The world’s high continental plateaux in Tibet, the Andes and East Anatolia are fascinating, but the causes for their uplift are enigmatic. We present evidence for two isostatic processes that may contribute substantially to the uplift.

Our seismic data shows that the thickest crust on Earth, in the central Lhasa terrane of Tibet, is felsic down to the Moho at 80 km depth. This low-density overthickened crust contributes to the high altitude of this part of Tibet. We propose that mafic lower crust produced by subduction transformed into eclogitic rocks immediately after formation. Due to their high density, these new rocks would delaminate each time their volume exceeded a critical mass.

A new receiver function profile in the East Anatolian Plateau indicates the presence of an up-to 20 km thick underplated layer and a 10 km thick intra-crustal partially molten layer. The low density of these layers explains isostatically the high topography in eastern Anatolia. The thicker crust in Tibet and the Andes show similar characteristics, and by comparison we show that the high topography of all three plateaux can be explained by isostatic uplift due the low density of these layers containing pockets of partially molten rocks.