This is one of the most attractive geographical regions of China. The Sichuan Basin is surrounded by mountains, which are higher in the west and north. Protected against the penetration of cold northern winds, the basin is much warmer in the winter than are the more southerly plains of southeast China. Except for the Chengdu Plain, the region is hilly. The relief of the basin’s eastern half consists of numerous folds, forming a series of ridges and valleys that trend northeast to southwest. The lack of arable land has obliged farmers to cultivate the slopes of the hills, on which they have built terraces that frequently cover the slopes from top to bottom. The terracing has slowed down the process of erosion and has made it possible to cultivate additional areas by using the steeper slopes—some of which have grades up to 45° or more.

The southeastern mountains

Southeastern China is bordered by a rocky shoreline backed by picturesque mountains. In general, there is a distinct structural and topographic trend from northeast to southwest. The higher peaks may reach elevations of some 5,000 to 6,500 feet (1,500 to 2,000 meters). The rivers are short and fast-flowing and have cut steep-sided valleys. The chief areas of settlement are on narrow strips of coastal plain where rice is produced. Along the coast there are numerous islands, where the fishing industry is well developed.

Plains of the middle and lower Yangtze

East of Yichang, in Hubei province, a series of plains of uneven width are found along the Yangtze River (Chang Jiang). The plains are particularly wide in the delta area and in places where the Yangtze receives its major tributaries—including large areas of lowlands around Dongting, Poyang, Tai, and Hongze lakes, which are all hydrologically linked with the Yangtze. The region is an alluvial plain, the accumulation of sediment laid down by the rivers throughout long ages. There are a few isolated hills, but in general the land is level, lying mostly below 160 feet (50 meters). Rivers, canals, and lakes form a dense network of waterways. The surface of the plain has been converted into a system of flat terraces, which descend in steps along the slopes of the valleys.

The Nan Mountains

The Nan Mountains (Nan Ling) are composed of many ranges of mountains running from northeast to southwest. These ranges form the watershed between the Yangtze to the north and the Pearl (Zhu) River to the south. The main peaks along the watershed are above 5,000 feet, and some are more than 6,500 feet. But a large part of the land to the south of the Nan Mountains is also hilly; flatland does not exceed 10 percent of the total area. The Pearl River Delta is the only extensive plain in this region and is also the richest part of South China. The coastline is rugged and irregular, and there are many promontories and protected bays, including those of Hong Kong and Macau. The principal river is the Xi River, which rises in the highlands of eastern Yunnan and southern Guizhou.

The Yunnan-Guizhou Plateau

This region comprises the northern part of Yunnan and the western part of Guizhou; its edge is highly dissected. Yunnan is more distinctly a plateau and contains larger areas of rolling uplands than Guizhou, but both parts are distinguished by canyonlike valleys and precipitous mountains. The highest elevations lie in the west, where Mount Diancang (also called Cang Shan) rises to 13,524 feet (4,122 meters). In the valleys of the major rivers, elevations drop to about 1,300 to 1,600 feet (400 to 490 meters). Particularly sharp differences in elevation and the greatest ruggedness of relief occur in the western part of the region, in the gorges of the large rivers. In the eastern part, karst processes (creating sinks, ravines, and underground streams in the limestone landscape) have developed very strongly. Scattered throughout the highlands are small lake basins, separated by mountains.

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The Plateau of Tibet

This great upland massif occupies about one-fourth of the country’s area. A large part of the plateau lies at elevations above 13,000 to 16,500 feet (4,000 to 5,000 meters). The border ranges of the plateau (the Kunlun Mountains and the Himalayas) are even higher, with individual peaks rising to heights of 23,000 to 26,000 feet (7,000 to 8,000 meters) and higher. As a rule, the interior (i.e., Tibet-side) slopes of these border mountains are gentle, while the exterior slopes are precipitous. The plateau’s eastern and southern periphery is the source of many of the world’s great rivers, including the Yangtze, Huang He, Mekong, Salween, Indus, and Brahmaputra. Only in the low valleys, chiefly along the Brahmaputra valley, are there centers of human settlement.

The Qaidam (Tsaidam) Basin, occupying the northwestern portion of the Plateau of Tibet, is the largest, as well as the lowest, depression in the plateau. The broad northwestern part of the basin lies at elevations between approximately 8,800 and 10,000 feet (2,700 and 3,000 meters), and the narrow southeastern part is slightly lower. Gravel, sandy and clay deserts, semideserts, and salt wastes predominate within the basin.

The Tarim Basin

North of the Plateau of Tibet and at the much lower elevation of about 3,000 feet (900 meters) lies the Tarim Basin. It is hemmed in by great mountain ranges: the Tien Shan (Tian Shan; “Celestial Mountains”) on the north, the Pamirs on the west, and the Kunlun Mountains on the south. Glacier-fed streams descend from these heights only to lose themselves in the loose sands and gravels of the Takla Makan Desert, which occupies the center of the basin. The Takla Makan is one of the most barren of the world’s deserts; only a few of the largest rivers—such as the Tarim and Hotan (Khotan)—cross the desert, but even their flow is not constant, and they have water throughout their entire courses only during the flood period. The area of the basin is about 215,000 square miles (557,000 square km), and its elevations range from 2,500 to 4,600 feet (750 to 1,400 meters) above sea level. Its surface slants to the southeast, where Lop Nur (a salt-encrusted lake bed) is situated.