| Lop Desert | |
|---|---|
 Satellite picture of the Lop Desert with the basin of the former sea Lop Nur. In the left Kuruk-tagh, in the right Astin-tagh. | |
| Area | 50,000 km2 (19,000 mi2) |
| Geography | |
| Country | China |
| Chinese Region | Xinjiang |
| Coordinates | 40°10′0″N90°35′0″E / 40.16667°N 90.58333°E /40.16667; 90.58333 |
 Interactive map of Lop Desert | |
TheLop Desert, or theLop Depression, is adesert extending fromKorla eastwards along the foot of theKuruk-tagh (meaning Dry Mountain) to the formerterminalTarim Basin in theXinjiang Uyghur Autonomous Region ofChina. It is an almost perfectly flat expanse with no topographic relief.Lake Bosten in the northwest lies at an altitude of 1,030 to 1,040 m (3,380 to 3,410 ft), while the Lop Nur in the southeast is only 250 m lower.
The desert lies within asediment basin that was separated from the Taklamakan basin in thePliocene and lowered towards the east by a tectonicdip-slip fault.The riversTarim andKonqi used to flow in the rift valley between both basins towards the south until they dried up around 1971 at Tikanlik. The road 218 fromKorla toQakilik follows the river beds. The desert is bounded in the west by this road, in the north by theKuruk Tagh mountain range, in the east by the Bei Shan range (betweenBarkol Tagh andBogda Shan), in the southeast by theKumtag Desert and in the south by the Aqikkol valley.
The Lop Desert is on the whole flat, but with three slightly more depressed areas which might form lakes if filled with water - theLop Nur dried basin,Kara-Koshun dried basin and the Taitema Lake basin.[1] These formed, at one time or another, the terminal lakes of theTarim-Konque-Qarqan river system. The Tarim River changes its course through time, and therefore the location of the terminal lake also changes, causing some confusion amongst the early explorers as to the exact location of Lop Nur, and the lake was thus referred to as the "Wandering Lake."[2]
In the past Lop Nur was a huge marsh in the eastern part of Xinjiang. Now the region is a broad, unbroken expanse ofclay intermingled withsand. The clay, mostly of a yellow or yellow-grey color, is hard and thickly sprinkled with finegravel. There are benches, flattened ridges and tabular masses of consolidated clay (yardangs) that are in a distinctly defined laminae, three stories being sometimes superimposed one upon the other, while their vertical faces are abraded, and often undercut, by the wind. The formations themselves are separated by parallel gullies or wind furrows, 6 to 20 feet deep, all sculptured in the direction of the prevailing northeast to southwest wind. There is no drifting sand orsand dunes, except in the south towards the outlying foothills of theAltyn-Tagh.[3]
The climate of Lop Desert is extremely arid, a study in 1984 gives a mean annual precipitation of generally less than 20 mm (0.79 in),[1] in another study in 2008 it was recorded as 31.2 mm (1.23 in).[4] In the depression centre below 800 m (2,600 ft) in elevation, aridity can be expected to be much more extreme. Relative humidity of the atmosphere frequently dropped to zero, with air temperature as high as 50 °C (122 °F). Annual evaporation was estimated in 1984 to be between 1,000 mm (39 in) and 1,500 mm (59 in), meaning that a lake with about 2 m (6.6 ft) in water depth will dry out within less than two years if cut off entirely from its feeding source. In 2008 the annual evaporation was reported as 2,901 mm (114.2 in).
Historically there were periods when the area was more favorable to farming and settlement than today. Studies showed that the area experienced seven major climate changes since the end of thePleistocene.[4][5]
There are numerous indications that suggest the presence of an extensive lake in this region which is now completely desiccated. These indications includesalt-stained depressions of a lacustrine appearance; traces of former lacustrine shorelines, more or less parallel and concentric; the presence in places of vast quantities of fresh watermollusc shells (species ofLymnaea andPlanorbis); the existence of belts of deadpoplars; patches of deadtamarisks and extensive beds of witheredreeds, all of these are always on top of theyardangs, never in the wind-etched furrows.[3]
InHanshu (theBook of Han, a history of China completed in 111), where it was called Puchang Hai (蒲昌海), the lake was suggested to be of a great size, with a dimension of 300 to 400li, roughly 120–160 km (75–99 mi), in length and breadth.[6] It was also called Yan Ze (鹽澤) inShiji, which means "salt marsh", indicating that the lake was salty.[7] The lake had already shrunk considerably by theQing dynasty. It had shifted its location toKara-Koshun by the latter half of the nineteenth century, then back again to Lop Nur in 1921 through human intervention. The building of dams by Chinese garrisons in the twentieth century blocked the water from the rivers feeding in to Lop Nur and it is now primarily salt flats.[8] The dried-up Lop Nur basin is covered with a salt crust from 0.3 to 1 m (0.98 to 3.28 ft) thick.
Natural vegetation is sparse in the region and poor in the number of species. A scientific expedition to the Lop Nur region in 1979-1982 collected only 36 species of plants, belonging to 13 families (mainlyChenopodiaceae andCompositae) and 26 genera. The expedition also collected only 127 species of animals (23 mammals, 91 birds, 7 reptiles, and 1 amphibian).[1]
ArchaeologistSven Hedin who travelled in the region in the late nineteenth as well as the twentieth century was able to travel by boat up the rivers to the lake and saw a multitude of wildlife.[8] However, many wild animals, such as tiger, wolf and wild hog which had been found by former explorers, have now disappeared. Nevertheless, it is still one of the last refuges ofwild Bactrian camel (Camelus ferus) in the world. These wild camels may be found in the reed oases on the north edge of the desert.Poplars forests andtamarix shrubs used to be extensively distributed along the lower Tarim River Valley forming the so-called "Green Corridor", but as the lower Tarim River has been drying since 1972 due to the construction of dams, they have greatly deteriorated and some have disappeared. TheLop Nur Wild Camel National Nature Reserve was created in 2001 to preserve wild Bactrian camels and other wildlife in the region.[9]
The whole of this region is swept bare of sand by the terrificsand storms (burans) of the spring months and the particles of wind-blown sand act like a sand blast. Abrasion of the rocks formsyardangs. The desert itself is abraded, filed,eroded and carried bodily away into the network of lakes in which theTarim River wanders. The sand also blows across the lower, constantly shifting waterways of the Tarim River and deposits itself onto gigantic dunes that choke the eastern end of theTaklamakan Desert.[3] The extreme weather and ever moving sand dunes have resulted in the deaths of hundreds of people. The esteemed biologistPeng Jiamu disappeared in the desert in 1980.[10]
One or more of the preceding sentences incorporates text from a publication now in thepublic domain: Bealby, John Thomas (1911). "Gobis.v.Desert of Lop". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 12 (11th ed.). Cambridge University Press. p. 166.{{cite journal}}: CS1 maint: multiple names: authors list (link)