Credit: RON BLAKEY/WWW.NAU.EDU

The migration speed of tectonic plates across the globe is largely controlled by the pull of old, dense oceanic lithosphere. As this lithosphere sinks into the mantle beneath the more buoyant continents, it gradually drags the surface part of the oceanic plate, as well as any adjoining continents, toward the subduction trench. This slab-pull force can move plates at a maximum rate of about 8 cm yr−1. Yet, around 67 million years ago, India began charging towards Asia more than twice as fast, by up to 18 cm yr−1.

To reassess the precise timing of India's movements, Steven Cande and Dave Stegman (Nature 475, 47–52; 2011) analysed magnetic anomalies in basaltic rocks on the Indian Ocean floor. They found that India's motion accelerated precisely when the Réunion plume, rising up through the mantle beneath India, reached the surface. The power of the upwelling mantle plume may have given India an extra push, they suggest. And, because the plume nudged India towards the subduction zone that was already dragging the continent towards Asia, the two forces — plume push and slab pull — combined to catapult India on its journey northwards.

The plate reconstructions also reveal that the motion of the African plate slowed down at about the same time. This retardation of Africa's movement could also be due to the influence of the Réunion plume: the plume is positioned in a way that the plume-push and slab-pull forces would have counteracted each other.

Between 15 and 22 million years later, the movements of both the Indian and African plates returned to normal. It could be that the Réunion plume, and its push, began to wane at this time.