The geography of Tibet consists of the high mountains, lakes and rivers lying between Central, East and South Asia. Traditionally, Western (European and American) sources have regarded Tibet as being in Central Asia, though today's maps show a trend toward considering all of modern China, including Tibet, to be part of East Asia.^[1][2][3]Tibet is often called "the roof of the world", comprisingtablelands averaging over 4,950 metres (16,240 feet) above the sea with peaks at 6,000 to 7,500 m (roughly 17,500 to 23,000 feet), includingMount Everest, on the border with Nepal.

It is bounded on the north and east by theCentral China Plain and on the west and south by theIndian subcontinent (Ladakh,Spiti andSikkim in India as well asNepal andBhutan). Most of Tibet sits atop a geological structure known as theTibetan Plateau, which includes theHimalaya and many of the highest mountain peaks in the world.

High mountain peaks includeChangtse,Lhotse,Makalu,Gauri Sankar,Gurla Mandhata,Cho Oyu,Jomolhari,Gyachung Kang,Gyala Peri,Mount Kailash,Kawagebo,Khumbutse,Melungtse,Mount Nyainqentanglha,Namcha Barwa,Shishapangma andYangra.Mountain passes includeCherko la andNorth Col. Smaller mountains includeMount Gephel andGurla Mandhata.

Physically, Tibet may be divided into two parts, the "lake region" in the west and north-west and the "river region", which spreads out on three sides of the former on the east, south, and west.^[4] The region names are useful in contrasting theirhydrological structures, and also in contrasting their different cultural uses which isnomadic in the "lake region" andagricultural in the "river region".^[5] Despite its large size and mountainous nature, variation of climate across the Tibetan Plateau is more steady than abrupt. The "river region" has asubtropical highland climate with moderate summer rainfall averaging around 500 millimetres (20 in) per year, and daytime temperatures ranging from around 7 °C (45 °F) in winter to 24 °C (75 °F) in summer – though nights are as much as 15 °C (27 °F) cooler. Rainfall decreases steadily to the west, reaching only 110 millimetres (4.3 in) atLeh on the edge of this region, whilst temperatures in winter become steadily colder. On the south the "river region" is bounded by theHimalayas, on the north by a broad mountain system. The system at no point narrows to a single range; generally there are three or four across its breadth. As a whole the system forms the watershed between rivers flowing to theIndian Ocean – theIndus,Brahmaputra andSalween and its tributaries – and the streams flowing into the undrained salt lakes to the north.^[4]

The "river region" is characterized by fertile mountain valleys and includes theYarlung Tsangpo River (the upper courses of theBrahmaputra) and its major tributary, theNyang River, theSalween, theYangtze, theMekong, and theYellow River. TheYarlung Tsangpo Canyon, formed by a horseshoe bend in the river where it flows aroundNamcha Barwa, is the deepest, and possibly longest canyon in the world.^[6] Among the mountains there are many narrow valleys. The valleys ofLhasa,Shigatse,Gyantse and the Brahmaputra are free from permafrost, covered with good soil and groves of trees, well irrigated, and richly cultivated.^[4]

TheSouth Tibet Valley is formed by theYarlung Zangbo River during its middle reaches, where it travels from west to east. The valley is approximately 1200 kilometers long and 300 kilometers wide. The valley descends from 4500 meters above sea level to 2800 meters. The mountains on either side of the valley are usually around 5000 meters high.^[7][8] Lakes here includeLake Paiku andLake Puma Yumco.

The "lake region" extends from thePangong Tso Lake inLadakh,Lake Rakshastal,Yamdrok Lake andLake Manasarovar near the source of theIndus River, to the sources of theSalween, theMekong and theYangtze. Other lakes includeDagze Co,Nam Co, andPagsum Co. The lake region is an arid and wind-swept desert. This region is called theChang Tang (Byang thang) or 'Northern Plateau' by the people of Tibet. It is some 1100 km (700 mi) broad, and covers an area about equal to that of France. Due to the extremely high mountain barriers it has a very aridalpine climate with annual precipitation around 100 millimetres (4 in) and possesses no river outlet. The mountain ranges are spread out, rounded, disconnected, separated by flat valleys. The country is dotted over with large and small lakes, generally salt oralkaline, and intersected by streams. Due to the presence ofdiscontinuous permafrost over the Chang Tang, the soil is boggy and covered with tussocks of grass, thus resembling the Siberiantundra. Salt and fresh-water lakes are intermingled. The lakes are generally without outlet, or have only a small effluent. The deposits consist ofsoda,potash,borax and commonsalt. The lake region is noted for a vast number ofhot springs, which are widely distributed between the Himalaya and 34° N., but are most numerous to the west of Tengri Nor (north-west of Lhasa). So intense is the cold in this part of Tibet that these springs are sometimes represented by columns of ice, the nearly boiling water having frozen in the act of ejection.^[4]

