Geography

　　Today, the People's Republic of China is divided into 23 provinces, five autonomous regions, four municipalities directly under the Central Government, and two special ad-ministrative regions. Tibet is one of the five autonomous re-gions, featuring autonomy mainly by the Tibetan race.
　　Location and Area. The Tibet Autonomous Region in southwest China forms the southwestern portion of the Qinghai-Tibet Plateau. It adjoins the Xinjiang Uygur Auton-omous Region and the provinces of Qinghai to the north, Si-chuan to the east and Yunnan to the southeast, and the nations of Myanmar, India, Bhutan, Sikkim and Nepal to the south and west along an international border of nearly 4,000 kilometers. The 1 .22-million-square-kilometer autonomous region accounts for 12.8 percent of China's total land area.
Topography and Mountain Ranges. Averaging more than 4,000 meters in elevation, Tibet forms the main part of the Qinghai-Tibet Plateau and is known as the "roof of the world". While the topography is complex, the area can be divided into three distinct natural zones:
· The North Tibet Plateau in the north, which, account-ing for two-thirds of the region in area, is surrounded by the Kunlun, Tanggula, Kangdese, and Nyainqentanglha moun-tains;
· The Tibet Valley in the south, where the Yarlung Zangbo River and its tributaries flow;
· High Mountains and Deep Valleys in the east, inclu-ding part of the Hengduan Mountains, which run east-west and then north-south.
　　Geomorphologically, there are six principal forms: polar altitude mountains, alpine mountains, medium-height moun-tains, low mountains, hills and plains. Volcanic, aeolian, karst and periglacial landforms are found as well.
The Himalayas are a group of mountain ranges running roughly parallel to one another in an east-west direction on the southern edge of the Tibet Plateau along China's border with India and Nepal. The mountains run for 2,400 kilometers at a width of 200 to 300 kilometers and altitudes averaging over 6,000 meters. Mount Qomolangma, the wor-ld's highest peak with an elevation of 8,848.13 meters, rising abruptly on the Sino-Nepalese border midway through the range. Four peaks each with an elevation of over 8,000 meters and 38 peaks each over 7,000 meters can be found in the more than 5,000 square kilometers surrounding Qomolangma.
　　Rivers and Lakes. More than 20 rivers with drainage areas in excess of 10,000 square kilometers and more than 100 with drainage areas of more than 2,000 square kilometers are found in Tibet. Best known are the Jinshajiang, Nujiang, Lancangjiang and Yarlung Zangbo rivers. Tibet has more ri-vers flowing into foreign countries than any other Chinese provinces, municipalities directly under the Central Govern-ment and autonomous regions. Great rivers of Asia that find their origin in Tibet include the Ganges, Hindus, Brahmapu-tra, Mekong, Salween and Irrawaddy. These rivers for the most.part arise from rains, melted ice and snow and under-ground water, hence their water is of excellent quality, their flow rate high and siltage low.
　　The Yarlung Zangbo River, the largest of its kind in Ti-bet, has its source in the Gyimayangzong Glacier at the north-ern foot of the Himalayas in Zhongba County. After flowing through Lhoyu and entering India it is known as the Brah-maputra. The 2,057-kilometer Chinese portion, with a drain-age area of more than 240,000 square kilometers at an ap-proximate average altitude of 4,500 meters high, is the wor-ld's highest-altitude river.
The 370-kilometer Yarlung Zangbo Grand Canyon, with a depth of 5,382 meters, the world's deepest, is only 74 meters wide at the narrowest point along its base and 200 meters at the widest.
　　The vast Tibet Plateau is bejeweled with more than 1,500 large and small lakes; the Nam Co, Siling Co and Zhaxi Narnco are larger than 1,000 square kilometers and 47 other lakes are larger than 100 square kilometers. All told there are 24,183 square kilometers of lakes, about one-third of China's total. The Tibet Plateau is the area in China with the most dense concentration of lakes; in terms of number, area and altitude of lakes it leads all the world's plateaus. Most of these lakes are saline. Seventeen, all larger than 50 square kilometers, are located about 5,000 meters.

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