Kazakh Melkosopochnik

(also Saryarka), a level upland region with low-mountain massifs and ranges, located in the central and eastern parts of the Kazakh SSR.

It stretches from west to east for about 1, 200 km, with a width of about 900 km in the west and some 400 km in the east. The western part of the region has elevations (absolute altitude) ranging from 300 to 500 m and a great deal of even terrain. Here are two low-mountain massifs, Ulutau (1, 133 m) in the west and the Kokchetav Upland (Mount Siniukha, 947 m) in the north. The eastern part of the Kazakh Melkosopochnik is characterized by greater elevations (averaging from 500 to 1,000 m) and a more dissected terrain. In the center of the eastern part rise the Karkaralinsk Mountains, in which is found the Aksoran Massif (1, 565 m), the highest in the Kazakh Melkosopochnik. Further to the east is the Chingiztau Range (1, 077 m). The low-mountain massifs, whose relative height does not exceed 500–600 m, are surrounded by a melkosopochnik, an elevated gently rolling plain; here in series or scattered are found numerous hills and low ridges composed of bedrock with relative heights ranging from 10–50 m to 100 m.

Geologically, the Kazakh Melkosopochnik is a part of the Ural-Mongolian geosynclinal zone. It is composed of highly dislocated metamorphic shales, quartzites, sandstones, and limestones of the Paleozoic overlaid in places by Mesozoic and Cenozoic deposits. As much as 60 percent of the area is occupied by intrusive rocks (granites, diorites, porphyrites) and extrusive rocks. Of great importance in the formation of the structures were the Caledonian and Hercynian stages of tectogenesis, which differ sharply in their overall structural plan. The Caledonian system of folds has a north-east strike, whereas the Hercynian has a north-west strike. The Caledonian structures are widespread in the western part of the region, and those of the Hercynian predominate in the east. In the late Paleozoic and early Mesozoic the entire region was fractured by faults. The end of the Carboniferous saw the onset of a continental period, which has lasted until the present. As a result of erosion and denudation, the high mountainous region formed by Hercynian orogeny was worn down and gradually acquired its present appearance. The melkosopochnik was formed by small tectonic uplifts of deformation and the repeated dissection of the ancient peneplain. The low-mountain massifs are the result of the most recent local uplifts of greater amplitude.

The climate is continental, becoming arid toward the south. The mean temperature in January ranges from −14° to − 18°C, and in July from 20° to 24°C. During winter frosts the temperature may fall to − 40°C, and in summer daytime temperatures may rise to 35°C and higher in the south. Annual precipitation totals 200–300 mm (up to 370 mm in the northern mountain massifs). In winter the snow cover is not deep, and in summer there are frequent droughts. The divide of the Irtysh basin and the subsurface drainage region of Middle Asia pass through the Kazakh Melkosopochnik. The largest rivers are the Ishim (Irtysh basin), Nura, and Sarysu; their rate of flow is very uneven. The rivers are fed mostly by spring snowmelt and partly by groundwater. In the spring there is high water, but during the summer the rivers become shallow. The spring discharge of the Nura River constitutes 88 percent of its annual flow, whereas the summer discharge is only 3 percent. In winter the rivers are frozen, the small ones freezing to the bottom. None of the rivers are navigable. There are many lakes, of which the largest is the shallow Tengiz Salt Lake.

The northern part of the Kazakh Melkosopochnik lies in the steppe zone. It is covered with mixed fescue and feather-grass vegetation growing on southern chernozems, which are partially tilled. The central part belongs to the dry-steppe zone, with fescue and feather-grass vegetation growing on dark chestnut soils (also partially tilled) and chestnut soils. The southern and eastern parts of the Kazakh Melkosopochnik are in the semidesert zone, where there is a combination of steppe (turfy-gramineous) and desert (polyn’ [Artemisia] and halophytic) vegetation and where light chestnut soil predominates. The southeastern part, near Lake Balkhash, lies in the desert zone. The virgin lands of the Kazakh Melkosopochnik are used for pasture.