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Plateaus which vary in both heights a physical features cover about one-fourth of China?s total area, mainly in its western and central parts, or the first and second steps of the topographical staircase. The major ones are the Qinghai-Tibet, Inner Mongolia, Loess, and Yunnan-Guizhou plateaus.
The Qinghai-Tibet Plateau in western and southwestern China is the highest plateau in the world, embracing the whole of Tibet and Qinghai, western Sichuan and southwestern Gansu- an area of 2.3 million square kilometers at an elevation of 4,000-5,000 meters. Known as the ? roof the world? it forms the top of China?s topographical staircase.
Geographers call the Qinghai-Tibet Plateau, which is composed of a series of imposing mountains, ? mountain-locked land?. Massive mountain ranges loom on all sides---the Himalayas to the south, the Kunlun and Qilian ranges to the north, the Hengduan Mountains to the east and Karakorum Mountains to the west. Many of their peaks exceed 6,000 meters above sea level. Many of the mountains on the plateau, such as the Gangdise, the Nyainqentanglha, the Tanggula and the Bayanhar, cut the plateau into numerous basins, wide valleys and lakes.
The Qinghai-Tibet Plateau can be divided into the northern Tibet Plateau, the Southern Tibet Valleys, the Qaidam Basin, the Qilian Mountain Area, the Qinghai Plateau and the Sichuan-Tibet Canyon.
With their melt-water the stupendous snow mountains on the Qinghai-Tibet Plateau supply headstreams to many of the major rivers in East, Southeast and South Asia. These rivers include the Yangtze River, the Huanghe, the Lancang (known as the Mekong outside China), the Nujiang (known as the Salween outside China), the Indus, the Yarlungzangbo (known as the Brahmaputra outside china) and Tarim. Rich in hydro-power, the plateau is studded with lakes, notably Qinghai Lake in Qinghai Province and Nam Co Lake in Tibet, which is 4,718 meters above sea level and the highest large salt lake in the world. With its many pastures ontleh lakesides, in the intermontane valleys and on the gentle, sunny slopes, the Qinghai-Tibet Plateau is the third stockbreeding region after Inner Mongolia and Xinjiang. The climate of the plateau differs greatly in the south and north. Because of the monsoon?s coming from the ocean, the Southern Tibet Valleys area is blessed with a warm and humid climate and is the major farming region on the plateau. The weather is capricious in the Central and Northern Tibet plateaus which are cold and dry and covered with ice and snow for six months in the year. Intense solar radiation and long hours of sunshine (2,500-3,200 hours a year) are the assets of the Qinghai-Tibet Plateau.
The Qinghai-Tibet Plateau, an out-of-the-way region before the founding of the People?s Republic, is now accessible by three major highways---the Sichuan-Tibet Highway (from Chengdu in Sichuan to Lhasa in Tibet), the Qinghai-Tibet Highway (from Yecheng in Xinjiang to Lhasa). These three highways, with a total length of 6,000 kilometers, are stupendous projects in engineering. The plateau can now take pride in an initial road transport network of 50,000 kilometers.
Some Chinese and foreign scientist hold that the northward drift of the Indian plate and its collision with the Eurasian Continent are responsible for the formation of the Qinghai-Tibet Plateau. The plateau has continued its uplifting movement, which averages more than 10 millimeters a year.
The Inner Mongolia Plateau in northern China extends from the Greater Hinggan and the Sukexielu ranges in the east to the Mazong Mountains in northern Gansu in the west and from the Great Wall in the south to the People?s Republic of Mongolia in the north. The second largest plateau in China, it includes the Inner Mongolia Autonomous Region and parts of Gansu and Ningxia and covers an area of over one million square kilometers ---2,000 kilometers long from west to east and 500 kilometers wide from north to south.
The Inner Mongolia Plateau stands at an average elevation of 1,000-2,000 meters above sea level, part of it, the Greater Hinggan range in the east and the Yinshan range in the middle, at 1,500 meters, with very little undulation in terrain. With the exception of the Yinshan and Helan ranges, many of the areas are boundless open country. Situated in the inland part of the country, the plateau has a climate with low temperature and strong wind in winter and scanty precipitation in summer due to the absence of monsoon from the Pacific. The eastern part, mostly grasslands, has a semi-arid climate and an annual precipitation of 300 mm. The western part with its vast tracts of desert has an arid climate and a precipitation of less than 200mm. The southern part consists of the oblong Hetao Plain and the Ordos Plateau. The Hetao Plain in the Huanghe River valley is the major farming area in the Inner Mongolia Plateau, known since ancient times as the ?land of affluence along the Great Wall?.
The eastern part of the Inner Mongolia Plateau has a comparatively humid climate. Carpeted with lush green grass, the grasslands in the Hulunboir and Xilingol leagues rank among China?s major grasslands and stockbreeding areas, and are famous for their fine breeds of horses, cattle and sheep.
The western part is desert area, consisting of the Badinjaran, Tenger, Ulanbuh and Muus deserts. With an arid, windy climate, the area is covered with drifting sands and poor soil. Since 1949, shelterbelts have been planted on the fringes of the deserts to control the sands.
