Great Lakes Depression

(or Great Lakes Basin), a vast tectonic depression in the western Mongolian People’s Republic (the northern edge is in the USSR). The basin is located between the Mongolian Altai, the Khangai, and the Tannu-Ola range. Area, more than 100,000 sq km. Gently sloping rock-debris and clay plains alternating with areas of low hills and isolated granite outliers and massifs dominate the relief. There are large stretches of sand desert with an area of about 14,000 sq km. Elevation ranges from 750-800 m to 1,500-2,000 m. The basin is composed primarily of Anthropogenic alluvial, lacustrine, and eolian deposits.

The climate is sharply continental with temperatures ranging from -50°C to 35°C. Precipitation is 100-150 mm a year and up to 350 mm in the mountains and in the north. Among the large lakes in the basin are Ubsu-Nur and Khirgis-Nur (salt-water) and Khara-Nur and Khara-Us-Nur (freshwater); there are also solonchaks. The principal rivers are the Kobdo, Dzabkhan, and Tesiin-Gol. In the north dry steppes with varied grasses prevail; in the south there are semideserts and deserts, with xerophytic dwarf semishrubs and saltworts predominating. Birch and poplar groves and brush thickets occur along the river valleys. Where there is ground moisture, thickets of cane and Lasiagrostis splendens are found. Livestock are grazed in the region, and there is irrigation farming in some sections.