Saturday, November 3, 2012

Ustyurt Plateau

 Illustration: Extent of the Ustyurt 

The Ustyurt Plateau, also spelled Ust-Yurt, Ust-Urt and Usturt (Kazakh: Üstirt, Turkmen: Üstyurt) lays between three Central Asian states of Uzbekistan, Kazakhstan and Turkmenistan.

The Ustyurt plateau in its entirety is some 200,000 square kilometres and stretches from the so-called "Western Chink" between the Gulf of Mangyshlak and the Karynzharyk Desert to the "Eastern Chink" on the west bank of the Aral Sea. It has an average elevation of 150 meters, and consists primarily of stony desert. The plateau’s semi-nomadic population raises sheep, goats, and camels. It also has a number of important Gas fields and production facilties on its perimeter and a growing population.

The Plateau's chalk escarpments, known as "chinks", are hugely impressive and starkly beautiful. The giant terraces stretch hundreds of kilometres to the north and south, reaching heights of up to 219 metres on the border with the Aral Sea, while those on the Caspian rise up to 341 metres high.

The plateau proper consists of a flat, waterless highland plain, covered with sand in some places and with gypsum crystal in others. It is the only place in the world where the Ustyurt urial can be seen. Four plant species and 33 animal species of the Ustyurt plateau are listed in the Red Book of the Republic of Uzbekistan and 40 are on the International Union for Conservation of Nature’s Red List because they are close to becoming extinct.

A type of black saksaul grows only in this region, in the form of proper trees rather than bushes. Relatively large groups of the unique Ustyurt moufflon (a rare type of wild sheep with a reddish coat) and kulan (asiatic wild ass) live on the plateau. As well as a small population of the lynx-like caracal which is threatened with extinction as are dwindelling populations of Indian porcupine, saiga antelope and dzheyran gazelle.

Many reptiles and rodents are endemic to the Ustyurt. Nocturnal animals such as the long-eared desert (Brandt's) hedgehog snuffles through the dark. Apart from the Houbara bustard, the large birds that live here are mainly raptors: the rare Turkmen owl (a subspecies of the Eurasian eagle owl), the Saker falcon, short-toed and golden eagles and scavengers such as the Egyptian vulture.

Every seven to nine years there is a time of glut for these birds when the zhut (a severe blizzard) leaves thousands of hoofed animals dead. This phenomenon, most feared by the local inhabitants, takes place when, after winter rains, temperatures suddenly drop sharply and the desert ground freezes over. Unable to find food, the animals swiftly die.

The continental climate of the region is extreme. Winters are harsh and windy and snow is rare. Spring is short, dry and windy. Summer is hot, cloudless and long lasting. Autumn is warm and long as well.

Annual average temperature is about +10.5 + 11.5°C. Absolute annual minimum temperature is +26 + 34°C; maximum + 43 +45°C; surface heat reaches +60 +70°C. The hottest period is from the middle of July to mid-August. Autumn frosts begin at the end of October, and the spring thaw starts in April.

Precipitation is poor. Annual average precipitation varies from 140-160mm in the north to 90-120mm in the south. Rain showers are common in spring and early summer; washouts and mudslides are common as there is often little vegetation holding the soil together.

Snow cover on the Ustyurt is thin (3-7 cm) and unstable. Not all areas are covered with snow. As a result of the high temperatures in the summer months, poor precipitation and windy weather, evaporation exceeds precipitation by 10-15 times and  humidity a low 40-60%.

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