering crust together with iron-ore bodies. In Siberia there are bauxite deposits in the Salair Ridge, the Angara River basin, and the Vostochnyi Saian Mountains.

The USSR was the first country in the world to master the production of alumina and the recovery of aluminum from nepheline ores, deposits of which are found on the Kola Peninsula (the nepheline syenites in the Khibiny and Lovozerskie Tundry), in Siberia (the Kiia-Shaltyrskii deposit of nepheline syenites in Kemerovo Oblast), and in Transcaucasia and Middle Asia. Alunite ores (the Zaglik deposit in the Azerbaijan SSR and others) also provide aluminum raw material.

COPPER ORES. Copper pyrite, porphyry copper, copper sandstones, sulfide copper-nickel, and complex copper ores are of greatest industrial importance. There are deposits of copper pyrite ores along the eastern slopes of the Urals, from Ivdel’ in the north to Mugodzhary in the south (the Degtiarsk, Bliavinskoe, Uchaly, Sibai, and Gai deposits), as well as in the Northern Caucasus. Deposits of porphyry copper ores include the Kounrad and Boshchekul’ deposits in the Kazakh SSR, the Kal’makyrskoe deposit (at Almalyk) in the Uzbek SSR, and the Kadzharan and Agarak deposits in the Armenian SSR. Deposits of copper sandstones are represented by the Dzhezkazgan deposit in Kazakhstan and the Udokan deposit in the northern part of Chita Oblast. The former deposit has been exploited for almost 40 years; the latter is located along the Baikal-Amur Railroad, and its industrial development is being planned. There are large reserves of copper in the sulfide copper-nickel ores of the magmatic deposits of the Noril’sk Ore Region in Krasnoiarsk Krai and on the Kola Peninsula. Complex copper-lead-zinc ores are an important source of copper.

LEAD-ZINC ORES. Lead-zinc ores are concentrated primarily in hydrothermal deposits. The largest ones are medium- and low-temperature stratiform deposits, occurring in striated layers of sedimentary and, in part, effusive-sedimentary rocks. Such deposits have been explored in the Central Kazakhstan Ore Region (Karagaily and Zhairem deposits), the Karatau Region (Mirgalimsai and Turlan, or Achisai deposits), the Dzungarian Alatau (Tekeli deposit), the Altai Mountains (Zyrianovsk, Ridder-Sokol’noe, Tishinskii, Irtysh, and Zolotushka deposits), the Uzbek SSR (the Kurgashinkan group and the Khandizinskoe deposit), the Buriat ASSR (Ozernoe deposit), the Nerchinsk area of Transbaikalia (Savinka no. 5 deposit), and the Azerbaijan SSR (Filizchai deposit). High-temperature metasomatic skarn deposits are an important industrial type, found in Primor’e Krai (Dal’negorsk deposit) and the Tadzhik SSR (Altyn-Topkan deposit). The Gorevskoe metasomatic deposit, associated with Precambrian carbonate rocks, has been explored in Krasnoiarsk Krai. Medium-temperature vein deposits in extruded and other rocks are being worked in the Northern Caucasus (Sadon, Kholstinka, and other deposits) and the Tadzhik SSR (Kani-Mansur deposit). Most deposits of lead-nickel ores have a complex composition and contain, in addition to lead and zinc, copper, tin, and silver. They also often contain gold, cadmium, and other rare elements, as well as iron pyrite and, sometimes, barite and fluorite. The copper pyrite ores of the Urals and other regions are an important source of zinc.

NICKEL AND COBALT ORES. The principal sources of nickel and cobalt metals are large magmatic deposits of sulfide nickel ores, found in the Noril’sk Ore Region in the northern part of Krasnoiarsk Krai and on the Kola Peninsula. Ore reserves of this type increased significantly after the discovery in the 1960’s of the Talnakh and Oktiabr’skoe deposits in the Noril’sk Region. An important characteristic of sulfide nickel ores is their complex composition; in addition to nickel and cobalt, the ores are also an important source of copper. Significant deposits of exogenic silicate nickel-cobalt ores are known in the Urals and Western Kazakhstan, for example, the Aidarbakskoe (Khalilovo), Akkermanovka, Buryktal’skoe, and Lipovka deposits. Hydrothermal deposits of copper-cobalt, iron-cobalt, and cobalt ores proper have been found in many parts of the country, for example, the South Dashkesan deposit in the Azerbaijan SSR and the Khovu-Aksy deposit in the Tuva ASSR.

TUNGSTEN AND MOLYBDENUM ORES. Tungsten and molybdenum ores are concentrated primarily in skarn contact-metasomatic and hydrothermal vein and stockwork deposits. An example of the former is the Tyrnyauz deposit of complex tungsten-molybdenum ores, located in the Northern Caucasus. Skarntype tungsten (scheelite) deposits are being worked in the Uzbek SSR and have been explored in the Far East. Hydrothermal tungsten deposits have been found in the Buriat SSR and the Kazakh SSR. Vein and stockwork molybdenum deposits of hydrothermal origin are known in Transbaikalia, Western Siberia, and Kazakhstan. An important source of molybdenum are the complex molybdenum-containing porphyry copper ores found in Kazakhstan and Armenia.

TIN. Most of the tin-ore deposits in the USSR are of Mesozoic age and are associated with the Pacific ore belt and the zone of Mesozoic activation in the eastern part of Transbaikalia. The most significant deposits, represented chiefly by cassiterite-sulfide ores, occur in the Yakut ASSR and Magadan Oblast (Deputatskii, Ege-Khaiskii, and Iul’tin deposits), Khabarovsk and Primor’e krais (Komsomol’skii Tinore Region and the Kovalerovskii Ore Region), and Chita Oblast (Khapcheranga and Sherlovaia Gora deposits). In the 1960’s tin-ore deposits of Paleozoic age were explored in the Kirghiz SSR. In addition to tin lodes, there are tin placer deposits in the Yakut ASSR and Magadan Oblast.

MERCURY AND ANTIMONY. Mercury and antimony deposits of hydrothermal origin have been found in many parts of the USSR. The most significant deposits are the Nikitovka mercury deposit in the Donets Basin of the Ukraine and the Khaidarkan and Chauvai mercury deposits and the Kadamdzhai and Kassansai antimony deposits in the Kirghiz SSR. Other major deposits occur in the Yakut ASSR, the Chukchi Autonomous Okrug (formerly Chukchi National Okrug), Kamchatka, and Gornyi Altai.

GOLD, SILVER, AND PLATINUM. In the mid-19th century, Russia accounted for approximately 40 percent of the world’s total extraction of gold, primarily from deposits in the Urals and Eastern Siberia (the Lena and other gold-bearing regions). Gold placer deposits and lodes are known in Magadan Oblast, the Yakut ASSR, Transbaikalia, Uzbekistan, Kazakhstan, and Armenia. Silver is extracted as a by-product from complex-ore deposits. In prerevolutionary Russia, platinum was extracted only from the placer deposits in the Urals. In the USSR ores of platinum and metals of the platinum group are extracted from magmatic deposits of sulfide copper-nickel ores.

Mined chemical raw materials. Among the minerals included in the group of mined chemical raw materials, of particular importance to the national economy are the phosphate ores and potassium salts used as mineral fertilizers in agriculture, rock salt, sulfur, sodium sulfate, fluorite, barite, and boron ores. Petroleum, natural gas, hard coal, and peat are also important raw materials for the chemical industry.

PHOSPHATE ORES. Phosphate ores are represented by apatites and phosphorites. The apatite deposits of the Khibiny group, currently being worked in Murmansk Oblast, are distinguished by the unique quality of the ores. They are of magmatic origin and occur among nepheline syenites. Deposits of apatite-containing ores have been identified in Transbaikalia and the Yakut ASSR. The largest deposits of sedimentary phosphorite in the European part of the USSR are the Viatka-Kama deposit in Kirov Oblast, the Egor’evsk deposit in Moscow Oblast, the Kingisepp deposit in Leningrad Oblast, and the Maardu deposit in the Estonian SSR. The most significant deposits in the Asiatic part of the USSR are the deposits of the Karatau phosphorite-bearing basin and the Chilisai deposit in the Kazakh SSR.

POTASSIUM SALTS. Deposits of potassium salts are concentrated primarily along the upper Kama River in Perm’ Oblast, where the Solikamsk and Berezniki potassium combines are located. Significant reserves of potassium salts have been explored in the Byelorussian SSR (Starobin salt-bearing basin), the Ukrainian SSR (the Carpathian salt-bearing basin), and the Turkmen SSR.

ROCK SALT. Deposits of rock salt occur in many parts of the USSR, including the Ukraine, Byelorussia, the Caucasus, the Cisurals, the Caspian Depression, Middle Asia, and Siberia. The largest in terms of reserves and extraction of rock salt are the Artemovsk deposit in the Ukrainian SSR and Lake Baskunchak in Astrakhan Oblast.

SULFUR. Sulfur deposits are found in the Western Ukraine, the Volga Region, and Middle Asia and on the Kuril Islands and Kamchatka. There are numerous deposits of sulfur pyrite. Copper and complex sulfide ores, during whose processing at copper smelting and lead-zinc plants sulfur is extracted from the waste gases, are important sources of sulfur. The sulfur-containing natural gas of many deposits, in particular the Orenburg deposit, is becoming an important source of sulfur.

OTHER RESERVES. Major reserves of sodium sulfate are concentrated in the brine of the Kara-Bogaz-Gol gulf, as well as the brine of salt lakes. The most significant deposits of fluorite are located in Primor’e Krai, Transbaikalia, Middle Asia, Kazakhstan, and the Ukraine.

Deposits of barite occur in Western Siberia, Kazakhstan, and Middle Asia. Large amounts of barite are often found in deposits of lead-zinc ores, for example, in Kazakhstan. Deposits of boron (borates and borosilicates), bromine, and iodine (often in brines near petroleum deposits), and many other types of chemical raw material have been found in numerous regions of the country.

Nonmetallic raw materials. The USSR is rich in various nonmetallic raw materials, including asbestos, graphite, mica, magnesite, corundum, industrial and precious stones, natural crystals (diamonds, piezooptical quartz, and Iceland spar), Dinas rocks, flux limestones, kaolin, and other types of ceramic and refractory raw materials. It is also rich in various mineral building materials, such as limestone and clay for cement production, glass sands, brick clays, basalts, granite, marble, and other rocks.

The best known deposits of asbestos are Bazhenov in the Urals, Dzhetygara in Kazakhstan, Kiembaev in Orenburg Oblast, and Ak-Dovurak in the Tuva ASSR. The Molodezhnyi deposit in the Buriat ASSR, located near the Baikal-Amur railroad, has a particularly high content of textile grades of asbestos.

Of the many graphite deposits, the most significant are located in the Ukraine, the Urals, Krasnoiarsk Krai, Uzbekistan, and the Far East. Various types of mica—muscovite, phlogopite, and vermiculite—are used in industry; deposits of these minerals have been explored in Murmansk Oblast, the Karelian ASSR, in the Mama River basin in Irkutsk Oblast, and in the Aldan mica-bearing region of the Yakut ASSR. The largest deposits of magnesite have been explored in the Urals and Eastern Siberia.

Diamond lodes and placer deposits have been found in the Yakut ASSR, and diamond placer deposits have been found in the Urals. Deposits of various colored, semiprecious, and precious stones used in various branches of technology and in the jewelry industry (agate, jasper, rhodonite, opal, rock crystal, emerald, topaz, sapphire, amethyst, turquoise) have been discovered in the Urals, as well as in Transbaikalia, the Gornyi Altai, the Saians, and other mountain regions.

Various rocks, sand-gravel mixtures, sands, marls, and clays serve as raw material for the production of nonore building materials. On the basis of origin, rock deposits are divided into three large groups: igneous, metamorphic, and sedimentary. The most frequently encountered igneous rocks are granites, syenites, diorites, gabbros, diabases, basalts, trachytes, andesites, and porphyrites. The most widespread metamorphic rocks are gneisses, quartzites, siliceous shales, and marbles. The sedimentary rocks most frequently used to produce nonore building materials are limestones, dolomites, marls, clays, and sandstones. The USSR has major reserves of raw materials for the production of nonore building materials.

Marine resources. Significant resources of mineral raw materials are contained beneath the internal and marginal seas of the USSR (the shelf and continental slopes), in littoral and bottom deposits of these seas, and in the seawater itself. The shelf contains deposits of the same useful minerals that are found beneath the land area. Offshore deposits of petroleum and gas are of the greatest practical importance. Offshore petroleum deposits, which are exploited in the Caspian Sea at Neftianye Kamni and elsewhere, occur in Neogene beds and are analogs of the petroleum deposits of Azerbaijan and Turkmenia. The shelf of the other seas and the continental slopes are potentially promising with respect to deposits of petroleum and gas.

Accumulations of tin, gold, titanium, zirconium, iron, manganese, and other useful minerals are concentrated in the coastal bottom deposits of the seas, primarily in the form of littoral placers. Significant beach and bottom deposits of magnetite sands occur along the Caucasian coast of the Black Sea. Placers of titanium-zirconium minerals have been found in littoral deposits of the Black and Baltic seas. Iron-manganese concretions have been found in the bottom deposits of the Black, Baltic, Barents, and Kara seas.

Seawater is an important source of various mineral components. The mineral salts dissolved in seawater are of the greatest practical importance. Large reserves of sulfate and chlorine salts of sodium and magnesium are concentrated in the brine of the Kara-Bogaz-Gol gulf of the Caspian Sea, where the largest enterprise in the USSR for the extraction of Glauber salt, or mirabilite (sodium sulfate), is located. Both rock salt and mirabilite are extracted from the brine of Sivash Bay of the Sea of Azov. Compounds of bromine, magnesium, and potassium are also extracted from seawater.

G. A. MIRLIN

Subterranean waters. Subterranean waters (freshwaters and mineral, household-drinking, therapeutic-balneological, and industrial waters) are one of the most important resources of major significance to the national economy. Reserves of fresh subterranean waters in regions without adequate resources of surface waters are particularly important. The largest reserves of therapeutic mineral waters are found in the Northern Caucasus (Narzan, Essentuki), Transcaucasia (Borzhomi, Arzni), Ciscarpathia, and many regions of Middle Asia and Siberia. Depending on the character of the cavities in the water-enclosing rocks, subterranean waters are subdivided into interstitial water, which occurs in loose sedimentary and detrital rocks (sands and gravels), fissure (joint and fracture) water, which occurs in dense rocks (granites, sandstones), and karst (fissure-karst) water, which occurs in soluble rocks (limestones, dolomites; gypsums).

In the hydrogeological zonation of the USSR, the following have been identified: geological massifs, dominated by fissure waters (the Baltic, Ukrainian, and Aldan shields); artesian regions, which are systems of large artesian basins with widespread interstitial-stratal and fissure-stratal waters; and geological folded mountain regions (the Caucasus, Urals, Central Kazakhstan, Saians and Altai, Koriak-Kamchatka), dominated by fissure and joint and fracture waters and the waters of the small artesian basins of the intermontane basins. Examples of large artesian basins are the Western Siberian, Moscow, Baltic, Dnieper-Donets, Caspian, and Azov-Kuban’ basins.

In practical geological exploration for water-supply purposes, the natural and exploitable resources of subterranean waters are usually evaluated. For a region with a permanent river network, subterranean waters average about 24 percent of the total water resources, expressed in terms of the magnitude of the annual river flow. On the average, about 9 percent of the total precipitation goes to replenish subterranean waters.

Bibliography

Bykhover, N. A. Ekonomika mineral’nogo syr’ia, books 1–3. Moscow, 1967–71.

Vol’fson, F. I., and A. V. Druzhinin. Glavneishie tipy rudnykh mestorozhdenii. Moscow, 1975.

Gorbunov, G. I. Mineral’no-syr’evaia baza SSSR. Moscow, 1969.

Levorsen, A. I. Geologiia nefti i gaza, 2nd ed. Moscow, 1970. (Translated from English.)

Kurs mestorozhdenii poleznykh iskopaemykh, 3rd ed. Moscow, 1964.

Matveev, A. K. Geologiia ugol’nykh basseinov i mestorozhdenii SSSR. Moscow, 1960.

Pervago, V. A. Usloviia formirovaniia i geologo-ekonomicheskaia otsenka promyshlennykh tipov mestorozhdenii tsvetnykh metallov. Moscow, 1975.

Rudnye mestorozhdeniia SSSR, vols. 1–3. Moscow, 1974.

Smirnov, V. I. Geologiia poleznykh iskopaemykh, 3rd ed. Moscow, 1976.

50 let sovetskoigeologii. Moscow, 1968.

Gidrogeologiia SSSR, vols. 1–45. Moscow, 1966–72.

Orography. On the basis of the predominant landforms, the land surface of the USSR is subdivided into a larger (66 percent) relatively low-lying area, which is open to the north and is dominated by plains, plateaus, and highlands, and the belt of mountains that borders this area on the south and east. The European part of the USSR is occupied primarily by the East European Plain, with an average elevation of 142 m. The low mountains of the Urals separate the East European Plain from the Western Siberian Lowland, which on the whole is slightly lower (average elevation, about 120 m). To the south of the lowland are the plains of Kazakhstan and the Turan Lowland, with individual low mountain ridges and massifs (the Kazakh Melkosopochnik), plateaus, and ranges. The Central Siberian Plateau, with an average elevation of 480 m, is located between the Enisei and Lena rivers. Along the northern margin of the country stretches a belt of low-lying plains—the Pechora, North Siberian, Iana-Indigirka, and Kolyma plains—which continue underwater into the shelf of the arctic seas. The generally flat landscape of the north is interrupted by the low mountains of the Kola Peninsula, Novaia Zemlia, Severnaia Zemlia, and the Novosibirskie Islands, by the Taimyr Peninsula, and by other features.

The mountains that frame the country on the south and east form systems differing in height and strike. The Ukrainian Carpathians, Crimean Mountains, and the mountains of the Caucasus lie to the southwest and south of the East European Plain. The Kopetdag, Pamirs, Gissar-Alai, and Tien-Shan stretch along the state border in Middle Asia. The Dzungarian Alatau and Tarbagatai, separated by the Sasykkol’-Alakol’ Hollow, and the Zaisan Depression lie between the Middle Asian mountains and the belt of mountains in Southern Siberia: the Altai, Kuznetskii Alatau, Zapadnyi and Vostochnyi Saians, and the mountains of Tuva and the Baikal and Transbaikal regions.

The northeastern USSR is dominated by the vast Verkhoiano-Chukotka mountain region, which includes the Verkhoiansk Range, the Cherskii Range, the Kolyma and Chukchi highlands, and the Yukaghir Plateau. The Tukuringra-Dzhagdy, Bureia, and Sikhote-Alin’ systems of ranges are located in the southern part of the Far East. The mountains of the Koriak Highland, the Kamchatka Peninsula, the Kuril Islands, and the island of Sakhalin form the extreme eastern part of the mountain belt of the USSR. It is here that the maximum contrast of relief occurs: the variation in elevation is almost 15 km, ranging from 9,717 m below sea level in the Kuril-Kamchatka Trench to 4,750 m above sea level at Kliuchevskaia Sopka on the Kamchatka Peninsula. Differences in elevation within the other mountain systems of the marginal belt reach 5–7 km; in the low-lying, primarily flat, part of the USSR, they are only dozens or sometimes hundreds of meters.

The highest point in the Soviet Union is Communism Peak, located in the Pamirs (7,495 m); the lowest point (-132 m) is the bottom of the Karagie Basin, located on the Mangyshlak Peninsula. The average hypsometric level is 430 m; the part of the USSR lying to the east of the Enisei River is generally above this level, while the western part is below it.

Features of relief formation. The principal features of the relief of the USSR reflect the deep structure of the earth’s crust and are related to the distribution of deep tectonic structures. One of the signs of this relationship is the correspondence between the thickness of the crust, that is, the depth to its base (the Mohorovičić discontinuity), and the character of the megarelief.

The relief of the earth’s surface presents a crude mirror image of the base of the crust. Vast areas of the USSR with predominantly flat topography correspond structurally to the cratonic platform, where the base of the crust occurs at depths ranging from 30–40 km (beneath the East European and Turan plains) to 40–50 km (beneath the Central Siberian Plateau, where the average elevation is significantly greater). The mountain structures of the Soviet Union, where areas of flat relief are comparatively small, belong to folded belts of different age, where the depth of the base of the crust drops to 65–70 km or more, forming what may be termed the roots of the mountains. The thickness of the crust within mountainous areas is not uniform and varies according to the disposition of the ranges, intermontane basins, and other elements of relief.

The thickness of the crust as a sign of its deep structure changes with the passage of geological time, as does the character of the surface topography. The most important milestones in the earth’s geological history responsible for the modern relief were the periods of transition of geosynclines into folded mountain structures as a result of the compression and uplifting of the crust and the periods of conversion of mountainous areas into plains as a result of the establishment of a cratonic regime and the predominance of denudation processes.

The East European Plain and the Central Siberian Plateau formed primarily on the Precambrian Eastern European and Siberian platforms. Folding and mountain building were completed in these areas by the beginning of the Middle Proterozoic, and in subsequent geological periods these areas developed under relatively tranquil tectonic conditions, affected primarily by sedimentation in shallow epicontinental seas and by the exogenic processes occurring under continental conditions. The plains areas of Western Siberia, the Turan Lowland, Ciscaucasia, and the Crimea occupy the platforms of younger (Epipaleozoic) era-tons. While cratonic conditions already predominated on the neighboring East European and Siberian plains, the processes of geosynclinal development followed by mountain building still continued in these regions, and only in the Late Paleozoic did evolution proceed under cratonic conditions. The prolonged subsidences, accompanied by the accumulation of thick sedimentary, primarily marine, strata, and the subsequent processes of denudation led to the flattening of their surfaces.

The mountain systems of the USSR differ with respect to geological age and origin. The mountains of Kamchatka, the Kuril Islands, and Sakhalin belong to the youngest (modern) geosynclinal region—the transitional zone between the continent and the ocean. Here, the relief is in a stage of active formation, characterized by highly intensive large tectonic movements and volcanic activity. The Carpathians, Crimea, Transcaucasia, Kopetdag, and Pamirs lie in the Alpide geosynclinal (folded) region.

Some of the mountains of the northeastern USSR and the Far East were originally formed by the mountain-building processes that occurred in the second half of the Mesozoic era, and after a denudation stage they were transformed by recent tectonic activation. The formation of the original mountain relief of the Urals, Novaia Zemlia, Taimyr, the Tien-Shan, and the mountains of Southern Siberia dates to the epochs of Baikal, Caledonian, and Hercynian folding. The long post-Paleozoic period of these regions was characterized by the absence of tectonic activity, and the mountain relief was obliterated by agents of denudation.

Tectonic movements were renewed in the second half of the Cenozoic, when repeated mountain-building processes began, which resulted in the formation of rejuvenated mountains.

The processes of epicratonic orogeny are associated with neotectonic movements, which have been largely responsible for the formation of the relief in the USSR. On the ancient Precambrian cratons, the intensity of the movements was ten to 100 times less than in the folded regions. This explains the modern hypsometric contrast between the primarily flat internal part of the USSR and the mountainous areas in the south and east. It appears that the greater average elevation of the part of the USSR east of the Enisei River is related to changes in the structure and relief that occurred in the Neogene and Anthropogene, as well as in earlier times (Early Cenozoic and Mesozoic); this can be explained by the greater intensity of the tectonic movements of the Pacific Ocean section of the earth’s crust.

The tectonic processes responsible for the primary features of the country’s relief are continuing in the present epoch in the form of slow movements of the earth’s surface, sometimes accompanied by earthquakes and volcanic eruptions. The young and rejuvenated mountains, particularly the mountains of Middle Asia, the Baikal Region, and the Kuril-Kamchatka Region, are highly seismic; earthquakes measuring 5–9 points have been recorded here. In most of the USSR, earthquake foci are located within the crust, for the most part 20–30 km below the surface. An exception is the geosynclinal region of the Pacific belt, where earthquakes are attributed to the Benioff zone, which outcrops in the sea floor within the deep-sea trenches east of Kamchatka and the Kuril Islands and which is inclined toward the Asian continent at an angle of about 45 degrees. In the western part of the zone, beneath Primor’e Krai and the western shore of the Sea of Okhotsk, the depth of the earthquake foci increases to about 600 km (the foci are not deep beneath the Kuril Islands). In the highly seismic regions, many landforms have been determined by movements along faults and by major cave-ins and landslides. There are active volcanoes in the Kuril-Kamchatka Region.

An analysis of planation is important for evaluating the role of ancient, recent, and modern crustal movements in the formation of the large-scale landforms of the USSR and for determining the principal stages in the development of the relief. Within plains areas of the craton, planation surfaces result from denudation and aggradation origin; they are only slightly deformed and preserve a nearly horizontal position. Of the two or three planation surfaces of different age observed in the plains region, the oldest is a watershed peneplain with a thick Early Mesozoic weathering crust overlying the shields of the Precambrian platforms. As many as eight to ten planation surfaces of different age are found in the mountains. The oldest of these probably dates from the Oligocene. Remnants of planation surfaces of the interorogenic (Mesozoic-Paleozoic) stage of development and “stairways” of planation surfaces of the age of recent activation are combined in the rejuvenated mountains of Middle Asia and Southern Siberia. A study of these surfaces reveals that in the Mesozoic and Cenozoic the development of the relief was characterized by a gradually increasing uplift, greater contrasts in relief, and greater complexity of orogeny.

The relief of the large, morphologically different regions of the USSR, which has come about primarily through the action of tectonic factors (above all, crustal movements at different times), forms the elements of what is called the morphostructure. The relief is made more intricate by landforms whose formation was dominated by exogenic processes; such landforms are categorized as morphosculptures.

The exogenic relief-forming processes are to a great extent determined by climatic conditions, which are subordinate to latitudinal zonation on the plains and altitudinal zonation in the mountains. The distribution of the morphosculptural complexes of various origin follows a similar pattern. Cryogenic (permafrost) forms, such as polygonal ground, felsenmeer, and stone polygons, are developed in the northern part of the USSR and in certain mountain regions. Landforms formed by the action of ancient glaciers are especially widespread, particularly continental glaciers (the northern half of the European part of the USSR and the northwestern part of Siberia). In these regions, exaration forms, such as sheepback rocks, are typical, as well as forms of glacial and fluvioglacial accumulation, such as hummocky morainic relief, eskers, and kames. Modern glacial landforms occur primarily near glaciers in the mountains.

Rivers and temporary streams have been largely responsible for the formation of the land morphosculpture, having created the erosion-aggradation (fluvial) landforms that are almost universally distributed. River valleys extend intrazonally, often following the patterns of tectonic structure of the terrain. In the forest, forest-steppe, and steppe zones, the valleys of small rivers, gulleys, ravines, and washes predominate, creating slope and interfluve morphology. In the coastal regions of the USSR, abrasion-aggradation plains are widespread, such as the Black Sea and the Northern Siberian Lowlands. Karst forms, such as caves, craters, and sinks, are developed in the Crimea, Caucasus, Urals, and many other regions. The arid steppes, deserts, and semideserts (Turan and Caspian lowlands, the Kazakh Melkosopochnik) are characterized by arid forms, whose development was largely the result of intensive physical weathering, deflation, eolian aggradation, sheetwash, and the erosive activity of temporary streams. Among these forms are low hill topography, alluvial cones and fans, the columnar remnants known as pedestals, barchans, and ridged sands. Anthropogenic relief, resulting from man’s activities, is a special type of relief. The USSR is subdivided into a number of large regions according to their principal morphogenetic characteristics.

Plain-platform regions. The low-lying part of the USSR, corresponding to ancient and young platforms, consists of several flat regions, or plains, whose relief comprises plains (in the narrow sense of the term), which predominate in area, and of plateaus, uplands, gently sloping hills, ridges, and low mountains. The plains regions are subdivided into low plains, with elevations of 100–300 m above sea level (the East European, Western Siberian, and Turan plains), and high plains, with elevations of 400–1,000 m (the Central Siberian Highland and the Kazakh Melkosopochnik).

The East European Plain can be subdivided into two parts according to topography. In the northwest, referred to as the Kola-Karelian part, the relief formed from the crystalline rocks of the Baltic Shield, which had undergone a long period of uplifting. The remaining, larger, part is the Russian Plain proper, occupying the platform of the same name, where the platform basement was deeply subsided and the relief developed in strata of gently bedded sedimentary rocks under conditions of prolonged subsidence. The principal relief-forming processes in the Kola-Karelian part were peneplanation and the subsequent disjunctive dislocations in recent times, which broke up the ancient Mesozoic peneplain into several blocks; these processes continued over a long period of geological history. Some of these blocks, for example, the Khibiny and Lovozerskie Tundry, were uplifted, while other blocks sank, forming such depressions as Lakes Ladoga and Onega and Kandalaksha Bay. Low (about 200 m) socle plains formed along the margins of the Kola Peninsula and Karelia, with individual ranges, such as Mansel’kia (elevations to 578 m), rising above them. Morphosculptural forms with Anthropogenic continental glaciation occur everywhere.

The Russian Plain proper is characterized by greater diversity in age and differs with respect to the origin of the structural relief. It consists primarily of aggradation and stratal-denudation lowlands and uplands of submeridional and sublatitudinal strike, to a considerable degree coinciding entirely or in part with areas of subsidence or uplift of the folded base. The formation of individual orogenic elements, related to the structures of the basement, such as anteclises, syneclises, and aulacogens, began as far back as the Riphean, when the Precambrian peneplain was broken into a number of subsided and uplifted blocks by a system of faults. The inherited development of the morphostructure occurred in subsequent stages, and only in the Mesozoic and Cenozoic did a partial restructuring begin, affecting primarily the central part of the plain, where inverted and heterogeneous morphotectonic relationships predominate. For example, the Severnye Uvaly and Galich Rise lie in the Moscow Syneclise, and significant parts of the Volga, Valdai, and Smolensk-Moscow uplands developed over Riphean aulacogens. The Central Russian Upland is a recent heterogeneous uplift that encompasses the Voronezh Anteclise and part of the southern wing of the Moscow Syneclise. Morphostructures per se predominate in the marginal parts of the Russian Plain, bordering on the zone of Alpide folding in the south and Hercynian folding in the east. The Stavropol’ Plateau and the Bugul’ma-Belebei Elevation correspond to projections of the basement, while the Caspian, Dnieper, and Pechora lowlands correspond to deeply subsided basement structures. Denudedsock uplands and ridges (Dnieper and Azov uplands and Donets and Timan ridges) correspond to outcrops of the basement.

The landforms created on the East European Plain by exogenic processes are equally diverse. The northern part of the plain is characterized by glacial landforms, formed during the most recent glaciation, often superimposed on projections of the original relief, and by eroded forms, originally produced by more ancient glaciers. Cryogenic morphosculpture is developed along the northern coast. The nonglacial regions are characterized by out-wash plains, broad terraced valleys, and ravine-gulley topography, which in the south give way to the flat relief of the marine aggradation plains.

The Western Siberian Lowland is a low-lying plain in the shape of an amphitheater, open to the north and corresponding to the bowl shape of the platform of the epihercynian craton, which lies at its base. Uplands, plateaus, and sloping plains stretch along the western, southern, and eastern margins, whereas lowlands predominate in the central and northern parts. In the central part elevations do not exceed 150 m, but toward the margins they increase to 300 m. Orogenic elements are oriented primarily submeridionally and sublatitudinally, corresponding to the strike of the deep basement faults. In general, the relief of the central part formed under conditions of stable basement subsidence under the action of undulating and block deformations of the sedimentary mantle. The exterior zone of the Western Siberian Lowland, which is developing closely with the activated regions of the folded regions, reveals inherited tectonic movements and, for the most part, a direct relationship between the relief and the direction of movement of the individual blocks of the basement (the North Sos’va and Shchuchinsk uplands and the Tura, Cisturgai, North Kazakh, East Barabinsk, Enisei, and other sloping plains). The part of the Western Siberian Lowland to the north of the Siberian Uvaly also exhibits inherited development of morphostructures. South of the Siberian Uvaly inversely correlated relationships between orogenic elements and structures prevail.

The relief of the northern part of the Western Siberian Lowland was formed primarily by Pleistocene glaciation, while south of the Siberian Uvaly it developed as a result of the erosion and aggradation action of the rivers of the Ob’ and Enisei river basins. In the modern relief, the Middle Pleistocene surface of glacial and fluvioglacial origin predominates in the north, while alluvial and erosion-alluvial surfaces predominate in the south. The role of cryogenic processes, reflected in the thermokarst topography, peat hummocks, and hydrolaccoliths, is also significant in the northern regions. Karst forms are widespread in the south, where ridge and hollow topography is typical.

In the vast flat area between the Western Siberian Lowland, the mountains of Middle Asia, and the Caspian Sea lies the Turan Lowland (Turan Plain), occupying the platform of the same name, with a folded Paleozoic basement overlain by a mantle of Mesozoic and Cenozoic sedimentary strata. Also located here is the Kazakh Melkosopochnik, formed within the Caledonian and Hercynian folded structures that had undergone prolonged uplifting. During the continental period, which began at the end of the Carboniferous, these structures were deeply cut and denuded, forming a landscape of gently sloping low hills—a high rolling plain (elevations from 300–500 m in the west to 500–1,000 m in the east) with numerous hills and ridges measuring up to 100 m in height. Rising above the average elevation of the low hill relief are low mountain massifs, such as Ulutau (1,133 m) and Kokchetav Elevation (947 m), and a number of ranges, such as the Karkaralinsk Mountains (1,566 m) and the Chingiztau Range (1,077 m), which owe their origin to recent, differentiated uplifts.

The Turan Lowland is distinguished by the large diversity of its orogenic elements. The troughs and depressions occupy the lowest hypsometric position: Karagie is at -132 m, and Akchakaia, at -81 m. The Southern Karakum, Aral, and Syr Darya lowlands lie at elevations less than 200 m. Plains—marine, alluvial, and arid denudation plains—and Neogenic plateaus with steep escarpments, called chinki (cuesta), rising to 300–400 m are widespread (Turgai, Ustiurt, Krasnovodsk, and Zaunguz plateaus). In places, isolated low-mountain, intraplatform massifs with relicts of Cretaceous, Paleogenic, and Neogenic weathering surfaces rise to 1,000 m (Bukantau, Kul’dhuktau, and Tamdytau). Spurs of ranges of the Tien-Shan, with surviving sections of a Mesozoic peneplain, protrude into the eastern part of the plain. The orogenic scheme and relief of the Turan Lowland depend on the direction and intensity of recent crustal movements. The lowlands and basins correspond to regions of subsidence or slowed uplifts, while the plateaus correspond to regions of moderate uplifts. The rate of ascending movement within particular massifs is commensurate with the rate in orogenic regions. A direct correspondence between the relief and elements of recent structure is characteristic. At the same time, the modern relief shows an inherited correspondence to the structural plan of the basement; the Zaunguz Plateau corresponds to the Karakum Arch, while the Syr Darya Lowland occupies the syneclise of the same name. Inverse morphostructures (the Ustiurt) and complex morphostructures (Turgai Plateau) also occur.

The Turan Lowland and Kazakh Melkosopochnik belong to the zone of arid morphosculpture, which is subdivided into two types: arid-denudation (landscapes composed of low mountains, hilly terrain, erosion remnants, plateaus, and elevated stratified plains) and arid-aggradation (eolian sand relief, proluvial fans, sloping submontane plains, and alluvial, lacustrine, and delta plains).

The Central Siberian Plateau is located within the Siberian Platform. It is composed of horizontally or monoclinally bedded formations and is relatively uplifted. The highest elevations occur along its margins. The Putorana Plateau rises to 1,701 m in the northwest. An ancient crystalline massif—the Enisei Ridge, with elevations to 1,104 m—stretches for 700 km along the Enisei River in the southwest. In the northeast the Anabar Plateau occupies an ancient cratonic massif of the same name.

The relief within the Central Siberian Plateau is relatively uniform. Different types of stepped plateaus (stratified, trap, and lava plateaus), with flat or gently rolling surfaces with elevations of 400–600 m, and deep valleys, with steep, terraced slopes, predominate. The terraced relief is related to the wide distribution of stratified trap intrusions that are resistant to water erosion and the presence of structurally denuded surfaces of Mesozoic (Cretaceous and Paleogenic) age. The elevations of the highest uplifted mesa-type erosion remnants within the plateau reach 1,500–1,700 m, and the depth of erosion cuts in as much as 500–700 m (in the marginal parts). The structurally denuded terraced relief of the Central Siberian Plateau formed under the influence of Mesozoic and particularly recent movements, which occurred with varying intensity in different parts of the region. As a result of the movements, the Siberian Platform was sharply uplifted and strongly dissected in some places, while its ancient structure was deeply denuded and considerably rejuvenated. Thus, the modern morphostructure combines elements of ancient and young relief. There are both direct and inverse relationships between major landforms and geological structures. For example, the most downwarped part of the Tungus Syneclise corresponds to the greatly uplifted Putorana lava plateau. The Enisei Ridge and the Central Yakut Plain, which occupies the Viliui Syneclise, are examples of directly corresponding morphostructures.

Southeast of the Central Siberian Plateau lies the Aldan Plateau, which basically coincides with the Aldan Shield of the Siberian Platform. A large part of the Aldan Plateau is a previously buried Precambrian peneplain uncovered by denudation and subsequently drawn into a general arching uplift by neotectonic movements. The relief is characterized by flat terraced interfluve surfaces (average elevations, 800–1,000 m), with erosion remnants and massifs (to 2,306 m) dissected by deep valleys. The exogenic processes that developed under conditions of the continental climate and the spread of permafrost rocks are responsible for the diversity of the landforms (cryogenic, erosion, glacionival, and other types of landforms).

Mountain (orogenic) regions. The association of mountain systems with folded belts of different age is responsible for the observed significant differences in their structure and the development of their relief. This is expressed above all in the relationship between the orogenic elements and geological structure.

KORIAK MOUNTAINS, KAMCHATKA, THE KURIL ISLANDS, AND SAKHALIN. The Kodak Mountains, Kamchatka, the Kuril Islands, and Sakhalin are young mountains in the modern geosynclinal region of the Pacific belt. Their relief, which is in the stage of active formation, developed as a result of the high intensity and differentiation of recent and modern crustal movements, powerful volcanic activity (on Kamchatka and the Kuril Islands), and seismicity. A maximum correspondence between major landforms and structures is characteristic. The mountain ranges of Kamchatka and the Kuril Islands are the above-water parts of the massive mountain structures of the island arcs, corresponding to geanticlines. The geosynclinal troughs are conjugate with them: the deep trenches (Kuril-Kamchatka and Aleutian trenches) on the ocean side and the depressions of the marginal seas (Bering Sea and the seas of Okhotsk and Japan). Smallerscale tectonic uplifts are expressed (on land) by the folded block mountains of the Koriak Mountains and the ranges of Kamchatka and Sakhalin, while the troughs are represented by lowlands (the Anadyr’ and Central Kamchatka lowlands). There are numerous volcanic cones.

UKRAINIAN CARPATHIANS, CRIMEAN MOUNTAINS, CAUCASUS, KOPETDAG, and PAMIRS. The Ukrainian Carpathians, Crimean Mountains, Caucasus, Kopetdag, and Pamirs are epigeosynclinal and partially epicratonic mountains of the region of Cenozoic folding of the Mediterranean belt. Folded structures that formed during the period of Late Cenozoic folding predominate in the foundation of these mountain structures. However, the Crimean Mountains, part of the northern slope of the Greater Caucasus, and the Pamirs represent marginal parts of the cratonic basement of Late Cimmerian and Hercynian age. They were drawn into the general uplift at the end of the Cenozoic folding in the Mediterranean geosynclinal belt and became part of the mountains that emerged at that time.

West of the basin of the Caspian Sea, the principal geostructural units of the mountain lands are intricately constructed folded geantisynclinal structures and submontane and intermontane troughs. The high ranges of the Greater Caucasus (the Glavnyi, or Vodorazdel’nyi, Range, the Bokovi Range), corresponding to the meganticlinorium of the same name, constitute the main part of the Caucasus. Many peaks in the central part rise above 5,000 m, including the cones of the extinct volcanoes El’-brus (5,642 m) and Kazbek (5,033 m). Denudation and aggradation glacial forms of Pleistocene age are numerous; modern glaciation is significantly developed. To the north stretch the lower foothill cuestas; the anticlinal Tevek-Sunzha Upland (962 m) is located in Ciscaucasia, and isolated protrusions—laccoliths (Beshtau and others)—also occur. Fragments of Miocene leveling plains of denudation, whose deformations indicate young (Pliocene and Anthropogene) uplifts of the Greater Caucasus, have been preserved in the watershed part and on the slopes of the ranges. South of the Greater Caucasus are flat aggradation lowlands—the Kura-Araks Lowland in the east and the Colchis Lowlands in the west—which are included in the Rioni-Kura zone of intermontane troughs. The southern part of the Caucasus is occupied by the Transcaucasian Highland, consisting of the folded ranges of the Lesser Caucasus, corresponding to a series of anticlinoriums, and the volcanic Armenian Highland, with its lava plateaus and cones of extinct volcanoes (Aragats, 4,090 m). The folded Talysh Mountains rise to 2,477 m in the southeastern part of the Caucasus.

In addition to the longitudinal geological structures in the Caucasus, transverse uplifts and troughs superimposed on them are developed, as are fault and flexure structures. It appears that some of the morphotectonic relationships are linked with transverse deformations. Inverse morphostructures are observed in certain areas of the peripheral parts of the ranges (the synclinal ranges and massifs of Dagestan and the Meskheti and Trialet ranges).

