Fast track India

The mantle plume that is thought to have broken up the supercontinent Gondwanaland may have melted the bottom half of the Indian tectonic plate, facilitating its high-speed drift.

Credit: © USGS

Seismic observations show that the lithosphere beneath India is surprisingly thin and lacks the deep continental root that is characteristic of the other Archaean continental plates that originated from Gondwanaland. This finding could explain why the Indian plate travelled so fast throughout the Cretaceous period.

Rainer Kind from the GeoForschungsZentrum Potsdam, Germany and colleagues¹ used a recently developed seismic technique to detect the lower boundary of all the plate fragments that once made up Gondwanaland. They found that the lithospheric roots of the South African, Australian and Antarctic plates extend to depths between 180 and 300 kilometres — almost double the depth of the Indian plate. This suggests that the bottom half of the Indian lithosphere may have been melted by the plume that broke up Gondwanaland.

Plate reconstructions show that the Indian plate then drifted at up to 20 cm per year — a lot faster than the other continental fragments — and only slowed down after the collision with Asia that formed the Himalayas and Tibetan plateau about 50 million years ago. The depth of the lithospheric root could therefore be critical in determining a plate's speed.