The Gobi, broadly defined, can be divided into five distinct dry
ecoregions, based on variations in
climate and
topography: •
Eastern Gobi desert steppe, the easternmost of the Gobi ecoregions, covering an area of . It extends from the
Inner Mongolian
Plateau in China northward into Mongolia. It includes the
Yin Mountains and many low-lying areas with salt pans and small ponds. It is bounded by the
Mongolian-Manchurian grassland to the north, the Yellow River Plain to the southeast, and the
Alashan Plateau semi-desert to the southwest and west. •
Alashan Plateau semi-desert, lies west and southwest of the Eastern Gobi desert steppe. It consists of the desert basins and low mountains lying between the Gobi Altai range on the north, the
Helan Mountains to the southeast, and the
Qilian Mountains and northeastern portion of the Tibetan Plateau on the southwest. •
Gobi Lakes Valley desert steppe, ecoregion lies north of Alashan Plateau semi-desert, between the Gobi Altai range to the south and the
Khangai Mountains to the north. •
Dzungarian Basin semi-desert, includes the desert basin lying between the Altai mountains on the north and the
Tian Shan range on the south. It includes the northern portion of China's Xinjiang province and extends into the southeastern corner of Mongolia. The Alashan Plateau semi-desert lies to the east, and the
Emin Valley steppe to the west, on the China-
Kazakhstan border. •
Tian Shan range, separates the Dzungarian Basin semi-desert from the
Taklamakan Desert, which is a low, sandy desert basin surrounded by the high mountain ranges of the Tibetan Plateau to the south and the
Pamirs to the west. The Taklamakan Desert ecoregion includes the
Desert of Lop.
Eastern Gobi desert steppe s in the
Bayankhongor Province of Mongolia ) on a hill in the eastern Gobi of
Mongolia at sunset The surface is extremely diversified, although there are no great differences in vertical elevation. Between
Ulaanbaatar () and the small lake of Iren-dubasu-nor (), the surface is greatly eroded. Broad flat depressions and basins are separated by groups of flat-topped mountains of relatively low elevation , through which archaic rocks crop out as crags and isolated rugged masses. The floors of the depressions lie mostly between above sea-level. Further south, between Iren-dutiasu-nor and the
Yellow River, comes a region of broad tablelands alternating with flat plains, the latter ranging at altitudes of 1000–1100 m and the former at . The slopes of the plateaus are more or less steep and are sometimes penetrated by "bays" of the lowlands. As the border-range of the Hyangan is approached, the country steadily rises up to and then to . Here small lakes frequently fill the depressions, though the water in them is generally salty or brackish. Both here and for south of Ulaanbaatar, streams are frequent and grass grows more or less abundantly. Through all the central parts, until the bordering mountains are reached, trees and shrubs are utterly absent. Clay and sand are the predominant formations; the watercourses, especially in the north, being frequently excavated deep. In many places in the flat, dry valleys or depressions farther south, beds of
loess, thick, are exposed. West of the route from Ulaanbaatar to
Kalgan, the country presents approximately the same general features, except that the mountains are not so irregularly scattered in groups but have more strongly defined strikes, mostly east to west, west-north-west to east-south-east, and west-south-west to east-north-east. The altitudes are higher, those of the lowlands ranging from , and those of the ranges from higher, though in a few cases they reach altitudes of . The elevations do not form continuous chains, but make up a congeries of short ridges and groups rising from a common base and intersected by a labyrinth of ravines, gullies, glens, and basins. But the
tablelands, built up of the horizontal red deposits of the Han-gai (
Obruchev's Gobi formation) which are characteristic of the southern parts of eastern Mongolia, are absent here or occur only in one locality, near the Shara-muren river. They are greatly intersected by gullies or dry watercourses. Water is scarce, with no streams, no lakes, no wells, and precipitation falls seldom. The prevailing winds blow from the west and northwest, and the pall of dust overhangs the country as in the
Taklamakan and the
desert of Lop. Characteristic of the flora are wild garlic,
Kalidium gracile,
wormwood,
saxaul,
Nitraria schoberi,
Caragana,
Ephedra, saltwort and the
grass Lasiagrostis splendens. The taana wild onion
Allium polyrrhizum is the main
browse eaten by many herd animals, and Mongolians claim that this is essential in producing the proper, hazelnut-like notes of camel
airag (fermented milk). The vast desert is crisscrossed by several trade routes, some of which have been in use for thousands of years. Among the most important are those from
Kalgan (at the Great Wall) to Ulaanbaatar (); from
Jiuquan (in
Gansu) to Hami ; from Hami to Beijing (); from
Hohhot to Hami and Barkul; and from
Lanzhou (in Gansu) to Hami.