The Crimean Mountains are a remnant of a once broader mountainous area geologically corresponding to an anticlinorium, of which part of the nucleus and the northern wing have been preserved, the rest having subsided along a fault to the level of the Black Sea. The mountains consist of three ridges. The highest, southern, ridge (Roman-Kosh, 1,545 m, and Ai-Petri 1,223 m) drops off sharply to the Black Sea. The two northern ridges resemble cuestas and have steep southern slopes and gentle northern slopes; their elevations range from 350 m in the north to 750 m in the south. The mountain summits (iaila) are flattened and exhibit fragments of a pre-Cenozoic (presumably Late Cretaceous) planation surface, which indicates that the relief of the Crimean mountains developed over a longer period than the relief of the Caucasus.

The extreme western link of the southern mountain belt of the USSR is formed by the Ukrainian Carpathians, which are medium-elevation mountains consisting of a series of parallel ranges with elevations of 600–2,000 m; the highest point is Mount Goverla (2,061 m). The Carpathians are characterized by broad flat summits of Neogenic age, gentle slopes, fantastical limestone cliffs, karst, and numerous landslides and cave-ins. They are bounded in the southwest by the Tisza aggradation plain, which occupies the Transcarpathian Interior Trough.

The medium-elevation anticlinal ranges of the Kopetdag and Pamirs are a continuation of the belt of Cenozoic folded mountains in Middle Asia. The Kopetdag is a system of medium-elevation ranges (average elevations, 1,000 m; highest peak, Mount Reza, 2,942 m), with flat, denuded crests, steep northern slopes, and gentle southern slopes. The ranges are bounded in the north by the Cis-Kopetdag Depression, which is reflected in the relief by plains.

The Pamirs constitute an enormous archlike uplift, whose elevation rose more than 7,000 m in the central part during the Neogene and Anthropogene, and 2,000–3,000 m along the margins. The highest peaks are in the northwest, in the Akademiia Nauk Range, and in the north, in the Zaalai (Transalai) Range (Lenin Peak, 7,134 m). This is the region where the principal centers of modern glaciation are concentrated (the Fedchenko glacier). Intensive erosion of the periphery of the Pamirs, especially the Western Pamirs, began in the mid-Miocene and has now reached a depth of 3.5 km. Narrow alpine-type sublatitudinal ranges, with snow and glaciers, predominate in the Western Pamirs, alternating with deep, narrow gorges. In the Eastern Pamirs, where retrograde erosion has not yet penetrated, the ancient medium-elevation mountain relief predominates, with remnants of Cretaceous, Paleogenic, and Neogenic leveling plains. The ranges and massifs are relatively smoothed, and the closed basins and broad valleys separating them lie at elevations of 3,700–4,200 m. The Pamirs are heterogeneous with respect to ancient geological structure and the age of primary folding. There are corresponding morphostructures (mountain ranges-anticlinoriums, valleys—synclinoriums), but inverse forms are also known. The alteration of the relief during the epoch of late Alpide folding found specific expression in the formation of transverse uplifts and troughs, resulting in the characteristic orogenic “lattice” pattern: the presence of sublatitudinal ranges (Zaalai, Vanch, Iazgulem, Vakhan), alongside the meridional ranges (Akademiia Nauk, Zulumart, and Sarykol’).

VERKHOIANO-CHUKOTKA FOLDED REGION AND SIKHOTE-ALIN’. The Verkhoiano-Chukotka folded region and the Sikhote-Alin’ are epicratonic mountains of the region of Mesozoic folding of the Pacific belt. Active fold-formation processes ended in the second half of the Mesozoic. There are traces of prolonged denudation in the relief, and relicts of Late Mesozoic and Early Cenozoic leveling plains are widespread. The orogeny followed the Mesozoic geostructural scheme; however, anticlinal and synclinal structures are not always clearly reflected in the relief.

The largest morphostructure of northeastern Siberia is the meganticlinorium of the medium-elevation (up to 2,389 m) Verkhoiansk Range. The Cherskii Highland is a folded block mountainous area, with elevations to 3,147 m (at Pobeda Peak). It is dominated by range-anticlinoriums and horst-anticlinoriums with very rugged relief. The interior of the region bounded by these ranges, which did not experience significant uplifts in the Mesozoic and Cenozoic, is represented by the Alazeia and Yukaghir plateaus, which are linked with ancient median massifs; the massifs are broken by numerous faults, reflected in the relief by horstlike ranges (Polousnyi Range) and graben-like depressions (the Chaunskaia Plain). The Kolyma and Chukchi highlands are block-arch type uplifts, with medium-elevation mountain relief characterized by brachyanticlines—small ranges transverse to the axis of the highlands—and by the valleys of secondary rivers that separate them. Permafrost landforms occur everywhere.

The medium-elevation Sikhote-Alin’ mountain system is a morphological expression of Mesozoic folded structures. The anticlinoriums and synclinoriums are complicated in places by faults, with which effusions of basaltic lava have been connected. In the west the Sikhote-Alin’ drops gently to the Middle Amur and Khanka lowlands, occupying superimposed tectonic depressions.

URALS. NOVAIA ZEMLIA, BYRRANGA MOUNTAINS, GISSAR-ALAI, TIENSHAN, AND THE MOUNTAINS OF SOUTHERN SIBERIA. The Urals, Novaia Zemlia, Byrranga Mountains, Gissar-Alai, Tien-Shan, and the mountains of Southern Siberia are epicratonic mountains of the region of pre-Mesozoic folding of the Ural-Mongolian geosynclinal belt and the southern periphery of the Siberian Platform. The rejuvenated mountains with Baikal, Caledonian, and Hercynian folded foundations exhibit great diversity of land-forms, reflecting prolonged denudation prior to development of the folded structure and alteration of the orogenic scheme by Mesozoic and Cenozoic tectonic movements. The period of formation of the rejuvenated mountains of the Ural-Mongolian belt (Late Oligocene through Anthropogene) coincides with the Alpide orogeny in the Mediterranean geosynclinal belt, but individual mountain systems were drawn into the process of mountain building at different times.

The Urals, the mountains of Novaia Zemlia, and the Byrranga Mountains are characterized by medium- and low-mountain relief, with extensive distribution of surviving segments of Mesozoic peneplains. They are viewed as areas of minor recent mountain building on a folded Hercynian foundation. The linear arrangement of the meridional ranges of the Urals reflects the strike of the ancient folded structure. However, structures that have an inverse expression in the relief (synclinal ranges) or that are not reflected at all have significant development. The central part of the Ural uplift is occupied by a broad, massive, flattopped range, whose individual rocky peaks slightly exceed 1,000–1,200 m. In the west the Urals are characterized by a belt of low foothills that drops gradually to the East European Plain; in the east the boundary is steeper, and in some places the mountains drop precipitously to the Western Siberian Lowland. From north to south the Urals are subdivided into several segments that differ with respect to elevation and morphology, the result of recent sublatitudinal uplifts and subsidences. The highest part of the mountain system is the Polar Urals (Mount Narodnaia, 1,895 m), with alpine landforms and small modern glaciers. The lowest part is the Central Urals, where low (300–700 m) smoothed mountains predominate. The widest part of the mountain system is the Southern Urals, with relatively high peaks (Mount Iamantau, 1,640 m). The low (250–400 m) Mugodzhar hills are a continuation of the Urals in the south.

The Tien-Shan and Gissar-Alai constitute a system of sublatitudinal arch-block ranges and vast basins (the Issyk-Kul’, Naryn, and Susamyr interior basins and the Chuia, Fergana, and Tadzhik marginal and intermontane basins), with low-mountain and plains relief. Many ranges exceed 4,000–5,000 m. There are some alpine-type peaks, and the ranges are centers of modern glaciation, for example, the Central Tien-Shan. The mountain structures developed as a result of mountain-building processes in the Oligocene, Neogene, and Anthropogene on the site of an Epipaleozoic peneplain, remnants of which are widespread in many regions of the Tien-Shan at elevations of 3,000–4,000 m in the form of mildly rolling denudation surfaces called syrty. The marginal parts of the mountainous areas are foothills (adyry or rock benches), composed of Cenozoic strata complicated by recent folding.

The boundaries of the arched uplifts and basins within the Tien-Shan and Gissar-Alai have been determined by young and rejuvenated faults that cut across the strikes of ancient (Caledonian and Hercynian) folding. An example is the Talas-Fergana fault, which is responsible for the northwesterly strike of the Fergana and Karatau ranges, which is unusual for the Tien-Shan.

The mountains of Southern Siberia are grouped into the Altai-Saian Region (the Altai Mountains, Salair Mountains, Kuznetskii Alatau, Zapadnyi and Vostochnyi Saians, and the Tuva Highlands), in which the dominant strikes are northwesterly and sublatitudinal, and the Baikal Region (the Baikal Region proper, Transbaikalia, Patom Highland, and the Stanovoi Range), in which the dominant strikes are northeasterly and latitudinal. The overall configuration of the mountain belt was predetermined by the positions of the Hercynian, Caledonian, Baikal, and more ancient folded systems that ringed the Siberian Platform in the south and formed its reactivated southern edge. The mountain systems and highlands are separated by submontane and intermontane basins (the Kuznetsk, Minusinsk, Tuva, and Todzha basins); the mountain ranges and high plateaus are separated by smaller intermontane basins (the Chuia, Kurai, Uimon, Uiuk, and other depressions in the Altai Mountains and the Saians; the Barguzin, Upper Chara, and Verkhniaia Angara basins and the Lake Baikal basin in the Baikal mountain region).

The Altai-Saian Region typically combines high ranges with alpine-type peaks (the Katun’ Range with Mount Belukha, 4,506 m, the Severo-Chuia and Iuzhno-Chuia ranges, and Tabyn-Bogdo-Ola), medium-elevation mountains, low mountains, and stratified aggradation plains. The Baikal Region is dominated by high plateaus with residual block mountains and massifs, as well as by highlands (the Stanovoe Highland) and mountain ranges (Kodar and others), with elevations to 2,500–3,000 m. Intermontane basins, lying at elevations of 500–1,000 m and characterized by a gently rolling plain relief, occupy a significant area.

Mesozoic and Cenozoic tectonic movements played a large part in creating the modern relief of the mountains of Southern Siberia. The ancient denudation surface that existed here in the Late Mesozoic and Early Cenozoic was uplifted, curved, and broken by a series of faults; its remnants have been preserved in the form of Cretaceous and Paleogenic planation surfaces. The most characteristic large morphostructures are the vast, gently sloping arches, along whose axes there occurs subsidence associated with faults and the formation of rifts. The Baikal-type basins are distinguished by the steep, terraced character of their slopes. Surrounded by very rugged medium-elevation and high mountains, they are filled with thick layers of Cenozoic deposits. In some cases, they were inherited from the Mesozoic but have been transformed by recent tectonic movements. Movement along ancient and rejuvenated faults (the mountain ranges are complex horsts and the basins are complex grabens) and gentle flexures of the crust play a large part in the formation of smaller morphostructures. Many elements of the modern orogeny (Khamar-Daban, Dzhida, and Iablonovyi ranges) cut across ancient folded structures or are inversions (for example, the Kitoi and Tunkinskie Belki and the Munku-Sardyk, which includes synclinorial elements).

T. K. ZAKHAROVA

Bibliography

Nikolaev, N. I. Neotektonika i ee vyrazhenie v strukture i reíefe territorii SSSR. Moscow, 1962.
Karandeeva, M. V. Geomorfologiia Evropeiskoi chasti SSSR. Moscow, 1957.
Voskresenskii, S. S. Geomorfologiia Sibiri. Moscow, 1962.
Voskresenskii, S. S. Geomorfologiia SSSR. Moscow, 1968.
Baranova, Iu. P., and S. F. Biske. Severo-Vostok SSSR. Moscow, 1964.
Strelkov, S. A. Sever Sibiri. Moscow, 1965.
Altae-Saianskaia gornaia oblast’. Moscow, 1969.
Ploskogor’ia i nizmennosti Vostochnoi Sibiri. Moscow, 1971.
Aleksandrov, S. M. Ostrov Sakhalin. Moscow, 1973.
Kamchatka, Kuril’skie i Komandorskie ostrova. Moscow, 1974.
Sever Dal’nego Vostoka. Moscow, 1970.
lug Dal’nego Vostoka. Moscow, 1972.
Kostenko, N. P. Razvitie rel’efa gornykh stran (na primere Srednei Azii). Moscow, 1970.
Meshcheriakov, Iu. A. Rel’ef SSSR (Morfostruktura i morfoskul’ptura). Moscow, 1972.
Ravniny Evropeiskoi chasti SSSR. Moscow, 1974.
Poverkhnosti vyravnivaniia i kory vyvetrivaniia na territorii SSSR. Moscow, 1974.
Gornye strany Evropeiskoi chasti SSSR i Kavkaz. Moscow, 1974.
Ravniny i gory Sibiri. Moscow, 1975.
Ravniny i gory Srednei Azii i Kazakhstana. Moscow, 1975.

The extreme northern part of the continental USSR and the islands of the Arctic Ocean lie in the arctic and subarctic climatic belts. Most of the country is located in the temperate belt, while the southern regions of the Crimea, the Caucasus, and Middle Asia are in the subtropical belt. A number of climatic regions are distinguished within the belts on the basis of genetic characteristics, primarily features of atmospheric circulation.

Main features and seasons. Depending on geographic latitude, the amount of solar radiation received by the earth’s surface per year in the USSR ranges from 251 megajoules/m2 (mJ/m2), or 60 kilocalories/cm2 (kcal/cm2), and even less (certain islands in the Arctic Ocean) to 670 mJ/m2 (160 kcal/cm2) and more (the southern part of Middle Asia). During the colder part of the year, scattered radiation slightly exceeds direct radiation or is approximately equal to it in most of the country. During the warmer part of the year, direct radiation predominates everywhere except in the arctic, where scattered radiation predominates in the summer as well. The radiation balance for the year is positive throughout the USSR, ranging from 210 mJ/m2 (50 kcal/cm2) and more (in certain parts of the extreme southern part of the country) to approximately zero in the heart of the arctic region. The radiation balance in January is negative everywhere. In the European part of the USSR, it is greater than in areas in the Asiatic part situated at the same latitude because of significant cloudiness and the shorter duration of the snow cover. In the temperate latitudes, radiation heat is used up primarily to evaporate water from the surface and to warm the soil directly and consequently the adjacent air. However, the ratio of energy expenditures for these processes varies considerably in different parts of the country. For example, in Byelorussia and the Baltic Region, a significant part of the radiation heat is expended for surface evaporation, while in the deserts of Middle Asia it is used to warm the air.

The most important circulation factors in the climate are the predominance of west to east air flow in the entire troposphere and the cyclonic activity that promotes the meridional exchange of warm and cold air masses and atmospheric precipitation. The climates of the USSR are formed primarily under the influence of the continental air of the temperate latitudes, especially in the Asiatic part of the country. However, the climatic features of the western regions are predominantly influenced by marine air masses from the Atlantic Ocean. Intrusions of dry tropical air are very important in the south, while arctic air is important in the north. Cyclonic activity is most intensive in the northern and western parts of the European USSR and in the northern part of Western Siberia, as well as in the Far East. Areas of increased pressure, known as the Asiatic, or Siberian, anticyclone, predominate over most of the Asiatic part of the country during the winter.

The combined action of circulation, radiation, and orogenic factors determines the amount of moisture. A line running approximately through Kiev, Kuibyshev, Sverdlovsk, and Novosibirsk forms a boundary, to the north of which moisture is adequate and precipitation generally exceeds evaporation and to the south of which moisture is insufficient, necessitating the irrigation of fields in many regions.

The year is clearly delineated into a colder period and a warmer period in all parts of the USSR. The presence of the Asiatic anticyclone, with a high-pressure spur known as the Voeikov axis extending westward and reaching the southern parts of the East European Plain, causes the processes of land cooling and formation of dry, cold continental air to predominate during the winter over most of the USSR. The average January temperatures gradually decrease from southwest to northeast, reaching the lowest values in the Yakut ASSR. The northern half of the European USSR is affected by the frequent Atlantic cyclones, which often cause thaws and precipitation. In the Far East a monsoon with cold and dry westerly and northwesterly winds prevails in the winter. The highest winter temperatures, rising in places above freezing, are observed in the southwestern part of Middle Asia and in Western Transcaucasia. With the exception of the southern and southwestern regions, winter precipitation is almost always in the form of snow.

During the summer, a vast low-pressure system forms over most of the USSR as a result of the strong warming of the land surface. Westerly winds prevail in the European part of the country at this time, while northerly winds prevail in the northern part of Soviet Asia and in Middle Asia. Summer southerly and southeasterly monsoons prevail in the Far East. The average July temperatures in the plains gradually decrease from south to north. In most of the country, most of the annual precipitation occurs during this season.

During the transitional season, the negative radiation balance changes to positive in the spring and to negative in the autumn.

Climatic belts and regions, ARCTIC AND SUBARCTIC BELTS. The arctic and subarctic belts, in which the Arctic Ocean seas, the arctic islands, and the northern margin of the continent are located, are distinguished by an exceptionally harsh climate, characterized by the alternation of the long polar day and polar night, the predominance of ice and snow cover and arctic air masses, and the interaction of the arctic air with the warmer air of the temperate latitudes. Air temperature inversions, low clouds, and fogs are typical in the summer, especially near the edge of the ice. Precipitation occurs in the form of snow or snow mixed with rain. The warmest summers are observed in the southern part of the Barents Sea, where the average monthly air temperatures remain above freezing for five months, reaching 8°C in July and August. In the eastern arctic, the frost-free period lasts only 2½ to three months. The lowest air temperatures at the earth’s surface are observed during the polar night, which lasts up to four months in some regions. During the colder part of the year, cyclonic activity intensifies, often causing gale winds and blizzards. The average temperatures of the winter months on the ice surface of the Laptev and East Siberian seas range from –30° to –35°C. The winter months are significantly warmer in the Barents, Kara, and Chukchi seas as a result of the influx of comparatively warm marine air masses into the arctic from the Atlantic and Pacific oceans. The lowest air temperatures over the northern seas rarely reach –50°C, but strong winds and high relative air humidity are common.

TEMPERATE BELT. Most of the USSR is located in the temperate belt, which is characterized by considerable diversity of climate, enabling the identification of several climatic regions within it.

Northwest European part of the USSR. The northwestern part of the European USSR is characterized by a climate transitional between the marine and continental climates, with unstable weather and frequent cyclones that bring marine Atlantic air, which causes thaws and sleet in the winter. Arctic air penetrates (in the rear part of cyclones) the region from the comparatively warm open surface of the Barents, Norwegian, and Greenland seas, and consequently winters are relatively mild. For example, the average January temperature on the coast of the Gulf of Finland is –7°C, whereas in the Yakut ASSR, situated at the same latitude (60° N lat.), it is –40°C. Summers are comparatively short and cool. The average July temperatures are 12°–14°C in the north and 16°–17°C in the south. Precipitation falls primarily during the warmer part of the year, with an annual total of 600–700 mm. As a result of considerable cloudiness and frequent rains, the soil does not warm up sufficiently during the summer; in most of the region there is too much moisture.

Northeast European part of the USSR. The northeastern part of the European USSR has a continental climate. Winters are long and cold, with average January temperatures varying from –16° to –20°C. Cyclones bring marine and continental temperate air or even colder arctic air. Thaws are rare. The snow cover varies from 150 days in the southeast to 200 days in the north. Its thickness ranges from 50 to 70 cm, in some places reaching more than 1 m by the end of the winter. The warm period lasts from May through August, with an average July temperature of about 18°C. The total annual precipitation is about 500 mm, with most falling during the summer.

Central regions of European part of the USSR. The central regions of the European USSR, which include the southern taiga and the zones of mixed and broad-leaved forests, have a relatively uniform climate, distinguished by moderately cold winters with frequent thaws and warm summers with occasional cold spells. The average January temperatures in the Baltic Region range from –3° to –4°C, while the average January temperature in the Tatar ASSR is about –15°C (the lowest recorded temperatures are –35°C and –50°C, respectively). In July, the temperatures vary between 18° and 20°C. The frost-free period is eight to 8V2 months in the west and about seven months in the east, and night frosts are common at the beginning and end of the period. The total annual precipitation, as well as the cloudiness and air humidity, decreases from west to east and north to south as the frequency of anticyclones increases. Precipitation, which amounts to 500–700 mm a year in the northwest and 300–400 mm in the southeast, falls primarily during the warmer part of the year.

Southern regions of European part of the USSR. The southern part of the European USSR is characterized by warm and comparatively dry summers. The average temperature never drops below 20°C in the summer months, and the relative air humidity during daytime hours usually does not exceed 35–40 percent. The frost-free period lasts nine to ten months in the west and eight to nine months in the east, although there are many more hot days in the east than in the west. Intensive air warming caused by insufficient moisture results in frequent droughts, associated with hot, dry winds (sukhovei), primarily in the southeast. Winters are moderately cold, with average temperatures in the west of –4°C and in the east of –5° to –7°C in January and February; the lowest recorded temperature is –40°C. Up to 450 mm of precipitation falls annually in the west and 250–300 mm in the east. A lasting snow cover does not form every year. Moisture is insufficient in most of the region.

Western Siberia. Western Siberia is distinguished by a continental climate, which is formed under the influence of air masses that are usually of arctic origin. During the summer, arctic air, penetrating the rear part of northern cyclones, interacts with the warmer continental air, causing clouds and precipitation. Humid Atlantic and dry Middle Asian air masses occasionally intrude into Western Siberia. In the winter, the region receives cold continental air from Siberia’s interior along the western edge of the Asiatic anticyclone and Atlantic air with cyclones from the arctic.

The primary paths of cyclones pass through the northern parts of Western Siberia, and consequently these regions are characterized by substantial cloudiness, strong winds, and abundant snowfall. The winters are long and harsh, with low temperatures. Temperatures lower than –30°C occur from November through March. The frost-free period lasts two to three months, but in some years frosts occur even in midsummer.

In the central part of Western Siberia, summers are warm but shorter than the summers in the same latitudes in the European USSR. The average July temperatures vary from 15.5° to 18°C. Freezing temperatures last about six months. The average January temperature is about –20°C, sometimes dropping to as low as –45°C. Winter weather is unstable: severe cold spells with no wind and clear skies are broken by abrupt warming, with temperature increases of 15° to 20°C, accompanied by blizzards (burans).

The climate is more continental in the southern part of Western Siberia, especially in the virgin-land regions. Winters here are long, with strong winds and severe blizzards. On the average, they are 10°C colder than winters in the same latitudes of the East European Plain. The lowest recorded temperature is –50°C. Less than 100 mm of precipitation falls during the colder part of the year; the snow cover is only 20–30 cm, and the soil freezes to great depths. Summers last about three months, with average July temperatures of 20° to 22°C and a maximum of more than 40°C. The relative air humidity is insignificant, less than 50 percent during daylight hours. Droughts and sukhovei are often observed, and dust storms sometimes occur.

In general, large climatic contrasts are observed in Western Siberia as a result of its enormous extent from north to south. The average annual temperature is –10°C in the north and 1°–2°C in the south. Annual precipitation ranges from 200–350 mm in the tundra and steppe zones to 500–600 mm in the forest zone. It is even higher in the Altai and Ural mountains, exceeding 1,000 mm a year in places on the windward western and northwestern slopes; on the southeastern slopes and in the intermontane basins, however, it decreases to 100–300 mm. Air temperatures decrease 5° to 10°C with elevation. Temperature inversions with trapped pockets of cold air above the intermontane basins are observed during the winter months.

Eastern Siberia. Eastern Siberia has the most continental climate in the country. Annual differences in air temperature reach 60° to 65°C, and the amount of precipitation and degree of cloudiness are relatively slight. Arctic air and the continental air of the temperate latitudes prevail throughout the year. Cyclonic activity is most developed during the warmer part of the year, primarily in the northern part of Eastern Siberia. During the colder part of the year, when temperature differences between the arctic and the Siberian interior are small, relatively stationary high-pressure areas become established over Eastern Siberia.

During the summer, the underlying surface warms up considerably. In Yakutsk, situated at 62° N lat., for example, the average July temperature is 19°C, which is higher than the temperature in Moscow; occasionally it even rises to 40°C. Eastern Siberia is characterized by exceptionally severe winters, and the coldest spots in the northern hemisphere are located in the intermontane basins along river valleys, where cold air has been trapped for long periods; temperatures of –68°C have been recorded near Verkhoiansk and Oimiakon. Winters last at least seven months, but the snow cover usually does not exceed 20–50 cm, since there is little precipitation (in the central regions of Eastern Siberia it does not exceed 50 mm). This causes the soil to freeze to great depths and preserves a thick permafrost layer. Moisture is moderate over most of Eastern Siberia. Significantly more precipitation falls during the warmer part of the year. On the western and southern slopes of the mountain ranges, 400–600 mm of precipitation falls between March and October, while 200–300 mm occurs in central Yakutia.

Sharp seasonal and daily fluctuations in air temperature and an uneven distribution of precipitation are observed in the southern part of Eastern Siberia and in the Baikal and Transbaikal regions. This leads to a diversity of landscape, with the alternation of mountain forests, steppes, and semideserts. Lake Baikal has a moderating influence on the climate of its immediate vicinity; the average temperatures of the lake are –16°C in January and 12°C in July. However, climatic differences increase noticeably in areas not too distant from the lake; at the western foot of the Baikal Range, the average January temperature is –28°C, and the average July temperature, 18°C. Winters are cold in the Vostochnyi and Zapadnyi Saian Mountains, with temperatures ranging from –17° to –25°C. Summers are cool, with temperatures reaching 12° to 14°C; the precipitation amounts to 800–1,000 mm on the windward slopes and 300–400 mm on the lee slopes and in the intermontane basins. The climate of the steppes of the Tuva Basin and Dauria is strongly influenced by the climate of Central Asia, reflected primarily in its greater aridity.

Far East. The Far East is located in a region where monsoons are widespread. The winter monsoon is characterized by a northwesterly and northerly transfer of continental air along the eastern periphery of the Asiatic (Siberian) anticyclone. As a result, winters in the Far East are cold, with clear weather prevailing and little snowfall; only 10–15 percent of the average annual precipitation occurs in the winter. The summer monsoon is characterized by southerly and southeasterly air flow, associated with cyclones in the eastern part of the continent and over the adjacent Pacific Ocean seas; rain is abundant, and fogs are frequent. The monsoonal climate is most clearly marked in the Amur Region and Primor’e Krai, where precipitation significantly surpasses evaporation throughout the warmer part of the year. The climate of the Okhotsk coast and the northeastern parts of the USSR is very cold as a result of their location in the high latitudes and the strong cooling influence of the seas, which are ice-covered most of the year. In the winter, gale winds and blizzards are frequent; summers are cool and cloudy, with high relative air humidity. The average January temperatures in southern Primor’e Krai range from –12° to –14°C, and on the Okhotsk coast, from –20° to –25°C; in the central regions, frosts as low as –40° to –45°C are possible. The average July temperatures in the southern part of Primor’e Krai are 14° to 20°C, and on the Okhotsk coast, 11° to 12°C; in the north, the average July temperature is less than 10°C. The total annual precipitation is 500–900 mm along the coast and 300–400 mm in the central parts of the Far East. The continental influence is weakened on Kamchatka, where the climate forms primarily under the influence of atmospheric circulation above the Sea of Okhotsk and the northern part of the Pacific Ocean. The coastal regions of the Far East experience a certain cooling effect from cold sea currents.

Plains of Middle Asia and southern Kazakhstan. The plains of Middle Asia and the southern part of Kazakhstan have an arid, sharply continental climate. The region receives the greatest total solar radiation in the USSR, amounting to 587–670 mJ/m2 (140–160 kcal/cm2) a year. For this reason, summer temperatures are very high, about 27°C in the north and 30° to 32°C in the south. There are days when temperatures reach 47°C. Summers are very long, with a prevailing anticyclonal regime and little precipitation. The period of freezing temperatures lasts three to four months in the north and about one month in the south; however, the winters in these latitudes are very cold, since continental air from Siberia penetrates unobstructed far south. The average January temperatures range from –5° to –10°C, sometimes reaching –30°C. The annual precipitation is 200–300 mm, with most occurring in the spring. The rate of evaporation exceeds precipitation throughout the year. Little precipitation falls during the winter, and the snow cover is brief or does not form at all.

SUBTROPICAL BELT. The subtropical belt includes the southwestern part of Middle Asia, Transcaucasia, and the southern coast of the Crimea.

Plains of southwestern Middle Asia and Transcaucasia. Middle Asia (southern Turkmenistan and Tadzhikistan) and Eastern Transcaucasia are characterized by an arid subtropical, continental climate, with long hot summers, low relative humidity, and little cloudiness. The average July temperatures vary between 25° and 28°C. Winters are unstable, with average January temperatures of 2° to 4°C, but intrusions of air from Siberia cause frequent cold spells. Annual precipitation is 100–200 mm. Areas with a semihumid subtropical climate are found in the Lenkoran’ Lowland, where in 1966 there was a torrential rain in the course of which 441 mm of precipitation fell in less than 24 hours.

Western Transcaucasia is characterized by a humid subtropical climate, with substantial precipitation: more than 1,000 mm a year on the plains, up to 3,200 mm in certain places in the mountains, and up to 5,000 mm in the high Caucasus in certain years. The region has the warmest winters in the USSR, with average January temperatures of up to 6°C, and hot, muggy summers, with average July temperatures of up to 24°C.

Southern Crimean coast. The southern coast of the Crimea has a Mediterranean-type subtropical climate, with mild wet winters and hot dry summers.

MOUNTAIN REGIONS OF THE SOUTHERN USSR. Although the climates of the various mountains of the southern USSR have a number of general features in common, there are significant differences caused by atmospheric circulation above individual mountain regions. The basic pattern of the climate of the Caucasus, Kopetdag, Pamirs, and Tien-Shan is governed by altitudinal zonation under conditions of general aridity, with the exception of the Western Caucasus, where moisture is adequate or excessive. Air temperatures decrease with elevation, as much as 10° to 15°C in the highest mountain systems, and annual precipitation increases from 300–400 mm at the foot of the Middle Asian mountains to 800–1,100 mm at the base of the glaciers. There are great differences in moisture between the windward and lee slopes of the mountains. For example, the Eastern Pamirs, situated in the “wind shadow,” receive several times less precipitation than the Western Pamirs. Such sharp contrasts over a comparatively small distance, usually tens of kilometers, are responsible for the extraordinary diversity of landscape in the mountain regions.

A. A. BORISOV

Bibliography

Alisov, B. P. Klimat SSSR. Moscow, 1956.
Borisov, A. A. Klimatografiia Sovetskogo Soiuza. Leningrad, 1970.
Voeikov, A. I. Klimaty zemnogo shara, v osobennosti Rossii: Izbr. soch., vol. 1. Moscow-Leningrad, 1948.
Klimat SSSR, fascs. 1–8. Leningrad, 1958–65.
Mikroklimat SSSR. Leningrad, 1967.
Spravochnik po klimatu SSSR, fascs. 1–34. Leningrad, 1964–75.

Permafrost occupies more than 10 million sq km in the USSR. In the European part of the country, it is found in the tundra and forest-tundra; the southern boundary of the permafrost extends from the Kola Peninsula to the mouth of the Mezen’ River and continues on almost following the arctic circle to the Urals. In Western Siberia the boundary stretches latitudinally as far as the Enisei River near the Podkamennaia Tunguska River, where it turns abruptly south and follows the right bank of the Enisei River. East of the Enisei, permafrost is widespread over most of the territory except the southern part of the Kamchatka Peninsula, the island of Sakhalin, Primor’e Krai, and a number of other regions.

Three types of permafrost are distinguished according to the character of its distribution: continuous permafrost, permafrost with islands of thawed ground, and discontinuous permafrost. Continuous permafrost is found in the northern part of the Bol’shezemel’skaia Tundra, in the Polar Urals, in the tundra of Western Siberia, in the northern part of the Central Siberian Plateau, on the Taimyr Peninsula, in the Severnaia Zemlia archipelago, on the Novosibirskie Islands, in the Iana-Indigirka and Kolyma lowlands, in the delta of the Lena River, on the Central Yakut Plain and the Lena Plateau, in the region of the Verkhoiansk, Cherskii, Kolyma (Gydan), and Anadyr’ ranges, and on the Yukaghir Plateau and the Anadyr’ Plain. Its thickness ranges from 300 to 500 m and more; temperatures range from –2° to –10°C and lower.

Permafrost with islands of thawed ground predominates in the Bol’shezemel’skaia and Malozemel’skaia tundras, on the Central Siberian Plateau between the Nizhniaia Tunguska and Podkamennaia Tunguska rivers, in the southern part of the Lena Plateau, and in Transbaikalia. Its thickness is usually 100–150 m, sometimes reaching 250–300 m; in some places it may be as little as 10–20 m. Temperatures range from –2° to 0°C.

Discontinuous permafrost occurs on the Kola Peninsula, in the Kanin-Pechora region, in the taiga zone of Western Siberia, in the southern part of the Central Siberian Plateau, in the Far East, along the coast of the Sea of Okhotsk, and on Kamchatka. Its thickness varies between a few and a few dozen meters. Temperatures are close to 0°C. Discontinuous permafrost is also typical of mountains, from the Saians to the Pamirs and in the Caucasus, where permanently frozen rocks are found primarily on the periphery of areas of modern glaciation.

The structure of permanently frozen rocks depends mainly on the distribution of the ice inclusions within them. Ice takes the form of veins filling cracks in crystalline and metamorphic rocks, in sand it takes the form of lenses or minute crystals, and in clays, loams, sandy loams, and peats it forms layers or lattices. Lattices of ice veins, which penetrate the rocks to depths of 20–40 m, are a unique phenomenon widespread in the Northern Siberian, Iana-Indigirka, and Central Yakut plains.

The freezing of the upper horizons of rocks often leads to the formation of seasonal or long-standing hummocks—hydro-laccoliths containing ice nuclei. They are most often encountered in Transbaikalia, on the Taimyr Peninsula, in the northern part of Western Siberia, and in Yakutia, where they are called bulgunniakhi. In these same regions, Aufeis are common, which are thin sheets of ice that form in river valleys and on slopes when groundwater is forced by the pressure that arises during seasonal freezing onto the surface, where it freezes. The thawing of ice formations contained in rock layers usually leads to subsidence and the formation of sinkholes, small circular depressions, and similar landforms (thermokarst).

The study of the specific characteristics of permafrost is a task of great practical importance in various branches of the national economy. Various factors must be taken into consideration in the construction of structures, railroads, and highways, such as the possibility of the swelling and subsidence of the ground, the downslope movement of thawed soil (solifluction), and the icing of roads and bridges. In agriculture, permafrost limits the possibilities of the growth of certain crops, but in other cases favors the cultivation of certain plants because of the supplementary moisture created by the seasonal thawing of the active layer.

A. I. POPOV

Bibliography

Dostovalov, B. N., and V. A. Kudriavtsev. Obshchee merzlotovedenie. Moscow, 1967.
Popov, A. I. Merzlotnye iavleniia v zemnoi kore (kriolitologiia). Moscow, 1967.
Obshchee merzlotovedenie. Novosibirsk, 1974.

The distribution of the waters of the rivers, lakes, bogs, reservoirs, and glaciers and subterranean waters in the USSR and the characteristics of the regimes are determined primarily by climatic factors and the heat and moisture balance. The average annual precipitation in the USSR is 530 mm, which constitutes 11,690 cu km of water. Sixty-three percent of this is lost through evaporation and transpiration, and 37 percent forms the runoff.

More than 80 percent of the river flow originates in the northern and eastern parts of the country, in the basins of the Arctic and Pacific oceans; 7.5 percent flows to the west and southwest to the Atlantic Ocean basin (the Baltic and Black seas and the Sea of Azov). Nine percent of the runoff never reaches the world ocean, emptying into various bodies of water that have no outlets, such as the Caspian and Aral seas and Lakes Balkhash, Issyk-Kul’, and Tengiz, or being lost through evaporation.

Table 1. Number of rivers in the USSR and their lengths
CategoryLength (km)Number of riversTotal length (km)
Smallest ...............<252,926,5607,323,000
Small ...............26–10032,7301,426,000
Medium-sized ...............101–5003,800670,000
Larae ...............>500260229,000

Rivers. The USSR has about 3 million rivers, whose total length is more than 9.6 million km (1975). Most are less than 100 km long (of the total number of rivers, 99.9 percent are less than 100 km long; of the total river length, rivers of less than 100 km account for more than 90 percent). (See Table 1.)

Four rivers are more than 4,000 km long—the Enisei, Lena, Ob’, and Amur. The longest river in the USSR is the Ob’, which is 5,410 km long; in the European part, the longest river is the Volga, with a length of 3,530 km (this figure takes into account the straightening of the river by reservoirs). The Enisei has the greatest flow, with an average annual discharge of 17,800 cu m per sec, and thus ranks fifth among the world’s rivers, after the Amazon, Congo (Zaire), Ganges, and Yangtze. The average annual discharge of the USSR’s 20 largest rivers exceeds 1,000 cu m per sec (see Table 2). The total annual discharge of the rivers of the USSR is about 4,500 cu km, including rivers that originate outside the USSR. Most of the rivers are flatland rivers, characterized by comparatively small gradients, slow and calm currents, and broad floodplains. The rivers of the Caucasus, Middle Asia, the mountains of Southern Siberia, and other mountain regions and the rivers of the Central Siberian Plateau are characterized by large discharges, turbulent currents, and many rapids.

Table 2. USSR rivers with highest rate of flow
RiverAnnual runoff (km3)Mean annual discharge (m3/sec)Specific discharge (liter/sec·km2)
Enisei ...............62417,8007.6
Lena ...............54017,0006.8
Ob’ ...............40012,3004.4
Amur ...............34310,8005.9
Volga ...............2437,7105.7
Pechora ...............1264,00012.1
Kolyma ...............1233,9005.9
Severnaia Dvina ...............1103,5009.7
Khatanga ...............1053,3209.1
Piasina ...............81.92,60014.6
Neva ...............79.72,5309.0
Amu Darya ...............63.12,0008.8
Indigirka ...............58.31,8105.0
Dnieper ...............53.01,7003.4
Anadyr’ ...............53.01,6808.7
Taz ...............45.71,4509.7
Olenek ...............38.21,2105.5
Pur ...............32.81,0409.6
Kamchatka ...............32.41,03018.4
Iana ...............31.51,0004.2

The rivers are subdivided into three main groups according to their regime: rivers with a spring high-water period; rivers with a high-water period during the warmer part of the year; and rivers with periodic flooding throughout the year. Most of the rivers in the USSR belong to the first group. Such rivers are characterized by an annual spring high stage, caused by the melting of the snow on the plains, low runoff in the summer, and a low stage in the winter. The second group includes the rivers of the mountain regions of the Caucasus and Middle Asia, where high water occurs in the summer, when the melting of high-mountain snow and glaciers is most intensive; it also includes the rivers of the Far East, where the summer high-water period is caused by heavy monsoon rains and there is virtually no spring high-water period because of insignificant winter snowfall. In the winter, the rivers of this group carry little water and sometimes freeze down to the bottom, especially those in the Far East. The third group includes the rivers of the Caucasian Black Sea coast. They are fed by rain and periodically overflow their banks in the course of the year.

The rivers in most of the USSR freeze during the winter, remaining thus for a period of two to seven or eight months. Many rivers freeze down to the bottom, developing a thick ice cover and forming Aufeis. The rivers of the western and southern parts of the European USSR, such as the Neman, Dnestr, and Kuban’, and the rivers of southern Primor’e Krai have a brief, unstable ice cover. The mountain rivers of the Caucasus, Middle Asia, and the Altai do not usually freeze over completely and are characterized by the formation of anchor ice, frazil ice, shore ice, and ice jams. In parts of the Caucasus and Middle Asia with a subtropical climate, some rivers exhibit no ice phenomena.

Table 3. Number of lakes in the USSR and total surface area
Surface area (km2)Number of lakesTotal surface area (km2)
Less than 1 ...............2,814,700159,500
From 1to 10 ...............36,90087,100
From 10 to 100 ...............2,40055,900
More than 100 ...............200185,900

Each year the rivers carry away more than 530 million tons of sediment, of which 211 million tons are carried into the Aral-Caspian basin. The most turbid water is found in the Terek, Kura, Amu Darya, and Syr Darya rivers, in whose basins loose rocks, which are relatively easily eroded, are widespread. In certain mountain regions of the Caucasus, Middle Asia, the Carpathians, and the Baikal Region, the sediment content in rivers during floods is so great that the rivers become transformed into mud or mud-rock streams.

The water of rivers in the zone of excess moisture is weakly mineralized, while a sharp increase in the mineral content is observed in the zone of insufficient moisture. In an average year, the rivers of the USSR carry off to the sea about 330 million tons of dissolved substances.

Lakes. The USSR has more than 2.8 million lakes, whose total area is about 490,000 sq km (excluding the Caspian and Aral lakes, which are generally classified as inland seas). Bodies of water with surface areas of less than 1 sq km, mostly occurring within bogs, account for 99.2 percent of all the lakes (see Table 3). The 14 lakes with surface areas of more than 1,000 sq km are among the world’s largest lakes (see Table 4).

The lakes contain 27,200 cu km of water, of which Lake Baikal accounts for 23,000 cu km, or 85 percent. Three of the largest lakes—Baikal, Ladoga, and Onega—account for 89 percent of all the lake water in the USSR.

Lakes are most numerous in the northwestern part of the European USSR, known as the lake district. Most of the lakes in this region are of glacial origin. There are numerous small lakes in the tundra, especially in the coastal lowlands of the northeastern part of the USSR, in Western Siberia, and in the steppe regions of Kazakhstan. Oxbow lakes abound in the river floodplains.

The largest mountain lakes are in the mountains of Middle Asia, the Altai Mountains, and the Caucasus, including Lakes Issyk-Kul’, Sevan, Teletskoe, Karakul’, Markakol’, Sonkel’, and Chatyrkel’. Many mountain lakes were formed by landslides; the best known such lake is Sarez Lake.

The lakes differ greatly in the degree of mineralization. While most have fresh water, there are many mineralized salt lakes, rich in mirabilite, soda, and rock salt, in the arid steppe and semidesert zones (for example, Lakes El’ton, Baskunchak, Sakskoe, Kulunda, and Doroninskoe).

