It has long been understood that the constant ‘pull’ and ‘push’ movements of the plates are responsible for creating many of the continental features present around the planet, from mountain chains to volcanoes. But Scripps scientists Steve Cande and Dave Stegman have now demonstrated that plumes of magma rising from the Earth’s deep interior also play a role in the plates’ movements.

Again, the existence of such plumes has long been known – they are responsible for volcanic activity in areas such as Hawaii, Iceland and the Galápagos. But by tracking plate motions through the Earth’s history, Cande and Stegman have provided evidence that these ‘hot spots’, which can last for tens of millions of years, are also causing the plates to move.

In a paper published in Nature, they present evidence of a clear connection between the arrival of a powerful mantle plume head around 70 million years ago and the rapid motion of the Indian plate. The plume’s arrival also coincided with the creation of immense formations of volcanic rock known as the Deccan flood basalts in western India.

As the force of the plume waned, the movement of the Indian plate slowed down. ‘There is a dramatic slowdown in the northwards motion of the Indian plate around 50 million years ago that has long been attributed to the initial collision of India with the Eurasian plate,’ said Cande. ‘An implication of our study is that the slowdown might just reflect the waning of the mantle plume – the actual collision might have occurred a little later.’

September 2011