The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or Qingzang Plateau, is a vast elevated plateau located at the intersection of Central Asia, South Asia, and East Asia. Geographically, it is located to the north of Himalayas and the Indian subcontinent, and to the south of Tarim Basin and Mongolian Plateau. Geopolitically, it covers most of the Tibet Autonomous Region, most of Qinghai, western half of Sichuan, Southern Gansu provinces, southern Xinjiang province in Western China, Bhutan, the Indian regions of Ladakh and Lahaul and Spiti (Himachal Pradesh) as well as Gilgit-Baltistan in Pakistan, northwestern Nepal, eastern Tajikistan and southern Kyrgyzstan. It stretches approximately north to south and east to west. It is the world's highest and largest plateau above sea level, with an area of .
The Tibetan Plateau contains the river source of the of most of the and in surrounding . This includes the three longest rivers in Asia (the Yellow River, Yangtze, and Mekong). Its tens of thousands of and other geographical and ecological features serve as a "water tower" storing water and maintaining streamflow. It is sometimes termed the Third Pole because its contain the largest reserve of fresh water outside the polar regions. The impact of climate change on the Tibetan Plateau is of ongoing scientific interest.
Description
The Tibetan Plateau is surrounded by the massive mountain ranges
of high-mountain Asia. The plateau is bordered to the south by the
Himalayas, to the north by the
Kunlun Mountains, which separate it from the
Tarim Basin, and to the northeast by the
Qilian Mountains, which separate the plateau from the
Hexi Corridor and
Gobi Desert. To the east and southeast the plateau gives way to the forested gorge and ridge geography of the mountainous headwaters of the
Salween River,
Mekong, and
Yangtze rivers in northwest
Yunnan and western
Sichuan (the Hengduan Mountains). In the west, the curve of the rugged
Karakoram range of northern
Kashmir embraces the plateau. The
Indus River originates in the western Tibetan Plateau in the vicinity of
Lake Manasarovar.
The Tibetan Plateau is bounded in the north by a broad escarpment where the altitude drops from around to over a horizontal distance of less than . Along the escarpment is a range of mountains. In the west, the Kunlun Mountains separate the plateau from the Tarim Basin. About halfway across the Tarim the bounding range becomes the Altyn-Tagh and the Kunluns, by convention, continue somewhat to the south. In the 'V' formed by this split is the western part of the Qaidam Basin. The Altyn-Tagh ends near the Dangjin pass on the Dunhuang–Golmud road. To the west are short ranges called the Danghe, Yema, Shule, and Tulai Nanshans. The easternmost range is the Qilian Mountains. The line of mountains continues east of the plateau as the Qinling, which separates the Ordos Plateau from Sichuan. North of the mountains runs the Gansu or Hexi Corridor which was the main silk-road route from China proper to the West.
The plateau is a high-altitude arid steppe interspersed with mountain ranges and large brackish water lakes. Annual precipitation ranges from and falls mainly as hail. The southern and eastern edges of the steppe have grasslands that can sustainably support populations of nomadic herdsmen, although frost occurs for six months of the year. Permafrost occurs over extensive parts of the plateau. Proceeding to the north and northwest, the plateau becomes progressively higher, colder, and drier, until reaching the remote Changtang region in the northwestern part of the plateau. Here the average altitude exceeds and winter temperatures can drop to . As a result of this extremely inhospitable environment, the Changtang region (together with the adjoining Kekexili region) is the least populous region in Asia and the third least populous area in the world after Antarctica and northern Greenland.
Geology and geological history
The geological history of the Tibetan Plateau is closely related to that of the Himalayas. The Himalayas belong to the
Alpine orogeny and are therefore among the younger mountain ranges on the planet, consisting mostly of uplifted
sedimentary rock and
metamorphic rock. Their formation is a result of a continental collision or
orogeny along the convergent boundary between the Indo-Australian Plate and the
Eurasian Plate.
The collision began in the Cretaceous period about 70 million years ago, when the north-moving Indo-Australian Plate, moving at about per year, collided with the Eurasian Plate. About 50 million years ago, this fast-moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined by settled on the ocean floor, and the that fringed its edges. Since these sediments were light, they crumpled into mountain ranges rather than sinking to the floor. During this early stage of its formation in the Late Palaeogene, Tibet consisted of a deep palaeovalley bounded by multiple mountain ranges rather than the more topographically uniform elevated flatland that it is today.
Much of the Tibetan Plateau is of relatively low relief. The cause of this is debated among geologists. Some argue that the Tibetan Plateau is an uplifted peneplain formed at low altitude, while others argue that the low relief stems from erosion and infill of topographic depressions that occurred at already high elevations.
Environment
The Tibetan Plateau supports a variety of ecosystems, most of them classified as
montane grasslands. While parts of the plateau feature an
alpine tundra-like environment, other areas feature monsoon-influenced shrublands and forests. Species diversity is generally reduced on the plateau due to the elevation and low precipitation. The Tibetan Plateau hosts the
Tibetan wolf,
and species of
snow leopard,
wild yak,
kiang, cranes, vultures, hawks, geese, snakes, and
water buffalo. One notable animal is the high-altitude jumping spider, that can live at elevations of over .