Bogs. Bogs and marshy lands (with a peat thickness of less than 30 cm) occupy about 2 million sq km, or about 10 percent of the entire country. Bogs are most highly developed in the forest zone, where 80 percent of all the peat reserves are concentrated. High-moor (oligotrophic) bogs predominate; low-moor (grass) bogs are also widespread. The swampiest regions are the northern European part of the USSR, the Poles’e, the Western Siberian Lowland, and the Northern Siberian, or Taimyr, Lowland.

Reservoirs. The USSR is currently operating or planning to operate about 1,000 reservoirs, each holding more than 1 million cu m of water. They are used for hydroengineering purposes, transportation, irrigation, controlled flooding, and water supply. The Volga, Dnieper, Angara, and a number of other rivers are almost completely regulated and have been converted into a series of reservoirs. The largest reservoirs alone have a total area of more than 85,000 sq km and a water volume as high as 800 cu km, of which about 300 cu km are usable (see Table 5). Tens of thousands of ponds have been created in the steppe regions to flood pastures, supply water to populated points, and breed fish.

Glaciers. There are icecaps in the USSR, which are developed on the arctic islands, and various types of mountain glaciers. The icecaps are characterized by the flow of ice from one common point and a surface profile in the shape of a semioval. Their shape and the direction of their movement do not depend on the relief of the earth’s surface. The glaciers of mountain regions, or runoff glaciers, are usually subordinate to the topography with respect

Table 4. Largest lakes in the USSR
LakeSurface area (km2)Elevation above sea level (m)Volume (km3)Greatest depth (m)River flowing out of the lake
1Turned into a reservoir; the figure does not take into account the parameters of the reservoir
2Surface area increases to 3,600 km2 at high water levels
3Not considering the drop in water level as a result of the long-term use of the lake’s waters
4Varies from 733 to 2,090 km2 depending on the water level
5According to some figures, 1,741 km2
Baikal1 ...............31,50045623,0001,6205Angara
Balkhash ...............18,30034011226
Ladoga ...............17,7004908230Neva
Onega1 ...............9,72033285120Svir’
Issyk-Kul’ ...............6,2801,6081,730702
Taimyr ...............4,56061326NizhniaiaTaimyra
Khanka ...............4,1906916.510.6Sungacha
Chudskoe-Pskov ...............3,5503025.215Narva
Chany ...............1,99021054.39
Zaisan1 ...............1,8003868Irtysh
Tengiz ...............1,5903048
Sevan ...............1,36031,90558.583Razdan
Beloe ...............1,2901135.220Sheksna
Vygozero1 ...............1,140897.1018Nizhnii Vyg
Topozero ...............98611014.956Kovda
Il’men ...............9824186Volkhov

to shape and direction of movement, occupying valleys and depressions on the slopes of mountains.

In the USSR, glaciers occupy an area of 71,700 sq km, of which about 50,000 sq km are in the arctic, primarily the western part. The principal regions of mountain glaciation, whose total area is 21,700 sq km, are Middle Asia, the Caucasus, the Altai, and the northeastern part of Siberia. The largest mountain-valley glacier in the USSR is the Fedchenko Glacier in the Pamirs, which is 77 km long.

Table 5. Largest reservoirs in the USSR
ReservoirRiverSurface area (km2)Total volume (km3)
1With Lake Baikal
2With Lake Onega
3With Lake Zaisan
4With Lake Piaozero
5With Lake Vygozero
Irkutsk ...............Angara31.685148.5
Verkhniaia Svir’ ...............Svir’9.9302260
Kuibyshev ...............Volga6,44858.0
Bukhtarma ...............Irtysh5.500353.0
Bratsk ...............Angara5,470169.3
Rybinsk ...............Volga4,58025.4
Volgograd ...............Volga3,11731.5
Tsimliansk ...............Don2,70023.9
Kremenchug ...............Dnieper2,25013.5
Kakhovka ...............Dnieper2,15518.2
Krasnoiarsk ...............Enisei2,00073.3
Kama ...............Kama1,91512.2
Kuma ...............Kovda1,910413.3
Gorky ...............Volga1,5908.7
Vygozero ...............Vyg1,25056.5
Votkinsk ...............Kama1,1209.4
Novosibirsk ...............Ob’1,0708.8
Kiev ...............Dnieper9253.7

The estimated water resources contained within the mountain glaciers in the USSR amount to approximately 2,430 cu km, of which 2,150 cu km are in Middle Asia. The hydrologic role of glaciers is to redistribute the runoff of atmospheric precipitation over time. Glaciers accumulate precipitation that falls during the colder part of year and release it during the summer.

A. A. SOKOLOV

Bibliography

Sokolov, A. A. Gidrografiia SSSR [2nd ed.]. Leningrad, 1964.
Kats, N. la. Tipy bolot SSSR i Zapadnoi Evropy i ikh geograficheskoe rasprostranenie. Moscow, 1948.
Avakian, A. B., and V. A. Sharapov. Vodokhranilishcha gidroelektrostantsii SSSR, 2nd ed. Moscow, 1968.
Kotliakov, V. M. Snezhnyi pokrov Zemli i ledniki. Leningrad, 1968.
L’vovich, M. I. Reki SSSR. Moscow, 1971.
Domanitskii, A. P., R. G. Dubrovina, and A. I. Isaeva. Reki i ozera Sovetskogo Soiuza. Leningrad, 1971.

Distribution and dynamics of water resources. Of the greatest importance for practical purposes are the resources of rivers, which are replenished each year and whose magnitude varies from year to year and within the year; subterranean waters are also an important source of water supply. River flow in the USSR occurs in two main directions. In the European part most of the rivers flow southward, into regions of insufficient moisture; the rivers of the Asiatic part and the northern European part of the USSR flow northward, into regions with excess moisture (see Table 6). The specific discharge in the southern and southwestern regions, where most of the country’s population lives and where most of the irrigated lands are located, is about one-third the rate of flow in the northern regions. The highest rate (up to 100 liters/sec · sq km) is observed in the basins of the southern slopes of the Glavnyi Range of the Caucasus; the lowest rate (as little as zero) occurs in the deserts of Middle Asia.

The practical use of river resources is impeded by fluctuations in flow. The total flow of the rivers in the USSR varies little: in years with abundant precipitation it increases and in dry years decreases by only 5–10 percent from the average. In the basins of some rivers, fluctuations are greater and depend on the geographic position of the basin and the area it drains (the flow varies more for small rivers). In years when precipitation is abundant, river flow in the basins of the Volga, Don, Dnieper, Pechora, and Severnaia Dvina rivers is 1½ to two times above the norm, while in dry years it drops to 50–70 percent of the norm. The flow of the large Siberian rivers is 20–30 percent above the norm in wet years and 70–80 percent of the norm in dry years. The greatest variations in flow are observed for the rivers in the arid regions of the Caspian Lowland and Kazakhstan, where river flow increases by a factor of 2 to 4 in wet years compared to the average and decreases virtually to nothing in dry years.

In general, even for the large rivers one cannot exclude the possibility that the flow, guaranteed for 95 percent of the years, may be 1½ to two times below average, but for the rivers of Kazakhstan it may be tens of times less (see Table 7). The seasonal unevenness of river flow is governed by the amount of meltwater, rainwater, and subterranean water the river receives. Most of the USSR has a clearly expressed spring high-water period: for the rivers of the middle belt of the European SSR and Western Siberia, the flow at high stage accounts for about 50 percent of the annual flow, while for the rivers in the Transvolga Region and Kazakhstan, it accounts for up to 90–95 percent. The amount of seasonal runoff is given in Table 8.

The distribution of river flow according to region and with time is not the only factor characterizing water-supply conditions. The governing factor is the relationship between the flow regime of a particular river, lake, or body of water and the needs of the users (water-use management balance).

The uses of natural waters can be arbitrarily grouped into consumptive uses, in which the water is removed from the source (for example, water supply for domestic, industrial, agricultural, irrigation, and fish-culture purposes), and nonconsumptive uses, which involves no removal of water (hydroengineering purposes, transportation, fishing, water-level management to flush polluted and salinized waters being discharged into rivers, and inundation of floodplain farmlands and deltas).

Table 6. Average long-term river discharge in the USSR according to ocean and sea basins
  Discharge
BasinArea (km2)km3/yearliter/sec·km2
Baltic Sea ...............660,0001708.2
Arctic Ocean ...............12,810,0002,7706.9
Pacific Ocean ...............3,270,0008908.6
Black Sea and Sea of Azov ...............1,350,0001603.7
Caspian Sea ...............2,930,0003003.1
Aral Sea and other closed lakes in Middle Asia and Kazakhstan ...............2,420,0001201.6
Total in USSR ...............23,440,0004,410
including discharge of rivers originating outside USSR ...............1,430,000210

A distinction is made between full consumptive use (the amount of water removed from the source) and unreturned consumptive use (the loss of water through evaporation and in the course of production processes). The water returned, which is the difference between the full consumption and the unreturned consumption, reenters the source through the sewer lines and drainage installations and as a result of filtration. In 1975 full consumptive use of water amounted to 300 cu km for the year, while unreturned consumptive use amounted to 150 cu km for the year. In 1975 all forms of water supply accounted for about 100 cu km of fresh water, while the total volume of water used reached approximately 300 cu km. About 5 percent of the total volume of fresh water removed from the rivers and various bodies of water was used for municipal water supply. Agriculture accounted for two-thirds of the remaining water. There is some evaporation water loss in nonconsumptive use of water if the water-use technology necessitates increasing the surface area of the water or the duration the water is at high level.

The use of water to satisfy drinking, household, therapeutic, recreational, health, and other needs of the population, as well as to meet agricultural, industrial, power, transportation, fishing, and other state and social needs, is governed by the Fundamentals

Table 7. Annual runoff of some rivers in the USSR
RiverObservation pointDrainage area (Km2)Annual runoff (km3)
   Average75% of years95% of years
1 Urban-type settlement
Volga ...............City of Volgograd1,360,000254220183
Moscow ...............City of Zvenigorod5,0001.020.850.66
Voronezh ...............City of Voronezh21,0002.131.621.13
Dnieper ...............City of Kiev328,00043.230.227.0
Don ...............City of Kalach222,00021.015.410.2
Ishim ...............City of Petropavlovsk106,0001.950.590.13
Kura ...............City of Tbilisi21,0006.505.584.50
Neva ...............Mouth281,00079.770.159.0
Ob’ ...............Belogor’e12,180,000331291245
Turgai ...............Tusum Desert52,0000.270.030.001
Bol’shoi Uzen’ ...............City of Novouzensk7,5000.280.130.04
Ural ...............City of Orenburg82,0004.421.550.36

of Water Legislation. Rivers, lakes, and other bodies of water may be used for the discharge of industrial, household drainage, and other wastes providing that such use does not raise the content of pollutants in the body of water above established norms and that the wastes are decontaminated in accordance with established standards. The discharge of waters retain about 10 percent of the original pollutants. Wastewater from industry and cities is the primary cause of water pollution.

Irrigation. Under present conditions, the nationwide unreturned consumptive use of water for regular irrigation exceeds 100 cu km per year; about two-thirds of the agricultural lands of the farming zone of the USSR receive insufficient moisture during the entire growing season or during certain months. Systematic irrigation is essential in areas with an annual precipitation of less than 250 mm. Where precipitation is greater, only water-loving plants require regular irrigation. In 1975 about 15 million hectares (ha) were irrigated in the USSR.

The water requirements of irrigated lands are uneven: waterings are carried out during the spring and summer growing season and in the winter to soak and leach the soil. Irrigation norms, which depend on soil and climatic conditions, are 2,000–5,000 cu m per ha for vegetables, 2,000–3,500 for grain crops, 6,000–8,000 for cotton, and 15,000–25,000 for rice. It is considered that for 75 percent of the years, the supply of water must be guaranteed at full irrigation norms and for another 15 percent of the years at norms 20–30 percent less. When water is transported by canals, 20 to 70 percent is lost to filtration and evaporation.

Hydroengineering projects are carried out to supply water to regions of the country that have little or no natural water resources. Water resources are developed and steps are taken to retain meltwater, rainwater, and springwater in ponds. Moisture retention cuts the amount of water in rivers but increases subterranean water resources.

Major irrigation systems have been constructed in Middle Asia, the Northern Caucasus, Transcaucasia, and the southern parts of the Ukraine and the RSFSR, for example, the Kuban’-Kalaus system and the Karakum Canal. The projected irrigation of the lands between the Volga and the Ural rivers is linked with the construction of the Volga-Ural Canal. According to calculations by planning organizations, the irrigated area in the USSR can be increased to 30–35 million ha and even to 70–80 million ha if some of the flow of the Siberian and northern rivers is diverted.

As a result of the intensification of agriculture and the development of irrigation, increasing amounts of fertilizers, toxic chemicals, and salts find their way into bodies of water with meltwater, rainwater, and wastewater. Pollutants of agricultural origin are noticeably beginning to affect the quality of water in rivers, lakes, and seas. The discharge of wastewater into bodies of water that are classified as therapeutic is forbidden. The use of subterranean drinking-quality water for needs other than drinking or household use is not generally permitted. However, when surface water is scarce but there are significant reserves of drinking-quality subterranean water, subterranean water may then be used for other purposes as well.

CONSUMPTIVE USES OF WATER. Water supply. Water supply is characterized by a number of special features, namely, the high quality of the water and guaranteed delivery to the consumer (restrictions or interruptions in water supply are generally not to be tolerated); seasonal variations in water consumption are not great, with summer consumption only 10–20 percent above the yearly average. In 1976 unreturned consumptive use of water accounted for nearly 10 percent of the total water used by the national economy. Because many large cities and industrial regions are located in parts of the country where rivers are small and flow is very uneven, many reservoirs and canals have been built to supply water, such as the Moscow, Severskii Donets-Donets Basin, Irtysh-Karaganda, and Dnieper-Krivoi Rog systems, and a number of canals are projected, such as the Oka-Kursk Magnetic Anomaly and Oka-Moscow canals.

Unreturned water losses in the course of supplying water to industry and populated points are comparatively small, but even with sophisticated methods of decontamination, returned introduction of biological methods of weed and pest control and the development of toxic chemicals that rapidly decompose into harmless constituents are becoming very important.

Pond fisheries. The spring filling of ponds in regions of large-scale fish culture can markedly affect the local water balance. A significant amount of the water removed is not returned to the source when the ponds empty in the autumn as a result of surface evaporation. Hatcheries built to reproduce fish artificially are a similar water consumer. Unreturned water losses by pond fisheries constitute about 1 percent of the total losses.

NONCONSUMPTIVE USES OF WATER. Hydroelectric power. Daily fluctuations in water consumption are clearly expressed during the low-water period, when hydroelectric power plants are working

Table 8. Seasonal distribution of river runoff in the USSR
RegionSeasonal runoff as percentage of annual runoff
 springsummer-autumnwinter
Southern Transvolga, southern Cisurals Region, Northern and Central Kazakhstan, and foothills of Middle Asia and the Altai ...............90–954–81–2
Eastern Siberia ...............70–8015–25less than 5
Northern European USSR (excluding the lake rivers of the Baltic Region) ...............55–6525–3510–20
Western and southwestern European USSR ...............30–5030–3520–35
Western Siberia ...............45–5535–45less than 10
Far North and northeastern part of Siberia ...............40–5045–55less than 5
Far East, Kamchatka, Transbaikalia, and the lana-lndigirka region ...............30–4055–65less than 5

at peak capacity. There are seasonal variations owing to changes in the length of the day and seasonality of production.

The USSR has an estimated water-power potential of 2.1 trillion kW-hr. In 1975, its hydroelectric power plants produced 126 billion kW-hr of electricity, which accounted for 13 percent of the total energy used. The total capacity of the existing hydroelectric power plants is 40 million kW, or 18 percent of the total capacity of all the country’s power installations. Series of large hydroelectric power plants have been built on the Dnieper and Volga, and hydroelectric power plants are now (1977) under construction on the Angara and Enisei.

Water transport. Water transport constitutes one of the important nonconsumptive uses of water on large rivers. Navigable depths are maintained during the navigation season in the free-flowing sections of rivers by the combined release of water from upstream reservoirs and deepening of the river channels. As a result of such measures, the water level on the lower Volga during the navigation season has been approximately doubled compared to natural conditions, while that on the lower Don has been tripled.

The degree of navigability depends on the class of the waterway. On the most important routes, such as the Volga, navigation must be guaranteed for 95 percent of the years, while on less important routes it drops to 60–70 percent. The construction of major navigation canals, such as the White Sea—Baltic, Moscow, and V. I. Lenin Volga-Don canals, and the construction of hydroengineering complexes on the Volga, Kama, Dnieper, Don, Svir’, and other rivers have guaranteed the necessary conditions for navigation. Conditions have been created for linking the river basins into a single deep-water route. In 1975 the first phase of the unified deep-water system of internal waterways in the European part of the country was completed. Future plans call for the rapid growth of water transport. At present, its overall share is relatively small, although in certain regions, such as the basins of the Siberian rivers, it is very important.

The country’s rafting routes exceed 100,000 km in length. They perform an important function—timber flotation in regions that have no other means of transport. Water is sometimes periodically released from upstream reservoirs to facilitate timber flotation. Driving (flotation of loose logs) and the transport of logs bound in bundles and packets without ships is prohibited on navigable rivers and rivers used for water supply and fishing.

Fishing. Fishing is becoming an especially important economic activity on inland waterways. Various measures that have been adopted favoring other users worsen conditions for fish life. The construction of reservoirs leads to the flooding of natural spawning grounds. It also leads to the lowering of the water surface and a decrease in the frequency of high-water periods in low-lying segments of the river, which likewise worsens spawning conditions. The reduction in river flow resulting from growing water consumption leads to a decrease in biogenic flow (the foundation of fish productivity) and to the inflow of saline seawater into river mouths, where fish feed and grow. Feeding and growth conditions are greatly worsened in closed bodies of water when their level drops as a result of reduction of flow in the basins, such as the Caspian Sea basin.

In rivers that are important for fishing, the minimum allowable high stage must be maintained, or the water level must be artificially increased to simulate the high stage, as is done on the Volga. A special water divider has been built on the lower Volga for spawning, and it is used to flood the spawning grounds in the eastern part of the delta with a comparatively small expenditure of water.

Water-level management. In order to maintain favorable sanitary conditions, the water level of rivers is kept above a certain minimum level to ensure the dilution of pollutants entering the river to permissible concentrations, the functioning of existing water intake structures, the prevention of freeze-ups during the winter, and the maintenance of current velocities of at least 0.2–0.3 m/sec in the open channel.

Regime of closed bodies of water. Many major rivers in the European part of the USSR and Middle Asia empty into closed seas and lakes, such as the Caspian Sea, the Aral Sea, and Lake Balkhash. The decrease in inflow as a result of the damming of rivers disrupts the natural regime of the seas and contributes to a decrease in their level, which impedes the operation of ports and other marine structures and the recreational use of the seas. Moreover, the salt and biochemical regimes of the seas are disturbed, and the disruption of aquatic ecosystems may reach significant proportions, which proves harmful to the fishing industry. Specific disruptions have been observed in the inland seas: the reduction of river flow into the Sea of Azov has disrupted the regime of exchange currents in the Kerch’ Strait, which has resulted in the increased inflow of saline water from the Black Sea into the Sea of Azov.

In order to maintain a favorable regime of the seas, future plans call for increasing river discharge into the seas and reducing surface evaporation by blocking off relatively unproductive shallow areas.

Integrated use of water resources. Bodies of water are used first and foremost to satisfy the drinking and household needs of the population. The priority for other types of water use is established in each individual case on the basis of economic and social considerations. The interests of water users often conflict: higher water levels are required in the summer for irrigation and water transport, whereas for hydroelectric power and the maintenance of sanitary conditions, higher water levels are needed in the winter. Fishing and estuary irrigation require high flow in the spring, but water supply requires uniform flow throughout the year.

The reduction in flow on certain rivers is quite high; for example, the flow at the mouth of the Syr Darya has decreased to one-quarter of the natural flow. In most of the river basins, water consumption is relatively low. However, owing to the demands made for water by nonconsumptive water users, there are occasional water shortages in dry years in densely populated, developed basins, such as the Volga, Don, Kuban’, Dnieper, Amu Darya, and Syr Darya basins.

The total demand for water is determined by adding chronological graphs of the nonconsumptive uses of water and graphs of the consumptive uses of water. Comparing them with a chronological graph of the amount of water available in a particular source establishes the possibilities of water provision. If in a dry year the available resources are in general sufficient but a shortage is established for certain periods of the year, the flow must be redistributed within the year by means of seasonal storage reservoirs. In areas where the total resources in a dry year are insufficient, it becomes necessary to make use of the resources of the wet years, stored in long-term reservoirs, or to bring in water from other sources.

Land irrigation in the forthcoming decades requires the diversion of water from the water-rich regions of the northern and western parts of the country to the river systems of the basins of the southern seas.

Water management, including the elimination of wastewater, necessitates increasingly more capital, and the availability of water is becoming one of the significant factors in determining the disposition of productive forces.

D. IA. RATKOVICH

Bibliography

Voskresenskii, K. P. Norma i izmenchivost’ godovogo stoka rek Sovetskogo Soiuza. Leningrad, 1962.
Vodnye resursy i vodnyi balans territorii Sovetskogo Soiuza. Leningrad, 1967.
Gangardt, G. G. Vodnye resursy SSSR. Moscow, 1968.
Dreier, N. N. “Vodnye resursy krupnykh ekonomicheskikh raionov RSFSR i soiuznykh respublik.” In Voprosy geografii, vol. 73. Moscow, 1968.
Kalinin, G. P. Problemy global’noi gidrologii. Leningrad, 1968.
Vodnyi balans SSSR i ego preobrazovanie. Moscow, 1969.
Voskresenskii, K. P. “Vodnye resursy i vodnyi balans SSSR.” Tr. Gos gidrologicheskogo in-ta, 1971, issue 171.
Gal’tseva, T. V. “Vodnye resursy SSSR.” In Geografiia SSSR, vol. 9. Moscow, 1973.
Voskresenskii, K. P., A. A. Sokolov, and I. A. Shiklomanov. “Resursy poverkhnostnykh vod Sovetskogo Soiuza i vliianie na nikh khoziaistvennoi deiatel’nosti cheloveka.” Chelovek i sreda obitaniia. Leningrad, 1974.
L’vovich, M. I. Mirovye vodnye resursy i ikh budushchee. Moscow, 1974. (Contains bibliography.)
Zarubaev, N. V. Kompleksnoe ispol’zovanie i okhrana vodnykh resursov. Leningrad, 1976.

The shores of the USSR are washed by 12 seas, belonging to the basins of the Atlantic, Arctic, and Pacific oceans. In addition, there are two inland seas (see Table 9).

Far Eastern seas. The Far Eastern seas—the Sea of Japan, the Sea of Okhotsk, and the Bering Sea—are marginal seas, occupying an area of about 5 million sq km. The relief of the floor is characterized by deep-water basins, with predominant depths of 3,500–4,000 m, and, in the north, by vast shallow regions of the continental shelf. The morphostructures of the transitional zone, including the basins of the marginal seas, island arcs, and deep ocean trenches, are most extensively developed. Individual ridges and rises dot the flat or rolling surface of the floor of the marginal seas, which has subsided to a depth of 300–400 m.

The region of the Far Eastern seas is marked by high seismicity and by modern volcanic activity. The influence of the Asiatic continent and the relatively unobstructed connection with the Pacific Ocean determine the climatic and hydrologic features of the seas. The seas are rich in fish and other marine products. Important waterways linking Vladivostok with many Soviet and foreign ports pass through the Far Eastern seas. The principal ports are Vladivostok, Nakhodka, Magadan, Petropavlovsk-Kamchatskii, and Korsakov (on the Island of Sakhalin).

Table 9. General information about the seas of the USSR
SeaArea (km2)Greatest depth (m)Salinity (%c)Greatest tide (m)
1 Salinity is more than 300%c in the Kara-Bogaz-Gol Gulf
2 With islands, 64,500 sq km
Atlantic Ocean
Baltic ...............386,0004593–80.4–0.1
Black ...............420,0002,21117–180.1
Azov ...............38,000142–110.1
Arctic Ocean
Barents ...............1,405,00060032–356.1
East Siberian ...............936,00015510–300.3
Kara ...............880,00062012–330.5–0.8
Laptev ...............700,0003,38510–340.5
Chukchi ...............582,00016024–321.5
White ...............90,00033024–3010
Pacific Ocean
Bering ...............2,304,0004,19128–336.4
Okhotsk ...............1,583,0003,37227–3213.6
Japan ...............978,0003,66934–352.8
Inland Seas
Caspian ...............371,0001,0251–1 3.31
Aral ...............64,00026710–14

Arctic seas. The arctic seas—the Chukchi, East Siberian, Laptev, Kara, Barents, and White seas—occupy a shelf measuring up to 1,300 km in width. They are shallow seas: the edge of the shelf is generally at a depth of about 500 m. The continental slope has depths ranging from 180 to 3,000 m, with several levels of inclined, terrace-like plains. The arctic seas have a total area of more than 4.5 million sq km. They are connected to one another by straits, the most important being the Karskie Vorota, Vil’kitskii Strait, Dmitrii Laptev Strait, and Long Strait. They receive a number of large rivers, including the Lena, Enisei, Ob’, and Pechora, and serve as a means of communication between the coastal regions and the interior of the country.

The climate is harsh, and the arctic seas are ice-bound most of the year, except for the southwestern part of the Barents Sea, which remains ice-free year-round because of the incursion of warm Atlantic waters. The Northern Sea Route passes through the arctic seas. The principal ports are Murmansk (which is ice-free), Arkhangel’sk, Belomorsk, Kern’, Kandalaksha, Mezen’, Dikson, Nordvik, and Tiksi. The White Sea-Baltic Canal connects the White Sea with the Baltic Sea and, through the V. I. Lenin Volga-Baltic Waterway, with the Sea of Azov and the Black and Caspian seas.

Baltic Sea. The Baltic Sea occupies the continental shelf and has an average depth of 71 m. It has many islands, most of which form island groups. The fauna is characterized by a mixture of marine and freshwater species, and much fishing is carried on. The sea is a major transportation artery, linking the USSR with many foreign ports. It is linked with the Volga through the Volga-Baltic Waterway and with the White Sea through the White Sea-Baltic Canal. The principal ports are Leningrad, Tallinn, Riga, Liepāja, Klaipeda, and Kaliningrad. The Baltic is famous for its resorts.

Southern seas. The southern seas—the Black Sea, the Sea of Azov, and the Caspian and Aral seas—occupy an area of approximately 900,000 sq km and are either very deep (more than 1,000 m) or very shallow (less than 15 m). Because of their location and hydrologic regime, they are classified as intracontinental seas; they have limited connection with neighboring seas and, through them, with the ocean.

The Sea of Azov occupies the Scythian Platform and the fore-deep of the Crimean-Caucasian folded region. Its floor is a flat aggradational plain that is inclined to the south, and its depths are only a few meters.

The shelf of the Black Sea, which varies from 1 to 200 km in width, occupies a vast area in the north. The northwestern part of the sea is a shallow plain, with traces of ancient Dnieper channels, sandbars, spits, and ridges. The continental slope descends to a depth of 1,800–1,900 m; south of the Crimea, there are terraces and scarps of fault origin. The floor of the deep-water basin (more than 2,000 m) is flat. About one-fourth of all the import shipping of the USSR and one-half of all the export shipping pass through the Black Sea.

The principal ports on the Black Sea are Odessa, Il’ichevsk, Nikolaev, Kherson, Sevastopol’, Kerch’, Novorossiisk, Poti, and Batumi; those on the Sea of Azov are Zhdanov, Taganrog, Eisk, and Berdiansk. Numerous resorts line the Black Sea coast.

The Caspian and Aral seas are isolated bodies of water with no outlets. The Aral Sea occupies the most subsided part of the Turan Plate. The floor of the sea, which is flat, is located entirely in the region of shelf depths.

The Caspian Sea is divided according to relief into three parts: the shallow (4–8 m) northern part, the central part (depths to 788 m), and the deep (more than 1,000 m) southern part. The northern part and significant parts of the central and southern parts are occupied by aggradational, abrasion-aggradational, and denudation plains of the shelf. The relief of the southern basin is complicated by a system of underwater ridges, and the southern and southeastern margins border on the continental slope. The Caspian Sea, located in the lowest part of a vast region with no outlet, is completely cut off from the world ocean and has an extremely unstable hydrologic regime. The great variability of its water balance and the considerable long-term variations in water level are a result of an intricate complex of climatic, hydrologic, and geological processes within its enormous drainage area. The Caspian Sea is connected by a system of internal waterways with the Sea of Azov and the Black and Baltic seas. The principal ports are Baku, Astrakhan, Krasnovodsk, Makhachkala, and Shevchenko.

(For information on marine resources, see above: Mineral resources; see below: Plant resources; and Animal resources.)

A. M. MUROMTSEV

Bibliography

Vize, V. Iu. Moria Sovetskoi Arktiki [3rd ed.]. Moscow-Leningrad, 1948.
Leonov, A. K. Regional’naia okeanografiia, part 1. Leningrad, 1960.
Dobrovol’skii, A. D., and B. S. Zalogin. Moria SSSR. Moscow, 1965.
Sovetskaia Arktika: Moria i ostrova Severnogo Ledovitogo okeana. Moscow, 1970.
Istoshin, Iu. V. Iaponskoe more. Moscow, 1959.
Egor’eva, A. V. Baltiiskoe more. Moscow, 1961.
Osnovnye cherty geologii i gidrologii Iaponskogo moria. Moscow, 1961.
Lymarev, V. I. Berega Aral’s kogo moriavnutrennego vodoema aridnoi zony. Leningrad, 1967.
Kaspiiskoe more. Moscow, 1969.
Giul’, K. K., P. V. Zhilo, and V. M. Zhirnov. Bibliograficheskii annotirovannyi spravochnikpo Kaspiiskomu moriu. Baku, 1970.

General features of the soil cover. The changes in space and over time in the soil-forming factors, such as climate, relief, parent rock material, and vegetation, and the resulting differences in the development of the soil cover in individual regions have led to the formation of various kinds of soils in the USSR. The geographic distribution of soils is governed by a number of regularities, the most clearly marked being latitudinal (lateral) zonality—the succession of different soil types from north to south, more precisely from northwest to southeast, as a result of variations in climatic conditions (heat and moisture) and vegetation.

On the East European Plain a succession of zones of tundra, podzolic, gray forest, chernozem, chestnut, and brown semidesert soils is observed from north to south. Most of the zones are subdivided into subzones, where definite soil subtypes predominate. For example, the chernozem zone is divided into subzones of podzolized, leached, typical, common, and southern chernozems. Soils within the zones and subzones also have their own characteristic features, reflecting the different climatic conditions, such as the length of the cold and warm seasons and the degree of summer warming and winter cooling in the eastern and western parts; this has made it possible to identify various soil provinces. For example, the Ukrainian chernozems have thick humus horizons and a low humus content in the upper part of the soil profile, while the chernozems in the Volga Region, particularly in the Cisurals, have much thinner humus horizons but greater accumulations of humus in the upper layers.

Latitudinal zonality is clearly expressed on the East European Plain and Western Siberian Lowland, where the soils formed on loose, deeply weathered Anthropogenic parent rocks. In the warmer (western) part of the East European Plain, however, podzolic brown earths and brown forest soils are frequently encountered in the zone of podzolic soils. Bog and waterlogged soils are widespread in the forest zone of the poorly drained Western Siberian Lowland; saline soils and solonetzes are common in the steppe zone.

East of Transbaikalia, the soils form primarily on weakly weathered detrital rocks; in vast areas they form under the influence of permafrost. The distinctive and highly intricate structure of the soil cover here has been determined by the type of parent material, the different heat and, in particular, water regimes resulting from the monsoon circulation of the atmosphere, and the mountainous relief. Soil zonality is less clearly marked. Frigid taiga soils predominate in vast regions of Central and Eastern Siberia. Drier fine-grained soils occur in the enclosed lowered plains and basins, for example, the pale yellow soils of the Yakut Basin and the chernozems of the Minusinsk and Kana basins. Because of a relatively warm and humid climate, the southern part of the Far East has extensive areas of wet podzolic brown earths. Unique ochreous soils have developed on the young volcanic soil-forming rocks of Kamchatka. Stony soils are characteristic of Kazakhstan, where the soils in extensive areas formed on dense parent material.

The regularities of soil geography in mountain regions are determined by altitudinal (vertical) zonality—the succession of different soils from the foot of the mountains to the peaks caused by a change in climate. In the western part of Transcaucasia, for example, zones of yellow earths, red earths, brown forest soils, and mountain meadow soils can be traced from the foot of the mountains to the peaks. In the Urals and the Altai, the sequence is chernozems, gray forest soils, mountain podzolic soils, mountain meadow soils, and mountain tundra soils. Submontane zonality, usually related to the increased precipitation on submontane plains in close proximity to the mountains, is very important. In Ciscaucasia this is expressed in the sequence of carbonate, typical, and leached chernozems, while in the Cisurals, it is expressed in the sequence of chernozems and gray forest soils. On the submontane plains of Middle Asia, desert soils are supplanted by light and conventional sierozems.

Each zone and subzone, which has been named after a predominant soil, also contains other soil types and subtypes. For example, bog podzolic and bog soils are commonly found among podzolic soils, meadow chernozems, and meadow soils; in some places, solonetzes frequently occur among chernozems, as well as among chestnut and brown semidesert soils. Such alternations create different soil combinations, which, when taken together, determine the soil structure. Individual structures differ with respect to the nature and degree of contrast in the properties of the constituent soils, the ratio of their areas, and the size and shape of the similar sectors that form the different combinations. Within the soil groupings there are soil complexes, in which small patches (a few dozen square meters in area) alternate, as well as combinations and mosaic surfaces, whose areas are measured in terms of hectares and tens of hectares. The structure of the soil cover largely determines both the possibility and effectiveness of soil use. Thus, some soil complexes cannot be cultivated without expensive and complex reclamation work. Combinations of small soil mosaics make it very difficult to establish extensive plowed areas.

The structure of the soil cover depends on zonal bioclimatic conditions, topography, and the parent material. Zonal conditions cause the development of a more intricate soil structure with the extensive distribution of soil complexes in the zone of tundra, chestnut, and brown semidesert soils. Mosaics of podzolic, bog podzolic, and bog soils are clearly expressed in the zone of podzolic soils in the northwestern part of the European USSR, a region of young glacial topography. In Central Siberia the alternation of fragmented and finely fragmented parent material produces complex and patterned surfaces of dry frigid soils and icy frigid soils, which are usually overmoist. On the Central Russian Upland, the extensively developed network of ravines and gulleys causes combinations of uneroded chernozems and chernozems eroded to varying degrees. The subsided relief of the southern Ukraine and the forest-steppe zone of Western Siberia, with many small downwarps and fissures, produces circular-spot combinations of chernozems, meadow soils, solodi; and solonetzes.

Four types of soil structures are identified on soil maps: soil complexes, for example, solonetzes with brown semidesert soils; combinations in which the components are of approximately equal ratio, for example, frigid taiga and bog soils; combinations in which one type of soil predominates, for example, yellow frigid taiga soils with bog soils and solodi; and uniform blocks, for example, gray forest soils.

The structure of the soil cover of soil zones in the mountains is determined by the elevation, the steepness and exposure of the slopes, the properties of the parent material, and the degree of erosion. In moderately humid mountain regions, the influence of slope exposure on the character of the soils acquires considerable importance and gives rise to a special type of soil cover known as exposure-differentiated. In mountain regions with excess moisture, the structure of the soil cover is very simple.

Mountain soils generally differ from the soils of the plains in the amount of detrital material, the thinness of the soil profile, and the greater compactness of the soil cover. Nonetheless, most mountain soils can be classified in terms of the corresponding soil types developed on the plains, for example, mountain chernozems and mountain podzolic soils. However, certain kinds of soils found in the mountains are rarely encountered on the plains. The most widespread of such soils are Alpine meadow, mountain meadow steppe, and mountain podbur soils. Alpine meadow soils form in high mountains with a humid climate. They have a humus-rich (up to 20–30 percent) soddy horizon, beneath which is a transitional horizon and then the parent material. Such soils are acid in reaction and are used for summer grazing. Mountain meadow steppe soils form in drier middle-altitude and high mountain areas. They differ from mountain meadow soils in a lower humus content and a reaction that is nearly neutral. In level areas they are used for summer grazing. Mountain podburs develop in humid, cold forested mountain regions. They are very acid, and their upper horizons are rich in tongued humus. The principal areas of mountain soils are forested. Many have high natural fertility, but great care must be taken when farming such soils because of the rapid development of erosion, which can completely wash away loose layers.

The plains soils of the USSR are grouped into two major groups: leached and unleached.

LEACHED SOILS. Leached soils develop under tundra, forest, and meadow vegetation, where moisture in the form of atmospheric precipitation and the like exceeds the potential for evaporation. As a result of the predominantly descending flow of moisture created in such a case, various water-soluble salts, such as chlorides, sulfates, and carbonates, that are contained in the soil-forming rocks and that arise in the process of soil formation are removed from the soil, which then becomes acid.

Tundra gleys. Tundra gleys are characterized by a surface peat horizon. The lower layers are characterized by very mobile forms of humus and by strong gleying, which imparts to the soil profile a grayish color, sometimes with rust-colored mottles.

Podzolic soils. Podzolic soils form under coniferous and mixed forests. Their profile is sharply delineated; the middle and lower (illuvial) horizons are rich in silt, while the upper (eluvial) horizons have little silt. Podzolic soils are divided into three subtypes: gley podzolic soils, with a gleysolic upper layer (they usually form in areas with the wettest conditions, in the northern taiga); podzolic soils proper, with the most typical profile (in the central taiga); and sod podzolic soils, with a clearly marked humus horizon, containing 1–6 percent humus (in the southern taiga). Adequate moisture and good responsiveness to fertilizer make it possible to use podzolic soils, primarily sod podzolic soils, extensively for grains, forage crops, and potatoes and other vegetables. Podzolic soils, which require liming, are the principal cultivated soils of the Nonchernozem Zone.

Podzols. Podzols develop on poor sandy soil-forming rocks. They differ from podzolic soils in the character of the illuvial horizon. The illuvial horizon of podzols contains iron, aluminum, and, frequently, humus but no silt.

Bog podzolic soils. Bog podzolic soils are found among podzolic soils and podzols. In general, they retain the structure and properties of the two, but as a result of increased moisture they take on a number of the properties of bog soils, such as gleying and a peaty upper horizon.

Sod coarse humic soils. Sod coarse humic soils are found under the grassy and scrub-grassy forests of Kamchatka and the Kuril Islands. The upper horizons are rich in humus (5–9 percent), and tongued humus occurs in the middle and even lower horizons. The mineral content changes little throughout the soil profile.

Frigid taiga soils. Frigid taiga soils are associated with a cold, sharply continental climate and occur in the light-coniferous taiga of Siberia. The permafrost horizon lies at a depth of 1–1.2 m. Various traces of permafrost phenomena are observed in the profile: the sorting of coarse-grained material, the shifting of soil masses, and fissuring. Frigid taiga soils have a significant humus content, as much as 6–7 percent. Agricultural development is fraught with difficulties.

Gray forest soils. Gray forest soils are widely distributed in the zone of deciduous, primarily broad-leaved, forests. They combine the characteristics of podzolic soils (silt-poor upper horizons and silt-rich lower horizons, acid upper horizons) and steppe chernozem soils (clearly developed textured upper humus horizon, saturation with bases, and frequent presence of carbonates in the lower horizons). Such soils are fertile and are used extensively for grains, forage crops, potatoes and other vegetables, and industrial and other crops.

Brown forest soils. Brown forest soils form on rich, frequently detrital, parent material under broad-leaved and southern coniferous forests in the Carpathians, the Crimea, the Caucasus, and the southern part of the Far East. Clay minerals and iron oxides accumulate in the profile, imparting a brown color to the soils. The soils, which range from slightly acid to acid in reaction, are rich in humus, which constitutes 6–10 percent of the upper horizon. Brown forest soils respond well to fertilizers and are used in agriculture.

Podzolic brown earth and brown forest surface gley soils. Podzolic brown earth and brown forest surface gley soils develop on comparatively poor, deeply weathered loam and clay rocks among brown forest soils. They occupy the flattest relief elements and differ from other soils in a silt-rich illuvial horizon that retains sediment, as a result of which the upper horizon is waterlogged to varying degrees. Such soils are extensively cultivated, but they must first be drained and fertilized.

Chernozem-like gleys. Chernozem-like gleys form under the meadows in the lowlands along the Amur River. They have a thick humus horizon, containing 7–8 percent humus, whose lower part is gleyed. They are waterlogged as a result of groundwater and atmospheric precipitation. They are extensively used for rice, soybeans, wheat, and potatoes and other vegetables, but they require draining.

Yellow earths. Yellow earths form under humid subtropical forests in the Western Transcaucasus and the Lenkoran’ Lowland on relatively acid parent material. They contain relatively high amounts of iron oxide, considerable silt, and 3–3.5 percent humus. They are acid in reaction. Podzolic yellow earth and waterlogged gley podzolic yellow earth soils are found along with yellow earths on the relatively poor loams and clays that occupy flat plains. All these soils are used for subtropical crops, such as tea and tung. When limed and fertilized, they produce high yields.

Red earths. The red earths, which occur in the western part of Transcaucasia, form under the same conditions as the yellow earths and differ only with respect to the parent material (primarily neutral igneous rocks). The content of humus is high, amounting to 5–6 percent in the upper horizons and gradually diminishing lower in the profile. The red earths are rich in aluminum and iron oxides and have texture and other favorable physical properties. They are used for subtropical crops but require liming and fertilization.

