Name of words: 456

Twenty million years ago Tibet lay at the bottom of the sea. The manner in which it was shaped into its present commanding position in Central Asia has been described as an epic in the long history of the formation of the earth’s crust. Caught between two approaching land masses, the sea bed buckled into a series of long parallel folds. The tops of these folds were levelled down by rain-bearing winds blowing up from the Indian Ocean, while the intervening depressions were filled with alluvial silt, creating the Chang Tang, the vast northern plateau of Tibet that stands at an average elevation of sixteen thousand feet above sea level. As the squeeze continued so the remaining sea waters drained southward into one enormous river system, the Indo-Gangetic river, which acted as a gutter to this newly-raised roof of the world and allowed it to evolve into a relatively fertile land of alpine forests and grasslands.

 These early stages in Tibet’s prehistory took place without human witnesses but are celebrated in Tibetan mythology with stories of a time before the advent of man when the plateau lay submerged under a vast lake – until a compassionate Bodhisattva (one who delays Buddhahood in order to help mankind) cut an outlet through the Himalayas for Tibet’s ‘great river, the Tsangpo. In reality, the Himalayas succeeded the formation of the Tibetan plateau. They represent the last and most dramatic phase of this extraordinary upheaval, a recent and rapid event in the geological time-scale, but one that added at least another mile to the general height of the Himalayas.       

The outcome of this prodigious burst of activity was a twenty-thousand-foot wall that spans twenty-five degrees of meridian from Namche Barwa in the east to Nanga Parbat in the west; a fifteen-hundred-mile barrier that has blocked the monsoon winds from the south and turned much of Tibet and Central Asia into desert. A leading authority in Himalayan geomorphology has gone so far as to suggest that some sections of the Himalayas may have risen as much as nine thousand feet and more within the last half-million years – and that the rise may be continuing at the rate of some thirty inches a century. What is certain is that the rapid growth of the Himalayan ranges took place not so very long ago, and that it effectively put a stop to man’s migrations to and fro across the steppes of Central Asia. Thus Tibet became the isolated and forbidding land that it is today, sealed off from the south and west, its lakes and rivers becoming increasingly desiccated as the Himalayan wall continues to capture more and more rainfall.

Excerpted from page 17–18 of ‘A Mountain Tibet ’ by Charles Allen