The Loess Plateau, named after the yellowish soil which covers the area, is the biggest loess plateau in the world. Bounded by the Qinling Mountains and the Weihe Plain in the south, the Great Wall in the north, the Taihang Mountains in the east and the Taohe River and Wuxiao mountains in the west, it includes the entire Shanxi Province, northern Shaanxi, the greater part of Ningxia, central and eastern Gansu and western Henan. Covering 400, 000 square kilometers and rising 800-2,000 meters above sea level (some of the higher peaks exceeding 2,500 meters), it is the third largest plateau of China. The Huanghe River and its tributaries?the Taohe, Weihe and Luohe rivers ?all flow across the Loess Plateau.
The Loess Plateau can be divided, according to topographical differences, into the Central Gansu Plateau, the Northern Shaanxi Plateau, the Shanxi Plateau and the Western Henan Highlands. Except for a few high lands and large river valleys, it is covered with a layer of loess generally 100 meters deep. In some parts of northern Shaanxi and eastern Gansu, the layer is 150 meters in depth while in western Gansu it exceeds 200 meters. There have been many explanations for the cause of the existence of the yellowish soil. The latest explanation, substantiated by extensive investigations conducted by Chinese scientists in recent years, is that the loess deposits were blown in over a period of hundreds of thousands of years by the north wind from the Inner Mongolia Plateau and the Mongolian inland regions.
The loess is composed of loamy sands with a rich content of nitrogen, phosphorus and potassium needed for farming. But the looseness of the soil, sparse vegetation and frequent rainstorms in summer have caused serious soil erosion, which has carved the land into gullies and reduced the fertility of the earth. In the middle part of the plateau, there are fewer gullies and many intact open spaces. In the outlying areas of the plateau, especially along the Huanghe river, the land is badly cut up into narrow ridges and mounds. These hilly regions, whose typical examples are in western Shanxi, northern shaanxi and eastern Gansu, are 100-200 meters higher than the bottom of the neighboring gullies.
But social factors have contributed far more to soil erosion than natural ones. Historical records revel that the greater part of the plateau once was covered with dense forests, lush grasslands and fertile soil. The birthplace of ancient Chinese culture, the area had over the centuries been known as the cradle of the Chinese nation. Predatory reclamation, indiscriminate felling of the trees and overuse of the grasslands by the landlords as well as destruction by frequent wars denuded the area practically of all its forests. Torrential summer rains, too, wrought its havoc, washing away the fertile topsoil at a rate of 0.5 cm. a year. Every year, more than a billion tons of mud and silt were carried down into the Huanghe, or 90 percent of the total mud and silt of the river. The river became choked, causing floods that brought disaster to the people along its middle and lower reaches. In the past decades, fundamental measures such as the planting of trees and grass to conserve soil and water have met with some success in changing the physiognomy of the Loess Plateau and controlling the Huanghe River.
The Yunnan ?Guizhou Plateau in southwestern China covers eastern Yunnan (east of the Ailao Mountains), the greater part of Guizhou, northwestern Guangxi and the Sichuan ?Hunan-Hubei border. Its elevation decreases from northwest to southeast. It is 2,000 meters in Yunnan and 1,000 meters in Guizhou. The plateau has the following distinctive physical features:
1) Mountains and rivers. The mountains in Yunnan generally run from north to south, notably the Diancang and Wumeng ranges; while those in Guizhou mostly follow a northeast-southwest direction, notably the Dalou and Wulin granges. The Yunnan-Guizhou Plateau becomes the watershed of the Yangtze River, Xijiang and Hongha rivers where these mountain ranges running in two different directions meet. The Pudu, Chishui, Wujiang and Hengjiang rivers flow northward into the Yangtze River; the Beipan and Nanpan rivers meander east into the Xijiang; the Yuanjiang River wanders southward to join the Hongha. These rivers cut mountain areas into numerous high and steep canyons sandwiched between towering peaks, making the plateau surface rugged and uneven. The 3,000-meter-deep. Hutiaojian Canyon along the Jinsha River is one of deepest canyons in the world. The gorges in the Wujiang valley range from 300 to 500 meters in depth. With a drop of scores of meters, the Hangguoshu Waterfall on the upper reaches of the Dabang River, a tributary of the Beipan River, is one the highest waterfalls in China , the plateau is well blessed with hydro-power.
2) Intermontance basins with level land and deep soil strata. In these basins are farming areas and populous, fair-sized towns. The plateau is also dotted with fault lakes, notably the Dianchi and Erhai lakes. The cities of Kunming and Dali are located on their shores.
3) The typical limestone strata have given shape to grotesque stone forests, pinnacles, caverns, subterranean channels and overhanging ? bridges? across gorges. The Stone Forest at Lunan, Yunnan, and the underground garden at Guiyang, Guizhou, are famous for their scenery.
The Yunnan-Guizhou plateau is smaller than the Qinghai-Tibet, Inner Mongolia and Loess plateaus. Situated in the sub-tropics, it has an average yearly temperature of 15℃. In some places, it is cool and spring like all year round, where plant life grows lush and green and two or even three harvests are reaped a year. Kunming, the capital of Yunnan Province, is known as the ? spring city?.
(china.org.cn)
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