Sod carbonate soils. Sod carbonate soils form under forests on carbonate-rich parent material. The largest areas with such soils occur in the Baltic Region and in Leningrad, Novgorod, and Perm’ oblasts. As a result of the conditions of formation, sod carbonate soils are neutral, have a high humus content (6–15 percent) and good structure, and are often quite stony. They are used extensively in farming.

Sod gleys. Sod gleys, which are similar to sod carbonate soils, develop under the influence of hard (calcium-rich) groundwater close to the surface.

Bog soils. Bog soils occupy significant areas, primarily in Western Siberia and in the northern part of the East European Plain; they also occur in Central and Eastern Siberia and in the Far East. They remain excessively wet throughout the year. They are subdivided into peat bog soils, with a thick surface horizon of peat; peat gley bog soils, in which the peat horizon is underlain by a gleysolic mineral horizon; silt bog soils, in which the silt horizon is a mineral mass mixed with decomposed organic matter that is replaced by gleysolic mineral matter; and meadow bog soils, in which the upper soddy mineral gleysolic horizon is replaced by a mineral gleysolic horizon. The humus content reaches 30 percent. The reaction varies from acid to alkaline. Peat and peat gley bog soils are subdivided into upper types, which are very acid and extremely poor in plant nutrients; lower types, which are neutral and rich in plant nutrients; and transitional types. Drainage and cultivation, which are done primarily on peat and peat gley bog soils, make bog soils suitable for farming.

UNLEACHED SOILS. Unleached soils develop when the potential for evaporation exceeds moisture (for example, precipitation). Simple salts are not washed out of the soil profile but accumulate at a certain depth. Unleached soils are neutral or alkaline in reaction.

Arctic soils. Arctic soils (arctic deserts on the islands of the Arctic Ocean) are thin and neutral, sometimes carbonate or even salinized. They are frozen most of the year, thawing out to small depths for only one or two months.

Pale yellow frigid taiga soils. Pale yellow frigid taiga soils occur in the driest regions of the light-coniferous taiga (central part of Yakutia). The upper part of the soil profile is neutral, while the lower part is often carbonate. The upper horizons contain 2–3 percent humus. The relatively warm summers make it possible to use these soils in agriculture.

Chernozems. Chernozems formed under the steppe and forest-steppe vegetation of the southern part of the East European Plain, Western Siberia, North Kazakhstan, and the basins of the southern part of Central Siberia. They have a thick (30–140 cm), well-structured humus horizon, with 4–10 percent humus, a horizon of carbonate accumulation, and, in arid regions, a gypsum horizon. Mycelial-carbonate chernozems from the Azov and Cis-caucasian regions, which form in areas where winters are warm and the soil does not freeze, are distinguished from chernozems that develop when winter temperatures are below freezing. Depending on moisturization, chernozems are subdivided into podzolized, leached, and typical chernozems (in the forest-steppe) and into common and southern chernozems (in the steppe). They range from slightly acid to slightly alkaline in reaction. They are very fertile and almost all are in agricultural use. Their productivity is limited by frequent droughts. Irrigation makes it possible to produce sustained yields of grains, sugar beets, sunflowers, and the irrigated farming of grains, melons, and other crops.

Chestnut soils. Chestnut soils formed under dry steppe vegetation in the southern Ukraine, Lower Volga Region, Kazakhstan, and Siberia. They differ from chernozems in a lower humus content (2–5 percent), thinner humus horizon (15–50 cm), and thinner carbonate and gypsum horizons. They frequently contain solonetzes, are alkaline in reaction and compacted, and swell significantly when wet. They are subdivided into dark chestnut soils, which occur in the wetter regions; chestnut soils; and light chestnut soils, which occur in the drier regions. Much of the areas with dark chestnut and chestnut soils are cultivated. Their productivity is limited by frequent droughts, and consequently the cultivation of crops, particularly grains, vegetables, and melons, often necessitates irrigation. Light chestnut soils are used primarily for hay production and for grazing.

Brown semidesert soils. Brown semidesert soils are found in the semideserts of Kazakhstan. They contain 1.5–2.5 percent humus in the upper horizon and are frequently alkaline in reaction. Carbonates and gypsum occur close to the surface. Brown semi-desert soils are used for grazing, hay production, and the irrigated farming of grains, melons, and other crops.

Gray-brown desert soils. Gray-brown desert soils are found in Kazakhstan, Turkmenistan, Uzbekistan, and Tadzhikistan. They accumulate less than 1 percent humus. The upper layers contain carbonates, and the gypsum layer lies at depths of 20–40 cm; still deeper are chloride and sulfate salts, which are toxic to plants. As a rule, the soils are alkaline. They are used for irrigated farming (cotton, alfalfa, vegetables, fruits) and for grazing.

Cinnamon and gray-cinnamon soils and sierozems. Cinnamon and gray cinnamon soils and sierozems occur in the dry subtropical regions of the eastern part of Transcaucasia and in the submontane and foothill regions of Middle Asia. The middle part of the soil profile is rich in clay particles (the clay accumulation horizon). Cinnamon soils develop under drought-resistant woody and scrub vegetation. They are characterized by a well-structured humus horizon, a dense clay horizon, and an illuvial horizon. The humus content is 5–9 percent. Cinnamon soils are used extensively for grapes, fruits, and grains.

Gray-cinnamon soils, which are found primarily in the eastern part of Transcaucasia, formed under grassy and phryganoid (thorny scrub, subshrub, and grassy) vegetation. They are low in humus (2–4 percent) and contain carbonates in the surface layer; gypsum and easily dissolved salts occur at shallow depths. Gray-cinnamon soils are used for cotton and grains, as well as for orchards and vineyards, which require irrigation.

Sierozems form under subtropical semidesert vegetation, primarily on the submontane plains of Middle Asia. The humus horizon is light gray and contains 1.5–4.5 percent humus. Beneath it is a compacted illuvial carbonate horizon, below which is gypsum-containing bedrock; easily dissolved salts occur at depths of 1.5–2 m. The surface layer is carbonate. The accumulation of clay in sierozems is less marked than in cinnamon and gray-cinnamon soils. Large areas of sierozems, which are for cotton, fruits, and other crops, are irrigated.

Meadow chernozem, meadow chestnut, meadow brown, and meadow sierozem soils. Meadow chernozem, meadow chestnut, meadow brown, and meadow sierozem soils are found among chernozemic, chestnut, and other soils, from which they differ in higher moisture (groundwater and, less often, surface water); moreover, they are often gleysolic and sometimes have more humus. They are used extensively for forage crops, vegetables, and other crops.

Meadow soils. Meadow soils develop in areas where the groundwater is close to the surface. Two horizons are identified, the upper soddy horizon, with up to 6–10 percent humus, and the horizon that is transitional to the gleysolic bedrock. Meadow soils are used primarily for hay production and grazing; they are sometimes tilled.

Solonchaks, solonetzes, solodi, takyrs, and takyric soils. Solonchaks, solonetzes, solodi, takyrs, and takyric soils form the group of saline soils. Solonchaks contain more than 1 percent water-soluble salts in the surface layer, which is usually associated with the presence of groundwater at a shallow depth. Proper irrigation and flushing and the establishment of artificial drainage to lower groundwater level make it possible to use solonchaks in agriculture.

Table 10. Soils of the USSR (1974)
Soil types and subtypesArea(million ha)Percent of total soils
1Includes inland waters
Plains regions
Arctic and tundra soils ...............180.68.2
Gley podzolic soils, including frigid taiga soils of northern Siberia and volcanic soils ...............159.27.2
Podzolic soils proper, including frigid taiga soils of the central regions of Siberia ...............176.78.0
Sod podzolic soils, including brown forest soils ...............203.59.3
Sod carbonate and sod gley soils ...............3.90.2
Bog podzolic soils ...............88.44.0
Bog soils ...............72.23.3
Meadow steppe frigid soils ...............0.9<0.1
Gray forest soils, including gleysolic soils and gleys ...............55.52.5
Podzolized, leached and typical chernozems ...............58.82.7
Common and southern chernozems ...............82.13.7
Meadow chernozem soils ...............27.51.3
Solonetz complexes and solonetzes of the chernozem zone ...............22.61.0
Dark chestnut and chestnut soils ...............50.12.3
Light chestnut and brown semidesert soils ...............46.92.1
Meadow chestnut and meadow brown soils ...............12.00.5
Solonetz complexes and solonetzes of the chestnut and brown semidesert zones ...............65.13.0
Gray-brown desert soils, including meadow-desert soils, and solonetz complexes ...............46.32.1
Takyric soils and takyrs ...............16.66.8
Northern low-carbonate sierozems, including meadow sierozem soils ...............10.60.5
Southern sierozems, including meadow sierozem soils ...............21.31.0
Solonchaks ...............18.10.8
Gray-cinnamon and cinnamon soils, including meadow gray-cinnamon and meadow cinnamon soils ...............3.30.2
Yellow earths and red earths, including soils water-logged to various degrees ...............0.5<0.1
Floodplain (alluvial) soils ...............55.52.5
Sands, primarily desert ...............64.72.9
Gulley-ravine, primarily forest-steppe and steppe ...............7.50.3
Total ...............1,550.470.5
Mountain regions
Mountain tundra soils ...............167.57.6
Mountain meadow soils ...............15.30.7
Mountain meadow steppe soils ...............11.50.5
Mountain podzolic, mountain frigid taiga, and volcanic soils ...............380.117.4
Mountain gray forest soils ...............16.20.7
Mountain sod carbonate soils ...............1.6<0.1
Mountain brown forest soils ...............18.70.8
Mountain yellow earths ...............0.1<0.1
Mountain cinnamon soils ...............7.60.3
Mountain chernozems ...............10.50.5
Mountain chestnut soils ...............12.70.6
Mountain sierozems ...............4.90.2
High-mountain desert soils ...............5.10.2
Total ...............651.829.5
Total all soils ...............2.202.21100

Solonetzes, which are most extensive in dry steppes and semideserts, form primarily when solonchaks are desalinized. They are strongly alkaline in reaction; they are compacted when dry and swell when wet. Crops can usually be grown only after soil improvement, for example, the application of gypsum and deep cultivation.

Solodi develop primarily when solonetzes are desalinized and desolonetzized under conditions of increased surface moisture. They are found in flat, enclosed “wet” low areas amid steppe and forest-steppe soils. The upper horizons are acid. Improvement through the regulation of the water regime and alteration of the physical properties is essential for agricultural use.

Takyrs are primarily soils of the flat clay depressions of the desert zone, which are occasionally watered by flash floods and heavy rains. After the water evaporates, the surface layer of the takyr cracks to a depth of 8–10 cm, forming polyhedral parquetlike patterns. Beneath the layer is an almost unchanging saline bedrock.

Takyric soils resemble young floodplain soils and takyrs. They occupy young river plains that have only recently ceased acting as floodplains.

Floodplain (alluvial) soils. Floodplain (alluvial) soils form floodplains that are inundated by flood waters. They are stratified and frequently contain buried humus horizons. In wet regions they are noncarbonate and nonsaline and often acid in reaction, and in dry regions they are usually carbonate and neutral or alkaline in reaction. Bog soils sometimes occur among floodplain soils. Floodplain soils are fextremely fertile and are used for hay production and grazing, as well as for vegetables, forage crops, rice, and other crops.

V. M. FRIDLAND

The USSR has enormous soil resources. The most extensive areas of highly fertile chernozems and meadow chernozem soils in the world are located in the USSR, totaling 168.4 million hectares (ha), or about 8 percent of the USSR’s total soil area. The chernozems, as well as the dark chestnut, chestnut, and gray forest soils, form the basis of the country’s agricultural land. The sod podzolic soils are also of agricultural importance. Tundra, gley podzolic, and frigid taiga soils, which amount to about 340 million ha, or more than 15 percent of the total area, are not cultivated, since the heat resources in the areas where they occur are extremely inadequate for farming; the soils of mountain regions with unfavorable topography are also not used.

In semidesert and desert regions, light chestnut, brown semidesert, gray-brown, sierozem, and gray-cinnamon soils form a considerable part of the land surface, more than 270 million ha, or more than 12 percent, and agriculture without irrigation on such soils is extremely unproductive. Many soils in these regions, such as the takyric soils, takyrs, solonchaks, and solonetzes, are salinized and require other methods of improvement in addition to irrigation. Bog and waterlogged soils, which must be drained before they can be tilled, occupy more than 160 million ha, or about 8 percent. Sands and sandy and stony soils, which are also unsuitable for agriculture without expensive reclamation work, constitute more than 150 million ha. Thus, although the land suitable for agriculture is quite extensive, it constitutes a smaller proportion of the country’s total area than in many other countries. The calculation of areas of different soil types and subtypes (see Table 10) and soil zones and subzones (see Table 11) carried out by the Soil Institute provide an idea of the soil resources of the USSR and their use.

In different soil zones and subzones different proportions of the land have been brought into use. In the zone of gray forest soils and the subzones of podzolized, leached, and typical chernozems, about 48 percent of the total land has been put to agricultural use and 63 percent of the chernozems. These figures constitute the maximum possible land that can be under agricultural development here, since the area occupied by populated points, industrial enterprises, and roads, as well as unsuitable land, such as ravines, gulleys, and areas with stony soils, is quite considerable. The zones of gray forest and chestnut soils are also close to maximum use; of the total arable agricultural land in the USSR, including cropland, idle land, and land under perennial plantings, 76 percent is located in these zones and the chernozem zone owing to the high fertility of the soils in the zones, favorable topography, which permits the use of modern machinery, and the relatively favorable climate, requiring no irrigation or drainage. However, inadequate precipitation in these zones and frequent droughts make it difficult to obtain high sustained yields. There-fore, the technology of growing crops must be directed at accumulating and preserving moisture in the soil, and consequently the expansion of irrigated areas is very important.

The subzone of sod podzolic soils, which has an adequately moist climate that is cooler than the chernozem climate, is the site of a large agricultural region, which includes the Nonchernozem Zone of the European part of the USSR, the southern taiga regions of Western Siberia, and the southern part of the Far East and which accounts for 16.5 percent of the total arable land in the USSR. Sod podzolic soils are acid in reaction; they are not as rich in nutrients as gray forest, chernozem, and chestnut soils, and their physical properties are not as good. However, because of the available moisture and good responsiveness to fertilizers, it would be feasible to increase agricultural production on land areas already developed and to expand crop areas, which has been envisioned in the decree of the Central Committee of the CPSU and the Council of Ministers of the USSR On Measures for the Further Development of Agriculture in the Nonchernozem Zone of the RSFSR of March 1974. Although the subzone of sod podzolic soils has enormous areas suitable for cultivation, only 13.3 percent is currently under agricultural use, significantly less than in the chernozem zone. The chief reasons are the ruggedness of the terrain, the widespread distribution of waterlogged and bog soils, which require treatment, and the presence of significant areas of unfertile sandy soils. The complex structure of the soil cover also impedes the development of a large part of this territory.

A fairly extensive area of arable land, about 3 percent of the country’s total, is located in the dry subtropics, the zone of southern sierozems and gray cinnamon soils. The sierozems and gray-cinnamon soils are rich in all nutrients except nitrogen, have fairly good physical properties, are generally found on plains, and are for the most part irrigated, which makes it possible to grow heat-loving crops, such as cotton, rice, and valuable fruits. The soils in these regions are subject to salinization and some have been salinized. Irrigation systems with drainage runoff networks have been constructed to control salinization, and flushing and proper irrigation schedules have been instituted.

During the years of Soviet power, the use of arable land has been improved and vast areas have been brought into agricultural use. The area under cultivation in Russia (within current boundaries) amounted to 118.2 million ha in 1913, whereas in the USSR it rose to 150.6 million in 1940, 209.1 million ha in 1965, and 217.7 million ha in 1975. The development of virgin and idle lands in the period 1954–60 increased the area of arable lands, including planted areas; these lands are primarily located in the steppe and forest-steppe zones with chernozem, chestnut, and gray forest soils, mostly in the eastern parts of the country (Siberia, Kazakhstan, the Urals, and the Volga Region), primarily for the production of grains. (See below:: Agriculture.)

Irrigation and drainage are of great importance for improving the productivity of various kinds of soils. The area of irrigated land, which totaled 4 million ha in 1913, rose to 8.1 million ha in 1940, 9.9 million ha in 1965, and 14.5 million ha in 1975. Most such lands are located in the semidesert and desert zones with sierozems, gray cinnamon soils, and other soils. The steppe, forest-steppe, and forest zones account for an insignificant share of irrigated farming (not more than 15 percent of all the country’s irrigated lands), but this share has been steadily increasing every year in connection with the construction of vast irrigation systems in the southern Ukraine, the Volga Region, the Northern Caucasus, and elsewhere. The total area of drained land in the USSR was 5.5 million ha in 1940, 10.6 million ha in 1965, and 13.7 million ha in 1975, compared to 3.2 million ha in 1913. Most of the drained lands are located in the subzone of sod podzolic soils: peat-bog, bog podzolic, and other soils. About one-half of the drained lands at kolkhozes, sovkhozes, and other state enterprises have enclosed drainage. A significant expansion of drainage and irrigation is planned for the future, as well as the introduction of measures to improve salinized, solonetz, and acid soils.

The control of water and wind erosion is an important problem in soil improvement. Approximately 30–35 million ha of arable land are subjected to varying degrees of destructive action by erosion. Recultivation—the restoration of the soil cover of unused mines, peat bogs, and the like—is becoming increasingly important. A great deal of attention is being devoted to the protection

Table 11. Agricultural use of soils1 (1974)
Soil zones and subzonesTotal area (million ha)Arable land, idle land, and perennial plantingsHayfieldsPastoresTotal agricultural lands
  million hapercentmillion hapercentmillion hapercentmillion hapercent
1 Excluding privategarden plots
Plains regions
Zone of tundra arctic soils ...............180.6
Subzone of gley podzolic soils ...............224.2<0.1<0.1<0.1
Subzone of podzolic soils proper ...............238.90.30.11.50.61.30.53.11.2
Subzone of sod podzolic soils ...............277.537.013.315.45.614.95.267.324.1
Zone of gray forest soils and subzones of podzolized, leached, and typical chernozems ...............145.669.747.812.58.618.812.9101.069.3
Subzones of common and southern chernozems ...............120.570.558.77.26.024.520.3102.285.0
Subzones of dark chestnut and chestnut soils ...............82.327.833.83.44.138.847.170.085.0
Subzones of light chestnut and brown semidesert soils ...............118.84.63.83.83.287.473.295.880.2
Zone of gray-brown desert soils ...............115.91.00.90.50.486.975.288.476.5
Zone of foothill northern sierozems ...............12.83.225.10.43.17.860.911.489.1
Zone of foothill southern sierozems ...............29.25.619.20.20.716.958.022.777.9
Zone of cinnamon and gray cinnamon soils ...............3.60.822.30.11.130.61.952.9
Zone of yellow earths and red earths ...............0.90.111.1<0.10.111.10.222.2
Total ...............1,550.4220.614.244.93.2298.519.1564.036.5
Mountain regions
Zone of mountain tundra soils ...............165.4
Zones of mountain meadow and mountain meadow steppe soils ...............27.30.62.26.022.06.624.2
Zones of mountain podzolic, mountain frigid taiga, volcanic, and gray forest soils ...............400.30.40.10.30.18.02.08.72.2
Zone of mountain brown forest soils ...............18.01.68.90.20.12.011.03.821.0
Zones of mountain chernozems, chestnut and cinnamon soils and sierozems ...............35.72.26.10.61.77.520.110.327.9
Zone of high-mountain desert soils ...............5.10.12.00.24.02.651.12.957.1
Total ...............651.84.30.71.90.326.14.032.35.0
Total soil area ...............2,202.2224.910.246.82.1324.614.8596.327.2

of soil resources against contamination by pesticides and industrial wastes. The use of soil resources is regulated by the Basic Principles of Land Legislation of the USSR and the Union Republics (1968). Increasing the productivity of cultivated lands is the most important task of land use.

V. M. FRIDLAND

Bibliography

Dokuchaev, V. V. “Uchenie o zonakh prirody i klassifikatsiia pochv.” Soch., vol. 6. Moscow-Leningrad, 1951.
Rozov, N. N. “Razvitie ucheniia V. V. Dokuchaeva o zonal’nosti pochv v sovremennyi period.” Izv. AN SSSR: Ser. geografii, 1954. no. 4.
Fridland, V. M. “K voprosu o faktorakh zonal’nosti.” Izv. AN SSSR: Ser. geografii, 1959, no. 5.
Fridland, V. M. Struktura pochvennogo pokrova. Moscow, 1972.
Kovda, V. A. Osnovy ucheniia o pochvakh, vols. 1–2. Moscow, 1973.
Atlas pochv SSSR. Edited by I. S. Kaurichev and I. D. Gromyko. Moscow, 1974.
Liverovskii, Iu. A. Pochvy SSSR. Moscow, 1974.
Prirodno-sel’skokhoziaistvennoe raionirovanie zemel’nogo fonda SSSR. Moscow, 1975.

The flora of the USSR is extremely diverse and rich in the number of plant species, especially in the southern mountain regions. All of the USSR lies in the Holarctic floristic region (kingdom), the earth’s northernmost floristic region.

The fundamental regularities of plant distribution are associated with many factors, principally with the distribution of heat and moisture, and it is this that has determined the formation of the various geobotanical regions (or zones, in the broad sense of the word). Most of the regions extend latitudinally, but a few, such as the European and Far Eastern broad-leaved regions, located in the oceanic parts of the continent, extend longitudinally or diagonally. However, even in the latitudinal geobotanical regions there are certain differences in the composition and structure of the vegetation owing to changes in climate from west to east, as a result of which geobotanical subregions, provinces, and the like have been identified. In mountain systems, vertical vegetation zonation is observed. Moreover, a specific type (or closely allied types) of vegetation zonation has developed in each geobotanical region. Other ecological factors, the history of the plant cover, and the effects of man’s economic activities have also greatly influenced the composition and structure of the vegetation.

Continental glaciers (ice sheets) and extensive mountain glaciers, which advanced and retreated several times during the Anthropogene, have played an enormous role in the formation of the vegetation. As a result of the glacial advances, all the vegetation under the ice cover was completely destroyed, and extensive areas of permafrost were formed in the periglacial zone, where tundras developed, as well as unique cryoxerophytic periglacial steppes and, in some places, sparse forests of birch, larch, and pine. Older vegetation of various types, including forests, was preserved during the glacial periods mainly in the southern part of the USSR, while heat-loving plants were preserved in the shelter of the mountains of Middle Asia and Transcaucasia.

High-arctic polar-desert region. The high-arctic polar-desert region occupies the areas of the northernmost islands of the Arctic Ocean that are not covered with glaciers; in the continental USSR it occupies only the extreme north of the Taimyr Peninsula. Vegetation is either absent or poorly developed on aggregations of large rocks and gravel; 20 to 30 percent of the fine-earth substrate, which is broken by frost cracks, is covered with crustose lichens, algae, and liverworts. Flowering plants are found in fissures between the stony polygons and in some depressions, where snow accumulates, as well as mosses and fruticose lichens, which occupy 10 to 15 percent of the entire surface.

Arctic tundra region. The arctic tundra region occupies a more or less narrow band in the north of the continent, as well as a few southern islands of the Arctic Ocean. The vegetation here is characteristically treeless, mainly because of insufficient warmth, and is represented by a cover of ground mosses (Bryales, such as Hylocomium, Aulacomnium, Tomenthypnum, Rhacomitrium, and Rhytidium, as well as Polytrichum and Sphagnum) or lichens (mainly fruticose lichens, such as Cladonia, Cetraria, and Alectoria, which predominate mainly on light and stony soils). In the tundra a stratum of dwarf shrubs and perennial herbaceous plants is also developed. Bogs, mainly hummocky ones, occupy a large area.

The characteristics of the plant cover in the tundra zone change substantially from north to south. The northernmost strip of the arctic tundra (transitional to the high-arctic deserts) is characterized by herbaceous-dwarf-shrub-moss and dwarf-shrub-lichen covers. Dwarf shrubs include mountain avens (in the west Dryas octopetala, and in the east, Dryas punctata and others) and willows (Salix polaris, Salix nummularia, and Salix reptans). Herbaceous plants include arctic and arcto-alpine species. Next is a strip of northern, or typical (moss-lichen), tundras, which differ from the preceding strip by the presence of a number of hypoarctic species, such as Eriophorum vaginatum, which form hummocky tundras east of the Lena River. Crowberry (Empetrum hermaphroditum), cloudberry (Rubus chamaemorus), and other such plants grow in places. The strip of southern, or shrub, tundras is characterized by a marked shrub stratum, consisting of dwarf birches (Betula nana in Europe and Western Siberia and Betula exilis in Eastern Siberia) and willows (Salix lanata, Salix glauca, Salix pulchra), and by a herbaceous-dwarf-shrub stratum, composed of mountain cranberry (Vaccinium vitis-idaea), the crowberry, and other plants. Marsh tea (Ledum palustre) occurs occasionally. The southernmost strip—the forest tundra, or subtundra sparse forests—is characterized by sparse-forest communities combined with large dwarf-birch tundras in the level divide areas (placors); hypoarctic and taiga species predominate. In the European part the sparse forests of the tree stratum are dominated by the birch Betula tortuosa and Siberian spruce (Picea obovata); in Western Siberia, by Siberian larch (Larix sibirica); and in Eastern Siberia, by the dahurian larch (Larix gmelina).

Northern Pacific tall-herb small-leaved forest low-mountain tundraregion. This region, which is marked by a cold, humid climate, occupies Kamchatka and the northern and middle Kuril and Komandorskie islands. It is characterized by forests with sparse stands of the birch Betula ermanii, usually with a heavy tall-herb cover consisting of the hellebore Veratrum oxysepalum, the meadowsweet Filipendula camtschatica, the angelica Angelica ursina, the cow parsnip Heracleum dulce, and the thistle Cirsium camtschaticum. High-altitude shrubs, such as the dwarf stone pine (Pinus pumila) and the alder Alnus camtschatica, often grow down to sea level. Coniferous forests of Yeddo spruce (Picea jezoensis) and dahurian larch are found only in the valley of the Kamchatka River, which is surrounded by mountains on the west, east, and south.

Northern European-Siberian taiga (coniferous-forest) region. The northern European-Siberian taiga region, which extends from the Baltic Sea basin to the Sea of Okhotsk, occupies about one-half of the USSR. Forests dominated by mesophilic coniferous trees prevail, including both evergreen species—spruce, fir, and pine—and deciduous species—larch. Dwarf shrubs and herbs include the mountain cranberry (Vaccinium vitis-idaea), the bilberry (Vaccinium myrtillus), the bearberry (Arctostaphylos uva-ursi), the twinflower (Linnaea borealis), and various ferns, such as Dryopteris lanceolatocristata, Gymnocarpium dryopteris, and Phegopteris connectilis. The ground cover consists of Bryales, mainly Pleurozium schreberi, Hylocomium splendens, and Dicranum polysetum, on light soils in pine forests. In the northern taiga and in other coniferous forests it consists of various lichens of the genera Cladonia and Cetraria, and in marshy forests, of various species of Polytrichum and Sphagnum. Upland sphagnum bogs often form large massifs; extensive areas of the Western Siberian Lowland are covered with bogs.

In the northern part of the European USSR and in Western Siberia east of the Enisei River, the Enisei Ridge, and the Saian Mountains (where the forests are mountainous), dark-coniferous forests of spruce, fir, and nut pines predominate, including the Norway spruce (Picea abies), the Siberian spruce (Picea obovata), the Siberian fir (Abies sibirica), and the Siberian stone pine (Pinus sibirica). In some places, especially in the north, there is an admixture of Siberian larch; on light soils there are pine forests of Scotch pine (Pinus sylvestris). Birch forests grow on sites of felled trees and fires, and such forests now prevail in many regions. Larch forests are predominant east of the Enisei River: dahurian larch in the northern part of Central Siberia and in Eastern Siberia and Siberian larch (Larix sibirica) in the southern part of Central Siberia (intermixed with Scotch pine in the south). The vast expanses of Central and Eastern Siberia, dominated by larch forests, are underlain by permafrost. Small, individual communities of the Central Asian (Mongolian) type are occasionally found in the easternmost continental part of the taiga region in the far northeast—in the central part of the Lena River basin (in the vicinity of the city of Yakutsk) and along the upper reaches of the lana, Indigirka, and Kolyma rivers.

In the Far East, in the basin of the lower and partly the middle Amur River, as well as in the central and southern parts of Sakhalin and in the southernmost Kuril Islands, large areas are occupied by dark coniferous, mainly mountainous, forests of Yeddo spruce and the firs Abies nephrolepis and Abies sachalinensis, which in the south are intermixed with Far Eastern broad-leaved trees and shrubs. In the mountains of the taiga region, coniferous forests cover the lower and middle elevations of the mountains. Higher up is a belt of low-growing high-altitude shrubs, for example, dwarf species of birch, and, in Eastern Siberia, dwarf stone pine. In the Far East there are thickets of Betula ermanii above the belt of coniferous forests, while the high-altitude zone is occupied by mountain tundras (bald mountains).

The species composition and structure of the taiga forests change from north to south. The northern taiga is characterized by sparse stands of trees. The underbrush consists of low-growing shrubs similar to the ones growing in the tundras, for example, the dwarf birch and the birch Betula exilis. The herbaceous-dwarf-shrub stratum has taiga and a few arctic species, including mountain cranberry and bilberry. The ground cover of mosses and lichens is well developed.

In the central taiga, the tree stand is denser and is characterized by a medium or high site index. Shrubs are usually absent, and there are no arctic species in the herbaceous-dwarf shrub stratum. The moss cover of Bryales is well developed, while lichens occur only in the pine forests.

In the southern taiga the tree stand is also dense and is characterized by a middle or high site index. In addition to mountain cranberry and bilberry, the herbaceous-dwarf-shrub stratum also includes the European wood sorrel (Oxalis acetosella). The ground cover here is less well developed than in the central taiga. In the southern taiga forests of the European USSR and the Far East, there are several herbaceous species that are characteristic mainly of broad-leaved forests, while in Southern Siberia, in the pine and larch forests, there is a herbaceous cover of forest species, as well as occasional meadow-steppe species.

In the extreme south of the taiga region in the European USSR and in the Far East, there is a strip of mixed broad-leaved and coniferous forests, with broad-leaved trees in the tree and shrub strata and with plants characteristic of oak forests in the herbaceous-dwarf-shrub stratum. The moss and lichen ground cover is less marked than in the more northerly strips. In Western Siberia, south of the southern dark-coniferous taiga strip, there is a narrow band of aspen-birch forests, consisting of the European, or silver, birch (Betula pendula), the downy birch (Betula pubescens), and the aspen (Populus tremula).

Far Eastern broad-leaved forest region. The Far Eastern broad-leaved forest region is represented in the USSR only by its northernmost part, a narrow strip in the basin of the middle Amur; the greater part of it lies in adjacent foreign regions of Asia. The region, as well as the neighboring dark-coniferous forest region to the north, is under the influence of a monsoon climate. Its flora is extremely rich, especially in the diversity of tree and shrub species. Broad-leaved forests predominate on the plains and in the lower mountain elevations; in the USSR they consist mainly of the Mongolian oak (Quercus mongolica) and the hornbeam (Carpinus cordata), as well as of such lindens as Tilia amurensis, several species of maple, and other trees. Above the broad-leaved forest belt are mixed cedar and broad-leaved forests, in which the dominant conifers are the Korean pine (Pinus koraiensis) and the fir Abies holophylla. In the broad-leaved forests and especially in the mixed forests, woody lianas abound: the Chinese magnolia vine (Schizandra chinensis), the Amur grape (Vitis amurensis), and several species of Actinidia. Still higher is a zone of dark-coniferous forests (Yeddo spruce and fir), which give way at the mountain summits to low-growing forests of Betula ermanii. In the southern part of the Sikhote-Alin’ Mountains, near the timberline, there are thickets of the coniferous creeping shrub Microbiota decussata, growing on rock streams.

European broad-leaved forest region. The European broad-leaved forest region encompasses the Carpathian Region and the Carpathian Mountains and extends eastward in a narrow strip to the western slopes of the Southern Urals, encompassing the Poles’e. In the south it extends to the mountains of the Crimea, the Greater Caucasus, and the Rioni Lowland (Colchis Lowland) and partly encompasses the mountainous regions of the Lesser Caucasus. Most of the European broad-leaved forest region is in Western Europe; it extends into the USSR in two narrow wedges. In the northern strip there are few tree species, especially in the east. In the Carpathian Region and on the Podol’e Upland, the Central European durmast oak (Quercus petrea) still covers considerable areas, but the greater part is dominated by the English oak (Quercus robur). The European hornbeam (Carpinus betulus) grows as far as the left bank of the Dnieper River, while the European ash (Fraxinus excelsior) grows almost as far as the right bank of the Volga. The littleleaf linden (Tilia cordata), Scotch elm (Ulmus glabra), and various maples, mainly the Norway maple (Acer platanoides), also grow in the oak forests. The European hazel (Corylus avellana) and other trees are common in the underbrush. Oak forests occupy the Podol’e Upland and the foothills of the Carpathians. Higher up are forests of European beech (Fagus sylvatica), followed by a belt of coniferous forests of spruce and fir, including the Norway spruce and the common silver fir (Abies alba). Higher still is a zone of subalpine dwarf shrubs, mainly Swiss mountain pine (Pinus mugo), and thickets of scrub alder—Alnus viridis. The mountain summits are occupied by alpine meadows; the herbaceous communities are for the most part secondary, having arisen on the site of destroyed forests.

In the southern strip of the European broad-leaved region, which encompasses the Caucasus and the mountains of the Crimea, the species composition is richer. Here too there is a predominance of oak forests, consisting of Quercus iberica and, in some places, of Quercus pedunculifera; growing on the northern slopes of the Greater Caucasus and in the mountains of the Crimea are the English oak, the durmast oak, and Quercus pubescens; above this is a zone of oriental beech (Fagus orientalis).

The vegetation of western Transcaucasia, where precipitation is abundant, is unique. Here, in the low mountain elevations and on the submontane plains, there are mixed broad-leaved forests of Spanish chestnut (Castanea sativa), oriental beech, and various oaks, including Quercus iberica and Quercus hartwissiana; evergreens often occur in the underbrush, for example, Laurocerasus officinalis and Rhododendron ponticum. The next higher level consists of beech forests, in some places with an evergreen underbrush of similar composition. Still higher is a zone of dark-coniferous forests of fir and spruce, such as the Nordmann fir (Abies nordmanniana) and the oriental spruce (Picea orientalis), with an admixture of broad-leaved species, for example, beech; evergreen underbrush is sometimes encountered in the more westerly regions. Elfin woodland of beech or birch forms the upper boundary of the forest. In the subalpine zone are thickets of tall herbs and Caucasian rhododendron (Rhododendron caucasicum), with savin (Juniperus sabina) occurring in the drier regions. The alpine zone of the mountains of the Caucasus is occupied by low-herb meadows rich in species composition.

The mountains of the Crimea are dominated by oak forests of European species, such as the durmast oak and Quercus pubescens; in some places there are forests of oriental beech. On the southern slopes of the Crimean Mountains, as well as on the northwestern part of the southern slopes of the Greater Caucasus, there are sylvan Mediterranean and sub-Mediterranean species of pine—Pinus pallasiana—as well as the spiny Greek juniper (Juniperus excelsa). The pine Pinus pityusa occurs in the Caucasus.

Eurasian steppe region. The Eurasian steppe region extends latitudinally in the interior of the continent within the temperate zone from the lower reaches of the Danube to the interior of Tungpei in the People’s Republic of China; in the USSR it is represented mainly in the southern European part of the country, in Western Siberia, and in northern Kazakhstan. It is characterized by the prevalence of perennial caespitose xerophilic herbaceous plants, mainly caespitose grasses of the genera Stipa, Festuca, Koeleria, and, more rarely, Carex (Carex pediformis and Carex humilis) and Allium (chiefly in Mongolia). The composition and structure of the plant communities change from west to east. Thus, in the Black Sea and Kazakhstan steppes there is a predominance of large feather grasses, such as Stipa zalesskii, Stipa ucrainica, and Stipa lessingiana, while the capillary feather grasses, such as Stipa capillata and Stipa sareptana, are less important; Festuca valesiaca and allied species are ubiquitous. In the Central Asian type steppes, which in the USSR occur in Transbaikalia (the island steppes of the upper Enisei), such capillary feather grasses as Stipa krylovii and Stipa baicalensis predominate. Various fescues, primarily Festuca lenensis, are distributed in the more northerly, mainly meadow, steppes; Cleistogenes squarrosa is characteristic. Owing to a relatively warm and wet spring, various ephemeroids develop in the spring and early summer on the Black Sea and Kazakhstan steppes, such as the bulbous bluegrass (Poa bulbosa), various species of Gagea, tulips (Tulipa schrenkii and Tulipa patens), and Rindera tetraspis, as well as various ephemerals, such as several species of the genus Bromus, Ceratocephala testiculata, Erophila verna, and Alyssum desertorum. Owing to cold, dry springs, there are few ephemeroids and ephemerals in the Central Asian steppes, but in wetter years long-vegetating (from spring to autumn) annual and biennial plants are abundant, especially wormwoods, including Artemisia scoparia, Artemisia pectinata, and Artemisia palustris.

In the steppe region changes in the species composition are observed from north to south, as well as changes in populations of various life forms. The drought resistance of plant species increases, and the number of species of ephemeroids and ephemerals increases. As a result, the steppe region is divided into four major latitudinal strips. The meadow steppes have species characteristic of meadows, such as Agropyron (quack grass); the principal feather grass is Stipa pennata. The arid forb caespitose grass steppes are characterized by steppe forb, which resembles that of the meadow steppes; the principal feather grass is Stipa zalesskii, with Stipa ucrainica occurring occasionally in the west. In the arid caespitose grass steppes, the role of steppe forb decreases, and the principal species of feather grass is Stipa lessingiana. The desert, subshrub caespitose grass steppes are dominated by steppe caespitose grasses—Stipa sareptana. Stipa lessingiana also occurs in the north, but subshrubs are also important: wormwood, such as Artemisia lercheana and Artemisia gracilescens, and some saltwort species, for example. Anabasis salsa. Forests occur in the level divide areas in the meadow-steppe strip—oak forests in the European part and birch forests in the southern part of Western Siberia.

In the steppes of Transbaikalia, which resemble the Central Asian steppes in composition, structure, and phenological rhythms of development, there is a predominance of meadow steppes, in which, in addition to capillary feather grasses and Festuca lenensis, a large role is often played by Tanacetum (tansy) of the family Compositae. Also represented in Transbaikalia are forb, capillary feather-grass steppes and partially arid capillary feather-grass steppes with an abundance of Cleistogenes squarrosa.

Sahara-Gobi (Afro-Asiatic) desert region. The Sahara-Gobi desert region extends in the USSR from the Western Caspian Region (including the eastern part of Transcaucasia) to the borders of the People’s Republic of China. It is characterized by a predominance of subshrub, shrub, and treelike species, including saltworts, saxaul, Anabasis, and Ceratoides. In the USSR the northern part of the region is located in the temperate climatic zone, while the southern part is in the subtropical zone.

Three latitudinal strips may be distinguished within the desert region: the northern deserts, the typical deserts, and the southern deserts. In the northern, or steppelike, deserts, which border on the steppe region in the north, there is a predominance of sub-shrub wormwoods similar to those of the desert steppes (Artemisia lercheana, Artemisia gracilescens, Artemisia pauci-flora) or typically desert wormwoods (for example, Artemisia terrae-albae), as well as desert subshrub saltworts (Anabasis salsa, Salsola arbusculiformis) and steppe caespitose grasses, including fescue (Festuca valesiaca) and feather grass (Stipa sareptana, Stipa richteriana).

In the typical deserts, there is a predominance of subshrubs similar to those of the steppe deserts, but there are no steppe caespitose grasses (they appear only on light soils).

In the southern deserts, which are confined to the southern part of the Turan Lowland and the eastern part of Transcaucasia, ephemeroids and ephemerals are developed—Poa bulbosa and Carex pachystylis; Carex physodes grows on sand in thickets of saxaul and Calligonium. The most common desert subshrubs are Artemisia fragrans, Salsola dendroides, Salsola nodulosa, and Salsola ericoides in Transcaucasia and numerous wormwoods, such as Artemisia turanica, Artemisia kemrudica, and Artemisia badhysi, and various saltworts, including Salsola gemmascens and Salsola arbuscula, in the southern part of Middle Asia. On the sands of southern Kazakhstan and Middle Asia are thickets of saxaul (Haloxylon ammodendron, Haloxylon persicum) and many species of Calligonium.

The plant cover of the mountain systems within the desert zone (in the southern and eastern parts of Transcaucasia, in Kazakhstan, and in Middle Asia) is diverse. It is here that more than one-half of all the species of higher plants in the USSR are found. The common features of all the mountainous areas are poor forestation or the complete absence of forests (in many areas the forests have been destroyed by man) and the general xerophilic nature of the vegetation. In the lower elevations in the eastern and southern parts of Transcaucasia, mats of Andropogon (beardgrass) are common. In the middle and some lower mountain elevations, there are caespitose grass steppes, similar to the steppes of the European USSR. On the rocky slopes there are communities of mountain xerophytes—mats of tragacanths (thorny subshrub species of Astragalus) and thyme (xerophilic subshrubs, especially of the family Labiatae). In some places of this zone, there are xerophilic sparse forests (to a considerable degree already destroyed) of treelike junipers, such as Juniperus foetidissima, and Juniperus polycarpos, and pistacias, for example, Pistacia mutica. Oak forests have been preserved in some places. In the southeastern part of Transcaucasia, in Talysh, there are forests with a predominance of chestnut-leaf oak (Quercus castaneifolia), oriental beech, and, in some places, Persian parrotia (Parrotia persica).

