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China's topography was formed around the emergence of the
Qinghai-Tibet Plateau, the most important geological event over the
past several million years. Taking a bird's-eye view of China, the
terrain gradually descends from west to east like a staircase. Due
to the collision of the Indian and Eurasian plates, the
Qinghai-Tibet Plateau rose continuously to become the top of the
four-step "staircase," averaging more than 4,000 m above sea level,
and is called "the roof of the world." Soaring 8,844.43 m above sea
level on the plateau is Mount Qomolangma (Mount Everest), the
world's highest peak and the main peak of the Himalayas. The second
step includes the gently sloping Inner Mongolia Plateau, the Loess
Plateau, the Yunnan-Guizhou Plateau, the Tarim Basin, the Junggar
Basin and the Sichuan Basin, with an average elevation of between
2,000 m and 1,000 m. The third step, dropping to 1,000-500 m in
elevation, begins at a line drawn around the Greater Hinggan,
Taihang, Wushan and Xuefeng mountain ranges and extends eastward to
the coast of the Pacific Ocean. Here, from north to south, are the
Northeast Plain, the North China Plain and the Middle-Lower Yangtze
Plain. Interspersed amongst the plains are hills and foothills. To
the east, the land extends out into the ocean, in a continental
shelf, the fourth step of the staircase. The water here is mostly
less than 200 m deep.??