Geomorphology

China is geomorphologically diverse, consisting of about 33 percent mountains, 25 percent plateaus (including Tibet), 20 percent basins, and 10 percent hilly terrain. In general, the land surface slopes from the high regions including Tibet in the west, to the 1,100-mile (1,800-km) coastline in the east.

Satellite image of Asia (M-Sat Ltd. Photo Researchers, Inc.)

There are three main physiographic provinces of China based on elevation. The Tibetan, or Qinghai-Xizang Plateau, in the south rises generally to more than 2.5 miles (4 km) above sea level, including the Himalaya Mountains, which rise above 3.7 miles (6 km), with many peaks surpassing 5 miles (8 km) above sea level. Mount Everest (Jolmo Lungma) is the highest peak in the world, reaching 29,133 feet (8,882 m) above sea level. A series of basins and plateaus are located north and east of the Tibetan, or Qinghai-Xizang, Plateau, with elevations between 0.5 and 1.3 miles (1-2 km). The most important plateaus in this region include the Inner Mongolia Plateau or steppe, the loess plateau, and the Yunnan-Guizhou Plateau, whereas the large basins include the Sichuan, Junggar, and Tarim. Eastern China consists mostly of hills lower than a half-mile (1 km) and broad plains, including the Northeast, Lower, Northern, and Upper Chang Jiang (Yangtze River) plains, whereas the low mountains include the shandong and southern Hills.

Mountains (the word shan means "mountain" in Chinese) in China are divided into different groups according to their orientations, or trend (measured relative to geographic north). These include the EW, or Altaid, trend, with major belts including the Tienshan, Kunlun, Tanglha, Kangkar Tesi, Qinling, Himalaya, Yinshan, and Nanling. Interestingly, the age of the activity becomes younger from north to south, reflecting processes related to the India-Asia collision. The NE-SW (Cathysian) trending mountains include the Greater Kingham, Taihang, Chang-bai, and Wui, mostly in eastern China. The N-S trending mountains include the Helan, Luban, and Hengduan. Other mountains trend NW-SE, such as the Karakoram and Altai Mountains in the west, and the Lesser Kinghan in the northeast.

The Tibet, or Qinghai-Xizhang, Plateau is the world's largest region of thickened, uplifted crust; it formed in response to the collision of India with Asia after the Cretaceous. Many rivers in Asia have their source on this plateau, and changing climate conditions with loss of glacial ice imperils many of these rivers. Many tectonically controlled lakes on the Tibet Plateau have formed in fault-controlled basins largely since the Eocene. In southwestern China the Yunnan-Guizhou Plateau has an average elevation of about 1.2 miles (2 km), but decreases to the east. This uplifted plateau is comprised largely of limestones and other soluble rocks, so as the uplift proceeded and groundwater levels dropped, a spectacular karst landscape developed across much of this plateau, forming some of the world's most impressive karst landscapes, such as the stone forest of Kunning and the karst towers of Guilin. Many Mesozoic red beds lie in the western part of this plateau. The Great Wall of China was built along the north edge of the loess plateau, which has an average elevation of 0.6 miles (1 km) over an area of 156,000 square miles (400,000 km2), encompassing the Yinshan, Qinling, Qilian, and Taishan Mountains. Wind-blown dust and silt on the plateau and extending eastward to the Yellow Sea form the thickest and most extensive loess deposits in the world. In most places the loess is 150-250 feet (50-80 m) thick, but in places is up to 3,200 (975 m) feet thick. The dust originates in the Gobi and ordos desert basins to the west, with much being deposited during the Quaternary, formed during the Pleistocene ice ages when strong winds blew from the NW to the SE. The plateau of Inner Mongolia has a similar height to the loess plateau, but this region is being actively extended and eroded, after a period of uplift in the Cenozoic.

China has many large basins of diverse origin. The Tarim, Junggar, and Qiadam basins in the west are relic back-arc basins developed on the margins of the Paleotethys ocean, although the basins have complex older histories. The Tarim basin, one of the largest interior basins in the world, has a Precambrian basement, overlain by thick Mesozoic and Cenozoic rocks, whereas the Junggar basin has Paleozoic basement overlain by Mesozoic and Ceno-zoic basinal sequences. The Sichuan basin has a complex history, including Precambrian basement overlain by Paleozoic and Mesozoic red beds, including foreland basin deposits from the Longmen and Qinling orogens. The ordos basin has Precambrian platformal sediments overlain by Paleozoic through Tertiary sedimentary layers. In the east the Bohai, or North China, basin is a complex rift-pull-apart basin of Paleogene age that has huge hydrocarbon reserves, including the Shenli, Dagong, and Renqin oil fields. In the north the Songliao basin is a Late Mesozoic rift basin that developed behind an active margin. on the eastern coast of China the East and South China Seas form passive margin-type basins formed in back-arc environments above the Pacific seduction system.

one of the world's great deserts, the Gobi, located in central Asia, encompasses more than 500,000 square miles (1,295,000 km2) in Mongolia and northern China. The desert covers the region from the Great Khingan Mountains northwest of Beijing to the Tien Shan north of Tibet, but the desert is expanding at an alarming rate, threatening the livelihood of tens of thousands of farmers and nomadic sheepherders every year. Every spring dust from the Gobi covers eastern China, Korea, and Japan, and may extend at times around the globe. Northwesterly winds have removed almost all the soil from land in the Gobi, depositing it as thick loess

Yunnan Guizhou Plateau

Tectonic map of Asia showing the relationships between the India-Asia collision, escape of the Indonesian and South China blocks seaward, and extension from Siberia to the Pacific margin, including opening of the Sea of Japan and the South China Sea (modeled after T. Kusky, M. Zhai, and W. J. Xiao)

in eastern China. Most of the Gobi is situated on a high plateau resting 3,000-5,000 feet (900-1,500 m) above sea level, and it contains numerous alkaline sabkhas and sandy plains in the west. Regions in the Gobi include abundant steppes, high mountains, forests, and sandy plains. The Gobi has yielded many archaeological, paleontological, and geological finds, including early stone implements, dinosaur eggs, and mineral deposits and precious stones including turquoise and jasper.

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