Scientists recently measured the thickness of the Indian crust, as well as that of Africa, Australia, and Antarctica. All these landforms were once connected in a super-continent called Gondwanaland.
Researchers found the thickness of the Indian plate to be as much as one third that of the other plates. They speculate a large molten mass pushed up from deep in the earth, fracturing Gondwanaland and melting away a large portion of the Indian lithosphere.
With the decrease in thickness, the Indian plate accelerated relative to the other plates and today is sliding under the Asian plate at the present-day Himalayas.