The climate of Tibet is severely dry nine months of the year, and average annual snowfall is only 46 cm (18 inches), due to therain shadow effect. Western passes receive small amounts of fresh snow each year but remain traversible all year round. Low temperatures are prevalent throughout these western regions, where bleak desolation is unrelieved by any vegetation bigger than a low bush, and where the wind sweeps unchecked across vast expanses of arid plain. The Indianmonsoon exerts some influence on eastern Tibet. Northern Tibet is subject to high temperatures in the summer and intense cold in the winter.^[4]

The Tibetan Plateau contains the world's third-largest store of ice. Qin Dahe, the former head of the China Meteorological Administration, said that the recent fast pace of melting and warmer temperatures will be good for agriculture and tourism in the short term; but issued a strong warning:

"Temperatures are rising four times faster than elsewhere in China, and the Tibetan glaciers are retreating at a higher speed than in any other part of the world." "In the short term, this will cause lakes to expand and bring floods and mudflows." "In the long run, the glaciers are vital lifelines for Asian rivers, including the Indus and the Ganges. Once they vanish, water supplies in those regions will be in peril."^[15]

Today Tibet is the most essential heating surface of the atmosphere. During theLast glacial period a c. 2,400,000 square kilometres (930,000 sq mi) ice sheet covered the plateau.^[16] This glaciation took place in correspondence to a lowering of the snowline by 1,200 metres (3,900 ft). For theLast Glacial Maximum this means a depression of the average annual temperature by 7 to 8 °C (13 to 14 °F) at a minor precipitation compared with that one of today.

Owing to this drop in temperature a supposed drier climate has partly been compensated with regard to the glacier feeding by a minor evaporation and an increased relative humidity.Due to its great extension this glaciation in the subtropics was the most important climatically foreign element on earth. With analbedo about 80-90% this ice area of Tibet has reflected an at least 4 times greater global radiation energy per surface into space than the further inland ices at a higher geographical latitude. At that time the most essential heating surface of the atmosphere – which at present, i.e. interglacially, is the Tibetan plateau – was the most important cooling surface.^[17]

The annual low-pressure area induced by heat above Tibet as a motor of the summermonsoon was lacking. The glaciation thus caused a breaking-off of the summer monsoon with all the global-climatic consequences, e.g. the pluvials in the Sahara, the expansion of the Thar desert, the heavier dust influx into the Arabian Sea etc., and also the downward shifting of the timber line and all forest-belts from the alpine-boreal forests as far down as to the semi-humid mediterranean forest which has replaced the Holocene monsoon-tropical forests on the Indian subcontinent. But also the movements of animals including theJavan Rusa far into South Asia are a consequence of this glaciation.

Despite heavyablation caused by heavyinsolation, the discharge of the glaciers into the Inner-Asian basins was sufficient for the creation of meltwater lakes in theQaidam Basin, theTarim Basin and theGobi Desert. The drop in temperature (see above) was in favour of their development. Thus, the clay fraction produced by the ground scouring of the important glaciation was ready to be blown-out. The blow-out of the limnites and theAeolian long-distance transport were connected to thekatabatic winds. Accordingly, the Tibetan glaciation was the actual cause of the enormousloess production and the transport of the material into the Chinese middle- and lowlands continuing to the east.^[18] During the Ice Age the katabatic air current – the name 'winter monsoon' is not quite correct – blew all year round.

The enormous uplift of Tibet by around 10 mm/year measured by triangulations since the 19th century and confirmed by glaciogemorphological findings as well as by seismological investigations equals the uplift of the Himalaya. However, these amounts of uplift are far too important as to a primarily tectonic uplift of the high plateau which only takes placeepirogenetically. Actually they can be understood the better by a superimposed glacioisostatic compensation movement of Tibet about 650 m.^[19]

An alternative view held by some scientists^[20] is that the glaciers on the Tibetan Plateau have remained restricted over the entire data published since 1974 in the literature referred to inKuhle (2004),^[21] which are relevant as to the maximum ice extent.

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  Himalayas nearLhasa
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  Tibet is located on theTibetan Plateau, the world's highest region.
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  Tibetan Plateau and surrounding areas above 1600-mtopography^[22][23]
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  The Tibetan plateau lies between theHimalayan range to the south and theTaklamakan plain to the north.
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  Lake Pangong Tso
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  Glacier-capped mountains in Tibet
• Animation of glacier-capped mountains in Tibet

Wikimedia Commons has media related toGeography of Tibet.

• Abongshan Formation
• Rongbuk Glacier
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•  This article incorporates text from a publication now in thepublic domain: Waddell, Lawrence Austine;Holdich, Thomas Hungerford (1911). "Tibet". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 26 (11th ed.). Cambridge University Press. pp. 916–917.

• Hopkirk, Peter.Trespassers on the Roof of the World: The Secret Exploration of Tibet (1983) J. P. Tarcher.ISBN 0-87477-257-5

• Kingdon-Ward, Frank (1923)Mystery Rivers of Tibet. London: Seeley Service and Co (reprinted by Cadogan Books, 1986 ISBN 0-946313-52-0)

• Online collection of maps of Tibet maintained by The Australian National University
• Geography of Tibet
• Full Map of Tibet from 1904

• Geography of Tibet
• Geography of Western China
• Geography of Central Asia
• Geography of East Asia

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