Central Asia

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Central Asia

 

a natural region in Asia that encompasses desert and semidesert plains, upland plains, and highlands. Central Asia is bounded on the east by the southern part of the Greater Khingan Mountains and by the Taihang Shan; the southern border is formed by the longitudinal tectonic trough of the upper Indus and Brahmaputra (Tsangpo) rivers. On the north and west the boundary is formed by the Vostochnyi Kazakhstan, Altai, and Zapadnyi and Vostochnyi Saian ranges and roughly corresponds to the national border between the USSR on one side and China and the Mongolian People’s Republic (MPR) on the other. According to various estimates, the area of Central Asia is 5–6 million sq km. Most of China and the MPR lies within Central Asia. The region’s population includes Chinese, Uighurs, Tibetans, and Mongolian peoples, such as the Khalkhas.

Terrain. Central Asia is distinguished by extensive elevated areas; two principal levels of relief can be clearly distinguished. The lower level comprises the Gobi and Ala Shan deserts, the Ordos Plateau, and the Dzungarian and Tarim plains, with predominant elevations of 500–1,500 m. The upper level is formed by the Tibetan Highlands, where elevations average 4,000–4,500 m. The plains and upland plains are separated from one another by linearly extended mountain systems of the eastern Tien-Shan, the Kunluns, Nan Shan, the Mongolian Altai, the Karakoram, and the Trans-Himalayas; these systems extend, for the most part, more or less latitudinally. The highest peaks of the Tien-Shan, Karakoram, and Kunluns reach 6,000–7,000 m; the highest point in Central Asia, at 8,611 m, is Mount Chogori (Godwin Austen), in the Karakoram.

Geological structure and mineral resources. The dominant geological structure of Central Asia is the western continuation of the Sino-Korean Platform; this extension is divided by zones of tectonic activity into relatively stable areas: the Tarim and Dzungarian plains, the Ala Shan Desert, and the Ordos Plateau. These areas are bounded on the north by the Mongolian-Kazakhstan belt of Paleozoic folded structures and on the south by the Kunlun belt of Paleozoic folded structures. Mesozoic folding can be seen in the Chang Tang region, in the northern Tibetan Highlands. At the end of the Mesozoic, denudation plains were predominant throughout Central Asia. They were dramatically uplifted and deformed by subsequent Cenozoic movements. The modern relief is complex and is characterized by gravelly and sandy plains interspersed with melkosopochnik (area of low hills) and by mountain ranges and massifs; the highest mountains have Alpine characteristics.

The mineral resources of Central Asia have not yet been adequately studied. Northwest China has large deposits of petroleum at Karamai, Urgo, Tushandzy, and Yumen and large coal deposits at Turfan and Hami. The MPR has deposits of coal at Darkhan and Tsogt-Tsetsii, brown coal at Choibalsan, and iron ore at Sharyn-Gol, Tamryn-Gol, and various other locations. Central Asia is rich in rare and nonferrous metals, common salt, and various other minerals.

Climate. In winter the Asian anticyclone is located over Central Asia, but in summer the region is an area of low atmospheric pressure with prevailing low-humidity air masses of oceanic origin. The climate is markedly continental and dry, with large seasonal and daily fluctuations in temperature. Mean January temperatures on the plains range from –10° to –25°C; mean July temperatures are from 20° to 25°C (about 10°C in the Tibetan Highlands). Annual precipitation on the plains generally does not exceed 200 mm, and regions such as the Takla Makan, Kashun Gobi, Tsaidam, and Chang Tang receive less than 50 mm, a figure that is only one-tenth of the potential evaporation. The greatest amount of precipitation falls in summer. The mountain ranges receive 300–500 mm, and the southwest, influenced by the summer monsoon, receives up to 1,000 mm annually. Strong winds and a large number of sunny days, 240–270 a year, are characteristic of Central Asia.

The aridity of the Central Asian climate is reflected in the great elevation of the snow line, which is the highest in the world. The elevation of the snow line reaches 5,000–5,500 m in the Kunluns and the Nan Shan and 6,000–7,000 m in the Chang Tang region of the Tibetan Highlands. Because of the high snow line, the mountains, despite their great elevations, have little snow, and the intermontane valleys and plains usually remain free of snow throughout the winter. Glaciation is negligible; glaciers cover an estimated area of 50,000–60,000 sq m in Central Asia. The principal centers of glaciation are in the highest mountain knots of the Karakoram and Kunluns and in the eastern Tien-Shan and the Mongolian Altai. Cirque, hanging, and small valley glaciers predominate.