found on the Tibetan Plateau, as defined by the World Wide Fund for Nature, are as follows:
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The Pamir alpine desert and tundra covers the western end of the Tibetan Plateau where it transitions to the Pamir Mountains
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The North Tibetan Plateau–Kunlun Mountains alpine desert covers the northwestern limits of the Tibetan Plateau along the Kunlun Mountains
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The Karakoram–West Tibetan Plateau alpine steppe covers the westernmost parts of the Tibetan Plateau and Ladakh
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The Northwestern Himalayan alpine shrub and meadows on the edges mountains bordering the extreme west of the Tibetan Plateau
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The Central Tibetan Plateau alpine steppe covers most of the central portions of the Tibetan Plateau and the eastern Changtang
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The Western Himalayan alpine shrub and meadows covers the southwestern plateau in the Garuda Valley region
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The Qaidam Basin semi-desert located in the Qaidam Basin on the northern Tibetan Plateau
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The Qilian Mountains subalpine meadows covering the Qilian Mountains in the northernmost portions of the plateau
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The Qilian Mountains conifer forests covering parts of the mountain ranges in the northeastern Tibetan Plateau
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The Tibetan Plateau alpine shrublands and meadows covering a swath of the central and northeastern Tibetan Plateau
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The Yarlung Tsangpo arid steppe in the Yarlung Tsangpo river Valley, where most of the permanent human population on the Tibetan Plateau lives
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The Eastern Himalayan alpine shrub and meadows cover the southern Tibetan Plateau on the north side of the Himalayas
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The Southeast Tibet shrub and meadows cover the southeastern and eastern parts of the plateau and are generally rainier than the other high-altitude Tibetan Plateau regions
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The Northeastern Himalayan subalpine conifer forests reach up mountain valleys in the southern plateau and contain some of the highest altitude forests in the world
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The Nujiang Lancang Gorge alpine conifer and mixed forests cover the mountain valleys that reach into the southeastern Tibetan Plateau
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The Hengduan Mountains subalpine conifer forests cover the southeasternmost mountain valleys on the plateau
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The Qionglai–Minshan conifer forests cover the eastern edges of the plateau and are the densest forests to be found anywhere on the Tibetan Plateau
Human history
Extinct humans (
Denisovan) lived on the Tibetan plateau from around 200,000 to 40,000 years ago, according to a study published in
Nature.
on the Tibetan Plateau and in the Himalayas are the remainders of nomadic practices historically once widespread in Asia and Africa.[
] Pastoral nomads constitute about 40% of the ethnic Tibetan people population.[ In pictures: Tibetan nomads BBC News] The presence of nomadic peoples on the plateau is predicated on their adaptation to survival on the world's grassland by raising livestock rather than crops, which are unsuitable to the terrain. Archaeological evidence suggests that the earliest human occupation of the plateau occurred between 30,000 and 40,000 years ago.
Impact on other regions
Role in monsoons
Monsoons are caused by the different amplitudes of surface-temperature seasonal cycles between land and oceans. This differential warming occurs because heating rates differ between land and water. Ocean heating is distributed vertically through a "mixed layer" that may be 50 meters deep through the action of wind and buoyancy-generated
turbulence, whereas the land surface conducts heat slowly, with the seasonal signal penetrating only a meter or so. Additionally, the specific heat capacity of liquid water is significantly greater than that of most materials that make up land. Together, these factors mean that the heat capacity of the layer participating in the seasonal cycle is much larger over the oceans than over land, with the consequence that the land warms and cools faster than the ocean. In turn, air over the land warms faster and reaches a higher temperature than does air over the ocean.
[Oracle Thinkquest Education Foundation. monsoons: causes of monsoons. Retrieved on 22 May 2008.] The warmer air over land tends to rise, creating an area of
low pressure. The pressure anomaly then causes a steady wind to blow toward the land, which brings the moist air over the ocean surface with it. Rainfall is then increased by the presence of the moist ocean air. The rainfall is stimulated by a variety of mechanisms, such as low-level air being lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows near the surface. When such lifting occurs, the air cools due to expansion in lower pressure, which in turn produces
condensation and precipitation.
In winter, the land cools off quickly, but the ocean maintains the heat longer. The hot air over the ocean rises, creating a low-pressure area and a breeze from land to ocean while a large area of drying high pressure is formed over the land, increased by wintertime cooling.
Monsoons are similar to
sea breezes, a term usually referring to the localized,
diurnal cycle of circulation near coastlines everywhere, but they are much larger in scale, stronger and seasonal.
The seasonal monsoon wind shift and weather associated with the heating and cooling of the Tibetan plateau is the strongest such monsoon on Earth.
Glaciers
Frozen biological samples
Ice of the plateau provides a valuable window to the past. In 2015, researchers studying the Plateau reached the top of the Guliya
glacier, with ice thickness of , and drilled to a depth of in order to recover
ice core samples. Due to the extremely low
biomass in those 15,000-year-old samples, it had taken around 5 years of research to extract 33 viruses, of which 28 were new to science. None had survived the extraction process.
Phylogenetic analysis suggests those viruses infected
or other microorganisms.
Climate change
The Tibetan Plateau contains the world's third-largest store of ice. Qin Dahe, the former head of the China Meteorological Administration, issued the following assessment in 2009:
The Tibetan Plateau contains the largest area of low-
latitude glaciers and is particularly vulnerable to global warming. Over the past five decades, 80% of the glaciers in the Tibetan Plateau have retreated, losing 4.5% of their combined areal coverage.
This region is also liable to suffer damages from permafrost thaw caused by climate change.
See also
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Annexation of Tibet by the People's Republic of China
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Bayan Har block
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Central Tibetan Administration
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Geography of Tibet
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Geology of the Himalayas
-
Tibet (1912–1951)
-
Tibetan culture
-
Tibetan sovereignty debate
-
Tibetan diaspora
Notes
Citations
Sources
External links