In the Dzungarian Alatau and in the northern and central Tien-Shan, in the lower and middle elevations, the landscape is dominated by caespitose grass and meadow steppes, similar to the steppes of northern Kazakhstan; shrub thickets occur in places. In the upper part of the middle-altitude belt there are massifs of mountain forests of Schrenk’s spruce (Picea schrenkiana). In the lower part of the high-altitude belt are sparse thickets of Juniperus turkestanica and high-altitude steppes and meadows; the latter include communities of Cobresia of the family Cyperaceae, which are especially characteristic of the central Tien-Shan.

In the western Gissar-Alai, the southern Tien-Shan, the western Pamirs, and the Kopetdag and on the submontane plains and low foothills (adyry) there are ephemeroid communities of bulbous bluegrass and the sedge Carex pachystylis, together with other ephemeroids, numerous ephemerals, and, sometimes, subshrub wormwood of the subgenus Seriphidium. The higher foothills and the lower parts of the middle-altitude belt are occupied by communities of tall, ephemeroid herbs, such as Elytrigia trichophora and Hordeum bulbosum. Similar communities are sometimes called semisavannas. Sparse forests of Pistacia vera have been preserved in some places at low elevations. The middle-altitude mountain belt is characterized by a combination of semisavanna, middle-altitude meadows, shrub thickets of various species of dog roses, almonds, and other plants, and occasional sparse juniper forests (Juniperus semiglobosa, Juniperus seravschanica). There are also communities of tragacanths (thorny xerophilic dwarf shrubs of the genera Astragalus, Onobryhis, and Acantholimon), especially on rocky slopes, as well as thyme mats and communities of herbaceous thorny Cousinia. True forests (of walnut, maple, and wild species of apple) are found rarely and then only in areas with greater precipitation, mainly on the northern slopes. In the high-altitude belt there are high-mountain steppes, meadows, and tragacanth mats, and in the lower elevations, sparse thickets of the prostrate shrub Juniperus turkestanica.

As a result of man’s economic activities, areas formerly occupied by forests have declined sharply. The eastern Pamirs are part of the Central Asian desert subregion and are dominated by high-altitude deserts of Eurotia ceratoides (or Ceratoides latens), Artemisia rhodantha, and Ajania tibetica.

The natural plant cover of the USSR has been altered considerably by the economic activities of man. Enormous areas of the steppes and many formerly wooded areas have been replaced by field crops. The forests of the European part of the USSR are no longer dominated by coniferous trees but by small-leaved species, such as birch and aspen. As a result of intensive cattle grazing, the vegetation of pasturelands has also been considerably altered.

The natural vegetation of the USSR is of great importance to the national economy (see below: Plant resources). The natural plant cover, formed over the course of countless centuries, is vital to the stability of the biosphere. Natural vegetation, which consists mainly of perennial plants, creates a gaseous composition of the atmosphere suitable for all living organisms, stabilizes the topography, and plays a major role in water conservation and in soil and wind protection. The plant cover is an important healthful factor and helps satisfy man’s cultural and aesthetic requirements. Natural vegetation should be regarded with care. In using it for the national economy, it is important to take into account the entire diversity of the complex relationships existing in living nature as a result of a long evolutionary process (see below: Conservation).

E. M. LAVRENKO

Bibliography

Pavlov, N. V. Botanicheskaia geografiia SSSR. Alma-Ata, 1948.
Alekhin, V. V. Rastitel’nost’ SSSR v osnovnykh zonakh, 2nd ed. Moscow, 1951.
Flora SSSR, vols. 1–30. Moscow-Leningrad, 1934–64.
Rastitel’nyi pokrov SSSR: Poiasnitel’nyi tekst k “Geobotanicheskoi karte SSSR” m. 1:4,000,000, parts 1–2. Moscow-Leningrad, 1956.
Cherepanov, S. K. Svod dopolnenii i izmenenii k “Flore SSSR,” (vols. 1–30). Leningrad, 1973.

Plant resources—the flora and the varied plains and mountain (zonal and intrazonal) vegetation—constitute part of the natural wealth of the USSR. The role of food and forage plants, which serve as a raw material in industry and the production of medicinal preparations, is very important.

Twenty thousand species of higher plants grow in the USSR, including Angiospermae (flowering plants), Equisotophyta (horsetails), Lycopodium (club mosses), and Polypodiophyta (ferns), as well as 15,000 to 20,000 species of mosses, which are widely distributed throughout the country (in forests, bogs, and tundras). Areas that are richest in plant species are Middle Asia (7,000 species), the Caucasus (6,000), the Crimea (2,000), and the Far East (1,900 to 2,000). The flora of the arctic islands of Siberia is the poorest, numbering no more than 100 to 150 species. The USSR has no less than 50,000 species of lower plants, including 10,000 species of algae, 5,000 species of lichens, and about 35,000 species of fungi. Thus, the total flora of the USSR comprises 90,000 to 100,000 species, excluding bacteria and actinomycetes.

Forests. Of the greatest economic significance are the forests, which are the source of hard and soft woods (for lumber and wood products) and raw material for the pulp and paper, hydrolysis, wood-chemical, and other branches of industry. Forests also serve as the habitat of many commercially useful animals. The area covered by forests (according to data compiled Jan. 1, 1978) is 791.6 million hectares (ha), which amounts to 35.6 percent of the country’s total area. The total lumber reserves are 84 billion cu m. Coniferous forests yield the largest quantity of lumber (80 percent). The most widespread tree species are larch (265 million ha), pine (115 million ha), Siberian stone pine (40 million ha), and spruce (77 million ha). Most of the forests occur in Siberia, the Far East, and the northern part of the European USSR; the forest wealth is unevenly distributed among the Soviet republics (see Table 12). Moreover, forests are the source of various secondary products—succulent fruits (wild apples, cherry plums, cornelian cherries, and pears), berries (blueberries, mountain cranberries, raspberries), and nuts (filberts, walnuts, and pine nuts), which amount to at least 11 million tons a year. Annual reserves of edible fungi do not exceed 4 to 5 million tons, which constitutes only a small percentage of the potential mushroom production.

Table 12. Forest resources of the USSR1
 Area covered with forestPercent of forested area
 Total (million ha)Per capita (ha) 
1 According to data from inventory of timber stock on Jan. 1,1978
USSR ...............791.63.0235.6
RSFSR ...............749.55.4543,9
Ukrainian SSR ...............8.30.1713.8
Byelorussian SSR ...............720.7534.5
Uzbek SSR ...............2.40.165.3
Kazakh SSR ...............900.613.3
Georgian SSR ...............2.70.5438.6
Azerbaijan SSR ...............0.90.1510.5
Lithuanian SSR ...............1.80.5327.6
Moldavian SSR ...............0.30.088.0
Latvian SSR ...............2.61.0340.7
Kirghiz SSR ...............0.70.203.5
Tadzhik SSR ...............0.40.113.6
Armenian SSR ...............0.30.109.9
Turkmen SSR ...............3.81.387.9
Estonian SSR ...............1.71.1638.4

Hayfields and pastures. Hayfields and pastures, which yield substantial quantities of phytomass for cattle fodder, are economically important. Approximately 10,000 species of plants, which produce 77 to 78 percent of raw fodder, grow in hayfields and pastures, mainly cereal grasses, legumes, and forbs, which grow on meadows and steppes; wormwoods and saltworts grow in the semideserts. In 1975 the natural pastures of the USSR (in all categories of farms) occupied 329 million ha. In addition, there were 334 million ha of reindeer pasture.

Pastures account for a considerable part of the total agricultural lands in Turkmenia (about 97 percent), Uzbekistan (84 percent), Kirghizia (84 percent), Kazakhstan (81 percent), Tadzhikistan (about 79 percent), and Latvia (24.6 percent). In the Ukraine, Lithuania, Byelorussia, and Moldavia and in the central regions of the RSFSR, they account for 10 to 20 percent of all agricultural lands. Irrigated hay-producing meadows have the highest yields of phytomass. On farms in Middle Asia and the Caucasus, winter pastures (wormwood deserts) and summer pastures (alpine and subalpine meadows), which serve as the basis for transhumant stock raising, are of great importance.

Medicinal and industrial plants. About 400 species of medicinal plants grow in the USSR, about 150 wild species are gathered, from which about 20,000 tons of raw material are obtained annually containing various compounds used in medicine. Up to 150,000 tons of tanbark is gathered yearly from spruce and willow and partly from oak for the production of tanning extracts. Good results have been obtained from plantings of root tanning plants (knotweed) and herbaceous tanning agents (cranesbill), which contain 12 to 30 percent tannins. Some plants produce resins, swelling and soluble gums, dye pigments, essential oils, and many other substances used in various branches of industry and technology. However, as a result of the intensive development of chemistry, the role of plants in these industries is gradually decreasing. Thus, rubber-bearing plants, gutta-percha plants, and some others have lost their importance.

Aquatic plants. The seas of the USSR are rich in marine plants, with macrophyte reserves amounting to 22 million tons (actual production, about 70 million tons). The northern seas of the USSR total 277 species of plant organisms. Vegetation is sparse in the arctic-desert zone, consisting of mosses and lichens. In the tidal zones of the White and Barents seas, as well as in the sublittoral zones, macrophytes are well developed; the total reserves of vegetation in these seas amount to more than 2 million tons. In the southern seas of the USSR, vegetation is represented by 291 species of algae and ten species of herbaceous plants; the Black Sea, with 278 species, is the richest. Confervoid algae and herbaceous plants are developed in the Sea of Azov and the Caspian Sea; total reserves amount to more than 10 million tons. The seas of the Far East contain as many as 550 species of algae and 15 species of herbaceous plants.

Some species of algae are used to obtain agar, iodine, and food products (sea kale); they are also used as fodder for cattle and as fertilizers. Research is being conducted on the use of algae, such as Chlorella and Scenedesmus, in the life-support systems of spacecraft.

Cultivated plants. Cultivated plants, which supply the principal food products for the population and the industrial raw materials for the food industry and light industry, constitute a considerable part of the plant resources of the USSR. Numerous plants of the natural flora possess many economically valuable features and consequently are important for improving the cultivated flora. (For measures to protect natural plant resources, see below: Conservation.)

AL. A. FEDOROV

Bibliography

Pavlov, N. V. Dikiepoleznye i tekhnicheskie rasteniia SSSR. Moscow, 1942.
Kormovye rasteniia senokosov i pastbishch SSSR, vols. 1–3. Edited by I. V. Larin. Moscow-Leningrad, 1950–56.
Rastitel’noe syr’e SSSR. vols. 1–2 (handbook). Moscow-Leningrad, 1950–57.
Sostoianie i perspektivy izucheniia rastitel’nykh resursov SSSR. Moscow-Leningrad, 1958.
Atlas lekarstvennykh rastenii SSSR. Moscow, 1962.
Vasil’ev, P. V. Lesnye resursy SSSRsegodnia i zavtra. Moscow, 1969.
Resursy biosfery na territorii SSSR. Moscow, 1971.
Lesa SSSR, vols. 1–5. Moscow, 1966–70.
Senokosy ipastbishcha. Edited by I. V. Larin. Moscow, 1969.
Biosfera i ee resursy. Moscow, 1971.

The fauna of the USSR is highly varied, both because of the fairly great diversity of conditions prevailing on land and on the seas and because of the great extent of the land mass from north to south and west to east. On the other hand, owing to the northern location of most of the USSR’s land mass and the bordering seas, the fauna of the USSR comprises fewer species than the fauna of tropical and equatorial countries.

The following is a list of the number of species in the USSR, including those inhabiting bodies of freshwater and seas. There are more than 300 species of mammals, about 760 species of birds, about 140 species of reptiles, and more than 30 species of amphibians. The number of fish species is about 1,400, including about 528 freshwater and migratory species. There are nine species of cyclostomes, one acraniate species, about 130 species of tunicates, about 410 species of echinoderms, and about 450 species of bryozoans, including 27 freshwater species, as well as 2,000 species of mollusks, including about 600 terrestrial species, about 470 freshwater species, and 1,100 marine species.

Insects are numerous, amounting to 80,000 to 100,000 species, of which there are about 20,000 species of dipterans (according to some sources, 10,000), about 10,000 species of hymenopterans, about 8,500 species of lepidopters, about 600 species of trichopterans, about 25,000 species of coleopterans, about 2,000 species of hemipterons, more than 800 species of aphids, about 250 species of scale insects, more than 700 species of orthopterons, and about 160 species of odonates. Of the total 5,000 species of Chelicerata, there are 2,500 species of acarians, about 2,000 species of arachnids, about 350 species of Pantopoda, about 70 species of tardigrades, about 70 species of Opiliones (or Phalangida), about 70 species of solpugids, and 12 species of scorpionids. Crustaceans number 3,000 species, annelid worms about 1,100 species, including about 750 species of polychaetes and about 300 species of oligochaetes, of which earthworm species number 100 and leech species number 60. In addition, there are more than 100 species of nemertines, about 1,800 species of nemathelminths (including about 115 species of acanthocephalans, about 700 species of rotifers, and about 1,000 species of nematodes), about 2,000 species of platyhelminths, about 500 species of coelenterates, more than 300 species of poriferans, numerous protozoans, and somewhat more than 100 species belonging to various different groups, including priapulids, sipunculids, echiuroids, and pogonophores.

The total number of known species occurring in the USSR ranges from 125,000 to 130,000 (or more according to some sources). Thus, if the total number of animal species now living is 1.3 million (about 1.5 million according to some zoologists), the USSR, which occupies about 15 percent of the world’s land area, or, taking the seas into account, about 8 percent of the earth’s surface, accounts for about 8 percent of the world’s fauna.

An important general feature of the distribution of the fauna in the USSR, as in the entire northern hemisphere, is that the number of total species, like the number of species in the individual groups, increases from north to south. Moreover, some southern Asian and African groups occur in the south. Another feature is zonation—the distribution of animals is distinctly related to natural zones on land and in the seas. The zonation is partly disrupted by the presence of some widely distributed species in several zones or throughout the entire country (or the seas), on the one hand, and by some aspects of the development of the fauna of the Soviet Union or its individual areas, on the other. However, the fauna of each of the main zones is an integral independent complex, intermingling with the neighboring fauna chiefly in the transitional zones, such as the forest tundra, forest steppe, and semidesert.

Terrestrial fauna. The USSR lies within the Palaearctic division of the Holarctic zoogeographic region. The zone of the northern islands and tundras forms part of the Arctic subregion, while the entire forest zone from the Pacific to the western borders of the USSR belongs to the Circumboreal subregion, the plains (deserts and semideserts) of Middle Asia and southern Kazakhstan, the Caspian Lowland, the Caucasus, Transcaucasia, and the southern part of the Crimea belong to the Mediterranean subregion, the mountains of Middle Asia and part of the mountains of Southern Siberia belong to the Central Asian subregion, and the Amur and Ussuri regions belong to the Sino-Himalayan subregion. Many zoogeographers assign the plains of Middle Asia and southern Kazakhstan to the Central Asian subregion.

Although the origin of the present-day fauna of the USSR can be traced to the Neogene, the main features of its distribution and composition developed during the Pleistocene, chiefly because of the glacial epochs and the changes in postglacial climatic conditions. The formation and historical fate of the fauna of the individual zones and zoogeographic regions proceeded in largely independent directions. An important factor affecting the distribution and, in part, the composition of the modern fauna is the direct and, especially, indirect (through changes in landscape) influences of man. It began in the distant past, in the Neolithic and even Paleolithic periods, and intensified in the last few centuries, particularly in the second half of the 20th century. There has been a marked tendency for the areas of distribution to decrease gradually in size and for the populations of species hunted by man to decline, as well as the populations of species that are incapable of existing in areas completely developed by man. On the other hand, those animals that were favored by economic changes in the landscape succeeded in settling more widely (synanthropic species). Some acclimatized species, for example, the muskrat and American mink, whose ranges widened considerably, have become an established part of the fauna.

COASTAL AND ISLAND FAUNA. Coastal and island fauna consists mainly of marine species of birds and mammals, whose distribution depends largely on prevailing marine conditions (food supply and ice). Such species are only partly linked to land (a narrow

Figure 1. Fauna of the oceanic coasts and islands: (1) black-legged kittiwake (Rissa tridactyla), (2) ivory gull (Pagophila eburnea), (3) fulmar (Fulmarus glacialis), (4) parasitic jaeger (Stercorarius parasiticas), (5) resplendent shag (Phalocroconax pelagicus), (6) least auk (Aethia cristatella), (7) thick-billed murre (Uria lomvia), (8) black guillemot (Cepphus grylle), (9) ancient murrelet (Synthliboramphus antiquus), (10) tufted puffin (Lunda cirrhata), (11) common puffin (Fratercula crctica), (12) dovekie (Alle alle), (13) Steller’s eider (Polysticta stelleri), (14) male common eider (Somateria mollissima), (14a) female common eider, (15) spoon-billed sandpiper (Eurynorhynchus pygmeus), (16) Steller’s sea lion (Eumetopias jubatus), (17) sea otter (Enhydra lutris), (18) walrus (Odobenus rosmarus), (19) northern fur seal (Callorhinus ursinus), (20) polar bear (Thalarctos maritimus), (21) harp seal (Phoca groenlandica), (22) ribbon seal (Phoca fasciata), (23) harbor seal (Phoca vitulina)

coastal strip), chiefly during the reproductive period. Characteristic of the fauna are various pinnipeds, including the walrus (Odobenus rosmarus), the bearded seal (Erignathus barbatus), the ringed seal (Pusa hispida), and the harbor seal (Phoca vitulina), as well as the polar bear (Thalarctos maritimus), and a number of birds, including guillemots (in the USSR found almost exclusively in this region), gulls, and eiders. The guillemots and gulls form huge nesting colonies, called rookeries, on the rocks. Extremely valuable fur-bearing species inhabit the Pacific seas, including the sea otter (Enhydra lutris; Komandorskie and Kuril islands) and the northern fur seal (Collorhinus ursinus; rookeries on Tiulenii, Komandorskie, and Kuril islands).

TUNDRA FAUNA. The tundra fauna comprises a small number of species. Among the characteristic mammals are various lemmings, such as the Norway lemming (Lemmus lemmus), the Ob’ lemming (Lemmus obensis), and the arctic lemming (Dicrostonyx torquatus), as well as the arctic fox (Alopex lagopus), the reindeer (Rangifer tarandus), and, in the eastern part of the country, the black-capped marmot (Marmota camtschatica). Among the species here that commonly inhabit other zones are a number of voles (Microtus), the blue hare (Lepus timidus), the ermine (Mustela erminea), the glutton (Guio guio), and the wolf (Canis lupus). Typical birds include the rock ptarmigan (Lagopus mutus), the willow ptarmigan (Lagopus lagopus), the snow bunting (Plectrophenax nivalis), the horned lark (Eremophila alpestris), the Lapland longspur (Calcarius lapponicus), the rough-legged hawk (Buteo lagopus), and the snowy owl (Nyctea scandiaca), as well as species associated with freshwater lakes and rivers, such as geese, ducks, and sandpipers. All the birds, except the ptarmigans and some snowy owls, migrate for the winter.

The number of invertebrate species is small; for example, there are only several hundred species of butterflies and moths. Sawflies and bumblebees are predominant among the hymenopterans. The coleopterans include many species of the families Staphylinidae (rove beetles), Carabidae (ground beetles), and Dytiscidae (predacious diving beetles). There are large numbers of bloodsucking dipterans, including those from the families Culicidae (mosquitoes), Simuliidae (blackflies), Ceratopogonidae (biting midges), and Tabanidae (horseflies).

FOREST-TUNDRA FAUNA. The forest-tundra fauna has no endemic species and consists of a mixture of tundra and taiga species that penetrated from the north and south.

TAIGA FAUNA. The fauna of the taiga is found in the northern part of the Far East, in Siberia, and in the northern part of the European USSR. It is most varied in Eastern Siberia and becomes less varied toward the west.

Characteristic mammals include several species of long-tailed shrews (Sorex), the northern red-backed vole (Clethrionomys rutilus), the gray red-backed vole (Clethrionomys rufocanus), the wood lemming (Myopus schisticolor), the Asiatic chipmunk (Eutamius sibiricus), the red squirrel (Sciurus vulpes), the Old World flying squirrel (Pteromys volans), the sable (Martes zibellina), the elk (Alces alces), and the musk deer (Moschus moschiferus), which lives in the Altai and east of the Enisei River. Marals (Cervus elaphus sibiricus and Cervus elaphus songaricus), the Manchurian red deer (Cervus elaphus xanthopygus), the Siberian roe deer (Capreolus capreolus pygargus), and the Siberian weasel (Mustela sibirica) inhabit the southern parts of the taiga zone. There are also mammals from other zones, for example, the blue hare, the brown bear (Ursus arctos), and the lynx (Felis lynx).

The most characteristic birds of the taiga are several species of warblers (Phylloscopus), a number of birds of the family Paridae, crossbills (Loxia), the brambling (Fringilla montifringilla), the Bohemian waxwing (Bombycilla garrulus), the pine grosbeak (Pinicola enucleator), the nutcracker (Nucifraga caryocatactes), the Siberian jay (Perisoreus infaustus), the three-toed wood-pecker

Figure 2. Fauna of the plains and mountainous tundras: (1) snow bunting (Plectrophenax nivalis), (2) Lapland longspur (Calcarius laponicus), (3) horned lark (Eremophila alpestris), (4) Siberian white crane (Grus leucogeranus), (5) arctic loon (Gavia arctica), (6) Bewick’s swan (Cygnus bewicki), (7) Ross’s gull (Rhodostethia rosea), (8) long-tailed jaeger (Stercorarius longicaudus), (9) white-fronted goose (Anser albifrons), (10) lesser white-fronted goose (Anser erythropus), (11) black brant (Branta bernicla), (12) red-breasted goose (Branta ruficollis), (13) king eider (Somateria spectabilis), (14) bluethroat (Luscinia svecica), (15) wolf (Canis lupus), (16) snowy owl (Nyctea scandiaca), (17) bighorn (Ovis canadensis), (18) the black-capped marmot Marmota camtschatica, (19) Middendorf’s vole (Microtus middendorti), (20) Norway lemming (Lemmus lemmus), (21) Ob’ lemming (Lemmus obensis), (22) arctic lemming (Dicrostonyx torquatus), (23) reindeer (Rangifer tarandus), (24) ermine (Mustela erminea), (25) arctic fox (Alopex lagopus), (26) rough-legged hawk (Buteo lagopus), (27) willow ptarmigan (Lagopus lagopus), (28) rock ptarmigan (Lagopus mutus), (29) Eurasian golden plover (Pluvialis apricaria), (30) bar-tailed godwit (Limosa lapponica)

pecker (Picoides tridactylus), the black woodpecker (Dryocopius martius), the hazel hen (Tetrastes bonasia), the capercaillie (Tetrao urogallus), Tengmalm’s owl (Aegolius funereas), the pygmy owl (Glaucidium passerinum), the great (or Lapp) owl (Strix nebulosa), the Ural owl (Slrix uralensis), and the hawk owl (Surnia ulula).

There are few reptiles and amphibians. The insect fauna is characterized by taiga and general forest species. Dipterans are

Figure 3. Taiga fauna: (1) pine grosbeak (Pinicola enucleator), (2) red crossbill (Loxia curvirostra), (3) Siberian jay (Perisoreus infaustus), (4) three-toed woodpecker (Picoides tridactylus), (5) black woodpecker (Dryocopius martius), (6) common goldeneye (Bucephala clangula), (7) Bohemian waxwing (Bombycilla garrulus), (8) redpoll (Acanthis flammea), (9) nutcracker (Nucitraga caryocatactes), (10) bullfinch (Pyrrhula pyrrhula), (11) capercaillie (Tetrao urogallus), (12) Siberian spruce grouse (Falcipennis falcipennis), (13) hazel hen (Tetrastes bonasia), (14) pygmy owl (Glaucidium passerinum), (15) Ural owl (Strix uralensis), (16) musk deer (Moschus moschiterus), (17) glutton (Guio guio), (18) European shrew (Sorex araneus), (19) sable (Martes zibellina), (20) wood lemming (Myopus schisticolor), (21) northern pika (Ochotona hyperborea), (22) the red-backed vole Microtus pullus, (23) gray red-backed vole (Clethrionomys rufocanus), (24) northern red-backed vole (Clethrionomys rutilus), (25) Old World flying squirrel (Pteromys volans), (26) Asiatic chipmunk (Eutamias sibiricus), (27) elk (Alces alces), (28) lynx (Felis lynx), (29) brown bear (Ursus arctos), (30) big brown bat (Eptesicus nilssoni), (31) Siberian weasel (Mustela sibirica), (32) European common lizard (Lacerta vivipara), (33) common viper (Vipera berus), (34) the tick Ixodes taigensis, (35) spruce longhorn (Tetropicum castaneum), (36) Siberian pine moth (Dendrolimus sibiricus), (36a) caterpillar of Siberian pine moth

numerous, primarily Tipulidae (crane flies) and Mycetophilidae (mushroom beetles). There are numerous bloodsucking insects, which are a great annoyance to animals and man. Lepidopters abound, especially Tortricidae (leaf-roller moths), Notodontidae

Figure 4. Fauna of the European and Far Eastern broad-leaved forests: (1) hawfinch (Coccothraustes coccothraustes), (2) thrush nightingale (Luscinia luscinia), (3) golden oriole (Oriolus oriolus), (4) blue tit (Parus caeruleus), (5) tawny owl (Strix aluco), (6) the long-horned beetle Cerambyx cerdo, (7) stag beetle (Lucanus cervus), (8) green lizard (Lacerta viridis), (9) smooth snake (Coronelia austriaca), (10) green woodpecker (Picus viridis), (11) bank vole (Clethrionomys glareolus), (12) common mole (Talpa europaea), (13) birch mouse (Sicista betulina), (14) European wildcat (Felis silvestris), (15) common tree frog (Hyla arborea), (16) fire-bellied toad (Bombina bombina), (17) the frog Rana temporaria, (18) European fire salamander (Salamandra salamandra), (19) hazel mouse (Muscardinus avellanarius), (20) garden dormouse (Eliomys quercinus), (21) tree dormouse (Dryomis nitedula), (22) European red deer (Cervus elaphus), (23) European mink (Mustela lutreola), (24) European, or pine, marten (Martes martes), (25) wild boar (Sus scrota), (26) roe deer (Capreolus capreolus), (27) Asiatic black bear (Ursus thibetanus), (28) aurochs (Bison bonasus), (29) raccoon dog (Nyctereutes procyonides), (30) goral (Nemorhaedus goral), (31) Japanese deer (Cervus nippon), (32) broad-billed roller (Eurystomus orientalis), (33) yellow-throated marten (Martes tlavigula), (34) Ussuri tiger, (35) azure-winged magpie (Cyanopica cyana), (36) mandarin duck (Aix galericulata), (37) Gould’s merganser (Mergus squamatus), (38) Bengal cat (Felis euptilura), (39) the long-horned beetle Cerambyx relictus, (40) the swallowtail Papilio machaon, (41) the soft-shelled turtle Amyda sinensis, (42) large Japanese mole (Mogera robusta), (43) the rat snake Elaphe schrenki, (44) Manchurian hare (Caprolagus brachyurus), (45) leopard (Panthera pardus), (46) ring-necked pheasant (Phasianus colchicus)

(prominent moths), Geometridae (inchworms), and Bombycidae (silkworm moths). Also abundant are hymenopterans (especially sawflies), aphids, and beetles, which are often associated with specific trees, for example, bark beetles. Spiders are more numerous here than in other zones.

BROAD-LEAVED FOREST FAUNA. The broad-leaved forest fauna occupies a triangular-shaped area in the European part of the country between the Gulf of Finland, the southern Urals, and Moldavia. The most typical mammals include the bank vole (Clethrionomys glareolus), the yellow-necked mouse (Apodemus flavicollis), and various microtines, such as the common dormouse (Glis glis), the tree dormouse (Dryomis nitedula), the garden dormouse (Eliomys quercinus), and the hazel mouse (Muscardinus avellanarius). Ungulates, including the roe deer (Capreolus capreolus), the European red deer (Cervus elaphus), and the aurochs (Bison bonasus), have survived in some wooded areas, as well as a number of other mammals, such as the European mink (Mustela lutreola), the European wildcat (Felis sylvestris), and the pine marten (Martes martes).

Among the characteristic birds are several species of warblers of the genera Phylloscopus and Sylvia, the chaffinch (Fringilla coelebs), the hawfinch (Coccothraustes coccothraustes), the nightingale (Luscinia megarhynchos), the oriole (Oriolus oriolus), the blue tit (Parus caeruleus), the green woodpecker (Picus viridis), the middle-spotted woodpecker (Picoides medius), and the tawny owl (Strix aluco).

Reptiles include the slow-worm (Anguis fragilis), the smooth snake (Coronelia austriaca), and Aesculapius’ snake (Elaphe longissima). Among the amphibians are the common European pond tortoise (Emys orbicularis), the tree frog (Hyla arborea), the edible frog (Rana esculenta), the common frog (Rana temporaria). Rana terrestris, the green toad (Bufo viridis), the fire-bellied toad (Bombina bombina), and the yellow-bellied toad (Bombina variegata), the last occurring in the Carpathian Region. Other amphibians include the great crested newt (Triturus cristatus), in the west, and the European fire salamander (Salamandra salamandra), in the Carpathians.

The insect fauna of the broad-leaved forest region is, in general, more varied than that of the taiga, but there are many common species, as well as several taiga species and a number of species that penetrated from the south.

FAR EAST (AMUR-USSURI) BROAD-LEAVED FOREST FAUNA. The fauna of the Far East (Amur-Ussuri) broad-leaved forests, found in the Ussuri River basin and the middle and lower Amur, is particularly abundant and varied and is characterized by a mixture of various northern and southern species. Among the latter, characteristic mammals include the large Japanese mole (Mogera robusta), the Manchurian hare (Caprolagus brachyurus), the Japanese deer (Cervus nippon), the goral (Nemorhaedus goral), the Asiatic black bear (Ursus thibetanus), the yellow-throated marten (Martes flavigula), the raccoon dog (Nyctereutes procyonides), the tiger, the snow leopard (Uncia uncia), and the Bengal cat (Felis euptilura).

Birds include several species of flycatchers, warblers of the genus Phylloscopus, buntings of the genus Emberiza, the Chinese oriole (Oriolus chinensis), the ashy minivet (Pericrocotus roseus), the Chinese white-eye (Zosterops erythropleurus), the azure-winged magpie (Cyanopica cyana), the broad-billed roller (Eury-stomus orientalis), the true pheasant (Phasianus colchicus), the mandarin duck (Aix galericulata), and Gould’s merganser (Mergus squamatus).

Reptiles include the spiny soft-shelled turtle (Trionyx sinensis), the long-tailed lizard (Tachydromus amurensis), the aquatic snakes Natrix tigrina and Natrix vibakari, and the rat snake Elaphe schrenki. Among the amphibians are the frog Hyla japonica and the triton Onychodactylus fischeri.

The insect fauna of the Far East broad-leaved forest is much more varied than in other parts of the USSR. Typical lepidopters

Figure 5. Steppe fauna: (1) European hare (Lepus europoeus), (2) steppe pika (Ochotona pusilla), (3) great bustard (Otis tarda), (4) collared pratincole (Glareola pratincola), (5) sociable plover (Chettusia gregaria), (6) white-winged lark (Melanocorypha leucoptera), (7) calandra lark (Melanocorypha calandra), (8) black lark (Melanocorypha yeltoniensis), (9) bobac (Marmota bobac), (10) spotted suslik (Citellus suslicus), (11) black-bellied hamster (Cricetus cricetus), (12) Eversmann’s hamster (Cricetus eversmanni), (13) whitetoothed shrew (Crocidura), (14) zokor (Myospalax myospalax), (15) major five-toed jerboa (Allactaga jaculus), (16) Russian mole rat (Spalax microphthalmus), (17) little bustard (Tetrax tetrax), (18) steppe, or tawny, eagle (Aquila nipalensis), (19) saiga (Saiga tatarica), (20) demoiselle crane (Anthropoides virgo), (21) steppe lemming (Lagurus lagurus), (22) steppe viper (Vipera ursini), (23) European sand lizard (Lacerta agilis), (24) lesser kestrel (Falco naumanni), (25) dahurian suslik (Citellus dauricus), (26) cape hare (Lepus capensio), (27) migratory locust (Locusta migratoria), (28) European whip snake (Coluber jugularis), (29) Mongolian gazelle (Gazella gutturosa), (30) manul (Felis manul), (31) Putorius eversmanni, (32) corsac (Vulpes corsac)

include Sericinus, Luehdorfia, many species of the families Notodontidae, Epicopidae, and others (found only here in the USSR), as well as the swallowtail Papilio bianor. The most common dipteran is the mosquito Megarhinus. Among the hemipterons are members of the tropical genera Plautia and Lelia. The largest insect in the USSR, Cerambyx relictus, is noteworthy. There are quite a few Tertiary relicts, for example, pedipalpids, which are characteristic of southern Asia.

The fauna of the southern part of Sakhalin is characterized by a mixture of northern and southern species, as is the fauna on the southern islands of the Kuril chain, which are also inhabited by several animal species that are native to Japan and not found elsewhere in the USSR, such as the Japanese grass vole (Microtus montebelli), the skink Eumeces latiscutatus, and three species of rat snakes (Elaphe).

FOREST-STEPPE FAUNA. The forest-steppe fauna contains very few species unique to the region and is characterized by a mixture of steppe and forest species.

STEPPE FAUNA. The steppe fauna contains comparatively few vertebrate species native to the steppes, but it is augmented by animals that penetrated from adjacent zones. This is particularly so in wooded areas (floodplain forests) or sandy areas (in the south). The Asiatic steppes of the USSR have the largest number of true steppe species, the number of which decreases westward. The European steppes have been virtually completely plowed up over the course of the last few centuries, and the composition of their fauna has been greatly altered. Some steppe species, such as the European hare (Lepus europoeus), the Hungarian partridge (Perdixperdix), the quail (Coturnix coturnix), and the pallid harrier (Cirus macrourus) are increasingly penetrating southward in the wake of extensive logging and cultivation deep in the broad-leaved forests and in the taiga.

Characteristic mammals of the European and Kazakh steppes include the bobac (Marmota bobac), various susliks, the blackbellied hamster (Cricetus cricetus), various cricetines, such as the migratory hamster (Cricetulus migratorius), several species of jerboas, the steppe lemming (Lagurus lagurus), mole rats, the steppe pika (Ochotonapusilla), the European hare, and the saiga (Saiga tatarica). Birds include the calandra lark (Melanocorypha calandra), the short-toed lark (Calandrella cinerea), the white-winged lark (Melanocorypha leucoptera), the black lark (Melanocorypha yeltoniensis), the bustard (Otis tarde), the little bustard (Tetrax tetrax), the lesser kestrel (Falco naumanni), the steppe (or tawny) eagle (Aquila nipalensi), the imperial eagle (Aquila heliaca), the demoiselle crane (Anthropoides virgo), the black-winged pratincole (Glareola nordmanni), and the sociable plover (Chettusia gregaria).

Reptiles, which are more numerous here than in the northern zones, include the steppe viper (Vipera ursini), the European whip snake (Coluber jugularis), the European sand lizard (Lacerta agilis), and a number of other species. Amphibians are few owing to the arid conditions. Locusts exist in great abundance, and many are major crop pests, such as the Asiatic, or migratory, locust (Locusta migratoria), which until recently had inflicted great damage. The hymenopterans are represented by a number of ant, wasp, sawfly, and other species. Among the coleopterans, the most common are the Curculionidae (snout beetles), the Carabidae (ground beetles), the Scarabeidae, and especially the Tenebrionidae (darkling beetles). There are many hemipteron and dipteran species.

The fauna of some areas of the Transbaikal steppes, which are more arid than the European and Kazakh steppes and which are inhabited by Mongolian fauna, differs significantly from the European and Kazakh steppes. The mammals that live here include the tarbagan (Marmota sibirica), the dahurian suslik (Citellus dauricus), the Mongolian vole (Microtus mongolica), Brandt’s vole (Microtus brandti), the dahurian pika (Ochotona daurica), and the cape hare (Lepus capensio); the Mongolian gazelle

Figure 6. Desert fauna: (1) great gerbil (Rhombomys opimus), (2) sand cat Felis margarita, (3) tiger weasel (Vormela peregusna), (4) saw-scaled viper (Echis carinatus), (5) caracal (Felis caracal), (6) porcupine (Hystrix cristata), (7) long-eared desert hedgehog (Hemiechinus auritus), (8) long-clawed ground squirrel (Spermophilopsis leptodactylus), (9) Selevin’s mouse (Selevinra betpakdalensis), (10) comb-toed jerboa (Parad i pus ctenodactylus), (11) cheetah (Acinonyx jubatus), (12) Pander’s ground jay (Podoces panden), (13) Pallas’s sandgrouse (Syrrhaptes paradoxus), (14) desert sparrow (Passer simplex), (15) desert warbler (Sylvia nana), (16) Houbara bustard (Chlamydotis undulata), (17) Asiatic wild ass (Equus hemionus), (18) brown-necked raven (Corvus ruficollis), (19) cobra (Naja naja), (20) the sand snake Eryx miliaris, (21) piebald shrew (Diplomesodon pulchellum), (22) the lizard Agama sanguinolenta, (23) the lizard Phrynocephalus, (24) whip scorpion, (25) variegated scorpion, (26) goitered gazelle (Gazella subgutturosa), (27) desert, or yellow, monitor (Varanus griseus), (28) Taphrometroron lineolatus

(Gazella gutturosa) may have penetrated from Mongolia. The Mongolian lark (Melanocorypha mongolica] is characteristic of the birds and the desert lacertid Eremias argus of the reptiles.

SEMIDESERT FAUNA. The semidescrt fauna, although noted for a few endemic species, is characterized primarily by a mixture of steppe and desert species.

DESERT FAUNA. The desert fauna is found on the plains of Middle Asia, including part of southern Kazakhstan, and in part of the Caspian Lowland. It differs somewhat in sandy deserts and other deserts. The typical desert fauna is intermixed with species associated with cultivated land, human settlements, and floodplain forests (tugais). The desert fauna is subjected to harsh

Figure 7. Mountain fauna: (1) bezoar goat (Capra hircus aegagrus), (2) snow vole (Microtus nivalis), (3) the vole Pitymys pitymys, (4) long-clawed mole-vole (Prometheomys schaposchnikowi), (5) chamois (Rupicapra rupicapra), (6) great rosefinch (Carpodacus rubicilla), (7) Caspian snow cock (Tetraogallus caspius), (8) Caucasian snow cock (Tetraogallus caucasicus), (9) Turkestan red pika (Ochotona rutila), (10) Royle’s pika (Ochotona macrotis), (11) Cornish, or red-billed, chough (Pyrrhocorax pyrrhocorax), (12) Guldenstadt’s redstart (Phoenicurus erythrogaster), (13) bar-headed goose (Anser indicus), (14) Malpolon monspessulanus, (15) East Caucasian tur (Capra caucasica), (16) Caucasian black grouse (Lyrurus mlokosiewiczi), (17) Tibetan snow cock (Tetraogallus tibetanus), (18) blue rock thrush (Monticola solitaria), (19) chukar partridge (Alectoris kakelik), (20) ibisbill (Ibidorhyncha struthersii), (21) wall creeper (Tichodroma muraria), (22) argali (Ovis ammon), (23) bearded vulture (Gypaetus barbatus), (24) streaked laughing thrush (Garrulax lineatus), (25) Siberian ibex (Capra sibirica), (26) white-winged grosbeak (Coccothraustes carnipes), (27) stone marten (Martes foina), (28) alpine weasel (Mustela altaica), (29) red marmot (Marmota caudata), (30) Menzbier’s marmot (Marmota menzbieri), (31) Asiatic wild dog (Cuon alpinus), (32) snow leopard (Uncia uncia), (33) markhor (Capra falconeri)

Figure 8. Freshwater fauna. Basins of the Arctic Ocean and the southern seas of the European USSR: (1) blackfish (Dallia pectoralis), (2) Atlantic salmon (Salmo salar), (3) river lamprey (Lampetra tluviatilis), (4) European stone loach (Nemachilus barbatula), (5) minnow (Phoxinus phoxinus), (6) taimen (Hucho taimen), (7) Siberian sturgeon (Acipenser baeri), (8) grayling (Thymallus arcticus), (9) burbot (Lota lota), (10) carp (Cyprinus carpio), (11) European bream (Abramis brama), (12) golden crucian carp (Carassius carassius), (13) sterlet (Acipenser ruthensis), (14) three-spined stickleback (Gasterosfeus aculeatus), (15) peled (Coregonus peled), (16) broad whitefish (Coregonus nasus), (17) pike (Esox lucius), (18) chub (Leuciscus cephalus), (19) common pike perch (Lucioperca lucioperca), (20) sheatfish (Silurus glanis), (21) the crayfish Astacus leptodactylus. Middle Asia: (22) Amu Darya shovelnose sturgeon (Pseudocaphirhynchus kautmanni), (23) common marinka (Schizothorax intermedias), (24) Turkestan catfish (Glyptosternum reticulutum), (25) Balkhash perch (Perca schrenki), (26) naked osman (Diptychus dybowski). Lake Baikal: (27) Baikal seal (Phoca sibirica), (28) the amphipod Axelboeckia carpenteri, (29) the amphipod Garjajewia cabanisi, (30) the sponge Lubomirskia baikalensis, (31) the mollusk Baicalia costata, (32) the mollusk Baicalia godlewskii, (33) yellowwing (Cottocomephorus grewingki), (34) stone sculpin (Cottus kneri), (35) Baikal arctic cisco (Coregonus autumnalis migratorius), (36) Baikal oil-fish (Comephorus baicalensis). Far East: (37) sockeye salmon (Oncorhynchus nerka), (38) coho salmon (Oncorhynchus kisutch), (39) pink salmon (Oncorhynchus gorbuscha), (40) Chinook salmon (Oncorhynchus tshawytscha), (41) chum, or dog, salmon (Oncorhynchus keta), (42) Chinese perch (Siniperca chuatsi), (43) snakehead (Ophicephalus argus), (44) Chinese chebachok (Pseudorasbora parva), (45) skygazer (Erythroculter erythropterus), (46) Chinese sleeper (Perccottus glehni), (47) yellowcheek (Elopichthys bambusa), (48) silver carp (Hypophthalmichthys molitrix), (49) fiddler fish (Leiocassis ussuriensis), (50) Soldatov’s catfish (Silurus soldatova), (51) kaluga (Huso dauricus), (52) Amur sturgeon (Acipenser schrenki), (53) black Amur bream (Megalobrama terminalis), (54) black carp (Mylopharyngodon piceus), (55) Amur false gudgeon (Pseudogobio rivularis), (56) eight-barbel gudgeon (Gobiobotia pappenheimi), (57) Amur pike (Esox reicherti).

conditions, such as high summer and low winter temperatures, aridity, and sparse vegetation. It consists of specialized species.

