During the Upper Cretaceous, about 70 million years ago, the north-moving Indo-Australian plate (which has subsequently broken into theIndian Plate and the Australian plate[6]) was moving at about 15 cm per year. About 50 million years ago this fast moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined by sedimentary rocks settled on the ocean floor, and the volcanoes that fringed its edges.