The Tibetan Plateau

The plateau of Tibet, roof of the world, owes its extreme elevation to tectonic uplift as a result of the collision of the Gondwana plate with the Angara plate. The land surface slopes towards the south-east with an average elevation of 5,000m. The plateau extends 2,600 km from west to east and is about half as wide from north to south. It is rimmed by high ranges in the south (Himalaya), west (Karakoram), and north (Kun Lun). In the east, the barrier is one of multiple ranges with deep gorges. Much of the interior is a tangled wilderness of mountains and plateaus interspersed with numerous lakes. One authority, Pierre Gourou, in his book L'Asie, claimed that there were 36 different mountain ranges in Tibet alone.

The structural strikes and thrusts on the plateau are mainly east-west oriented with a north-west loop in the west and a south loop in the east. The alignment of major relief features conforms to such a pattern. This is most evident from the long trench of the Indus-Brahmaputra which demarcates the Trans-Himalaya in Tibet from the Main Himalaya to the south. The parallel ranges of Nganglong and Gangdise in the west are a structural extension of the Karakoram and Ladakh Ranges. The high points are the Alung Kangri (6,450m) in the Nganglong and the famous Kailash/Kang Rimpoche (6,660m) in the Gangdise Range. The highest peak of all in the area is the Gurla Mandhata (7,739m) which lies south of Kailash across the Manasarovar Lake. The Gangdise Range forms the watershed between the continental plateau and the Indian Ocean drainage systems.

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9. Environs of Lhasa, Tibet. The wide valley is drained left to right by the Kyi Chu of the two hillocks on the plain, the left one is crowned by Potala palace between the old town (middle distance) and new complex (foreground). The western hillock, Choghuri, had a medical university in the old days.

The Gangdise continues as an emphatic range as far as the longitude 90°E. Further north, the Tanggula Range is aligned east-west, traversing the vast expanse of the Changthang (Northern Plain). It has some peaks approaching 6,900m. The Nyaingentanglha Range, north-east of Lhasa, is much dissected and rugged. Its spurs are linked to the Tanggula in the north and the Hengduan towards the east. The highest point, Namjabarwa (7,353m), lies about 200 km north-west of the Tsangpo-Dihang bend. Namchabarwa massif's south side is fully exposed to the monsoon regime, with an annual mean precipitation of 2,276mm, while the north side only receives 510mm. Thus, the south has nine forest zones compared to only six in the north (Peng et al. 1997). Further east, there are three parallel ranges aligned north-west/south-east. These are the Ning Ling at the head of the Mekong River, the Bayan Har at the head of the Yangtze River, and the Anyemaqen at the head of the Huang He. The last range also marks the boundary between the Tibetan plateau and the Qaidam basin. It extends east through the rugged Min Shan which has two branches. One branch trends south as the Qionglai Shan and another farther east as the Daba Shan. The average elevation of the former is 2,500m and that of the latter above 2,000m.

The desert climate situation of the western section of the plateau supports only nomadic pastoralism. The chief population centres are in the south-east, mainly along the Tsangpo and valleys further east. The encapsulation of the harsh physical environment led to the evolution of social mechanisms such as fraternal polyandry that prevented land fragmentation and decreased aggregate fertility (Goldstein 1981). Yet it was this remote plateau that spawned Lamaism, a form of tantric Buddhism, that radiated far and wide, including Mongolia. Therefore, while other mountain people are referred to as cultural groups, the Tibetans are associated with a civilisation that is basically mountain-based.