The mystery of why the Himalaya mountains and the Tibetan plateau are the highest in the world has at last been answered, with the discovery of a gigantic chunk of rock slowly sinking towards the centre of the Earth.
The discovery of the missing mantle - the cold, heavy rock beneath the crust - was revealed last week by Professor Wang-Ping Chen at the University of Illinois, whose team used more than 200 super-sensitive seismometers strung across the Himalayas, from India deep into Tibet.
Some scientists have even suggested that the rise of the Himalayas could have triggered the Ice Age by increasing the total amount of global rain and removing vast amounts of carbon dioxide from the air.
Scientists can't even be sure how high the land was before India crashed into Asia, obliterating the Tethys Ocean which used to separate them. Like western South America, the coast could have been lined by mountains.