Rivers and lakes. Because of its arid climate, Central Asia has little water. Most of the region lacks external drainage and forms a series of closed basins, including the Tarim Basin (Kashgar Plain), the Dzungarian and Tsaidam plains, and the Great Lakes Depression. The principal Central Asian rivers—the Tarim, Khotan, Aksu, Konche Darya, Urungu, Manas, Kobdo, and Dzhabkhan—rise in the high-altitude peripheral mountain ranges; when they enter the plains, however, much of their flow percolates into the linear outwash deposits at the bases of the mountain, evaporates, or is used for irrigation. As a result, the amount of water in the rivers usually decreases in the rivers’ lower courses, and many rivers dry up or carry water only during the summer high water, which primarily results from the melting of snow and ice in the mountains. The driest regions of Central Asia—the Ala Shan, the Pei Shan, the Gashun and Trans-Altai Gobi, and the central Takla Makan Desert—are virtually without surface flow. Their surfaces are crossed by dry channels in which water appears only after occasional heavy rains. Only the margins of Central Asia drain into the oceans. Many of the great rivers of Asia—the Huang Ho, Yangtze, Mekong, Salween, Brahmaputra, Indus, Irtysh, Selenga, and Amur—rise in the mountains of Central Asia.

Of Central Asia’s many lakes, the largest is Koko Nor, and the deepest is Khubsugul. The lakes are most numerous in the Tibetan Highlands and in the northern MPR. Many of them, such as Lop Nor, are the termini of rivers, and therefore their outlines and dimensions change frequently, depending on fluctuations in the flow of the rivers. Salt lakes predominate. The largest freshwater lakes are Khara-Us-Nur, Bagrash Kol, and Khubsugul. Many lakes on the plains are contracting.

Soils. Chestnut soils predominate in northern Central Asia, gray-brown and desert soils predominate in the deserts of Northwest China, and permafrost soils typical of high-altitude (cold) deserts are found in the Tibetan Highlands. Solonchaks and takyrs are encountered in low areas. In the highest belt of mountains there are mountain meadow and, in the north, mountain forest soils. The Central Asian plains usually have a thin soil cover; the soils have a negligible humus content and frequently contain large amounts of carbonates and gypsum. Large areas of sandy and stony desert have no soil cover whatsoever. Gravelly and coarse skeletal soils are encountered in the mountains.

Flora. On most of the Central Asian plains the vegetation is sparse, consisting of desert and semidesert vegetation of only a few species. Subshrubby flora is predominant and includes Nitraria, reamuria, Ceratoides, the pea tree, salsola, Kalidium, Calligonum, and the ephedra. Large areas of takyrs, solonchaks, and loose sand have no vegetation at all. In the Tibetan Highlands, the vegetation often consists of procumbent Ceratoides subshrubs; sedge, Kobresia, reamuria, meadow grass, and fescue grow in the hollows, which are protected from the cold winds. In the north, the semideserts and deserts give way to steppes, where the prevalent vegetation includes stipa grass, Leymus chinensis (an Asiatic wild grass), and wheatgrass. On the northern slopes of the mountains there are tracts of coniferous forests of spruce, fir, and larch. Belts of tugai (floodplain forest), in which oleaster, sea buckthorn, and heterophyllous poplar predominate, occur in the valleys of many allogenic rivers, (Tarim, Khotan, Aksu, and Konche Darya), in the deserts, and in the foothill oases. Reed and bulrush thickets grow along bodies of water.

Fauna. The predominant large animals in Central Asia are ungulates and rodents. In the deserts of the MPR and Northwest China are found the wild camel, the Asiatic wild ass, Przheval-ski’s horse, the Persian and Mongolian gazelle, the hare, marmots, jerboas, pikas, gerbils, and mole lemmings. In the Tibetan Highlands are found the wild yak, the Asiatic wild ass, the chiru, the addax, mountain goats, argali, pikas, marmots, and voles. Among the predators, the wolf, true fox, and corsac are ubiquitous.

REFERENCES

Murzaev, E. M. Mongol’skaia Narodnaia Respublika, 2nd ed. Moscow, 1952.
Murzaev, E. M. Priroda Sin’tsziana i formirovanie pustyn’ Tsentral’noi Azii. Moscow, 1966.
Zarubezhnaia Aziia: Fizicheskaia geografiia. Moscow, 1956.
Sinitsyn, V. M. Tsentral’naia Aziia. Moscow, 1959.
Fizicheskaia geografiia Kitaia. Moscow, 1964.
Petrov, M. P. Pustyni Tsentral’noi Azii, vols. 1–2. Moscow-Leningrad, 1966–67.

V. M. SINITSYN