Terrain and vegetation vary greatly in China. Mountains, hills, and highlands cover about 66 percent of the nation's territory, impeding communication and leaving limited level land for agriculture. Most ranges, including all the major ones, trend eastwest . In the southwest, the Himalayas and the KunÍÍÍÍlun Mountains enclose the Qing Zang Plateau, which encompasses most of Xizang Autonomous Region (also known as Tibet) and part of Qinghai Province. It is the most extensive plateau in the world, where elevations average more than 4,000 meters above sea level and the loftiest summits rise to more than 7,200 meters.

From the Qing Zang Plateau, other less-elevated highlands, rugged east-west trending mountains, and plateaus interrupted by deep depressions fan out to the north and east. A continental scarp marks the eastern margin of this territory extending from the Greater Hinggan Range in northeastern China, through the Taihang Shan (a range of mountains overlooking the North China Plain) to the eastern edge of the Yunnan-Guizhou Plateau in the south (see fig. 4). Virtually all of the low-lying areas of China--the regions of dense population and intensive cultivation--are found east of this scarp line.

East-west ranges include some of Asia's greatest mountains. In addition to the Himalayas and the Kunlun Mountains, there are the Gangdise Shan (Kailas) and the Tian Shan ranges. The latter stands between two great basins, the massive Tarim Basin to the south and the Junggar Basin to the north. Rich deposits of coal, oil, and metallic ores lie in the Tian Shan area. The largest inland basin in China, the Tarim Basin measures 1,500 kilometers from east to west and 600 kilometers from north to south at its widest parts.

The Himalayas form a natural boundary on the southwest as the Altai Mountains do on the northwest. Lesser ranges branch out, some at sharp angles from the major ranges. The mountains give rise to all the principal rivers.

The spine of the Kunlun Mountains separates into several branches as it runs eastward from the Pamir Mountains. The northernmost branches, the Altun Shan and the Qilian Shan, rim the Qing Zang Plateau in west-central China and overlook the Qaidam Basin, a sandy and swampy region containing many salt lakes. A southern branch of the Kunlun Mountains divides the watersheds of the Huang He and the Chang Jiang (Yangtze River). The Gansu Corridor, west of the great bend in the Huang He, was traditionally an important communications link with Central Asia.

North of the 3,300-kilometer-long Great Wall, between Gansu Province on the west and the Greater Hinggan Range on the east, lies the Nei Monggol Plateau, at an average elevation of 1,000 meters above sea level. The Yin Shan, a system of mountains with average elevations of 1,400 meters, extends east-west through the center of this vast desert steppe peneplain. To the south is the largest loess plateau in the world, covering 600,000 square kilometers in Shaanxi Province, parts of Gansu and Shanxi provinces, and some of Ningxia-Hui Autonomous Region. Loess is a yellowish soil blown i 100n from om the Nei Monggol deserts. The loose, loamy material travels easily in the wind, and through the centuries it has veneered the plateau and choked the Huang He with silt.

Because the river level drops precipitously toward the North China Plain, where it continues a sluggish course across the delta, it transports a heavy load of sand and mud from the upper reaches, much of which is deposited on the flat plain. The flow is channeled mainly by constantly repaired manmade embankments as a result the river flows on a raised ridge fifty meters or more above the plain, and waterlogging, floods, and course changes have recurred over the centuries. Traditionally, rulers were judged by their concern for or indifference to preservation of the embankments. In the modern era, the new leadership has been deeply committed to dealing with the problem and has undertaken extensive flood control and conservation measures.

Flowing from its source in the Qing Zang highlands, the Huang He courses toward the sea through the North China Plain, the historic center of Chinese expansion and influence. Han (see Glossary) people have farmed the rich alluvial soils of the plain since ancient times, constructing the Grand Canal for north-south transport (see The Imperial Era , ch. 1). The plain itself is actually a continuation of the Dongbei (Manchurian) Plain to the northeast but is separated from it by the Bo Hai Gulf, an extension of the Huang Hai (Yellow Sea).

Like other densely populated areas of China, the plain is subject not only to floods but to earthquakes. For example, the mining and industrial center of Tangshan, about 165 kilometers east of Beijing, was leveled by an earthquake in July 1976 that reportedly also killed 242,000 people and injured 164,000.

The Qin Ling mountain range, a continuation of the Kunlun Mountains, divides the North China Plain from the Chang Jiang Delta and is the major physiographic boundary between the two great parts of China Proper (see Glossary). It is in a sense a cultural boundary as well, influencing the distribution of custom and language. South of the Qin Ling divide are the densely populated and highly developed areas of the lower and middle plains of the Chang Jiang and, on its upper reaches, the Sichuan Basin, an area encircled by a high barrier of mountain ranges.

The country's longest and most important waterway, the Chang Jiang is navigable over much of its length and has a vast hydroelectric potential. Rising on the Qing Zang Plateau, the Chang Jiang traverses 6,300 kilometers through the heart of the country, draining an area of 1.8 million square kilometers before emptying into the East China Sea. The roughly 300 million people who live along its middle and lower reaches cultivate a great rice- and wheat-producing area. The Sichuan Basin, favored by a mild, humid climate and a long growing season, produces a rich variety of crops it is also a leading silk-producing area and an important industrial region with substantial mineral resources.

Second only to the Qin Ling as an internal boundary is the Nan Ling, the southernmost of the east-west mountain ranges. The Nan Ling overlooks the part of China where a tropical climate permits two crops of rice to be grown each year. Southeast of the mountains lies a coastal, hilly region of small deltas and narrow valley plains the drainage area of the Zhu Jiang (Pearl River) and its associated network of rivers occupies much of the region to the south. West of the Nan Ling, the Yunnan-Guizhou Plateau rises in two steps, averaging 1,200 and 1,800 meters in elevation, respectively, toward the precipitous mountain regions of the eastern Qing Zang Plateau.

The Hai He, like the Zhu Jiang and other major waterways, flows from west to east. Its upper course consists of five rivers that converge near Tianjin, then flow seventy kilometers before emptying into the Bo Hai Hai Gulf. Another major river, the Huai He, rises in Henan Province and flows through several lakes before joining the Chang Jiang near Yangzhou.

Inland drainage involving a number of upland basins in the north and northeast accounts for about 40 percent of the country's total drainage area. Many rivers and streams flow into lakes or diminish in the desert. Some are useful for irrigation.

China's extensive territorial waters are principally marginal seas of the western Pacific Ocean these waters wash the shores of a long and much-indented coastline and approximately 5,000 islands. The Yellow, East China, and South China seas, too, are marginal seas of the Pacific Ocean. More than half the coastline (predominantly in the south) is rocky most of the remainder is sandy. The Bay of Hangzhou roughly divides the two kinds of shoreline.

Data as of July 1987