KUEN-LUN or KWEN-LUN, a term applied generally to mountain ranges on the north edge of the great Tibetan plateau.
In a wider application it means the succession of ranges which extend from the Pamirs to 113° E. In the narrower sense it applies only to those ranges which part the desert of Takla-makan from the Tibetan plateau, between the Pamirs and the transverse glen of the Kara-muren (about 851° E.). Although the name is thus restricted, the mountain system so designated in fact, extends eastwards as far as the Tsaidam depression (say 95° E.).
Broadly defined, the range of the Kuen-lun Mountains thus ex tends for nearly 2,500 m. from east to west, and while in the west their constituent ranges are folded and squeezed, to some 150-200 m. broad, their summits being correspondingly high, in the east they spread out to some 600 m., the ranges being here less folded, and consequently flatter and lower. The folding of the Kuen-lun commenced in Hercynian times but was continued in early Tertiary times, when the direction of movement was north ward, that of the Himalayas being southward whilst the Tibetan plateau was driven upwards between the two. Although the crests of its component ranges reach altitudes of 21,500 to 22,000 ft., there are few individual peaks of commanding elevation, as in the Himalayas. The outermost border range of the Western Kuen lun and Ustun-tagh is throughout double; and this feature, as also the intermont lake-basins among the Kuen-lun ranges, is a peculiar feature of the Tibetan plateau.
the east the Pamir is separated from the East Turkistan lowlands by the double border-ridge of Sarik kol (the Sarik-kol and the Murtagh ranges), with the Tarim basin
ft.) on the east and the Pamirs (10,500 to 53,000 ft. above sea-level) on the west, while its own summits, e.g., the Murtagh-ata (24,388 ft.), are far above the snow line. This double border-ridge is continued east of the meridian of Yarkand
E.) by a succession of twin ranges, under different names. These eastward continuations of the double border-range of the Pamirs are the constituent ranges of the Kuen-lun proper. The names given to them are the Kilian, the Khotan and the Keriya Mountains in the northern range and the Raskan, the Sughet and the Ullugh-tagh Mountains in the southern range. Although they all decrease in altitude from west to east, they nevertheless reach elevations of 19,000 ft., with individual peaks, some 2,000-2,500 ft. higher. On the north the ascent is steep, and the passes across both sets of ranges lie at great altitudes; e.g., the Sanju-davan in the lower range is 16,325 ft. above sea-level, and the Kyzyl davan, farther east, is 16,900 ft., while the Sughet-davan in the higher range is 17,825 ft. The latter range is separated from the Karakorum Mountains by the deeply trenched gorge of the Ras kam, while the deep glen of the Kara-kash intervenes between the upper (Sughet Mountains) and the lower (Kilian Mountains) border-ranges. This western extremity of the Kuen-lun system is a very rugged mountainous region. In the broad orographical dis position, the ranges of north Tibet are crowded together in the west, but spread out towards the east. To the two principal
ranges in this part of the system the names, the Altyn-tagh and Ustun-tagh are given although there are no less than six parallel ranges altogether.
Between the upper transverse glens of the Karamuren and the Cherchen-darya stretches the short range of Tokuz-davan. From it, on the east side of the Cherchen-darya in about 86° E., the component ranges of the middle Kuen-lun begin to diverge like the fingers of the outspread hand. And here at least four principal ranges or groups of ranges admit of being discriminated, namely the Ustun-tagh, the Chimen-tagh, the Kalta alaghan and the Arka-tagh, all belonging to the mountainous country which borders on the north the plateau region of Tibet. Although these several ranges differ considerably in orography the following description will apply generally to the entire region. The broad features of the surface configuration are a series of nearly parallel mountain-ranges, and separated by high intermont valleys, choked with disintegrated material and divided into shal low lacustrine basins. Usually the crests of the ranges are worn down to rounded domes by sub-aerial denudation. Hard rock (mostly granite and crystalline schists, with red sandstone in places) appears only in the transverse glens, which are often choked with debris. The flanks of the mountains are deeply buried in disintegrated material. As each successive range, proceeding south, represents a higher step in the terraced ascent from the desert of Gobi to Tibet, the ranges when viewed from the north frequently appear like distinct mountain ranges and this appear ance is accentuated by the steepness of the ascent ; but, when viewed from the south, owing to their long and gentle slope in that direction, they have the appearance of comparatively gentle swell ings. As a rule, the streams flow alternately east and west down the intermont latitudinal valleys, until they break through some transverse glen on the north side of the valley. In the western parts they mostly feed the Kara-muren or the Cherchen-darya, while farther east they flow down into some basin of internal drainage, e.g., the Achik-kol, the two lakes Kara-kol, or the Ghaz kol, and even yet farther east make their way into the lakes of the Tsaidam depression or are lost in its sands or in those of the Kum tagh desert, or go to feed the great rivers, the Hwang-ho and the Yangtsze-kiang. The rivers which reach the deserts of Gobi and Takia-maken grow increasingly larger in magnitude from east to west. The great latitudinal streams in the Arka-tagh and the Chimen valley flow close under the foot of the range that shuts in each individual valley on the north. There is a marked difference in precipitation between the valleys of the north and those of the south. Those in the north are arid and desolate in the extreme, whilst those of the Arka-tagh and beyond are so damp that, in summer, the surface is in many parts little better than a quag mire. Vegetation throughout is scanty and faunal life poor in species.