The Tibetan Plateau holds more fresh ice than anywhere outside the poles
Nicknamed the Third Pole, the Tibetan Plateau's tens of thousands of glaciers form a water tower that feeds the Yellow, Yangtze and Mekong, Asia's three longest rivers. It spans some 2.5 million km² at an average height above 4,500 metres, walled in by Everest and K2.
Also called the Qinghai–Tibet or Qingzang Plateau, this upland sits where Central, South and East Asia meet, north of the Himalayas and south of the Tarim Basin and the Mongolian Plateau. It measures roughly 1,000 km from north to south and 2,500 km from east to west, making it the largest and highest plateau on Earth, and its ring of peaks, including the world's two tallest, earned it the name Roof of the World. The Kunlun Mountains fence it off from the Tarim Basin, the Qilian range from the Hexi Corridor and Gobi, and the Karakoram curves around its western edge.
Along the northern rim the Altyn Tagh escarpment drops from an interior of 4,000 to 5,000 metres to the Tarim Basin at only 1,000 to 1,400 metres. Most of the surface is dry, high steppe broken by ranges and big brackish lakes. Grasslands on the southern and eastern margins can sustain nomadic herders even with six months of frost, while the north and northwest grow steadily higher, colder and drier, with just 100 to 300 mm of precipitation a year, similar to a polar desert, and widespread permafrost.
The plateau's story is tied to the Himalayas. India broke away from Gondwana about 70 million years ago and raced north at around 15 cm a year, most likely striking Eurasia 55 to 50 million years ago, though the timing is still argued. By about 50 million years ago the Tethys Ocean had closed. Fossil plants show that two suture zones stayed tropical or subtropical lowland until the late Oligocene or early Miocene, and faulted valleys suggest the plateau had neared its present height by 14 to 8 million years ago. Why so much of it is fairly flat remains debated, with some geologists seeing an uplifted lowland and others erosion and infill at altitude.
Most ecosystems are montane grassland, ranging from tundra-like ground to monsoon-watered shrubland and forest, and height and dryness keep species counts low. Residents include the Tibetan wolf, snow leopard, wild yak, wild ass, cranes and vultures, plus a jumping spider that survives at extreme elevation. The World Wide Fund for Nature divides the region into ecoregions from the Pamir alpine desert in the west to the Qilian conifer forests in the northeast.
Source: Tibetan Plateau
