GOBI (for which the alternative Chinese names are Sha-mo, "sand desert" and Han-Iiai, "dry sea"), a term which in its widest significance includes the stretch of desert country extending from the foot of the Pamirs eastwards to the Great Khingan moun tains, and from the foothills of the Altai, the Khangai and the Yablonoi mountains on the north to the Altyn Tagh and Nan-shan on the south. The western portion of this desert belt, however, forms part of the well-defined physiographic unit of the Tarim basin and is considered separately under that head.
The Gobi proper occupies a broad, shallow depression in the wide plateau between the northern chains of the Tibetan massif and the Altai. It is approximately 600 miles from north to south and r,000 miles from east to west. The average relief is slight. There is an alternating succession of broad gravelly plains irreg ularly split up by low flat-topped ranges and detached residual hills. The altitude varies from 3,00o ft. in the east to about 5,000 ft. in the south and west. The relief features are chiefly the result of warping and uplift. This sometimes gives rise to moun tain structure on the borders, as in the case of the Altai, formed by a series of complex uplifted fault-blocks. The less prominent hill masses mark areas of gentler warping and smaller vertical displacement, while some are older fault-blocks which have been more completely worn down. Sometimes in the plains, the edges of the sedimentary strata are exposed to view, and these form the great fossil fields of Mongolia. There are evidences of cli matic changes in the Gobi desert in remote ages. Dry river beds, and strand lines on lake shores marking former higher levels of the lake are reported. Although the central portion of the desert can hardly have been attractive to primitive man, several culture horizons have been distinguished in the Gobi area. Finds have been made of relics representing Eolithic, Upper Palaeolithic, Azilian, Neolithic and Metallic cultures. Curiously enough, no relics of early Mongolian civilization have, as yet, been found.
Although the name Sha-mo means "sand desert" this descrip tion by no means applies to the whole of the Gobi. The actual waterless desert of Gobi, including the Ordos country and the Ala-shan, is confined to the south-western portion of the plateau and covers barely one-quarter of its whole area. The Ordos desert, a southern extension of the Gobi plateau is enclosed within the great northward bend of the Hwang-ho. It furnishes scanty pasture to the flocks and herds of the Mongolian nomads who are scattered throughout the area.
West of the Ordos, but separated from it by the mountain peninsula of the lofty Ala-shan range, which is enclosed in a northward extension of the province of Kansu, lies the Ala-shan desert. This desert owes its existence to the interception of the rainfall by the high ranges along its southern border; the Ala shan range rising to io,000 and Ii,000 ft. on the south-east, and the Richthofen range with peaks reaching 20,000 ft. on the south west. There are vast expanses of absolutely waterless desert in the Ala-shan country. No oases relieve the unbroken stretches of sand which alternate with vast areas of saline clay, or, nearer the foot of the mountains, with barren gravel. The only human in habitants of Ala-shan are the Torgod Mongols.
Trees are almost unknown in the Gobi. The vegetation com prises grass, thorns and patches of scrub in a soil varying from fine gravel and sand to coarse loam. Water in the Gobi is found only at wells or in occasional small lakes and is alkaline in taste. On the south-eastern borders of the Gobi, the desert proper gives way to steppe-land. Water can be found within fifteen or twenty five feet of the surface and the country approximates to the type represented by the Canadian prairies. Some of the moisture from the south-east monsoon reaches these borders in the summer and this eastern part of the Gobi area offers a field for agriculture and for sheep and cattle breeding. Chinese influence is pushing out in a north-westerly direction and it is this south-eastern border-land (Inner Mongolia) which is being gradually formed into "provinces." The northern and north-western borders of the Gobi also merge into grass-land and, farther north, into forest. The wide stretch of undulating land along the northern border, which is drained by the Orkhon and its tributaries, supports many Chinese colonists who cultivate the rich soil to be found in many of the valleys. These northern borders fall within the region of cyclonic rain: the average annual rainfall at Urga being 9.7 inches.
The Gobi desert is crossed by several caravan routes, some of which have been in use for thousands of years. The most impor tant are those from Kalgan, on the Chinese frontier, to Urga ; from Su-chow, in Kansu, to Hami; and from Kwei-hwa-cheng to Barkul.