Earthquake-prone Himalayas under stress

New theory explains the fragility of the mountain range

Earthquake-prone Himalayas under stress

 
A new theory on the formation of the world’s youngest mountain range suggests that the ongoing movement of India towards central Asia could be driven by a downward pull from the Indian continental plate.

This work provides a different interpretation of the forces that governed the collision of India and Asia between about 55 and 30 million years ago. It could also suggest why the Himalayas are so fragile and earthquake-prone. The research may eventually help understand why so many earthquakes occur in the Himalayas.

Almost 50 million years ago, the Greater Indian plate collided with the Eurasian plate leading to the formation of the mighty range. Usually, when two continental plates collide, the movement of the two plates stop. That did not happen with the Indian-Eurasian convergence.

The two plates continue to rub against each other generating stress, which is later released as earthquakes. An international team has now offered an explanation. In Sunday’s edition of “Nature Geoscience,” they suggest an internal mechanism that creates  the drag which pulls the Indian plate towards its boundary with Eurasia.

“The India-Asia convergence cannot be explained by plate tectonics theory, which is deeply challenged,” said team leader Fabio Antonio Capitanio, a geoscientist at the University of Monash, Australia.

The scientists used a cutting edge software, aptly named “UNDERWORLD code,” to simulate the collision of the Indian plate and Eurasia before and during the collision. They found that the density of the uppermost layer of the Greater Indian plate is more than the underlying mantle. This would have continued to drag India towards Asia.

When the upper crust is scraped off at the Himalayan front during continental collision, the remaining dense continental lithosphere sinks into the mantle dragging the Indian plate with it. The bulk of the Indian plate was sufficiently dense to sink into the underlying mantle.

It is this sinking pull that has probably led to Indian plate’s continuous push along the plate boundary, which leads to stress generation and quakes later. “How the stress transforms into deformation, which is not always accompanied by earthquakes is another subject. But the boundary conditions are now a bit more clear,” Capitanio told Deccan Herald.

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