Relics and rocks found in the Himalayas have resolved a long standing puzzle on India’s record speed when it crashed into Eurasia 80 million years ago, revealed geologists from the Massachusetts Institute of Technology (MIT).
India, after breaking away from supercontinent Gondwana – which also comprised present day Madagascar, Arabia, Africa and South America – started drifting at a remarkable speed around 120 million years ago. Moving at a speed of 40mm or 1.57 inches per year about 80 million years ago, India suddenly accelerated to 150mm or 5.9 inches per year and continued at the same pace for 30 million years till it collided with Eurasia and gave rise to the Himalayas.
According to the study published in Nature Geoscience, a combination of two subduction zones was responsible for the speed at which India kept moving northwards after splitting from Gondwana in the southern hemisphere. Double subduction zones refer to the Earth's mantle where the edge of one tectonic plate sinks under another plate, and pulls along any connected landmasses owing to twice the pulling power.
“In earth science, it's hard to be completely sure of anything," said Leigh Royden, professor of geology and geophysics in MIT's Department of Earth, Atmospheric and Planetary Sciences in a release. “But there are so many pieces of evidence that all fit together here that we're pretty convinced.”
Having found relics of what may have been two subduction zones and dating rocks from the Himalayan region, the MIT team developed a computer simulated model for a double subduction system and incorporated the measurements they obtained from the Himalayas into their model.
According to the study, the speed India’s landmass drifted was likely to have depended on the width of the subducting plates, and the distance between them. If the plates are relatively narrow and far apart, they would likely cause India to drift at a faster rate.
“When you look at simulations of Gondwana breaking up, India comes slowly off of Antarctica, and suddenly it just zooms across,” said Royden.