地球科学：インドプレートとユーラシアプレートの収束の加速を説明する

The sudden acceleration of the convergence between the Indian and Eurasian tectonic plates around 65 million years ago could have been aided by sediment, according to a paper published in Nature.

The increase in the convergence rate between India and Eurasia — from about 8 centimetres per year to a peak rate of about 18 centimetres per year — around 65 million years ago, is one of the most documented plate reorganization events in the Phanerozoic era (from about 541 million years ago to today). However, the mechanisms underlying the movement of the Indian and Eurasian plates during this period remain unclear.

Jiashun Hu and colleagues combined geochemical data from magmatic rocks in the Gangdese arc, southern Tibet, with numerical modelling. They suggest that large-scale erosion at the Indian passive margin (formed at the edge of the continents as they break apart) produced significant amounts of sediments. These sediments, once subducted beneath Eurasia, may have lubricated the plate interface, facilitating the faster convergence of the Indian and Eurasian plates.

The findings offer new insights into the driving forces of plate tectonics. They suggest that such accelerations in subduction rates might be a common feature at the final stage of continental assembly as continents collide.