Among the characteristic animals are several gerbil and jerboa species, the large-toothed suslik (Citellus fulvus), the suslik Spermophilopsis leptodactylus, which is related to the African ground squirrel, the goitered gazelle (Gazella subgutturosa), the Asiatic wild ass (Equus hemionus; very rare), the tiger weasel (Vormela peregusna), the caracal (Felis caracal; rare), the sand cat (Felis margarita), the African wildcat (Felis libyca), and the cheetah, which is now probably extinct.

Birds include Pander’s ground jay (Podoces panderi), the brown-necked raven (Corvus ruficollis), the saxaul sparrow (Passer ammodendri), the desert sparrow (Passer simplex), the desert warbler (Sylvia nana), sandgrouses of the genus Pterocles, and the Houbara bustard (Chlamydotis undulata).

Reptiles abound, including such lizards as Phrynocephalus, the agama Agama sanguinolenta, the desert (or yellow) monitor (Varanus griseus), Eremias, and geckos, and such snakes as Psammophis lineolatus, the sand snake Eryx miliaris, and vipers, namely, the saw-scaled viper (Echis carinatus) and the Levantine viper (Vipera lebetina). Steppe turtles (Agrionemys horsfieldi) abound. Amphibians are found only in the river valleys.

The rich and varied insect world includes many endemic coleopteran species, including several species of the families Tenebrionidae, Scarabeidae, Carabidae, Curculionidae, Oedemeridae (false blister beetles), and Elateridae, as well as many endemic hymenopteran species, including many species of bees, wasps, ants, velvet ants, butterflies, and moths. Termites are characteristic of the region. There are also species common to Transcaucasia and the Crimea and even the tropics. Several solpugid and scorpion species inhabit Middle Asia and have not penetrated the northern regions. There are also a number of arachnids, such as tarantulas and karakurts.

The fauna linked with cultivated areas and the tugais is more varied and includes some unusual forms, for example, the green toad (Bufo viridis), the pond frog (Rana ridibunda), the scincoid lizard Ablepharus, the true pheasant, the bandicoot (Nesokia indica), the wild boar (Sus scrofa), the tugai deer (Cervus elaphus bactrianus), and the jackal (Canis aureus). Central Asia appears to have been the place of origin of the Middle Asian desert fauna, which, in addition to Central Asian species, also includes species of African origin. A special “desert” coloring (sandy and yellow tones) is characteristic of desert vertebrates and many insects.

MOUNTAIN FAUNA. The mountain fauna is highly varied owing to differences in elevation and the rugged terrain. The most typical mountain animals are associated with high elevations. The fauna of the lower belts consists mainly of species of the zone in which the particular mountain system is situated and of the species of the adjacent zones. However, since the principal place of origin of the Eurasian mountain fauna is Central and Middle Asia, the number of high-mountain species in the fauna of an individual mountain system depends on how far the fauna is from the place of origin. Thus, the fauna of the mountains of the Kola Peninsula, the Urals, and the northern part of Siberia differs little from that of the expanses of the plains taiga. The Crimean fauna too is almost entirely lacking in specifically mountain features. Alpine faunistic elements, such as the alpine shrew (Sorex alpinus) and the snow vole (Microtus nivalis), are found in the Carpathians, but in view of the marked predominance of European forest species their role is slight. The high-mountain fauna of the Altai and Saian mountains, for example, the mountain voles (Alticola), the Siberian ibex (Capra sibirica), and the Altai snow cock (Tetraogallus altaicus), is more varied, but its zoogeographic makeup is, in general, typically Siberian and taiga.

The animal world of the Caucasus and the Middle Asian mountains is more varied. The differences in the faunas of the two regions are more pronounced than the similarities. The origin of the Caucasian fauna is closely linked with that of Southwest Asia and Southern Europe. Characteristic mammals are pine mice (Pitymys), the snow vole, various goats, such as the bezoar (Capra hircus aegagrus), the West Caucasian tur (Capra caucasica), the East Caucasian tur (Capra cylindricornis), and the chamois (Rupicarpa rupicarpa), and the endemic long-clawed mole-vole (Prometheomys schaposchnikow). Birds include the Caucasian snow pheasant (Tetraogallus caucasicus), the Caspian snow cock (Tetraogallus caspius), the Caucasian black grouse (Lyrurus mlokosiewiczi), the great rosefinch (Carpodacus rubicilla), and Guldenstadt’s redstart (Phoenicurus erythrogaster). The number of reptile and amphibian species is very large. The insect fauna is one of the richest in the USSR, along with the Middle Asian and Ussuri fauna, and is markedly southern in character.

The fauna of the mountain systems of Middle Asia, with the exception of the Kopetdag, which has the Irano-Transcaucasian type of fauna, is closer to that of the Central Asian highlands. Among the typical animals are the juniper vole (Pitymus juniperus), the vole Microtus pamiris, Royle’s pika (Ochotona macrotis), the Turkestan red pika (Ochotona rutila), the gray marmot (Marmota baibacina), the red marmot (Marmota caudata), Menzbier’s marmot (Marmota menzbieri), several forms of argali (Ovis ammon), the Siberian ibex, and, in some areas, the markhor (Capra falconeri) and the snow leopard. Other animals include two species of Tetraogallus, the ibisbill (Ibidorhyncha struthersii), the bar-headed goose (Anser indica), the white-winged grosbeak (Coccothraustes carnipes), and several species of finches, buntings, and redstarts.

V. G. GEPTNER

Freshwater fauna. The freshwater fauna of the USSR belongs to two regions in accordance with the zoogeographic zonation of the continental bodies of waters—the Holarctic region and the Amur transitional region.

HOLARCTIC REGION. Of the total number of subregions into which the Holarctic region is subdivided, the fresh bodies of water of the USSR belong to four: the Circumpolar, the Baikal, the Mediterranean, and the Asian Highland subregions.

Circumpolar subregion. The Circumpolar subregion encompasses the basins of rivers emptying into the Arctic and North Pacific oceans. The fauna is very meager, numbering about 100 species of fish, of which the salmonids account for about one-third. Invertebrates are represented either by widespread species or by cold-loving species characteristic of arctic and high-mountain regions. Marine forms, such as the crustacean Mesidotea and various amphipods, are concentrated mainly in the mouths of rivers and in some large lakes. The fauna of the rivers of the Pacific Ocean basin is poorer than that of the rivers of the Arctic Ocean basin.

Baikal subregion. The Baikal subregion consists solely of Lake Baikal, whose fauna is very rich, numbering about 1,000 species, and extremely unusual. More than three-fourths of the species are endemic. Among the typical fish are two endemic families of Baikal gobies, the Baikal oil-fish (Comephorus), the arctic cisco (Coregonus autumnalis), and the European stone loach (Nemachilus barbatulo). The Baikal seal (Phoca sibirica) is a typical mammal. Invertebrates originated mainly from ancient Tertiary freshwater fauna, whose survivors gave rise to numerous new forms in the lake. Amphipods, which number about 300 species, endemic gastropod mollusks and sponges, and numerous oligochaetes and ciliated worms (turbellarians) are characteristic. Groups of freshwater animals that are widely distributed elsewhere are not found in Lake Baikal.

Mediterranean subregion. The Mediterranean subregion encompasses the basins of rivers emptying into the Baltic and Black seas, the Sea of Azov, and the Caspian and Aral seas. The dominant species are from the families Cyprinidae, as well as from the families Acipenseridae, Clupeidae, and Gobiidae. Salmonids are comparatively rare. Among the mollusks, members of the genera Theodoxus, Melanopsis, and Lithoglyphus dwell only here and do not occur in the Circumpolar subregion. Crustaceans include crayfish, freshwater crabs, and some genera of Caspian amphipods. The fauna is most abundant and varied in the basin of the Black, Aral, and Caspian seas, where the freshwater lakes and rivers abound in marine elements.

Asian Highland subregion. The Asian Highland subregion encompasses the basin of Lake Balkhash, as well as the upper reaches of the Amu Darya, Syr Darya, and Zeravshan rivers. The fauna is meager but quite unusual. Among the characteristic fish are members of the genera Schizothorax, Diptychus, Nemachilus, and Glyptosternum. The family Cyprinidae is represented by a large number of species. Unique species of Lymnaeidae, Planorbidae, and Bithynia are typical mollusks.

Figure 9. Marine fauna. Caspian Sea: (1) the crustacean Didacna trigonoides, (2) Caspian seal (Phoca caspica), (3) stellate sturgeon (Acipenser stellatus), (4) roach (Rutilus rutilus), (5) Caspian shad (Caspialosa caspia), (6) the crustacean Mesidotea entomon caspica, (7) Caspian tiul’ka (Clupeonella delicatula caspia). Black Sea: (8) the crab Pachygrapsus marmoratus, (9) striped mullet (Mugil cephalus), (10) the jellyfish Rhizostoma pulmo, (11) the oyster Ostrea edulis, (12) the mussel Mytilus edulis, (13) bottle-nosed dolphin (Tursiops truncatus), (14) Atlantic mackerel (Scomber scombrus), (15) tub, or yellow, gurnard (Trigla lucerna), (16) the red mullet Mullus barbatus, (17) horse mackerel (Trachurus trachurus), (18) sea horse (Hippocampus guttulatus microstephanus), (19) rascasse (Scorpaena porcus). Northern seas: (20) beluga (Delphinapterus leucas), (21) killer whale (Orcinus orea), (22) narwhal (Monodon monoceros), (23) Atlantic cod (Gadus morhua), (24) arctic cod (Boreogadus saida), (25) pollack (Gadus virens), (26) the crab Hyas araneus, (27) the skate Raja radiata, (28) the sea urchin Strongylocentrotus droebachiensis, (29) the brittle star Gorgonocephalus eucnemis, (30) hermit crab (Pagurus pubescens), (31) the shrimp Sabinea septemcarinata, (32) Atlantic wolffish (Anarhi lupus), (33) Greenland shark (Somniosus macrocephalus). Far Eastern seas: (34) cutlass fish (Trichiurus iaponicus), (35) Far East pilchard (Sardinops sagax melanosticta), (36) the herring Clupea pallasi, (37) the mollusk Rapana venosa, (38) finback (Balaenoptera physalus), (39) sperm whale (Physeter catodon), (40) Pacific saury (Cololabis saira), (41) Atka mackerel (Pleurogrammus monopterygius), (42) walleye pollock (Theragra chalcogramma), (43) glassfish (Salangichthys microdon), (44) Atlantic halibut (Hippo-glossus hippoglossus), (45) the plaice Liopsetta pinnifasciata, (46) the squid Ommatostrephes sloani, (47) the shrimp Pandalus hypsinotus, (48) the surf clam Mactra sachalinensis, (49) the oyster Mizuhopecten jessoensis, (50) the trepang Stychopus japonicus, (51) king crab (Paralithodes camschatica).

AMUR TRANSITIONAL REGION. The Amur transitional region encompasses the basins of the Ussuri and Amur rivers, as well as the lakes and rivers of the island of Sakhalin and the Kuril Islands. Its fauna includes not only endemic forms but also elements of two neighboring regions, the Holarctic in the north and the Sino-Indian in the south. Among the southern fish species are the snakehead (Ophicephalus argus), the zheltoshchek, or yellowcheek (Elopichthys bambusa), the grasscarp, or white amur (Ctenopharygodon idella), and the silver carp (Hypophthalmichthys molitrix), while Pacific salmons (Oncorhynchus), graylings (Thymallidae), the burbot (Lota lota), lampreys (Petromyzon), and an endemic pike species are typical northern animals. Because of historical conditions, the fauna has come to resemble somewhat the fauna of the Mediterranean subregion.

N. IU. SOKOLOVA

Marine fauna. The northern seas of the USSR—from the Barents Sea to the Chukchi Sea (except the extreme southwestern part of the Barents and the shallow southern part of the White Sea)—and the northern part of the Bering Sea constitute the Arctic zoogeographic region. These seas are characterized by relatively few species (about 1,500 species of free-living animals), a small number of commercially valuable fish and invertebrates, and a substantial admixture of saltwater forms in the southern coastal areas of the Siberian seas. The southwestern part of the Barents Sea and the southern shallow waters of the White Sea belong to the North Atlantic boreal region, which is much richer in species and individuals, and most of the commercially valuable fish of these seas are boreal. The Baltic Sea belongs to the same region, but owing to its low salinity its fauna is extremely meager, only about 100 species within USSR waters, primarily highly euryhaline boreal species and arctic relicts.

The Bering Sea, the Sea of Okhotsk, the Sea of Japan, and the Pacific waters near the Kuril Islands and Kamchatka belong to the North Pacific boreal region, whose fauna is extremely rich, numbering about 5,000 species, and independent; many arctic, arctic-boreal, and amphiboreal species originated from the region. In addition to boreal and arctic-boreal species, some subtropical and subtropical-southern boreal species occur in the extreme southern part of the Far East (Petr Velikii and Post’et bays, Moneron Island, Busse Lagoon in Aniva Gulf, and the southern part of the Kuril Ridge).

The Black Sea and the Sea of Azov belong to the Mediterranean-Lusitanian region, but owing to low salinity and marked cooling in winter, their fauna is very meager, approximately one-third that of the Mediterranean region. The Black Sea and the Sea of Azov are reached only by very hardy species, which also live in the boreal Atlantic and thus impart uniquely Atlantic features to the Black Sea fauna. In addition to species common to the Mediterranean, there are also Pontic-Caspian saltwater relicts and a few originally freshwater species. The Black Sea, excluding the freshwater parts, has about 1,500 free-living species, while the Sea of Azov has about 350 species.

The Caspian Sea and the coastal lagoons of the Black Sea and the Sea of Azov belong to the Pontic-Caspian saltwater region, whose principal fauna consists of relicts, descendants of Sarmatian (Upper Miocene) fauna, as well as forms that were originally freshwater forms, fish introduced from the Mediterranean, and a few arctic immigrants. The fauna of the Caspian, which numbers about 650 species, is much poorer than that of the Black Sea. The Aral Sea fauna is even poorer, numbering about 220 species and consisting mainly of freshwater forms intermixed with some Caspian and Mediterranean forms. The Aral Sea is an unusual salt-water province of the Palaearctic region.

K. N. NESIS

Bibliography

Zhivotnyi mir SSSR, vols. 1–5. Moscow-Leningrad, 1936–58.
Fauna SSSR, vol. 1—. Moscow-Leningrad, 1935—.
Ognev, S. I. Zveri SSSR i prilezhashchikh stran (Zveri Vostochnoi Evropy i Severnoi Azii), vols. 1–9. Moscow-Leningrad, 1928–57.
Zhizn’ presnykh vod SSSR, vols. 1–4. Edited by V. I. Zhadin. Moscow-Leningrad, 1940–59.
Ptitsy Sovetskogo Soiuza, vols. 1–6. Edited by G. P. Dement’ev and N. A. Gladkov. Moscow, 1951–54.
Berg, L. S. Ryby presnykh vod SSSR i sopredel’nykh stran, 4th ed., parts 1–3. Moscow-Leningrad, 1948–19.
Opredeliteli po faune SSSR, izdavaemye Zoologicheskim institutom AN SSSR, vols. 1–108. Leningrad, 1927–75.
Zhadin, V. I., and S. V. Gerd. Reki, ozera i vodokhranilishcha SSSR, i kh fauna i flora. Moscow, 1961.
Mlekopitaiushchie Sovetskogo Soiuza, vols. 1–2 (parts 1–3). Edited by V. G. Geptner and N. P. Naumov. Moscow, 1961–76.
Zenkevich, L. A. Biologiia morei SSSR. Moscow, 1963.
Flint, V. E., Iu. D. Chugunov, and V. M. Smirin. Mlekopitaiushchie SSSR. Moscow, 1965.
Bobrinskii, N. A. Zhivotnyi mir i priroda SSSR, 3rd ed. Moscow, 1967.
Ptitsy SSSR. Moscow, 1968.
Lebedev, V. D., V. D. Spanovskaia, and K. A. Savvaitova. Ryby SSSR. Moscow, 1969.
Starobogatov, la. I. Fauna molliuskov i zoogeograficheskoe raionirovanie kontinental’nykh vodoemov zemnogo shara. Leningrad, 1970.
Gornostaev, G. N. Nasekomye SSSR. Moscow, 1970.
Bannikov, A. G., I. S. Darevskii, and A. K. Rustamov. Zemnovodnye ipresmykaiushchiesia SSSR. Moscow, 1971.

The USSR is one of the world’s leading countries in commercial fish and game resources, which serve as the basis for such important branches of the economy as fishing, seal hunting, whaling, and game hunting. Of the 125,000–130,000 animal species that inhabit the USSR, many are of great practical importance.

A distinction is made between beneficial animals and destructive animals. In addition to animals that are directly beneficial and destructive, there are animals that are indirectly beneficial to man (various birds, mammals, reptiles, amphibians, and predatory insects that destroy destructive insects, predatory mammals, owls and diurnal predatory birds that feed on mouselike rodents, pollinating insects, and soil-forming animals) and animals that are indirectly harmful (for example, birds that feed on useful insects). The relationship between animals and man is often highly complex and contradictory. For example, wolves attack domestic animals, yet at the same time they are hunted for their fur and themselves perform a beneficial role by destroying sick and weak wild animals. Some rodents, for example, susliks, inflict considerable damage on the economy, yet at the same time they serve as food for several valuable furbearers, such as the weasel Putorius eversmanni and the stone marten (Martes foina).

In recent decades (1930’s through 1960’s), the range of distribution of many animal species decreased in size, both as a result of pursuit by man and the deterioration of the habitats, and consequently a number of animals have become quite rare, such as the goitered gazelle (Gazella subgutturosa). Other animals dispersed widely, chiefly with the help of man, and their numbers increased, for example, the sable, the elk, the beaver, and the saiga (Saiga tatarica). Many have once again become game animals. Some endemic species were brought to new areas and acclimatized there, for example, the raccoon dog and the Japanese deer (Cervus nippon), which were moved from the Far East to the European part of the USSR, and the squirrel, which was relocated from Siberia to the Crimea and the Caucasus. Other species, such as the muskrat, coypu, and the American mink, were imported from America.

Beneficial animals. Useful animals include various game animals and birds, as well as commercially valuable fish, marine mammals, and some aquatic invertebrates.

COMMERCIALLY VALUABLE ANIMALS. The USSR has more than 90 species of furbearers and wild ungulates, but only a few dozen are of any major economic importance. Products obtained through hunting, including medicinal and industrial raw materials, are valued at about 140 million rubles annually. About 30,000 regular and more than 200,000 seasonal hunters work in specialized hunting areas alone. The importance of sport hunting is increasing, with a total of about 2.5 million sportsmen (1975).

Furbearers. About 70 species of fur-bearing animals inhabit the USSR. They are the most important animals hunted commercially, although wild ungulates are steadily gaining increasing importance with both commercial and sport hunters. Twenty million pelts, worth 26 million rubles, were purchased by the state in 1975. The sable, squirrel, muskrat, fox, and arctic fox are the main fur-bearing species. The rest are of secondary importance, although about 20 species are hunted by commercial and sport hunters, including the mole, the European, or pine, marten (Martes martes), the stone marten, the ermine, the weasels Putorius putorius and Putorius eversmanni, the Siberian weasel (Mustela sibirica), the European mink (Mustela lutreola), the American mink (Mustela vison), the otter, the brown bear, the wolf, the raccoon dog, the lynx, various hares, the beaver, and various susliks.

The sable, a typical animal of the Siberian taiga, was threatened with extinction by the beginning of the 20th century. It was designated a protected species and by the 1960’s and 1970’s had regained its former range. The total number varies (1970’s) between 500,000 and 600,000, of which 60 percent are concentrated in the mountains of Southern and Central Siberia. The average annual take in the period 1959–69 was more than 170,000. The total number taken declined slightly in the 1970’s.

The squirrel is the second most important furbearer. Its numbers decreased sharply in the 1920’s and 1930’s. In the 1930’s about 14–15 million pelts were procured annually. The squirrel is hunted in the RSFSR, mainly in Siberia; for example, in 1975, Irkutsk Oblast accounted for 16 percent of the pelts procured, Yakutia for 14 percent, and Krasnoiarsk Krai for 12 percent. Only 3.4–4.8 million pelts were procured annually in the 1970’s, probably because of poor organization of work and a decline in the squirrel population as a result of a decrease in the area of mature coniferous forests and an increase in the population of sables, which attack squirrels.

The muskrat is a North American rodent, whose acclimatization in the USSR was begun in 1928. About 2,500 animals were imported, and shortly thereafter more than 280,000 of their offspring were released into the wild. The muskrat dispersed widely in the course of the next 30 years. The size of its new area of distribution in Eurasia soon exceeded the area of distribution in America, and the muskrat became the third most important fur-bearer in the USSR and, in years of a low squirrel population, the second most important. In the period 1955–57, the muskrat population peaked and then declined for a number of reasons, including overhunting, insufficient supply of food plants, disease, the drainage of lands inhabited by the muskrat, and the drying up of lakes and rivers. In 1975,1.4 million pelts were procured, with the RSFSR accounting for 88 percent, Kazakhstan for 10 percent, and the Ukraine for 1.1 percent.

The fox is found in all open and cultivated landscapes except the tundra. It avoids dense forests and is encountered in the taiga zone only in river valleys. About 54 percent of the animals are concentrated in the forest and forest-steppe zones and 22.7 percent in the forest zone, including 10 percent in the taiga and 18.2 percent in the Middle Asian deserts (1966–70). The fox population is increasing with the development of agriculture, reaching 1.5 million in a favorable year. About 460,000 pelts were procured annually in the 1960’s and 1970’s. In 1975, the RSFSR accounted for 40 percent of the country’s total procurement, Middle Asia for 33 percent, and the Ukraine for 12 percent. In Kazakhstan the most experienced hunters kill about 350 foxes in one season; the average take is several dozen. Foxes also serve a beneficial purpose, since they destroy harmful rodents (about 3,000 voles and mice a year per fox). However, they are destructive in areas where game birds are raised.

The arctic fox accounts on the average for 90–95 percent of the total value of furs obtained in the tundra and 7–8 percent of the total value of the entire fur trade in the USSR. In a favorable year, its population may number half a million individuals, and in poor years, 80,000–100,000. The total annual take is comparatively stable, numbering 52,000–110,000 (1960’s and 1970’s). The main reason for the fluctuations in the arctic fox population is sharp changes in the abundance of its principal food—the lemming. Arctic foxes are hunted chiefly in the northern part of Western Siberia (29–34 percent), in the northern part of Krasnoiarsk Krai (25–33.5 percent), and in Yakutia (22–32 percent).

The European mole is an inexpensive and common furbearer, inhabiting the southern forest zone and the forest steppe of the European USSR. A total of 5.9–13.4 million pelts were procured annually in the period 1971–75. The RSFSR accounted for 90 percent, and the Ukrainian and Byelorussian SSR’s, for 10 percent.

The pine marten inhabits the forests of the European USSR, and the stone marten, the open and mountainous areas of the southern part of the European USSR, Transcaucasia, and Middle Asia. The pine marten population varies from 200,000 to 300,000, while the stone marten population numbers about 100,000. In the period 1965–72, 80 percent of the pelts from both marten species were procured in the RSFSR, 8.8 percent in Transcaucasia, 4 percent in Byelorussia, and 3.7 percent in the Ukraine. The pine marten is taken primarily in the RSFSR and the Byelorussian SSR, and the stone marten, in Transcaucasia and the Ukraine.

The ermine is found almost everywhere. About 95,000–141,000 pelts were procured annually in the period 1971–75, of which up to 98 percent were taken in the RSFSR (58 percent in Yakutia, 10 percent in Tiumen’ Oblast, and 7 percent in Krasnoiarsk Krai).

The brown bear is hunted chiefly by sport hunters. There are about 100,000 bears (1970’s), of which about 96,000 are in the RSFSR, about 3,000 in the mountains of Transcaucasia and Middle Asia, and less than 1,000 in the Ukraine, Byelorussia, and the Baltic Region.

The wolf is characteristic of open and virtually snowless landscapes; it avoids dense forests. When present in large numbers, it poses a threat to domestic and beneficial wild animals, and consequently the control of the wolf population is essential. In 1973 there were about 50,000 wolves, of which 13,000–14,000 were in the RSFSR, about 30,000 in Kazakhstan, 500 in the Ukraine, 1,000 in Byelorussia, and 5,000 in Middle Asia. Wolves are particularly destructive in Kazakhstan.

Wild ungulates. About 20 species of wild ungulates inhabit the USSR, but only six species are of practical importance.

The elk inhabits almost the entire forest zone; it is also found in the forest tundra and tundra and, in the south, in the forest steppe and island forests. In 1970 the elk population totaled 700,000, of which 500,000 were in the RSFSR, 133,000 in the Ukraine, 23,000 in Byelorussia, 10,000 in Estonia, 17,000 in Latvia, 7,000 in Lithuania, and 1,000 in Kazakhstan. About 60,000–70,000 elks, including 30,000 actually accounted for, are taken annually. The elk is hunted by both commercial and sport hunters. In some parts of the RSFSR, the value of the products obtained from the elk exceeds that of the fur trade in these regions.

The wild reindeer inhabits the tundras and most of the taiga. It was almost exterminated by the beginning of the 20th century, but by the 1970’s the population had increased to 600,000–700,000. The largest herd, which numbers about 350,000 individuals, is concentrated on the Taimyr Peninsula; about 200,000 live in Yakutia and 14,000 on the Kola Peninsula. The reindeer in Yakutia and on the Taimyr Peninsula are not being sufficiently exploited. About 60,000–70,000 are taken annually (1970–75).

The red deer is an important game animal, hunted by both commercial and sport hunters. It is widely distributed in mixed and broad-leaved forests of the European USSR; it is also found in some parts of the tugai and mountain forests of the Asiatic part of the USSR. There were 120,000–130,000 animals in 1972, up to 50 percent of which were in game preserves. Of the 110,000–120,000 deer in the RSFSR, 87 percent are in the Asiatic part (more than 60 percent in the mountains of Southern Siberia and 20 percent in the Far East). About 15,000–17,000 are taken annually (1970–73). Red deer—maral and wapiti—are bred on specialized farms to obtain panty (unossified deer antlers used as a source of medicinal preparations).

The roe deer inhabits the forest steppe, wooded fields, and the virtually snowless southern part of the forest zone. It survives without difficulty in a cultivated agricultural landscape. The roe deer is a promising and valuable species for sport and commercial hunting. The population (1970) varies from 600,000 to 900,000 individuals, of which 166,000 inhabit the Baltic Region, 20,000 Byelorussia, and 123,000 the Ukraine. Its numbers are growing in the European part of the country, where it is most effectively protected. In the 1960’s, at least 65,000 (estimate) were taken annually.

The wild boar is widely distributed but is rarely found north of the southern taiga. The population numbered several hundred thousand individuals in the 1970’s. More than 25 percent live in the southern regions of the Far East and about 25 percent in the Northern Caucasus. A large and ever-increasing number of wild boar are found in the southern and central parts of the European USSR. Although it appears to be a promising game animal, it is destructive to agriculture. At least 30,000–40,000 are killed annually (1970’s).

The saiga is characteristic of the dry steppes and semideserts of Kazakhstan and the Caspian Region. It had become almost extinct by the beginning of the 20th century, but owing to protective measures, its population increased sharply and in 1974 numbered 1.5 million individuals in Kazakhstan and 400,000 in the RSFSR.

Among other species, the musk deer is of particular importance. It inhabits the mountains of Siberia and yields, in addition to meat and hides, valuable musk. Its population numbers about 300,000 (1970); the deer is little exploited.

About ten species of mountain ungulates are few in number, including the argali (Ovis ammon), turs (Capra caucasica and Capra cylindricornis), the chamois (Rupicarpa rupicarpa), the Siberian ibex (Capra ibex), and the bighorn sheep (Ovis canadensis), and two desert dwellers—the goitered gazelle and the Asiatic wild ass (Equus hemionus). The hunting of all these animals is prohibited or greatly curtailed.

GAME BIRDS. About 100 species of game birds inhabit the USSR. The annual take in the period 1971–75 was as follows: waterfowl, 33.1 million; tetraonids, 9.2 million; quails, 4.1 million; and other game birds, 5.1 million. The total annual weight of the meat from game birds is 42,100 tons.

Waterfowl. Waterfowl are the most traditional and popular game birds. At the end of the 1960’s, 45–55 million waterfowl (autumn population) were nesting in the USSR, primarily in the tundra and forest tundra (20–25 million), where almost all the geese (1.5 million) are concentrated. Among ducks, the most numerous are the old-squaw (Clangulla hyemalis), which numbers 2 million, the king eider (Somateria spectabilis), and the scaup (Aythya marilla). In the taiga, the autumn duck population numbers 6–7 million; the common species include the pintail duck (Anas acuta), the mallard (Anas platyrynchos), and the true teal (Anas creced). In the mixed and broad-leaved forests of the European USSR and the Far East, it numbers 4.5–5.5 million; the main species are the mallard, the true teal, the garganey (Anas querquedula), the pintail duck, the shoveler (Anas clypeata), and the widgeon (Anas penelope). In the forest steppe and steppe, where the lakes and rivers abound in waterfowl, 9.5–11 million birds remained by the mid-1970’s, while in semidesert and desert bodies of water 5–5.6 million remained. Their numbers have decreased not only as a result of hunting and environmental changes in the nesting areas, but also as a result of the destruction of the birds while in flight and at the wintering areas, which are often outside the USSR.

Gallinaceous birds. Of practical importance are the willow ptarmigan (Lagopus lagopus), the rock ptarmigan (Lagopus mutus), the black grouse (Lyrurus tetrix), the hazel hen (Tetrastes bonasia), the common capercaillie (Tetrao urogallus), the black-billed capercaillie (Tetrao parvirostris), and the quail (Coturnix coturnix). The significance of gallinaceous birds compared to waterfowl is underestimated because commercial hunting has declined and sport hunting is not well developed. Gallinaceous birds number in the tens of millions. About 10 million were taken annually (late 1960’s).

The willow and rock ptarmigans, which are most numerous in the southern tundra, account for about 80 percent of the centralized procurement of gallinaceous birds, of which there are about 20–30 million. The hazel hen and the common and black-billed capercaillies are taiga species, numbering approximately 30–40 million, most of which are concentrated in the European north and in Western Siberia. The common capercaillie is found west of the Enisei River, and the black-billed capercaillie, east of the Enisei; there are about 2–3 million capercaillies. The grouse population has declined; the autumn population is about 27 million (mid-1960’s). The number of Hungarian partridges (Perdix perdix), pheasants, and quails has also decreased considerably; nevertheless, in the autumn quails are still widely hunted in the southern European USSR.

Other game birds include many species of Limicolae, especially the woodcock (Scolopax rusticola) and various snipes of the genus Gallinago, including the great snipe (Gallinago media).

N. A. GLADKOV and E. V. ROGACHEVA

FRESHWATER ANIMALS. The freshwater fauna of the USSR is rich and varied; there are 27 fish families, encompassing 301 species. Although fish catches in inland waters are approximately nine times less than the catches in the seas, freshwater fish are important as a source of food. The bulk of the fish caught are chastikovye fish (fish caught in fine-mesh nets), both large and small fish. The former include a number of cyprinids, such as the ide (Leuciscus idus) and European bream (Abramis brama), as well as the common pike perch (Lucioperca lucioperca), the pike (Esox lucius), and the burbot (Lota lota). The latter are primarily cyprinids, such as the crucian carp (Carassius carassius), the roach (Rutilus rutilus), and the dace (Leuciscus leuciscus), as well as the Eurasian perch (Perca fluviatilis) and the ruff (Acerina cernua).

Acipenseroids are the most valuable fish. Only the sterlet (Acipenser ruthensis) and the Old World shovelnose sturgeons are purely freshwater species. The sterlet inhabits primarily the rivers of the European USSR and the Ob’ and Enisei river basins, while the shovelnose sturgeons inhabit the Amu Darya and Syr Darya. Among the salmonids, freshwater trout of the genera Salmo and Oncorhynchus, the European stone loach (Nemachilus barbatulo), and the taimen (Hucho taimen) are purely freshwater species, while fish of the genus Coregonus are mostly freshwater. The trouts are freshwater forms of the migratory salmon trout (Salmo trutta) and inhabit the cold-water lakes and rivers of Europe. The stone loaches are found in most bodies of water in the Far North; the lake form—the lake char (Salvelinus lepechini)—lives in the northern lakes of Siberia, as well as in Lakes Ladoga and Onega. The taimen and the lenok (Brachymystax lenok) live in the northern rivers of Eurasia. The genus Coregonus includes such major commercial fish as various ciscos, the tugun (Coregonus tugun), the arctic cisco (Coregonus autumnalis), the common whitefish (Coregonus clupeiformes), the peled (Coregonus pelea), the broad whitefish (Coregonus nasus), the muksun (Coregonus muksun), and the round white-fish (Coregonus cylindraceus). The European cisco (Coregonus albulo) and the common whitefish live in the northern European USSR; the remaining species of the genus Coregonus live in Siberia, where they are unusually varied and numerous. The ichthyo-fauna is changing radically because of the sharp increase in the number of reservoirs. One of the most important economic goals is to transform the reservoirs into highly productive fisheries. Among the large chastikovye fish in most reservoirs of the European USSR, the European bream and occasionally the pike are particularly numerous. Large stocks of various whitefish (peled, common whitefish, broad whitefish) can be created in the major reservoirs of Siberia.

Pond fish culture, an intensive form of fish culture that helps boost the productivity of lakes and rivers, is playing an increasingly important role in the Soviet fishing industry. It is mainly concerned with raising domesticated carp, as well as the grasscarp, or white amur (Ctenopharyngodon idella), the bighead carp (Aristichthys nobilis), and the rainbow trout (Salmo gairdnerii). Pond fish catches increased by a factor of 5 in the period 1955–70. Pond fish production rose from 630,000 quintals in 1970 to 1,368,700 quintals in 1975. The combined raising of two and even three species is now routine. The trout, the peled, and other species are also bred. Sport fishing is a major pastime in densely populated parts of the country; for example, in the city of Moscow and Moscow Oblast alone, there are about 1 million sport fishermen.

The preservation and restoration of fish stocks are dependent on the solution of such problems as lowering the water level in the Caspian Sea and increasing the salinity of the Sea of Azov, as well as problems related to the implementation of ameliorative and other measures and the construction of hydroengineering structures on rivers, lakes, and reservoirs.

Characteristics of freshwater fish stocks in individual regions. Lakes Ladoga and Onega are very important in the northern part of the European USSR. At the end of the 1960’s, 70 percent of the catches in Lake Ladoga consisted of smelts, small ciscos, the Eurasian perch, the ruff, the roach, and the silver bream (Blicca bjoerkna). The annual commercial fish catch in the most important river, the Pechora, is 20,000 quintals, about 70 percent of which consists of such valuable fish as salmons and graylings. In some years, as much as 7,500 quintals of Atlantic salmon (Salmo salar) are caught here, which constitutes 60 percent of the national catch. Most of the valuable fish, including the arctic cisco, the nelma (Stenodus leucichthys nelma), the European cisco, the common whitefish, the broad whitefish, and the peled, are caught in the lower Pechora. In the upper Pechora are the spawning grounds of most of the country’s Atlantic salmon.

In the central part of the European USSR, the ichthyofauna has undergone fundamental and frequently irreversible changes, but the fish stocks are still quite substantial. The most promising sources are the rivers and lakes of the Baltic Sea basin, where salmonids abound, including the Chudskoe whitefish (Coregonus lavaretus maraenoides), the Volkhov whitefish (Coregonus lavaretus baeri), the European cisco, the lacustrine smelt (Osmerus ereplanus ereplanus morpha spivinchus), and the common Atlantic salmon (Salmo salar). The fish of the Dnieper and Volga river basins are of little value, possessing only local significance.

In the southern part of the European USSR, there are no large lakes, fishing in rivers is poorly developed (except in the lower reaches), and the fishing industry is part of the ocean fishing industry. Common freshwater species include the European bream, the pike perch, the pike, the roach, the wild carp (Cyprinus carpio), the blue bream (Abramis ballerus), the saber carp (Pelecus cultratus), the ide, and the perch. Of particular importance are reservoirs, in which the feeding conditions are favorable for the rapid growth of many valuable fish, such as the wild carp, the European bream, and the pike perch. The fish productivity in such reservoirs is 2–60 kg/hectare (kg/ha) or more, and in the early 1960’s more than 200,000 quintals of fish were caught there. Pond fish culture involving the use of inferior and artificial bodies of water is being successfully developed. The principal fish raised is the domesticated carp, along with the grasscarp, the European bream, and even the peled. In the Ukraine, 436,000 quintals of pond fish were produced in 1975. The bulk of the crayfish is caught in the southern part of the European USSR (1,450 quintals in the Tsimliansk, Kakhovka, and Volgograd reservoirs in 1964).

Pond fish culture is developing in the Caucasus, especially in Azerbaijan and Georgia. The fish productivity of the reservoirs on the Manych River is substantial. Lake Sevan is the most important lake; the Sevan trout (Salmo ischchan) is raised in hatcheries.

Endemic genera are characteristic of the lakes and rivers of Kazakhstan and Middle Asia: Schizothorax, Diptychus, and Nemachilus. The basis of the catches in Lake Balkhash is the acclimatized wild carp and the endemic balkhash perch (Perca schrenki; 80,000–100,000 quintals caught annually in the 1950’s). Marinkas and osmans are typical of mountain lakes and rivers. The roach, the ide, the crucian carp, and barbels are widespread in the rivers. Pond fish culture is most developed in Uzbekistan. About 18,000 quintals of pond fish were obtained in Uzbekistan and Kazakhstan in 1965 and 95,000 quintals in 1975.

Western Siberia is the principal fishing region of Siberia, accounting for more than 70 percent of all the fish caught in Siberia (600,000–700,000 quintals annually at the end of the 1960’s). The catches in the Ob’ and Irtysh river basins are eight to ten times greater than those in the Lena or Enisei river basins because of the developed floodplain and the large number of floodplain lakes and rivers. The principal fish caught are various whitefish, the nelma, and acipenseroids. Whitefish are the most valuable. The Ob’ river basin accounts for 52 percent of all the whitefish caught in Siberia. Whitefish catches in Tiumen’ Oblast increased between 1969 and 1974 from 46,600 to 95,600 quintals. The relative share of chastikovye fish—cyprinids [ide, roach, dace, crucian carp, tench (Tinca tinca)], the pike, the burbot, the perch, and the ruff—is large. More than 100,000 quintals of pike, 25,000–40,000 quintals of ide, about 100,000 quintals of burbot, and about 60,000 quintals of ruff are caught in the most favorable years.

Central Siberia encompasses almost the entire basin of the Enisei basin (one of the five largest rivers with respect to the size of fish stocks), which is famous for its acipenseroids and salmonids. Its fish productivity is low, 2.7–5.2 kg/ha. The share of valuable fish in the catches is particularly considerable north of the Turukhan River, constituting 60–94 percent of all the catches (common whitefish, muksun, arctic cisco, cisco). In the middle and lower reaches of the Enisei, the burbot, the pike, the perch, and various cyprinids (dace, roach) make up the bulk of the catches. The large arctic lakes in northern Krasnoiarsk Krai are important. Whitefish and other salmonids make up about 90 percent of the catches. The stocks of the main commercial fish of the Enisei (acipenseroids and salmonids) were largely restored by the beginning of the 1970’s as a result of extensive conservation measures.

The principal body of water in the mountainous part of Southern Siberia is Lake Baikal, which accounts for about 70 percent of the fish catch in the region. Of commercial significance are the arctic cisco (39,400 quintals in 1961), the roach, the Eurasian perch, the pike, the crucian carp, various gobies, and the burbot.

The Baikal seal (Phoca sibirica) is also caught (2,500–3,000 animals a year from a population of 25,000–30,000).

In Yakutia, the main fishing waters are the Lena River, whose lower reaches are inhabited by the Siberian sturgeon (Acipenser baeri), the taimen, the nelma, and various whitefish. The river delta has been designated a fish sanctuary because of the decline in the population of a number of valuable fish species. There are many lakes (more than 650,000, with a total area of 6.7 million ha), but only 5,700 quintals of fish, primarily crucian carp, were caught in the 1960’s. The total supply of commercial fish in Yakutia has been estimated at 90,000–100,000 quintals.

In the southern part of the Far East and Primor’e Krai, the Amur River is the principal freshwater body. Its commercial fish stocks long consisted chiefly of Pacific salmon, which come to spawn here. Their fishing is now prohibited, as well as the fishing of local acipenseroids, such as the kaluga (Huso dauricus) and the Amur sturgeon (Acipenser schrenki). Chastikovye fish, such as the wild carp, the grasscarp, the silver carp (Hypophthalmichthys molitrix), the skygazer (Erythroculter erythropterus), the European bream, the yellowcheek (Elopichthys bambusa), the Amur pike (Esox reicherti), the sheatfish (Silurus glanis), and the crucian carp, constitute the bulk of the fish catches. A few whitefish, taimens, lenoks, and graylings are found in the catches. About 100,000 quintals of fish were caught annually at the beginning of the 1970’s. The small rivers that empty into the Sea of Japan and the Sea of Okhotsk are important spawning grounds of migratory salmon.