Alashan Plateau semi-desert ,
Inner Mongolia, China The southwestern portion of the Gobi (known also as the
Xitao or the "Little Gobi") encompasses the distance between the great northern loop of the
Yellow River to the east, the
Ejin River to the west, and the
Qilian Mountains and narrow rocky chain of Longshou, in altitude, to the southwest. The
Ordos Desert, which covers the northeastern portion of the Ordos Plateau (also near the great northern loop of the Yellow River) is part of this ecoregion within the middle basin of three great depressions into which Potanin divides the Gobi. "Topographically," says
Nikolai Przhevalsky, "it is a perfectly level plain, which in all probability once formed the bed of a huge lake or inland sea." He concludes this based on the level area of the region as a whole, the hard saline clay and the sand-strewn surface and, lastly, the salt lakes which occupy its lowest parts. For hundreds of kilometers, nothing can be seen but bare sands; in some places, they continue so far without a break that the Mongols call them
Tengger (i.e. sky). These vast expanses are absolutely waterless, nor do any oases relieve the unbroken stretches of yellow sand, which alternate with equally vast areas of saline clay or, nearer the foot of the mountains, with barren shingle. Although on the whole a level country with a general altitude of , this section, like most other parts of the Gobi, is crowned by a network of hills and broken ranges of at least 300 m in elevation. The vegetation is confined to a few varieties of bushes and a dozen kinds of grasses and herbs, the most conspicuous being saxaul (
Haloxylon ammondendron) and
Agriophyllum gobicum. The others include prickly
convolvulus, field wormwood (
Artemisia campestris),
acacia,
Inula ammophila,
Sophora flavescens,
Convolvulus ammanii,
Peganum and
Astragalus species, but all dwarfed, deformed and starved. The fauna consists of little but antelope, wolf, fox, hare, hedgehog, marten, numerous lizards and a few birds, e.g. the sandgrouse, lark, stonechat, sparrow, crane,
Mongolian ground jay (
Podoces hendersoni),
horned lark (
Eremophila alpestris), and
crested lark (
Galerida cristata).
Dzungarian Basin semi-desert The Yulduz valley or valley of the Haidag-gol (–) is a mini desert enclosed by two prominent members of the Shanashen Trahen Osh mountain range, namely the chucis and the kracenard pine rallies, running perpendicular and far from one another. As they proceed south, they transcend and transpose, sweeping back on east and west respectively, with
Lake Bosten in between. These two ranges mark the northern and the southern edges respectively of a great swelling, which extends eastward for nearly twenty degrees of longitude. On its northern side, the Chol-tagh descends steeply, and its foot is fringed by a string of deep depressions, ranging from
Lukchun ( below sea level) to
Hami ( above sea-level). To the south of the Kuruk-tagh lie the desert of
Lop Nur, the
Kum-tagh desert, and the valley of the
Bulunzir-gol. To this great swelling, which arches up between the two border-ranges of the Chol-tagh and Kuruk-tagh, the
Mongols give the name of
Ghashuun-Gobi or "Salt Desert". It is some across from north to south, and is traversed by a number of minor parallel ranges, ridges and chains of hills. Down its middle runs a broad stony valley, wide, at an elevation of . The Chol-tagh, which reaches an average altitude of , is absolutely sterile, and its northern foot rests upon a narrow belt of barren sand, which leads down to the depressions mentioned above. The Kuruk-tagh is the greatly disintegrated, denuded and wasted relic of a mountain range which used to be of incomparably greater magnitude. In the west, between Lake Bosten and the
Tarim, it consists of two, possibly of three, principal ranges, which, although broken in continuity, run generally parallel to one another, and embrace between them numerous minor chains of heights. These minor ranges, together with the principal ranges, divide the region into a series of long; narrow valleys, mostly parallel to one another and to the enclosing mountain chains, which descend like terraced steps, on the one side towards the depression of Lukchun and on the other towards the desert of Lop. In many cases these latitudinal valleys are barred transversely by ridges or spurs, generally elevations en masse of the bottom of the valley. Where such elevations exist, there is generally found, on the east side of the transverse ridge, a cauldron-shaped depression, which some time or other has been the bottom of a former lake, but is now nearly a dry salt-basin. The surface configuration is in fact markedly similar to that which occurs in the inter-mount latitudinal valleys of the
Kunlun Mountains. The
hydrography of the Ghashiun-Gobi and the Kuruk-tagh is determined by the aforementioned arrangements of the latitudinal valleys. Most of the principal streams, instead of flowing straight down these valleys, cross them diagonally and only turn west after they have cut their way through one or more of the transverse barrier ranges. To the highest range on the great swelling
Grigory Grum-Grshimailo gives the name of
Tuge-tau, its altitude being above the level of the sea and some above the crown of the swelling itself. This range he considers to belong to the
Choltagh system, whereas
Sven Hedin would assign it to the Kuruk-tagh. This last, which is pretty certainly identical with the range of
Kharateken-ula (also known as the
Kyzyl-sanghir,
Sinir, and
Singher Mountains), that overlooks the southern shore of the Lake Bosten, though parted from it by the drift-sand desert of
Ak-bel-kum (White Pass Sands), has at first a west-northwest to east-southeast strike, but it gradually curves round like a scimitar towards the east-northeast and at the same time gradually decreases in elevation. At 91° east, where the principal range of the Kuruk-tagh system wheels to the east-northeast, four of its subsidiary ranges terminate, or rather die away somewhat suddenly, on the brink of a long narrow depression (in which Sven Hedin sees a northeast bay of the former great Central Asian lake of Lop-nor), having over against them the écheloned terminals of similar subordinate ranges of the
Pe-shan (Boy-san) system (see below). The Kuruk-tagh is throughout a relatively low, but almost completely barren range, being entirely destitute of animal life, save for hares, antelopes and wild camels, which frequent its few small, widely scattered oases. The vegetation, which is confined to these same areas, is of the scantiest and is mainly confined to bushes of
saxaul (Haloxylon),
anabasis, reeds (kamish),
tamarisks,
poplars, and
Ephedra. ==History==