Kopetdag

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Kopetdag

 

(also Koppeh Dagh), a mountain system in the northern part of the Iranian Plateau, located primarily in Iran; the smaller, northern branch is situated in the USSR (southern Turkmen SSR). The Kopetdag is part of that section of the Turkmen-Khorasan Mountains which lies north of the Gorgan River and the Quchan-Mashhad Valley. Length, approximately 650 km. Width in the northwest, up to 200 km; width in the central region, 80–95 km; width in the southeast, 40 km.

Geological structure and minerals. The Kopetdag is located in the Alpine folded region. The folded structure of the Kopetdag meganticlinorium was formed as a result of alpine folding, and intensive neotectonic uplifts during the Pliocene and Anthropogene created the larger features of the present mountain relief. Frequent, powerful earthquakes, including those of 1869, 1893, 1895, and 1929 and the Ashkhabad earthquake of 1948, are evidence of continuing mobility. The Kopetdag is composed of sedimentary (mostly Cretaceous, Paleogene, Neocene, and, partly, Jurassic) limestone, marl, sandstone, conglomerates, and clays, crushed into broad, steep folds and tilted toward the northeast. Along the northeastern foot of the Forward Chain the folds are bounded by a fault zone and thrust along a series of imbricate thrusts north onto structures of the Cis-Kopetdag Depression. This zone is noted for numerous mineral springs, including hot springs. The area contains building stone and ore deposits of mercury, arsenic, barite, and witherite.

Relief. Ancient stages of planation created several layers of leveled surfaces, which were subdivided during the most recent uplift. Relict residual plateaus contrast sharply with recent steep-sloped entrenchments. Synclinal ridges capped with Sarmatian limestone are encountered along with anticlinal ridges and synclinal valleys. Asymmetric cuesta ridges and tablelands are widespread. Argillaceous karst is distributed in clayey-marly beds. The Bakharden karst cave and Kou, an underground lake, were formed in Jurassic limestone. The broken Forward Chain, which is separated by the Great Kopetdag Valley from the system of border and axial ranges, stands out in the relief of the Kopetdag because of its rectilinearity. The highest of the border and axial ranges is Hazar Masjid, with a peak (3,117 m) of the same name; it is situated in Iran. The Saandak Range with the peak Rize (2,942 m) rises up over Ashkhabad. The Forward Chain and the majority of axial ranges extend from the southeast to the northwest. In the west the Kopetdag divides into several ranges that diverge toward the west and the southwest. The southwestern and southeastern outliers of the Kopetdag are cut by open gorges of the middle course of the Atrek River and the lower course of the Kashaf River. In the southeast the open gorge of the Tedzhen River (Harirud) separates the Kopetdag from the Badkhyz Elevation. Stepped, flat-topped, steep-sloped ridges with altitudes of 1,500–2,000 m (in the northwest, 300–1,000 m) are broken by transverse gorges and divided by terraced longitudinal valleys, the largest being those of the Sumbar, Chandyr, and Durungar rivers. Areas of hills sharply cut by ravines (badlands) are common along the lower sections of the various ranges. Loess trains are widespread at the bases of the mountains.

The climate is of the dry, subtropical, eastern Mediterranean type. The average temperature in January is as low as 1° to −4°C, depending on elevation, and in July it varies from 29° to 18°C. Annual precipitation ranges from 150 mm in the lower sections to 500 mm in upper parts of windward mountain slopes. The greatest precipitation occurs in March and April, owing to polar front Mediterranean cyclones. In summer evaporation exceeds precipitation by a factor of three or four. In the winter, valleys often experience sharp rises in temperature owing to foehn activity.

Rivers and lakes. In consequence of the dry climate and wide-spread distribution of permeable rock, all rivers dry up over large areas of their beds or turn into chains of salt lakes. Rivers are fed primarily by subsurface drainage as well as spring and episodic rains. Water emerging to the surface at the foot of piedmont trains is used by the system of karezes (underground irrigation canals).

Types of landscapes. Altitudinal zonation of the landscape is pronounced on the slopes. Loess submontane trains and hilly piedmont areas up to 300 m high are covered by wormwood-ephemeral desert with light sierozem soils. Primary vegetation is represented here by “meadows” of spring ephemeral sow thistles and meadow grass, which are green for two or three months, and by a small mix of perennials that vegetate in the summer. Oases adjoin the northeastern foothills of the Kopetdag. The largest are in the Turkmen SSR’Akhal-Tekke (with the city of Ashkhabad) and Atekskii, where cultivated fields and gardens with artificial irrigation predominate. At altitudes of 300–600 m, with an increase in annual precipitation to 250 mm, there is a prevalence of mountain deserts and sow thistle and meadow grass semideserts with darker mountain sierozems and a large admixture of perennials (Umbelliferae and Cousinia cass). Many animals of the desert foothill plains penetrate the desert and semidesert piedmont areas of the Kopetdag. The Persian jird, mouselike hamster, and Afghan pika are characteristic inhabitants of these piedmont areas and are not found in the foothill plains. Predators include the manul, hyena, and Indian honey badger; reptiles include the snake Taphrometopon lineolatum and very poisonous desert snake Vipera raddei. At elevations of 600–1,000 m, where annual precipitation totals approximately 300 mm, subtropical mountain steppes with wheatgrass and tall grasses on mountain light-chestnut soils are developed. The Afghan mole-vole, gray hamster, and blunt-nosed viper are found in the mountain steppes of the Kopetdag; porcupines and mountain sheep are encountered. The wild boar, leopard, and forest dormouse live in the woody-shrub growths of gorges. The green woodpecker and blackbird also build their nests here. At altitudes of 1,000–1,500 m, where annual precipitation increases to 400-500 mm, mountain feather-grass and sheep-fescue steppes with dark-chestnut soils and areas of open woodland with juniper are characteristic. Thickets of prickly, cushion-type shrubs (such as Acantalimon boiss and gum-bearing Astragalus) are common on drier rocky slopes. Animals frequently encountered are the wild boar, Tolai hare, and Afghan pika; in summer mountain sheep are common. Birds found in juniper stands include the ringdove, white-winged grosbeak, and black vulture. The wild goat is found on precipitous cliffs and steep slopes. Above 2,200 m, mountain steppes give way to mountain meadows. Woody plants are also found in the southeast (pistachio woodlands) and in wetter valleys of the western Kopetdag into which representatives of Hyrcanian (North Iranian) flora have penetrated. This flora includes many wild fruit-bearing varieties, such as pomegranate, fig tree, almond, Mespilus, pear, barberry, hawthorn, and wild grape, which forms belts of “forest-gardens” on valley floors.

The resort of Firiuza is located in the canyon of the Firiuzinka River, near Ashkhabad.

REFERENCE

Val’be, S. P. “Osnovnye cherty tektoniki Kopetdaga.” Izv. AN SSSR: Seriia geologicheskaia, 1970, no. 6.
Efremov, Iu. K. “O rel’efe Kopetdaga.” In Voprosy geografii, collection 40. Moscow, 1957.
Rezanov, I. A. Tektonika i seismichnost’ Turkmeno-Khorasanskikh gor. Moscow, 1959.
Korovin, E. “Osnovnye cherty v stroenii rastitel’nogo pokrova gornoi i podgornoi chasti Kopetdaga … .” Izv. In-ta pochvovedeniia i geobotaniki Sredne-Aziatskogo gos. un-ta, 1927, issue 3.

IU. K. EFREMOV

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