In relatively recent geologic times, less than forty million years ago, the Indian subcontinent crashed into the Eurasian tectonic plate. As the South Asian plate began to subduct under the Eurasian plate, it pushed up the Himalayas, the Plateau of Tibet, and folded the ranges of mountains to the east of the Plateau of Tibet. The Indian plate is still converging on the Eurasian plate at a little over three-quarters of an inch per year, deforming the boundary and raising the Himalaya Range. This rate is faster than fingernails grow.
Major Asian Rivers of the Plateau of Tibet: The Basics