The Tibetan Plateau is a unique feature of the Earth’s surface. Its elevation, 5 km above sea level, and a crust twice the normal thickness, have long been recognized as resultin g from the collision o f the Indian and Eurasian continents. The region is regarded as the prime example of collision tectonics. However, because Tibet was for long virtually inaccessible to geologists from the rest of the world, the mechanism by which the Plateau evolved and by which the crust was doubled in thickness, remained speculative. During the past two decades, Chinese geologists have explored and systematically mapped much of this vast and largely uninhabited region ; Academia Sinica mounted a series of geological expeditions. The results of this and other work were presented at an international symposium on the Qinghai—Xizang (Tibet) Plateau in Beijing in 1980 and demonstrated on a traverse through southern Tibet from Lhasa to Kathmandu .