E. V. ROGACHEVA

MARINE ANIMALS. Fish, invertebrates (crustaceans, mollusks, echinoderms), and mammals are among the marine animals of the inland waters and adjacent marginal seas of the USSR that are of commercial significance. Fishing and whaling outside the territorial waters of the USSR are also very important economically.

Fish. About 250 species are commercially important. Most of the catches consist of gadids and clupeids; the former include the walleye pollock (Theragra chalcogramma), the Atlantic cod (Gadus morhua), the haddock (Melanogrammus aeglefinus), and the pollack (Gadus vireni), while the latter include various herrings and sprats. Osmerids, such as the capelin (Mallotus villosus) and smelts, are somewhat less important, as are pleuronectids and scorpaenids. Migratory fish that fatten in the sea but reproduce in rivers (acipenseroids and salmonids) are particularly valuable.

The USSR leads the world in the abundance and variety of acipenseroids; there are 13 species, including the beluga (Huso huso), the kaluga, and the ship sturgeon (Acipenser nudiventris) the stellate sturgeon (Acipenser stellatus), and five other acipenseroid species. The Caspian Sea is the main source of acipenseroids. Catches are strictly regulated and are even prohibited in some places; as a result, the population, which by the beginning of the 20th century had been nearly exterminated as a result of rapacious fishing, has begun to grow. Considerable attention is given to the artificial breeding of young acipenseroids in order to ensure their reproduction, since they have been deprived of their natural spawning grounds as a result of the construction of various hydroengineering structures. In 1975, 110 million young belugas, common sturgeons (Acipenser sturio), and stellate sturgeons were bred in sturgeon hatcheries.

The most important salmonids are the Pacific salmon, including the pink salmon (Oncorhynchus gorbuscha), the chum, or dog, salmon (Oncorhynchus keta), the sockeye salmon (Oncorhynchus nerka), and the chinook salmon (Oncorhynchus tschawytscha), which spawn in the rivers of the Far East. The hatcheries of the Far East release more than 800 million chum salmon and pink salmon fry every year. The most valuable Atlantic salmon—the common Atlantic salmon (Salmo salar) and the salmon trout (Salmo trutta)—fatten in the North Atlantic but spawn in the rivers of Northern Europe, including the rivers of the USSR.

Invertebrates. Crustaceans are commercially important. The king crab (Paralithodes camtschatica) constitutes 80 percent of the world production of canned crabmeat; it is prepared on floating canneries. The main concentrations are found off western Kamchatka. Attempts are under way to acclimatize crustaceans in the Barents Sea. The shrimp industry is well developed in the Far East and in the Black Sea. Mollusks (oysters, mussels, pectens, squids) and echinoderms (sea urchins, trepangs) are also harvested.

Mammals. The northern part of the Pacific is the only region in the northern hemisphere where whaling is carried on. The animals are hunted in the open sea by the USSR and Japan. Whaling has been prohibited in the northern part of the Atlantic since 1938. The USSR is a member of the International Whaling Commission, which sets annual quotas for the number of whales taken. Strict measures to regulate the industry have resulted in an increased whale population in the northern part of the Pacific Ocean. Delphininae, primarily the common dolphin (Delphinus delphi), were hunted in the Black Sea before the practice was banned in 1966, and by the early 1970’s the population numbered 200,000. The beluga (Delphi nepterus leucas) can be hunted in several arctic regions and in the Far East.

Among the pinnipeds, the principal animal hunted is the Greenland seal (Tursiops truncala; population 3 million in 1928 and 500,000–600,000 in 1974), a small number of which are taken in the Barents and White seas (the USSR and Norway together account for 30,000–40,000 animals per year). Their hunting was prohibited in 1965, and their numbers have gradually increased. The limited hunting of whitecoats—young seal pups—was authorized in 1972. The ringed seal (Pusa hispida) is also hunted in the arctic (about 10,000 a year). Small numbers of the bearded seal (Erignathus barbatus) were taken before 1970. The ringed seal (population in 1974 about 800,000) and, less commonly, the Pacific harbor seal (Phoca vitulina), the ribbon seal (Phoca fasciata), and the bearded seal are hunted in the Far Eastern seas (total number, 735,000 individuals). Their hunting is limited to 65,000 per year.

Walruses are hunted only in the northern part of the Far East. The indigenous inhabitants of Chukotka and Alaska are permitted to kill 3,000–3,500 animals per year. Whitecoats of the Caspian seal can be hunted on a small scale. The number of Far Eastern eared seals, such as the northern fur seal (Callorhinus ursinus) and Steller’s sea lion (Eumetopias jubatus), is insignificant. Northern fur seals were almost completely exterminated by the beginning of the 20th century. In 1957, the USSR, the United States, Canada, and Japan adopted a temporary convention for the protection of northern fur seals in the northern part of the Pacific. Only strictly regulated hunting was permitted along the coast at the beginning of the 1970’s. The USSR accounts for 15,000–20,000 per year, and the United States, for 50,000–60,000. The northern fur seal population in the USSR in the mid-1970’s was about 200,000. Steller’s sea lion in USSR waters numbers (1970’s) 40,000–45,000. A small number (6,000–8,000) are taken by local inhabitants.

E. V. ROGACHEVA

Characteristics of the fauna of inland waters and adjacent seas. The Barents and White seas are commercially important. There are 114 species in the Barents Sea, of which the following are of commercial value: the cod, the haddock, the pollack, fish of the genus Sebastes, the Greenland halibut (Reinhardtius hippoglossodes), various flatfish, the Atlantic wolffish (Anarhichas lupus), herrings, the arctic cod (Boreogadus saida), and the capelin. Of particular importance are cod and haddock, which constitute 60–90 percent of the total catch. The catches of Sebastes, flatfish, and the Greenland halibut have declined. The total annual fish catch in 1973–74 amounted to 6.4–9.8 million quintals.

The White Sea has more than 60 fish species, of which the herring, the navaga (Eleginus navaga), the Atlantic salmon, and various whitefish are commercially important. The navaga is the principal fish caught. Herring and Atlantic salmon catches have declined in recent years. The total annual fish catch in 1973–74 was 17,000–25,000 quintals.

About 70 fish species inhabit the Baltic Sea, with the following possessing commercial importance: the Baltic sprat (Sprattus sprattus balticus), the Baltic herring (Clupea harengus membras), the Baltic cod (Gadus mohua callarlas), and flatfish, smelts, eels, salmon, and lampreys. Most of the catch consists of the Baltic herring (about 80 percent), the Baltic sprat, and the Baltic cod. Owing to a reduction in the stocks and the intensification of fishing, the catches of Baltic herring and cod have declined. The annual volume of fish caught in the period 1965–76 varied from 1.8 to 3.4 million quintals.

The ichthyofauna of the arctic seas (Kara, Laptev, East Siberian, and Chukchi seas) is quantitatively and qualitatively poor. Of the approximately 60 fish species, only the arctic cisco, the cisco, the navaga, the stone loach, and the muksun are commercially important. The catches are small and restricted to coastal waters.

The ichthyofauna of the Far Eastern seas is rich and varied. Of the approximately 800 fish species, the walleye pollack, the herring, various Pacific salmon, gadids, flatfish, the halibut, Sebastes, the Atlantic mackerel (Scomber scombrus), the Pacific saury (Cololabis saira), and the atka mackerel (Pleurogrammus monopterygius) are of commercial importance. The principal resources of the Far Eastern seas are the salmonids, including the coho salmon (Oncorhynchus kisutch), the chinook salmon, the pink salmon, and the chum salmon, but their stocks and catches have declined everywhere. The catches of the Pacific saury and the Atlantic mackerel fluctuate from year to year, depending on the size of the generations that replenish the commercial stock. The walleye pollack, available in large numbers (15–17 million quintals caught annually in the 1970’s), is a promising fish source. The total annual fish catch in the Far Eastern seas is about 30 million quintals. The main fisheries are in the Bering Sea and the Sea of Okhotsk.

The ichthyofauna of the southern seas is very uniform because of the common origin of the fish. There are about 300 fish species and subspecies in the Aral and Caspian seas, the Sea of Azov, and the Black Sea. Many endemic and relict forms exist here. The Caspian fish stocks have decreased because of the lowering of the sea level and the regulation of the river flow owing to the construction of the hydroelectric power plant cascade. The total fish catch in the Caspian in 1974 was 4.6 million quintals. The sprat is the main commercial fish. The catch of acipenseroids increased in the 1970’s as a result of ameliorative measures, while the stocks and catches of the roach, the European bream, the wild carp, and the pike perch declined sharply.

The ichthyofauna of the Aral Sea is meager. The main commercial fish are the European bream, the pike perch, the wild carp, the barbel, the asp (Aspius aspius), and the sheatfish. The pike perch and the asp make up 65 percent of the catch. Work on the acclimatization of fish and food organisms is needed in order to improve the species composition of the ichthyofauna. The total annual catch in 1973–74 was 162,000–188,000 quintals. The principal commercial fish in the Black Sea are the Black Sea anchovy, the horse mackerel (Trachurus trachurus), and sprats. Flounder, mullets of the genus Mugil, and the red mullet Mullus barbatus constitute an insignificant fraction of the catch. The total annual catch in 1973–74 was 1.1–1.3 million quintals. The principal fish caught in the Sea of Azov are anchovies and tiulkas. Changes in prevailing marine conditions have caused the European bream and pike perch stocks and catches to decrease. The initiation of fish breeding has resulted in the growth of the acipenseroid population. The total annual fish catch in 1973–74 was 1.6–2.0 million quintals.

The USSR has developed and is implementing various measures to ensure the efficient management of the fishing industry (see below: Conservation).

E. G. PETROVA

Destructive animals. Among the animals that inflict damage to the economy and injure human health are forest and crop pests, bloodsucking flies, and animals that are sources of diseases of man and beneficial wild and domestic animals.

CROP PESTS. The principal crop pests are insects, as well as mites and ticks, nematodes, terrestrial mollusks, and rodents. Crop pests are subdivided into polyphagous pests (those that injure various crops) and specialized pests (those that feed on a single crop or several related crops). A distinction is made between grain, industrial crop, vegetable, melon, potato, and other types of pests.

The principal polyphagous grain pests are various owlet moths, the European corn borer (Pyrausta nubilasis), wireworms, false wireworms, and locusts. The most destructive specialized pests in the steppe zone are the Hessian fly (Mayetiola destructor), the grain pentatomid Eurygaster integriceps, grain beetles of the genus Anisoplia, Zabrus tenebrioides, Euxora nigricans, and the wheatworm (Anguina tritici), and in the nonchernozem zone, the frit fly (Oscinella frit), the gout fly (Chlorops pumilionis), the stem flea beetle (Chaetocnema hortensis), and the owlet moth Apamea paludis (or Amphipoea fucosa). The polyphagous species are particularly dangerous for corn, for example, the mole cricket Gryllotalpa gryllotalpa, the European corn borer, Agrotis segetum and other gnawing owlet moths, and the cotton bollworm (Heliothis armigera).

Of the industrial crops, the sugar beet is most subjected to injury. Its most dangerous pests are the beet webworm (Lyxostege stricticalis), Agrotis segetum and other gnawing owlet moths, wireworms, beet weevils, and the beet bug (Poeciloscytux cognatus). All the cotton pests in the USSR are polyphagous; they include locusts, cotton aphids, the cotton bollworm, wire-worms, false wireworms, and red spider mites. The most dangerous specialized cotton pests are not found in the USSR owing to the well-developed quarantine service.

Forty species of vegetable and melon pests are particularly dangerous. Vegetables of the family Cruciferae, such as cabbages and turnips, are the most susceptible. They are attacked by the cabbage maggot (Hylemyia brassicae), curculionid wireworms, Ceutorrhynchus pleurostigma, flea beetles, cabbage butterflies, the cabbage cutworm (Barathra brassicae), and the diamondback moth (Plutella xylostella). Potatoes are attacked by more than 60 species of pests, chiefly the Colorado potato beetle (Leptinotarsa decemlineata), which has penetrated into the western part of the USSR, where systematic control measures have been instituted. Wireworms and the Far Eastern 28-spotted ladybug (Epilachna virgintioctomaculata) are also dangerous.

Of the fruit pests, various beetles, butterflies, and aphids are the most dangerous. The most susceptible are apple trees [codling moth (Carpocapsa pomonella)] and pear, plum, and cherry trees, grape vines, and various berries, including strawberry and raspberry. Many pests were brought in from other countries before the organization of the quarantine service in the USSR, including Phylloxera and the San Jose scale (Quadraspidiotus perniciosus). Citrus crops are injured by the citrus whitefly (Dialeurodes citri), the dictyospermum scale (Chrysomphalus dictyospermi), and the armored scale Leucaspis japonica.

The damage inflicted by many pests is decreasing as a result of major contouring of fields, the use of advanced farming techniques, and constant control efforts.

FOREST PESTS. Trees and shrubs in the USSR are attacked by a variety of pests. Extensive insect reproduction is especially frequent in Siberia and the central part of the European USSR. Primary pests (needle- and leaf-gnawing pests) attack healthy trees. Such pests are mostly caterpillars, especially of silkworm moths, and some beetles, hymenopterans, homopterons, and hemipterans. The most dangerous pest of Asiatic coniferous forests is the silkworm moth Dendrolimus sibiricus, which attacks mainly cedar, fir, and larch and about 17 other coniferous species. In the central part of the European USSR, the pine moth Dendrolimus pini, the nun moth (Ocneria monacha), the pine moth Panolis flammea, and the pine looper Bupalus piniarus attack pines and other trees. Other pests include pine-shoot moths and, among the hymenopterans, sawflies of the family Pamphiliidae. The gypsy moth (Porthetria dispar) is a dangerous pest of hardwood trees in the European USSR. Oaks are attacked by the gold-tail moth (Euproctis chrysorrhoea) and the European oak roller moth (Tortrix viridina), birches by sawflies, and aspens, poplars, and willows by the satin moth (Leucoma salicis) and the aspen leaf beetle (Melasoma tremulae). Secondary (trunk) pests, which damage weak or dying trees, include various beetles, carpenter moths, and, of the hymenopterans, horntails. Most live in or under the bark (bark beetles), while some live in the xylem, for example, long-horned beetles (Cerambycidae) and jewel beetles (Buprestidae). Root (soil-inhabiting) pests, such as chafer larvae, wireworms, and false wireworms, are especially dangerous for young trees in natural forests, nurseries, and planted forests.

Fruits and seeds are injured primarily by leaf-roller moth caterpillars, pyralids, and curculionids, as well as by the eastern larch beetle (Dendroctonus simplex) and olethreutid caterpillars.

WILD ANIMALS HARMFUL TO MAN AND DOMESTIC ANIMALS. Wild animals carry, transmit, or cause many diseases (zoonoses). Some bloodsucking arthropods, such as ticks, dipterans, and fleas, are transmitters and reservoirs of diseases. Wild mammals and, less commonly, birds and domestic animals may be carriers (hosts). Helminths and protozoans are causative agents of various diseases. Human beings and domestic animals may serve as hosts. Among the main zoonoses prevalent in the USSR are the plague, encephalitis, leptospirosis, hemorrhagic fevers, tularemia, toxoplasmosis, malaria, and leishmaniasis. Bloodsucking dipteran insects, such as bloodsucking flies and gadflies, are very injurious to the health of human beings and domestic animals.

N. A. GLADKOV and E. V. ROGACHEVA

Bibliography

Monchadskii, A. S. Letaiushchie krovososushchie dvukrylyegnus. Moscow-Leningrad, 1952.
Luzanskaia, D. I. Rybokhoziaistvennoe ispol’zovanie vnutrennikh vodoemov SSSR. Moscow, 1965.
Kirikov, S. V. Promyslovye zhivotnye, prirodnaia sreda i chelovek. Moscow, 1966.
Moiseev, P. A. Biologicheskie resursy Mirovogo okeana. Moscow, 1969.
Resursy biosfery na territorii SSSR. Moscow, 1971.
Akklimatizatsiia okhotnich’e-promyslovykh zverei i ptits v SSSR, parts 1–2. Kirov, 1973–74.
Okhotnich’e khoziaistvo SSSR. Moscow, 1973.
Resursy zhivotnogo mira SSSR. Moscow, 1969. (Itogi nauki: Geografiia SSSR, fase. 7.)
Arsen’ev, V. A., V. A. Zemskii, and I. S. Studenetskaia. Morskie mlekopitaiushchie. Moscow, 1973.
Biologicheskaia produktivnost’ Kaspiiskogo moria. Moscow, 1974.
Syroechkovskii, E. E., and E. V. Rogacheva. Zhivotnyi mir SSSR: Geografiia resursov. Moscow, 1975.
Kolosov, A. M. Okhrana i obogashchenie fauny SSSR. Moscow, 1975.

The USSR spans four geographic belts: the arctic belt, in which the arctic desert zone is located; the subarctic belt, in which the tundra and forest-tundra zones are located; the temperate belt, in which the zones of taiga and mixed and broad-leaved forests are located (these can also be considered subzones of a single forest zone), as well as the forest steppes, steppes, semideserts, and deserts; and the subtropical belt, in which the semidesert zone and the Mediterranean zone of dry-summer forests and shrubs are located (the Mediterranean zone is sometimes considered a subzone within the zone of subtropical forests). Most of the USSR is in the temperate belt.

Zonality is best expressed on the East European Plain and in the Western Siberian Lowland. In Central and Eastern Siberia latitudinal zonality is less marked, primarily owing to the ruggedness of the topography, greater continentality of the climate, and the presence of permafrost. In the Far East it is disrupted by the effect of the seas, with their cold and warm currents, and by the monsoon circulation of air masses and the complex topography. In the mountains latitudinal zonality is further complicated by altitudinal landscape belts, differences in slope exposure, the barrier role of mountain ranges, and various other factors.

Arctic desert zone. The zone of arctic deserts is characterized by a harsh arctic climate; glaciers are widespread on Novaia Zemlia, Franz Josef Land, and Severnaia Zemlia, and the snow cover lasts virtually the entire year. Even in the southern part of the zone, the temperature of the warmest month (July or, in some regions, August) seldom rises above 4°–5°C, although along the southern shore of the Barents Sea it occasionally reaches 8°C. The ground is permanently frozen everywhere. The phenomena of solifluction, ground swelling, and thermokarst are widespread. Vast areas are covered by detritus. The processes of water erosion are virtually nonexistent, since they occur only during the period with above-freezing temperatures, which is very short in the arctic desert zone. Only a thin layer of arctic soils, which are neutral or weakly alkaline and ferruginous, develops on the fine-earth subsoil.

The vegetation is extremely sparse, dominated by mosses, lichens, and algae. Arctic poppies occasionally occur, as well as low-growing willows and dryas (in the southern part). The total reserve of phytomass is less than 5 tons of dry matter per hectare (ha); living, aboveground material predominates over underground material, unlike the structure of the phytomass in the tundra and desert zones of the other geographic belts, where the opposite occurs. The harshness of the climate and low plant productivity are the primary reasons for the scarcity of fauna. Lemmings, arctic foxes, and polar bears are encountered. Reindeer occasionally wander in from the tundra, and there are bird colonies along the rocky shores.

Tundra zone. The tundra zone is unforested and is characterized by excess moisture under conditions of little heat and by extensively developed moss-lichen and dwarf-shrub vegetation. The average July temperature in the southern part of the tundra is 10°–11°C; temperatures higher than 15°C seldom occur. Winters are cold. The average January temperature in the Siberian tundras varies from – 20° to – 34°C; in the European part of the USSR it ranges from – 8° to – 20°C (along the lower course of the Pechora). Strong winds occur frequently, and the relative air humidity is high. Because of the low rate of evaporation of the moisture, the surface is excessively moist despite low precipitation, which varies from 200 to 400 mm a year. Together with the permafrost, which forms a water resistant stratum, this results in significant river runoff during the summer. In the winter, runoff is slight or nonexistent; many small rivers freeze down to the bottom. Shallow lakes of thermokarstic or morainic origin are widespread.

The soils are thin, acid, and poor in bases and humus, with vigorous manifestations of gleying processes. The soil thaws to a depth of 30–40 cm during the summer in the north and to a depth of 60–70 cm in the south. The northern and central parts of the zone are characterized by sparse moss and lichen vegetation and by the presence of bogs; sedge-cottongrass hummocky tundras are found east of the Kolyma River. In the southern part, dwarf-shrub tundra with thickets of dwarf birch alternates with sphagnum and grass-hypnum hummocky bogs. The total reserve of phytomass is 12.5–25 tons/ha.

Among the permanent inhabitants of the tundra are the reindeer, the lemming, the arctic fox, the wolf, the snowy owl, the willow ptarmigan, and the rock ptarmigan. Waterfowl abound on the lakes and rivers in the summer. Mosquitoes and blackflies are abundant.

The tundra has vast pasturelands for domestic reindeer and is a major fur-producing area.

Forest-tundra zone. The forest-tundra zone is a transitional zone between the tundra and the taiga, forming a strip 20–30 to 200 km wide (north to south). The summers here are somewhat warmer than those in the tundra zone, with an average July temperature of 11°–14°C. The sum of the average daily temperatures for the period with temperatures above 10°C is 400°–800°C.

The surface is extremely marshy, with hypnum and sphagnum bogs and deep peat bogs with hummocky surfaces. Thermokarst is widespread, and hydrolaccoliths (high mounds of swollen permafrost) are encountered. There is an intricate combination of peat gley soils typical of the tundras and gley podzolic soils of the northern taiga. The watershed areas are characterized by sparse forests combined with dwarf-shrub tundra. The flat low-lying areas are covered chiefly by tundra vegetation, while the river valleys are covered by taiga-type forests. Birches predominate in the sparse forests of the Kola Peninsula. Spruces predominate east of the peninsula, as far as the Urals, and larches predominate in Siberia. The reserve of phytomass is 25–50 tons/ha.

The fauna of the forest-tundra zone consists of taiga species, such as the elk, the brown bear, the blue hare, and the glutton, as well as of tundra species, such as the lemming, the arctic fox, and the willow ptarmigan. Mosquitoes and blackflies are abundant in the summer.

The forest-tundra zone has reindeer pasturelands.

Taiga zone. The taiga zone is characterized by a cool, relatively humid climate. Coniferous forests predominate, and bogs abound. The summers are warmer than those in the forest tundra and tundra and the winters, in places, are colder. The average July temperature ranges from 13°–14°C in the north to 18°–19°C in the south. The sum of temperatures for the period with temperature above 10°C increases from 800° to 1800°–2000°C from north to south. The average January temperature ranges from – 10°C in Karelia to –43°C on the Central Siberian Plateau. The snow cover, which is 50–80 cm thick, lasts six to eight months. The annual precipitation, which is 400–600 mm, exceeds the rate of evaporation everywhere except in the central parts of Yakutia. Permafrost is widespread in the east. The relief-forming role of water erosion is greater in the taiga zone than in the tundra and forest-tundra zones. Hummocky morainic landscapes have been well preserved in many regions. The runoff is high, measuring 300–500 mm in the north and about 200 mm in the south, and consequently the taiga rivers are high in volume in the summer.

Podzolic soils form beneath the forest canopy. In the north they are supplanted by gley podzolic soils, and in the south, by sod podzolic soils. Frigid taiga soils have developed in the taiga of the Central Siberian Plateau. The natural fertility of taiga soils is low, and consequently they require the application of organic and mineral fertilizers.

Coniferous forests of spruce, larch, pine, and Siberian fir predominate in the taiga. Dark-coniferous forests, primarily spruce forests, are widespread in the western and eastern margins of the taiga zone, where the climate is moderately continental. The central parts of the zone are covered by light-coniferous taiga, primarily larch taiga. The underbrush and herbaceous cover are sparse, although a solid cover of green hypnum mosses and lichens is observed. Dwarf shrubs, such as bilberry and mountain cranberry, are abundant in places. In addition to coniferous forests, small-leaved forests (birch and aspen forests) and mixed forests, usually of secondary origin, often develop. The total reserve of phytomass in the spruce forests of the middle and southern taiga reaches 150–300 tons/ha, with an annual growth of 70–85 quintals/ha. The taiga is extremely boggy, especially in Western Siberia. High-moor (oligotrophic) domed bogs, with significant peat reserves, predominate. Animal life is represented primarily by the brown bear, the elk, the lynx, the squirrel, the Old World flying squirrel, the blue hare, and red-backed mice. The most common birds are the capercaillie, the hazel hen, and various species of woodpeckers, while the most characteristic reptiles are the common viper, various colubrids, and the European common lizard. In many parts of the taiga, mosquitoes and blackflies are abundant in the summer. The taiga is the principal fur-trade region in the USSR (sable, Siberian weasel, squirrel, hare).

The principal resource of the taiga zone is timber. Agriculture is developed in the southern regions, and the meadows and pasturelands are used extensively for dairy and meat stock raising. The gathering of berries (cranberries, mountain cranberries, blueberries, and raspberries), mushrooms, and pine nuts is commercially important.

Mixed-forest zone. The mixed-forest zone is represented in the USSR primarily on the East European Plain and in the Far East. Within the East European Plain it is characterized by a comparatively humid climate and by dark-coniferous-broad-leaved forests growing on sod podzolic soils in the watershed areas. Summers are cool, with an average July temperature of 17°–18°C. The sum of temperatures for the period with temperatures above 10°C is 1800–2200°C. Winters are relatively mild, with an average January temperature of –3° to –4°C in the west and about – 12°C near the city of Gorky. As a result of frequent thaws, the snow cover in the west is shallow, usually less than 30 cm, and unstable; in the east, it reaches 50 cm and lasts up to five months. The annual precipitation is 500–800 mm, which somewhat exceeds the evaporation rate. The runoff reaches 150–300 mm. The river network is dense, and the rivers have a high water volume. Shrub-invaded spruce and oak forests on sod podzolic soils usually grow on the hills. The sandy plains are occupied by pine forests, while bogs develop in the basins and lowlands with limited drainage. The total reserve of phytomass in the forests of the mixed-forest zone reaches 300–400 tons/ha.

The flora and fauna have been enriched by species characteristic of Western Europe. The hornbeam occurs in the oak forests west of Vilnius and Minsk. Yew, ivy, and beech grow on the western shore of the Baltic Sea. The fauna is characterized by the brown bear, the wolf, the fox, and the elk, which exist side by side with the roe deer, the pine marten, the European mink, the tree dormouse, and the weasel Putorius putorius.

Most of the forests have been cut, and only about 30 percent of the region is forested today. The relative proportion of spruce and oak has decreased, while the proportion of birch and aspen has risen. The zone is densely populated, and about one-third of its area is under cultivation. Climatic conditions are favorable for growing potatoes, vegetables, flax, grains, forage grasses, and, in some places, sugar beets.

In the Far East mixed forests occupy the plains and low foothills of the Central and, in part, Lower Amur regions and the southern part of Primor’e Krai. The principal natural features here are the result of the monsoon climate. In the winter, when cold winds from the continent prevail, consistent freezing weather occurs, with an average January temperature of –28°C in the north and –16° to – 18°C in the south. As a result, the soil freezes to a great depth and the growing season begins late in the spring. Monsoon rains, which result in floods, are frequent during the summer, which has an average July temperature of 21°–22°C. Many regions are boggy. The sum of temperatures for the period with temperatures above 10°C reaches 2800°C.

The forests are characterized by a diversity of tree and shrub species, by multiple strata, and by an abundance of lianas and epiphytic mosses. The forests, which grow on brown forest soils, are composed of Korean pine, Mongolian oak, Amur linden, fir, and the birch Betula costata. Meadow vegetation, which in some places is steppe-like, and meadow chernozem soils predominate in the Zeia-Bureia and Khanka lowlands. The fauna is represented by both taiga species and southern species of East Asian and Indo-Malayan origin. Squirrels and chipmunks are common; other animals include the Ussuri tiger, the Asiatic black bear, the Japanese deer, the yellow-throated marten, the wild boar, and the racoon dog.

Most of the plains have been brought into agricultural use.

Broad-leaved forest zone. The broad-leaved forest zone is characterized by a mild, fairly humid climate and by extensive oak forests on sod podzolic and gray forest soils. It encompasses the East European Plain, gradually tapering in the east and forming a narrow strip between the mixed-forest zone in the north and the forest-steppe zone in the south. The average January temperature varies from –5° to –7°C; the average July temperature is 19°–20°C. The sum of temperatures for the period with temperatures above 10°C is 2200°–2500°C. The zone is characterized by optimal moisturization: the annual precipitation, which totals 600–700 mm, is close to the evaporation rate. Loesses and loesslike loams are common soil-forming rocks. When subjected to water erosion, they facilitate the formation of gulleys on plowed slopes.

Forests of oak are characteristic, intermixed with ash, linden, maple, elm, and other broad-leaved species, with a dense underbrush (hazelnut, staff tree, honeysuckle) and a well-developed herbaceous cover. Steppe-like pine forests occur in the sandy lowlands and on the river terraces. Bogs are few; high-moor and transitional bogs, characteristic of the northern regions of the country, are supplanted by low-moor bogs. Many steppe species occur among the grasses and wildlife. In the southern part of the zone, pockets of podzolized and leached chernozems are found among the gray forest soils.

The zone is densely populated, and a significant share has been brought under cultivation.

Forest-steppe zone. The forest-steppe zone, with forests on gray forest soils alternating with forb steppes on chernozems, stretches in a continuous band from the Carpathian Mountains to the Altai Mountains. The average July temperature is 20°–22°C. The sum of the average daily temperatures for the period with temperatures higher than 10°C is 2600°–2800°C in the southwest and 1800°–2000°C in the east. The average January temperature ranges from –5° in the east to –20°C in the west. The snow cover is unstable in the west but lasts more than five months in the east, where it reaches a depth of 30–50 cm. The annual precipitation is 500–600 mm in the west and 300–400 mm in the east, which is just slightly less than the rate of evaporation. Moisturization is close to optimal but does not occur evenly throughout the year; summer precipitation usually takes the form of heavy rains. Compared to the runoff in the forest zone, the runoff in the forest-steppe zone is low, and the spring high stage on the rivers is more turbulent. The topography, characterized by asymmetric river valleys and numerous gulleys and ravines, was carved out by erosion processes. Small, shallow depressions, formed as a result of undermining and subsidence, are common in the level areas between the rivers.

The forest steppe of Western Siberia, which is not as heavily dissected by gulleys and ravines, has numerous lakes. Oak forests grow on the East European Plain, birch-aspen groves in Western Siberia, and birch-pine-larch forests in Central Siberia. The oak forests are characterized by the greatest biological productivity in the temperate latitudes. The phytomass reserve is 400–500 tons/-ha, with an annual growth of up to 90 quintals/ha. Pine forests occur on the sandy soils in the river valleys. The steppes, which today are almost entirely under cultivation, were once covered primarily by forbs. Steppe areas have survived primarily in the preserves. The alkali and typical chernozems that formed under the forb steppes are distinguished by a high humus content, great thickness, and fine-grained texture. They are among the most fertile soils in the world.

The forest-steppe fauna is characterized by an intricate mixture of forest and steppe species. The elk, the squirrel, and the pine marten live side by side with susliks, marmots, the jerboa Allactaga major, and mouselike rodents.

The forest steppe is one of the most developed natural regions of the USSR; 70–80 percent of the land in the west has been brought under cultivation.

Steppe zone. The steppe zone is characterized by a temperate continental climate. The natural vegetation is dominated by grassy steppes on chernozem and dark chestnut soils. Most of the steppe zone, which extends from the western boundary of the USSR to the Altai Mountains, is under cultivation. In the east, there are distinct areas of steppe landscapes, primarily in the intermontane basins. The average July temperature is 22°–23.5°C. The sum of the average daily temperatures for the period with temperatures above 10°C is 2800°–3400°C in the west and 2000°–2600°C in the east. The average January temperature ranges from –2°C along the western borders of the USSR to – 20°C in the eastern part of the zone; in the steppes of Transbaikalia it drops to as low as – 30°C. In the steppes of the Ukraine the snow cover usually does not exceed 10–20 cm in thickness and lasts one to two months; in the Transural Region the snow cover is up to 30 cm thick and lasts about five months. The annual precipitation is 250–450 mm; it is considerably less than the rate of evaporation. An unstable supply of moisture is typical of the steppes. Droughts occur periodically, and dry winds are observed, sometimes accompanied by dust storms. The rivers have little water. Loess and loess-like loam soils are widespread. The zone has rill and gully erosion topography, with numerous ravines on the slopes; there are many sinks in the interfluvial areas and occasional hills. The common and southern chernozems that have developed in the steppes, as well as the dark chestnut soils, are not as rich in humus and are not as thick as the chernozems of the forest-steppe zone. Solonetzes occur in some areas. In some years there is considerable wind erosion.

Cultivated landscapes predominate in the steppe zone, which is intensively farmed. The surviving areas of natural vegetation are primarily grassy steppes, with feather grass, fescue grass, wheat-grass, and Koeleria, as well as representatives of the genus Cleistogenes (in the steppes of Transbaikalia.). Thickets of steppe shrubs are found on the East European Plain and in the foothills of the Urals and Altai Mountains (matrimony vine, blackthorn, cherry, Russian almond, spirea).

The fauna is characterized by numerous rodents that live in dens, and some are major agricultural pests. Typical animals include the weasel Putorius eversmanni, the corsac fox, susliks, jerboas, pikas, lemmings, and red-backed mice. Common birds inelude the great bustard, the little bustard, larks, the Hungarian partridge, the steppe eagle, and the pallid harrier.

The forest steppe and the steppe constitute the principal grain-growing regions of the USSR. Irrigation, snow retention techniques, and the planting of shelterbelts are important land-improvement techniques.

Semidesert zone. The semidesert zone is characterized by a dry, sharply continental climate, as well as by the predominance of sparse wormwood grassy steppes on light chestnut soils in the watershed areas. Located south of the steppe zone, it stretches in the form of a band from approximately the Ergeni Upland to the Zaisan Depression. There is an area of subtropical semidesert in the Kura-Araks Lowland south of the Greater Caucasus. The average July temperature is 23°–25°C. The sum of the average daily temperatures for the period with temperatures above 10°C is 3200°–3400°C in the west and 2400°–2800°C in the east. The average January temperature drops from west to east from –4° to – 16°C. The depth of the snow cover decreases from west to east from 30 to 10 cm, and its duration is shorter. The annual precipitation is 150–250 mm; it is three to four times less than the rate of evaporation. Runoff is negligible; the rivers are primarily intermittent. Groundwater is often salinized.

The semidesert zone is characterized by light chestnut soils that are poor in humus and exhibit solonetz characteristics. Solonetzes are widespread; meadow chestnut soils occur in the sinks and estuaries. Sod has not developed in all places. Caespitose grasses and low-growing subshrubs (wormwood, vitex, pyrethrum) alternate with ephemerals and ephemeroids. The reserves of phytomass are 5–12.5 tons/ha.

Rodents abound, including susliks, lemmings, jerboas, and red-backed mice. Larger animals include the saiga, the weasel Putorius eversmanni, and the corsac. The bird population is diverse. Insects are numerous, including locusts.

The semidesert zone is a zone of selective irrigated farming. Pasturelands occupy large areas.

Desert zone of the temperate belt. The desert zone of the temperate belt is characterized by an extremely arid, sharply continental climate and by sparse vegetation consisting of low-growing sub-shrubs on brown desert-steppe and gray-brown soils. It encompasses the Caspian Lowland, Kazakhstan, and Middle Asia, stretching south to approximately 40° N lat. The average July temperature is 25°–29°C. The sum of the average daily temperatures for the period with temperatures above 10°C is 3200°–5000°C. Winters are cold, with an average January temperature of about – 12°C in the north and about 0° in the south. The snow cover is shallow (about 10 cm) in the north and lasts about three months; in the southwest it lasts less than one month. This makes it possible to use the desert as winter pasture. The annual precipitation is usually less than 200 mm, and the evaporation rate is 800–1,400 mm. There is virtually no runoff in the deserts; the rivers usually begin in the distant mountains and within the desert zone are intermittent. Physical weathering and wind action are extremely intensive. Sand ridges and barchans, undrained basins, inselbergs, and dry river channels are typical relief forms. Takyrs, solonchaks, and sandy areas with an undeveloped soil cover occupy large areas.

The acute shortage of moisture and the frequent salinization of soils result in sparse vegetation, in which perennial xerophilous low-growing subshrubs predominate. Shrubs grow on the sand, and ephemerals and ephemeroids are found in some places. Wormwood-saltwort communities are typical of the clay and loam soils. The phytomass reserve is negligible (2.5–5 tons/ha); the underground part far exceeds the aboveground part of the phytomass. The phytomass reserve increases to 25–50 tons/ha in saxaul thickets.

Typical animals include the goitered gazelle, jerboas, the great gerbil, the wildcat Felis margarita, the manul, the cape hare, and the tortoise Testudo horsfieldi. There are many snakes, including poisonous ones, and numerous lizards.

Rice and cotton are raised on irrigated lands; there are orchards and vineyards in the oases. Significant areas are used as pastures.

Desert zone of the subtropical belt. The desert zone of the subtropical belt, unlike the desert zone of the temperate zone, is characterized by relatively warm winters, without a stable snow cover. It encompasses the plains of Middle Asia south of 40° N lat. The average July temperature is 30°–32°C. The average January temperature is close to 0°C, and plant growth does not ordinarily stop in the winter. The sum of temperatures for the period with temperatures above 10°C is 5000°–5600°C. Ephemerals and ephemeroids are widespread. The phytomass reserve in ephemeral-dwarf-subshrub deserts is 5–12.5 tons/ha. Animal species of southern origin, such as the striped hyena, Brandt’s hedgehog, the Levantine viper, and the cobra, are often encountered. Typical animals of the ephemeral deserts are the tortoise Testudo horsfieldi and the suslik Citellus fulvus, while typical animals of the sandy deserts include the sand snake Eryx miliaris, the snake Taphrometroron lineolatus, the saw-scaled viper, and the desert monitor.

Heat-loving crops are raised in the oases; in some places, two harvests a year are grown. The principal economic problem is water supply for irrigation and for watering pastures.

Mediterranean zone of the subtropical belt. The southern coast of the Crimea and the western part of Transcaucasia occupy the eastern margins of the Mediterranean zone of Eurasia. Along the southern coast of the Crimea and along the Black Sea coast of the Caucasus north of the city of Tuapse, a moderately hot, dry summer alternates with a comparatively warm, humid winter; near Yalta, the average January temperature is about 3°C, the average July temperature is 24°C, and the annual precipitation is about 600 mm. Xerophytic shrubs and forests of oak and pine on cinnamon soils are typical. The Colchis Lowlands and the Lenkoran’ Lowland, which lie in the semihumid subtropics, have a more humid climate owing to their location at the foot of coastal mountain ranges. The annual precipitation is about 1,500 mm in the Colchis Lowlands and slightly less in the Lenkoran’ Lowland. In the southern part of the Colchis Lowlands, the average January temperature is 6°–7°C. Dense broad-leaved forests, overgrown with lianas and occasionally interspersed with evergreen species, are widespread. They are composed of oak, hornbeam, beech, chestnut, and alder; evergreens include the ponticum rhododendron, the box tree, and the cherry laurel. The main soils are red earths and yellow earths.

The Lenkoran’ Lowland is characterized by an abundance of unique animals, including the porcupine, the leopard, and the jungle cat; flamingos are encountered along the Caspian Sea.

Subtropical fruits and grapes are grown in the Mediterranean zone. Tea and citrus fruits are cultivated in the Colchis and Lenkoran’ Lowlands.

Altitudinal zonality. Altitudinal (vertical) zonality is determined primarily by the elevation of the mountains and by their position within the natural zones and proximity to the oceans. It differs fundamentally from latitudinal zonality, since sharp changes in the entire spectrum of natural conditions occur in the mountains in a relatively small area. The exposure of the slopes and the position of the slopes relative to the prevailing transfer of air masses play a major role in altitudinal zonality.

The mountains of the southern part of the USSR typically have more altitudinal zones on the more humid macroslopes. Landscapes similar to those of the adjacent plains usually occur in the lower strata. At higher elevations, the entire aggregate of natural conditions often changes as air temperature decreases and moisture increases. For example, the western slopes of the Urals, moistened by the prevailing westerly winds from the Atlantic, are characterized by a more complex spectrum of altitudinal zonality than the eastern slopes. Because of the significant meridional extent of the Urals, the spectrum of altitudinal zonality changes greatly from north to south. In the Far North, to approximately 66° N lat., only the belt of mountain tundra is developed. Farther south, to 59° N lat. the lower belt is represented by mountain taiga and the upper belt by elfin woodland of spruce and birch, combined with mountain tundra.

In the Central Urals and in some parts of the Southern Urals, the taiga forests in the lower belt are supplanted by mixed forests, with linden, maple, and oak; the mountain tundra belt is found only at the summits. Forest steppes, mountain steppes, and, in some places, semideserts are found in the southernmost parts of the Urals, at the base of the mountains and on the lower slopes. In the mountains of Eastern Siberia the lower belt is usually represented by mountain taiga, while mountain tundra occurs at higher elevations. In the mountains of the Baikal Region and Transbaikalia, forest steppes and steppes are encountered within the intermontane basins. In the mountains of the Sikhote-Alin’, Pacific monsoons and cold marine currents are responsible for the more complex altitudinal zonality on the windward eastern and southeastern slopes.

On the northern slopes of the Caucasus the steppe landscapes of the lower belt are followed by a belt of broad-leaved and coniferous forests, which is supplanted first by a subalpine belt of elfin woodlands and tall-herb meadows and then by an alpine belt of low-herb meadows and rock vegetation. At the top lies the nival zone of snow and ice. The belt of broad-leaved and coniferous forests is often missing on the southern slopes. In the mountains of Middle Asia, a belt of mountain deserts and semideserts is found at the bottom of the sequence and, because of the great continentality and aridity of the climate, the belt of mountain forests is relatively insignificant, with forests usually confined to the northern slopes. At higher elevations are meadows, cliffs, névés, and glaciers.

