An area of Tibet with an elevation of approximately 2 km above sea level, below which the crust is more than 80 km thick; this has been ascribed to underthrusting of the crust of the Indo-Australian Plate (i.e. by A-subduction) or to horizontal shortening as a result of thrust tectonics. The uplift has been both rapid and recent: one estimate is 2500–3000 m since the Pliocene.