Ustiurt

a plateau in the Kazakh and Uzbek SSR’s, located between Mangyshlak and the gulf of Kara-Bogaz-Gol in the west and the Aral Sea and the delta of the Amu Darya in the east. The Ustiurt has an area of approximately 200,000 sq km. It is bounded by precipitous scarps, with elevations of 150 m and more. The plateau itself has elevations of up to 370 m in the southwest. It is composed primarily of Neogene rocks—limestones, marls, clays, and sandstones. The Neogene layer forms two gentle syneclises, one in the north and one in the south, complicated by upwarps and downwarps, the effects of which are evident in the topography and reflect the steplike structure of the epi-Paleozoic basement.

The Ustiurt as a whole is a tableland with a number of elevations in the form of uvaly (gently sloping hills) such as the Muzbel’ and Karabaur. It also has vast, closed depressions, such as the Barsakel’mes Salt Bottom, the Assake-Audan Depression, and the Northern Ustiurt Depression, which exhibits tracts of sand (the Sam and others) and sory (seeSOR). Various forms of karst are associated with the leaching of limestones and gypsums.

The climate is dry and markedly continental, with little more than 100 mm of precipitation annually. There are gray-brown soils with a low carbonate content in the north and typical calcareous soils in the south. Solonchaks, including gray-brown solonchaks, are widespread, especially in the north. Vegetation, which is sparse, consists of wormwood and saltwort. The desert landscape of most of the Ustiurt is categorized as clay wormwood or wormwood-saltwort desert, but the southeastern part is claycobble desert. There are sections of salt desert and, in the north, sandy desert. Most of the Ustiurt is used as spring, summer, and autumn pasture.