F. N. MIL’KOV

There are several schemes for the physicogeographical regionalization of the country. This section uses a scheme in which the land area of the USSR, with certain adjacent regions of non-Soviet Eurasia, encompasses 19 physicogeographical countries. In the process of regionalization, all the natural conditions of a particular region were taken into account, as well as the zonal and nonzonal factors responsible for the formation of the landscape.

Arctic islands. The arctic islands are the only part of the USSR entirely surrounded by ocean. They include the archipelagoes and individual islands of the Arctic Ocean. Among them are flat islands, such as the Novosibirskie Islands, and mountainous islands, for example, Novaia Zemlia and Vrangel’ Island. Glacial landscapes are characteristic, as are arctic deserts, which are virtually devoid of vegetation and, in some places, arctic tundras.

Fennoscandia. Most of Fennoscandia is located in Western Europe, except the Kola Peninsula and Karelia, which are located in the USSR. The Baltic Shield constitutes the principal element of the surface. During the ice ages of the Anthropogene, Fennoscandia was a region of glacial ablation. The hilly plains and low mountains (Khibiny) are interspersed with lake basins. The lakes are usually interconnected by short, rushing rivers. The climate is cool and humid. The surface is abundantly moistened and often boggy. Northern taiga forest vegetation predominates. Pine forests are most common on the rocky hills, while ridges and spruce forests are found in the lowlands. Birch forest tundra and tundra occur on the northern edge of the Kola Peninsula.

East European (Russian) Plain. Most of the East European Plain coincides with the Russian Platform of the Eastern European Platform; in the south it also includes the Crimean steppe and the western and central parts of Ciscaucasia. During the ice ages of the Anthropogene, the northern part of the plain was covered by a continental ice sheet. Morainic and hill-ridge topography has remained, with numerous depressions that are often occupied by lakes and bogs. The nonglacial regions are characterized by broad terraced river valleys dissected by the ravines and gullies of the interfluvial areas and, in the south, by flat aggradational plains with marine deposits.

Loesses are well developed. The river network is heavily branched. The climate is moderately continental and is quite humid in the northwest and west and somewhat dry in the southeast, with a marked increase in temperature toward the south.

The latitudinal and sublatitudinal zonality of landscapes is clearly expressed. The tundra and forest tundra stretch along the Arctic Ocean. More than one-half of the East European Plain is occupied by taiga and mixed and broad-leaved forests. Timber is an important natural resource; significant areas, especially in the south, have been brought into agricultural use. Further south stretch the forest-steppe zone, the steppe zone, and, in a small part of the southeast, the semidesert zone. Most of the areas of the forest-steppe and steppe zones with chernozems and, in the south, with dark chestnut soils are under cultivation.

Urals. The Urals are a system of folded and block-folded mountain ranges, stretching almost 2,000 km in a meridional direction and consisting primarily of medium-elevation mountains. The greatest elevations occur in the north, in the Polar Urals, where small glaciers occur. The clearly marked altitudinal zonality of landscapes is manifested in a setting of latitudinal zonality. In the lower elevations of mountains the landscape sequence from north to south is tundra, taiga, mixed forest, forest steppe, and steppe. Small areas are occupied by mountain-forest landscapes; mountain tundra and bald-mountain landscapes are widespread in the north.

Ukrainian Carpathians and Transcarpathian Lowland. The Ukrainian Carpathians and the Transcarpathian Lowland are part of the Alpine-Carpathian country, most of which lies outside the USSR. The mountains are primarily of medium elevation, with flattened summits. Oak and beech forests predominate in the lower elevations. At higher elevations they are replaced by mixed and coniferous forests, which above 1,500 m are replaced by mountain, primarily subalpine, meadows. The Transcarpathian Lowland forms the northeastern margin of the alluvial Middle Danubian Plain. A significant portion of the area has been brought under cultivation. There are small areas of oak-hornbeam forests.

Crimean-Caucasian mountain country. The Crimean-Caucasian mountain country encompasses the Crimean Mountains, the Greater Caucasus, the Lesser Caucasus, and the Talysh Mountains, as well as the Lenkoran’ Lowland, which lies at their foot, and the intermontane basins separating the Greater and Lesser Caucasus—the Rioni Basin with the Colchis Lowlands and the Kura Basin with the Kura-Araks Lowland. The entire region is seismic. Mountain-forest landscapes predominate in the Crimean Mountains, and denuded, partially turf-covered karst landscapes find classical expression on the summits of the Iaila Ridge. The natural features of the southern coast of the Crimea appear to be Mediterranean. Mountain-forest landscapes (with coniferous-broad-leaved forests) and high-mountain meadow (subalpine and alpine) landscapes predominate in the Greater Caucasus, whose sharp, jagged peaks are covered with permanent snow and ice; the meltwater from the snow and ice plays a significant part in feeding the rivers. The western part of the mountains receives considerable precipitation, up to 3,200 mm a year on the southwestern slopes, the highest annual precipitation in the USSR. The landscapes of the eastern part form under drier, more continental, conditions. Karst topography has developed on the foreranges, especially in the southwest. Mountain-steppe and mountain-meadow landscapes predominate in the Lesser Caucasus. Meadow steppes are developed in the crest zone of the Talysh Mountain, while the slopes are covered by forests. The Lenkoran’ and Colchis lowlands and the surrounding low mountains lie in the humid and semihumid subtropics, and the predominant landscapes are broad-leaved forests and bogs. The Kura-Araks Lowland is an area of subtropical semideserts.

Armenian Highland and the Kopetdag. The Armenian Highland and the Kopetdag are part of the Southwest Asian Highlands, which are chiefly in non-Soviet Asia. Only the northeastern margin of the Armenian Highland extends into the USSR. Volcanic mountain-steppe and mountain-meadow landscapes predominate. The flat steppe surfaces of the lava plateaus are often cultivated, as are the plains with mountain chernozems. The Kopetdag is part of the mountainous northern margin of the Iranian Highland. Subtropical semidesert and mountain-steppe landscapes predominate, with highland xerophytes and juniper elfin woodlands occurring in the upper zone; broad-leaved gallery forests are found in the mountain valleys in the west. Both the Armenian Highland and the Kopetdag are seismic regions.

Middle Asian mountain country. The Middle Asian mountain country includes the mountain systems of southeastern and eastern Kazakhstan and Middle Asia: the Saur Range, the Tarbagatai Range, the Dzungarian Alatau, the Tien-Shan (without the highest eastern and southeastern parts), and the Gissar-Alai system. It has undergone extensive neotectonic uplifts, and seismicity is associated with neotectonic movements along faults. Semidesert landscapes predominate in the foothills, while mountainsteppe landscapes predominate in the low and middle-elevation mountains. Subtropical landscapes are found at the foot of the Gissar-Alai. Shrub thickets and forest stands occur on the more humid slopes. There are walnut forests in the south and southwest and aspen and apple forests in the north. Coniferous forests consisting of Schrenk’s spruce and juniper occur at higher elevations. Mountain meadows and meadow steppes occur in the highest mountains. Glaciation is well developed, with valley, cirque, hanging, and, in some regions, flat-summit glaciers.

Syrt region of the Tien-Shan and the Pamirs. The syrt region of the Tien-Shan and the Pamirs includes the highest mountains in the USSR, which are part of the natural countries of the highlands of Central Asia, most of which are outside the USSR. The area is seismic and characterized by greatly uplifted flat valleys and basins (known locally as syrty). The landscapes are formed under the conditions of a sharply continental climate, particularly in the enclosed intermontane basins. The climate of the mountains is harsh owing to the great absolute elevations; in some parts of the syrt plains, the climate is arid.

The highest mountain uplifts accessible to the westerly streams of air that carry moisture have thick glaciation, with enormous dendritic valley glaciers, for example, the Inyl’chek and Fedchenko glaciers. There are also small valley, cirque, hanging, and flat-summit glaciers. Landscapes characteristic of cold deserts and semideserts and mountain stony tundras have formed in the syrty of the Tien-Shan and in the eastern Pamirs. Permafrost covers significant areas. High-mountain steppes and meadow steppes are widespread in the more humid areas; forested areas also occur.

Middle Asian plains country. The Middle Asian plains country includes the deserts and semideserts of the Turan and Caspian lowlands and the southern part of the Balkhash Region. Its principal part corresponds to the Turan Plate. A region of internal drainage, it receives many rivers that originate in the mountains of Middle Asia. Plains predominate in the topography. Ridged and hilly sands cover significant areas. The climate is sharply continental and arid, with hot summers. The northern part lies in the temperate belt, while the southern part lies in the subtropical belt and is characterized by relatively mild winters. Semideserts and deserts, primarily clay and sandy deserts in the north and clay and loess deserts in the south, are widespread. There are patches of stony desert and solonchaks. The Middle Asian plains country is characterized by psammophytic and wormwood-saltwort vegetation, with numerous ephemerals in the south.

Turgai Plateau and central Kazakhstan. The region of the Turgai Plateau and central Kazakhstan occupies an intermediate position between the plains of Middle Asia and Western Siberia. Its western part, where flat plains predominate, corresponds to the Turgai Trough. The Kazakh Melkosopochnik occupies the central and eastern parts. Plains with hills and gentle ridges, composed of parent rock, predominate. Rugged residual massifs occur. From north to south the latitudinal steppe zone gives way to the semidesert zone.

Western Siberian Lowland. The Western Siberian Lowland is an aggradational plain, whose tectonic foundation is the Western Siberian Plate. It is very flat and poorly drained, and several more dissected ridges up to 300 m in elevation are observed on its surface. The northern part lies in the permafrost zone, which is conducive to the formation of bogs. Various zones are traced from north to south in Western Siberia, namely, the tundra, forest-tundra, forest (with coniferous and small-leaved forest), foreststeppe (with birch-aspen forests), and steppe zones. There are solonchaks and solonetzes in the forest-steppe and steppe zones of the south. Salt lakes with no outlets occur.

Central Siberia. Most of Central Siberia is occupied by the Central Siberian Plateau, which is bounded by the Central Yakut Plain on the east and the North Siberian Lowland and the Taimyr Peninsula with the Byrranga Mountains on the north. Igneous rocks (known as Siberian traps) are widespread. The Central Siberian Plateau is most uplifted in the northwest (the Putorana Plateau) but has a relatively level surface.

The climate of Central Siberia is sharply continental, and permafrost is ubiquitous. The rivers have a high water volume. Arctic tundras predominate on the Taimyr Peninsula, with arctic deserts occurring occasionally in the hills and mountains. The North Siberian Lowland is dominated by tundra, which is supplanted in the south by forest tundra and elfin woodlands. In the northern half of the Central Siberian Plateau there are mountain tundra, bald-mountain, and larch elfin woodland landscapes. To the south stretch vast taiga forests, with pockets of forest steppe in the southernmost parts. The latitudinal zonality of landscapes is modified by the influence of altitudinal zonality and permafrost. Small areas of meadow and solonetz steppes occur amid larch taiga on the plains of Central Yakutia.

Altai-Satan mountain country. The Altai-Saian mountain country includes the Altai and Saian mountain systems, the Salair Ridge, the Kuznetskii Alatau, and the mountains of Tuva. Planation surfaces and deep intermontane basins are characteristic. The climate is sharply continental. In the west, which has more moisture, dark-coniferous forests predominate, which at higher elevations give way to cedar elfin woodlands and alpine meadows. There are steppes and semideserts in the intermontane basins and at the foot of the ranges on the south and east. At higher elevations they are replaced by forests of larch and cedar. Still higher are bald-mountain and mountain-tundra landscapes. Areas of permafrost occur, and glaciers have developed in the high mountains.

Baikal Region and Transbaikalia. The Baikal Region and Transbaikalia are characterized by high ranges, separated by longitudinal troughs and alternating with medium-elevation mountains and plateaus, such as the Aldan Plateau. The summits of the high mountains are primarily flat; some are jagged. The climate is sharply continental; it is dry in the basins and more humid and cooler in the mountains. Permafrost is widespread. Forest-steppe landscapes and, in the south, steppe landscapes occur in the basins, as well as pine forests and meadows. Coniferous forests, both larch and cedar-fir taiga, grow on the mountain slopes. The mountain summits are bald.

Dahurian country. The Dahurian (Daur) country lies primarily in Mongolia and China, with only a small part included within the boundaries of the USSR. It is dominated by vast rolling plains, with isolated flat-topped mountain ranges rising to 1,000–1,500 m. The climate is sharply continental; areas of permafrost occasionally occur. Steppe and forest-steppe landscapes predominate; solonchaks and solonchak meadows are found in some places, such as the Borzia Steppe. Pine forests occur in sandy areas, while steppe-like larch forests are found on the northern slopes of the higher ranges.

Northeastern Siberia. Most of northeastern Siberia is mountainous. Framed on the west by the arc-shaped Verkhoiansk Range, northeastern Siberia is occupied by plateaus, for example, the Yukaghir Plateau, and by marshy lowlands with numerous lakes in the north, for example, the Iana-Indigirka and Kolyma lowlands. There are glaciers high in the mountains, for example, in the Buordakh Massif of the Cherskii Range and in the Suntar-Khaiata Range; permafrost is widespread. The climate is harsh and sharply continental, especially in the Verkhoiansk and Oimiakon basins, where the coldest places in the northern hemisphere are located. Larch elfin woodlands, mountain-tundra, and bald-mountain landscapes predominate, with tundra occurring in the north.

North Pacific country. The north Pacific country includes the Chukchi Peninsula, the Anadyr’ Plateau, the Anadyr’ Lowland, the Koriak Highland, the Kamchatka Peninsula, and the Komandorskie and Kuril islands. It is characterized by mountain ranges with sharp peaks, volcanic plateaus with volcanic cones, and medium-elevation massifs. There are numerous active volcanoes, and earthquakes occur frequently in the southern half. Permafrost is found in the northern and central parts of the region. The climate is cold marine and subject to the long-range effects of monsoons. Summers are cloudy and rainy; fogs, are frequent. Tundras stretch from the Chuckchi Peninsula far to the south, where taiga landscapes are encountered. Mixed forests with lianas and bamboos occur in the southern part of the Kuril Islands. Meadows and bogs are found in the coastal lowlands. The mountains have sparse forests of Erman’s birch, thickets of dwarf stone pine, and alder groves. Mountain tundras and bald-mountain landscapes are found on the peaks.

Amur-Sakhalin country. The Amur-Sakhalin country includes the area along the Amur, with its mountains and lowlands, Primor’e Krai (Sikhote-Alin’ Range and the plains to the west), and the island of Sakhalin. There is significant seismic activity in the east. The climate is monsoonal, with warm, rainy summers and cold winters. Taiga landscapes with larch forests and, in the east, dark-coniferous forests predominate. Bogs with stunted larch forests, called mari, cover large areas. Thickets of dwarf stone pine and bald-mountain landscapes occur on the mountain summits. Unique Far Eastern coniferous-broad-leaved and broadleaved forests are found at lower elevations in the Sikhote-Alin’ Mountains, in the southern part of the Amur Region, and in the southwestern part of Sakhalin; on the plains, most of the forests no longer exist.

N. A. GVOZDETSKII

Conservation in the USSR includes a system of state and public measures (biotechnical, technological, economic, and administrative and legal measures) that makes it possible to maintain the productivity and beauty of nature and to preserve the natural conditions necessary to supply the national economy with raw materials and energy. Conservation is also essential in helping provide man with recreational enjoyment and maintain human health. It helps preserve typical natural complexes and interesting features of living and nonliving nature. Conservation in the USSR is based on the socialist ownership of land and its resources. Conservation is a constituent part of the system for effecting the rational use of natural resources.

Legal aspects. The objectives and forms of conservation have differed considerably at various stages of society’s development, since the relative assessments of the value of natural conditions and resources have changed and the human threat to nature has grown with the evolution of the technology and economics of exploiting nature. The desire to protect nature existed in the popular consciousness long before the appearance of administrative and legal forms of conservation. The first legal restrictions on the use of natural resources were imposed in Kievan Rus’ in the 11th century. The Russkaia Pravda of Iaroslav the Wise speaks of limiting the hunting of wild animals and birds. In the 14th and 15th centuries forest clearings in the central part of the East European (Russian) Plain were important for the defense of the country and consequently were accorded special protection by the state. The codes of laws of the Grand Duchy of Lithuania of the 16th century included logging, fishing, and hunting quotas. In the midnth century, 67 ukases on hunting were issued in Russia, the first preserves were created (the Kuntsevo and Sem’ Ostrovov preserves), and the sable-rich areas along numerous rivers were placed under protection. In 1683 the cutting of trees was also prohibited in the sable-rich areas of Siberia. Legislation protecting nature increased significantly under Peter the Great, who also organized a forestry service and placed water-conservation forests and certain tree species under protection. With the growing threat of the deforestation of the European part of Russia, a statute was introduced in 1888 on the conservation and protection of forests. The statute and the subsequent law on hunting (1892) reflected the desire to regulate the corresponding industries, whose intensive development as a result of accelerated technological progress was beginning to threaten the preservation and regenerative capabilities of nature.

In the early 20th century the Russian scientific community began to promote conservation. The Conservation Commission was formed in 1909 as part of the Russian Geographic Society (in 1912 it was renamed the Permanent Conservation Commission), and the first Russian law on preserves was passed in 1916 on its initiative. However, these legislative measures proved to be inadequate, and the uncontrolled development of the capitalist economy resulted in considerable damage, sometimes irreversible, to the environment in Russia, especially in the European part.

The victory of the October Revolution of 1917 marked the beginning of a qualitatively new stage in conservation. More than 200 decrees pertaining to conservation and general problems of the use of nature were issued in the first five years of the Soviet state’s existence. Most were developed in accordance with V. I. Lenin’s instructions, and some even bear his signature. The fundamental legislative act was the Decree on Land, adopted by the Second All-Russian Congress of Soviets in 1917, which abolished the private ownership of land; the decree created fundamentally new opportunities for organizing conservation efforts. It was soon followed by several other decrees, including the decree of the All-Russian Central Executive Committee On Forests (May 27, 1918) and the decree of the Council of People’s Commissars of the RSFSR On State Therapeutic Localities (Apr. 4,1919), all of which ensured the rational use of particular natural resources. These were subsequently supplemented by the decree of the Council of People’s Commissars of the RSFSR On the Preservation of Monuments of Nature, Gardens, and Parks (Sept. 16, 1921), according to which “natural regions of considerable size noted for their remarkable features are declared to be preserves and national parks.” The People’s Commissariat for Education was placed in charge of conservation, since it was a department with no interest in the exploitation of natural resources.

The foregoing documents established a unified system of principles for the socialist use of natural resources, which served as the basis for all future conservation legislation. Extensive departmental statutes and instructions on water, forest, and soil conservation, on sanitation measures, on hunting, and the like were an important part of the system. The interdepartmental State Committee for Conservation was formed to coordinate the activities of various people’s commissariats and departments pertaining to the exploitation of natural conditions and resources. Local interdepartmental commissions were set up under the provincial executive committees of the soviets. The State Committee for Conservation was placed in charge of all conservation activities, recommending ways of preventing the overuse of natural resources (that is, excessive logging, fishing, fur procurement, and the like); it also identified objects necessitating protection.

The All-Russian Society for the Conservation of Nature was organized in 1924, and similar societies were later founded in the other Union republics. The First All-Union Congress on Conservation was held in 1933. Its resolutions, which were primarily concerned with the resources of living nature, emphasized that conservation should also seek to prevent the destructive and mismanaged use of natural resources and to promote the regeneration of various resources.

In conformity with the tasks of the national economy, a decree of the All-Russian Central Executive Committee and the Council of People’s Commissars of the USSR of June 20, 1930, reorganized the State Committee for Conservation into the Interdepartmental State Committee for Promoting the Development and Protection of Natural Resources under the People’s Commissariat for Education of the RSFSR. The focus of the new committee’s activities shifted to the rational use and regeneration of natural resources. On Sept. 20, 1933, the Interdepartmental Committee was reorganized into the Committee on Preserves under the presidium of the All-Russian Central Executive Committee (in 1938 its control was transferred to the Council of People’s Commissars of the RSFSR), and in 1939 it was reorganized into the Central Board for Preserves of the Council of People’s Commissars of the RSFSR. Similar boards were organized at the councils of people’s commissars of the other Union republics. In addition to managing preserves, the Central Board for Preserves was charged with monitoring various departments and adopting measures to ensure the rational use of valuable objects, primarily of living nature. However, the measures adopted were primarily concerned with biological matters and had little to do with other aspects of conservation work.

In the late 1950’s, conservation entered a new stage with the updating and expansion of conservation legislation. During the period 1957–63, all the Union republics adopted conservation laws, which focused not only on the problems of living nature but also on the entire aggregate of natural conditions and natural resources with due regard for their interrelations; in addition, the laws dealt with the problems of protecting not only the natural features that are preserved (withdrawn from economic use) but also the natural resources that are being exploited. The conservation laws also stress the need to ensure the extensive regeneration of natural resources.

The late 1960’s ushered in a new era in conservation with the formulation of the basic principles of all-Union legislation pertaining to the protection and use of the resources and conditions of all aspects of nature. The laws passed included the Basic Principles of Land Legislation of the USSR and the Union Republics (1968), the Basic Principles of Public Health Legislation of the USSR and the Union Republics (1969; conservation of air, drinking water, and the like), the Basic Principles of Water Legislation of the USSR and the Union Republics (1970), the Basic Principles of Legislation of the USSR and Union Republics on Mineral Resources (1975), and the Basic Principles of Forest Legislation of the USSR and the Union Republics (1977).

The management of resource use in the USSR takes into account the multifaceted importance of natural resources; a distinction is made between resources that are expended during extraction, use, and processing (nonrenewable resources) and environmental resources that are important for the conservation of the soil, water, and the like. The Council of Ministers of the USSR and the councils of ministers of the Union republics have issued a series of decrees regulating various sectoral or regional aspects of conservation and outlining long-term conservation programs. The decrees include On Measures for the Prevention of the Pollution of the Volga and Don Rivers (Dec. 31, 1964), On Measures for the Prevention of the Pollution of the Caspian Sea (Sept. 23, 1968), On Measures for the Preservation of the Natural Complexes of the Lake Baikal Basin and Their Rational Use (Jan. 21,1969), and On Measures for the Prevention of the Pollution of the Basins of the Volga and Ural Rivers by Contaminated Waste Water (March 1972). The most complete solution to the problem of conservation is provided by the decree of the Supreme Soviet of the USSR On Measures for the Further Improvement of the Conservation of Nature and the Rational Use of Natural Resources, adopted in September 1972, and the decree of the Central Committee of the CPSU and the Council of Ministers of the USSR On Strengthening Conservation Efforts and Improving the Use of Natural Resources, adopted in December 1972. In the current phase of the development of the national economy and scientific-technological progress, the conservation and rational use of natural resources are becoming the key state tasks.

Among the measures expected to ensure effective protection of the environment are the comprehensive use of natural resources, the introduction of technological processes that eliminate harmful wastes, the use of biological methods to decontaminate water and control agricultural pests, afforestation, and land improvement. Also essential are scientific predictions of the possible consequences of future resource use, the development of measures to prevent impairment of the environment, and the improvement of planning, since the proposed conservation measures are a constituent part (since 1947) of the long-range and annual plans for the development of the national economy for all the ministries and departments and for the country as a whole. Actual conservation measures must be carried out by technical means that are the equal of the measures used to exploit natural resources. A powerful technical base using the latest scientific advances is being developed to protect the environment. Low-waste and waste-free production facilities and closed production cycles are being introduced, the production of synthetic substitutes for natural materials is expanding, planning is being improved, and the production of equipment and monitoring and measuring devices for decontamination units is increasing.

Resource inventory in the USSR is ensured by a system of cadastres, for example, the land cadastre and the water cadastre, and by state evaluations of the status of reserves and extraction of mineral products. On Oct. 16, 1974, the Ministry of Agriculture of the USSR instituted the Red Book of the USSR to protect rare and endangered plants and animals.

The USSR has made great advances in conservation. Clear and multifaceted conservation legislation, high public awareness, and public activism help keep the environment productive, attractive, and capable of providing for the growing needs of the population and the economy for raw materials, energy, water, and food. However, the successes of conservation have been tempered by a number of shortcomings. Some damage inflicted in the past to the natural environment in the USSR was unavoidable, for example, during the Great Patriotic War and in the first postwar years. Some damage has resulted from miscalculations and mistakes in planning. There have also been instances of mismanagement and even the existence of exploitative attitudes toward nature (for example, poaching). Much of this has been the result of the insufficient use of the opportunities available in the socialist system to further conservation.

Protection of individual components of nature and natural resources,AIR. The basic principles of legislation of the USSR and the Union republics pertaining to public health and the republic conservation laws include measures to protect the air from pollution. Air is protected as the habitat of man and all terrestrial organisms, as a condition of human health, and as a substance that participates in technological production processes (air contaminated by chemical and mechanical impurities may be unsuitable for use in technology). Protection of the air also entails protecting the organic world against the effects of harmful chemical and mechanical impurities in the atmosphere. To prevent the pollution of air by smoke, dust, gases, and other impurities, purification units are used in industry and municipal services, and production technology is being improved to minimize wastes or render them harmless. Enterprises that pollute the atmosphere are built outside populated points, and industry and transportation are gradually changing over to the use of clean fuels and sources of energy. The planting of trees and shrubs in cities and along roads and the development of suburban green zones improve air quality. Health standards stipulate the maximum allowable concentrations of harmful gases and other harmful impurities in the atmosphere. The air-pollution supervisory service imposes penalties on those responsible for pollution, and penalties may go as far as prohibiting or halting the operation of polluting enterprises.

WATER. The conservation of water resources is included in the Basic Principles of Water Legislation of the USSR and the Union republics and in special articles on conservation in the republic laws.

Surface waters serve a variety of purposes: they provide water to the population and the national economy, they are a source of energy, they serve as transportation routes and the habitat of aquatic plants and fish and other animals, and they serve as hunting areas and places of recreation and tourism and as a source of therapeutic remedies. For these reasons, their regime is subject to regulation, and the waters themselves are worthy of protection against pollution, contamination, and depletion.

Measures for the protection of water resources and for their rational use are based on the study of the water management balance. Water users must see to it that water is used economically, resources are renewed, and water quality is improved, and to this end various technological, forest-improvement, agrotechnical, hydroengineering, and other measures are carried out. Enterprises, municipal facilities, and other such installations cannot operate without purification units. Special measures are being taken to prevent the contamination of water by fertilizers and toxic chemicals washed away from agricultural lands. Improvements in production technology, such as the use of waterless production processes and the recycling of water, help reduce waste-water runoff.

The depletion of water resources can be prevented by the introduction of measures to regulate and maintain favorable regimes in various bodies of water and rivers, for example, the establishment of water-protection zones and hydroengineering and land-improvement measures. When operating water reservoirs and water-intake structures, the inflow and outflow of water is regulated with due regard for the needs of other water users.

Special attention is given to protecting the seas and lakes, first and foremost the Caspian and Black seas, the Sea of Azov, and Lake Baikal. The task in these cases is not just the maintenance of clean water and biological productivity but also the maintenance of a constant water volume. The maintenance of the level of the Caspian and Aral seas and Lake Balkhash involves solving broader, multifaceted problems of the national economy, including the regulation of the flow of the sources that feed these bodies of water, resorting even to the interbasin transfer of water.

In the basins of the Black Sea and the Sea of Azov, important work is under way to eliminate the discharge of household and industrial waste products into the seas. Conservation measures for the Sea of Azov also include those to forestall further increases in the sea’s salinity and to restore fish productivity. The protection of the seas in the USSR is a constituent part of global efforts to protect the world ocean, and consequently international cooperation plays a significant part. Measures to protect the seas involve not only objects located directly in the sea but also the coastal regions, which can affect marine bodies of water.

Subterranean waters are a constituent part of the unified state water supply and one of the components of the earth’s interior, and consequently their conservation is envisioned by the Basic Principles of Water Legislation of the USSR and the Union Republics, the Basic Principles of Legislation of the USSR and the Union Republics on Mineral Resources, and various republic laws.

As a source of drinking water and water for economic use, subterranean waters are protected primarily against chemical, bacterial, and thermal pollution; steps are also taken to prevent the nonrational use of reserves (for example, in free-flowing springs). Chemical pollution poses the largest threat, since it can spread considerable distances and can remain effective for a long time. A system of preventive measures helps protect subterranean waters against pollution: the siting and equipping of enterprises such that the harmful effects on subterranean waters are mitigated, the prevention of the contamination of surface waters and the air, the sealing off of waste flows, treatment of water, and the establishment of water-protection zones in regions where subterranean waters form and where they are used intensively. Measures to protect subterranean waters against contamination are subdivided into localized measures (restriction of the movement of pollutants through a water-bearing stratum) and restorative measures (the pumping out of polluted waters and flushing with clean water and special solutions).

The struggle against existing pollution is realistically feasible only in areas where pollution is not widespread, since it requires significant outlays of capital and a great deal of time.

GEOLOGICAL RESOURCES. Geological resources are protected by the Basic Principles of Legislation of the USSR and the Union Republics on Mineral Resources. Their conservation includes their comprehensive geological study and the observance of established procedures for their exploitation in order to extract minerals efficiently and maintain the industrial value of deposits, as well as for needs unrelated to the working of deposits (maintenance of excavations and underground structures, prevention of contamination of mineral resources in the course of constructing underground structures and burying industrial wastes, and preservation of segments of the interior that are of special scientific or cultural value).

The task of conserving mineral resources differs from that of conserving other systems of the biosphere, since mineral resources are not renewable. Thus, attention is focused on the rational use of mineral deposits. This envisions the reduction of quantitative and qualitative losses of useful minerals during extraction and processing; the comprehensive use of mineral raw materials; and the development of efficient methods of extracting and processing nonpayable ores and making use of production wastes and the enclosing rocks.

Opencut mining achieves the most complete extraction of deposits. Mineral losses are reduced in underground mining using mining systems with the backfilling of the excavation space. Non-payable ores may be extracted using geotechnological methods, that is, through openings drilled from the surface. To improve the utilization of mineral reserves, monetary incentives for complete and good-quality extraction are provided, while penalties for excessive losses are imposed. The conservation of mineral resources also includes the prevention of the adverse effects of underground excavations on the natural landscape, for example, cave-ins. Natural and artificial geological outcrops are protected, as well as geological, mineralogical, paleontological, and other natural sites of scientific, cultural, or aesthetic value.

LAND. Conservation of land, including soils, is ensured by the Basic Principles of Land Legislation of the USSR and the Union republics, as well as by republic codes and legislation.

Soviet law protects all land that is part of the land resources of the USSR. Land users are required to carry out whatever agro-technical, land-improvement, and hydroengineering measures a particular area requires to preserve the soil cover and improve soil fertility. This is done through the use of effective farming systems and crop rotations, the irrigation, flushing, and drainage of lands, and the introduction of measures to prevent water and wind erosion, bog formation, and salinization. In addition, shelterbelts are established to protect fields, and sandy soils and gullies are stabilized.

Special attention is given to the restoration of land areas disturbed by mining operations to a condition suitable for agriculture, forestry, fishing, or some other purpose, such as public recreation.

FLORA. Conservation of the flora includes the protection of forests and other natural vegetation, as well as the protection of forest-park shelterbelts, suburban green zones, and planted areas in populated points. It is provided for by the republic conservation laws.

Forests are not just a source of timber. They are an important part of the environment possessing “intangible uses”; for example, they help conserve water, soil, and fields and help purify the air. They also serve as the habitat of many wild animals. The use of forests is regulated to maintain their productivity and usefulness. Legislation prohibits the cutting of trees (except for management purposes) in forests that are important for soil, field, and water conservation and water regulation and in forests along spawning bodies of water and streams; it also prohibits the clear-cutting of mountain forests and the use of methods of timber transport that damage forest soils and the undergrowth.

In the USSR, forests are subdivided into three groups according to cutting conditions. The first group includes forests of the green zones of cities and resorts and protective strips along rivers and transportation routes, where cutting is allowed only for improvement and regeneration. The second group includes forests of the densely populated areas of the European USSR and certain areas of Siberia, where logging is allowed with restrictions. The third group includes the forests of densely wooded areas, where there are only a few specific restrictions on cutting. Forest management and logging are planned with due regard for the need to preserve and regenerate forests. Increasingly more logging is being carried out in timber-rich regions to prevent over-cutting in areas where the forests have been significantly reduced.

In addition to forests, other types of natural vegetation are protected as well, particularly vegetation that serves as a source of food for domestic and wild animals and as a source of food products and industrial, including medicinal, raw materials for man. Natural vegetation stabilizes and enriches the soil and, as part of the natural environment, influences climate and water regimes. Protection is given not only to certain rare and endangered plant species but also to the plant gene pool as a whole, which serves as a reserve of species for possible future cultivation and for use in selection research. The use of natural nonforest plants is also regulated to maintain and increase productivity. The time required for the development of a grass cover is taken into account when using pasturelands, and the order and regularity of grazing is planned.

FAUNA. Wildlife conservation is based on republic conservation laws and on a series of decrees, including the decrees of the Council of Ministers of the USSR On Measures for Improving Game Management (May 11, 1959) and On the Replenishment and Protection of Fish Stocks in Internal Soviet Waters (Sept. 15, 1958), the Statute for the Protection of Fish Stocks and the Regulation of Fishing in Soviet Waters (Sept. 15, 1958), and the decree of the Council of Ministers of the RSFSR On Measures for the Protection of the Animals of the Arctic (Nov. 21,1956).

Protection is accorded first and foremost to wild animals that are objects of the hunting, whaling, fishing, and other industries and to animals that are important as exterminators of harmful animals and as the source of food (prey) of commercially valuable animals. Rare and endangered animal species and the faunistic gene pool as a whole are of great value to science.

Legislation requires the strict observance of established rules for hunting and fishing; the improvement in the living and reproduction conditions of wildlife; and the regulation of the use of commercially valuable animals and the maintenance of conditions suitable for their reproduction. It is illegal to kill noncommercial wild animals that do not inflict damage on the economy or that do not adversely affect human health. Wildlife conservation does not preclude the regulation of harmful animals, but many predators are themselves protected as natural regulators of the ecological balance. Wildlife conservation has made it possible to restore populations and resettle many animals that had become rare (elk and beaver) or that are endangered (saiga and aurochs) and to increase the population and commercial importance of valuable furbearers (northern fur seal and sable).

PROTECTED NATURAL REGIONS. Among the protected natural regions are typical or unique examples of natural conditions in the landscape zones and regions that are of scientific, cultural, educational, historical, or aesthetic interest and that have a salutary effect on human health. They also include rare and interesting objects of living and nonliving nature and tourist and excursion areas. Preserves, which serve, in a sense, as laboratories for the study of naturally occurring processes, are accorded special protection.

In addition to the preserves, protected natural regions include game preserves, special natural landmarks, unique forests, national, natural, and memorial (historical-natural) parks, resort areas, and protected belts along popular hiking trails.

With the growth of tourism, the problem of protecting natural landscapes against overuse has arisen and trends toward urbanization have emerged. The economic and cultural-educational interests of the development of tourism itself as a sector of the economy and culture provide incentive to maintain the integrity and attractiveness of landscapes. In 1978 there were 123 preserves and four national parks in the USSR.

REGIONAL ASPECTS OF CONSERVATION. The USSR is characterized by a great diversity of natural landscapes and resources, the result of a number of factors: the vastness of the country’s land and water areas, the country’s location in different geographic zones (arctic, subarctic, temperate, subtropical) and numerous natural zones, and the effects of a multitude of azonal influences. These very same factors are responsible for significant differences in the dynamics of the development, productivity, and vulnerability of the natural world from place to place and, consequently, for the diversity of problems and methods of conservation under different zonal conditions. In addition to the general tasks of conservation, there are specific tasks, associated with unique zonal and local features.

TUNDRA AND FOREST TUNDRA. In the tundra and forest tundra, with their harsh climatic conditions that are close to extremal for living organisms (short growing seasons, low temperatures, strong winds, frozen soils), the organic world is highly vulnerable. The slow growth and maturation of organisms makes the regeneration of flora and fauna difficult should they be destroyed. Burnt tundras (pyrogenic tundras) require a particularly long time for regeneration. Frozen ground and boggy ground are irreversibly altered as a result of traffic by caterpillar-type vehicles. Aboveground pipelines cut across the migratory paths of reindeer herds.

Among the tasks faced by conservation in these regions are above all the protection of the surface against off-road traffic, the restriction or prohibition of the cutting of trees in the forest tundra and on the northern boundary of the forests, the protection of tree stands, shrubs, mosses, and lichens from fires, the prevention of overgrazing by reindeer, and the maintenance of the natural migratory paths of various wild animals. An additional special problem is the protection of the frozen ground against warming influences, which destroy or weaken it, and other disturbances of its characteristic thermodynamic balance, since frozen soils provide the base for buildings and roads and are used to construct underground storage facilities.

FOREST ZONE. In the forest zone the principal tasks of conservation are linked with forest-protection measures. Special problems of protecting natural features against chemicals arise when toxic chemicals are carelessly used to control forest pests and bloodsucking insects. In this case, forest protection measures are directed at preventing the incidental killing of birds and useful insects and averting soil contamination. The vast bogs typical of the forest zone are the object of land reclamation work, primarily drainage; however, complete drainage must be avoided because it leads to excessively dry land, impedes the continuous feeding of rivers, and destroys hunting and berry-picking areas.

FOREST-STEPPE AND STEPPE ZONES. Among the conservation problems unique to the forest-steppe and steppe zones are protection against water and wind erosion, dust storms, and salinization of soils and the maintenance of field-protection shelterbelts. The isolated forests and gallery forests on the southern boundaries of the forest’s distribution deserve special protection, as do sections with steppe vegetation that have survived among the cultivated fields.

SEMIDESERTS AND DESERTS. In the semideserts and deserts of the temperate subtropical belts, the most important conservation measures are directed at the prevention of the deflation of stabilized sands, the maintenance of sand-protection and wind-protection plantings, and the prevention of secondary salinization of topsoils and subsoils and the overgrazing of pasturelands, which are especially vulnerable owing to the extreme deficiency of moisture in deserts.

MOUNTAINS. In mountain landscapes, which are characterized by altitudinal zonality, conservation efforts are associated with the need to maintain the soil-protection role of vegetation. The destruction of vegetation on steep slopes leads to the erosion of topsoils and subsoils, which are then washed away; this results in the irreversible alteration of the topography and, possibly, in the formation of badlands. Measures to protect people, roads, and populated points, as well as forests and animals, against landslides are also part of the conservation efforts in the mountains.

Specific conservation measures are needed for azonal and intrazonal landscapes, such as caves, regions of ancient and modern volcanic activity, and fantastical shapes created by weathering. As natural landmarks, such landscapes are accorded preserve status to protect them, for example, the Kungur Peshchera, the Novyi Afon Cave, the Valley of Geysers on Kamchatka, and the Krasnoiarsk Columns.

State and public organizations. In the USSR conservation work is conducted by specialized statewide bodies: the State Planning Committee of the USSR (which has a department of conservation), the State Committee for Science and Technology of the Council of Ministers of the USSR (which includes the Interdepartmental Science and Technology Council on Complex Problems of Conservation of the Natural Environment and Rational Use of Natural Resources), and the Ministry of Agriculture of the USSR (which includes the Central Board for Conservation, Hunting, and Preserves).

A number of other ministries and state committees have narrower functions, involving the protection of particular components of the environment, for example, the Ministry of Land Reclamation and Water Use Management of the USSR, the Ministry of Geology of the USSR, the State Committee for Supervision of Work Safety in Industry and for Mining Supervision of the Council of Ministers of the USSR, the State Forestry Committee of the Council of Ministers of the USSR, the Ministry of Fisheries of the USSR, the Ministry of Public Health of the USSR, and the State Committee on Hydrometeorology and Monitoring the Natural Environment of the Council of Ministers of the USSR.

In addition, there are specialized comprehensive and branch committees and commissions in the Union republics. Both houses of the Supreme Soviet of the USSR have permanent commissions on conservation.

Conservation research is carried out by many research establishments of the Academy of Sciences of the USSR, as well as by the V. I. Lenin All-Union Academy of Agricultural Sciences, the hydrometeorological services of the ministries and departments, the preserves, and the universities and other educational institutions. The fundamentals of conservation are included in the curricula of secondary schools, many technicums, and universities and other higher educational institutions (usually related to the problems of resource use in the particular specializations). The Conservation Society, Geographic Society of the USSR, All-Union Znanie Society, and other voluntary organizations play an important role in educating the public about conservation. The USSR takes an active part in various international conservation efforts.

Iu. K. EFREMOV

Bibliography

Materialy XXV s”ezda KPSS. Moscow, 1976.
“O merakh po dal’neishemu uluchsheniiu okhrany prirody i ratsional’nomu ispol’zovaniiu prirodnykh resursov: Postanovlenie Verkhovnogo Soveta SSSR.” Pravda, Sept. 21,1972.
Pravovaia okhrana prirody v SSSR. Moscow, 1976.
Gladkov, N. A. Okhrana prirody v pervye gody Sovetskoi vlasti. Moscow, 1972.
Efremov, Iu. K. Priroda nasluzhbe obshchestva. Moscow, 1968.
Blagosklonov, K. N., A. A. Inozemtsev, and V. N. Tikhomirov. O khrana prirody. Moscow, 1967.
Zapovedniki Sovetskogo Soiuza. Moscow, 1969.
Laptev, I. P. Teoreticheskie osnovy okhrany prirody. Tomsk, 1975.
Fedorov, E. K. Vzaimodeistvie obshchestva i prirody. Leningrad, 1972.
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