The Himalayas, the highest mountain range in the world, are the product of the collision of two tectonic plates located just below the crust of the Tibetan Plateau. This is the continental plate of India and Eurasian.
In theory, a pair of converging continental plates—that is, colliding with each other—would not cause one of them to break in two but rather cause one to sink beneath the other. However, a recent study has identified that one of the plates beneath Tibet may be rupturing unusually.
A rare fracture of the crust
Tectonic plates can be of two types: continental and oceanic.
When two different types of plates collide, the oceanic plate slides under the continental plate in a process called subduction. However, when two continental plates collide, there is no way to tell which one will end up under the other since both have the same density. And that is the complicated situation that happened in southern Tibet, where the Himalayas are located.
Map of the main tectonic plates. Photo: Storyboard that
Some experts suggest that the Indian plate is subducting under the Eurasian plate while preventing the mantle from sinking. Others have pointed out that the most superficial part of the Indian plate is excavated like a carpet and that only the deepest edge is submerged in the mantle.
But, now, a group of geologists from China and the United States has discovered a third scenario that was not imagined: in the collision of two plates, the Indian plate split in half, as if it were the lid of a can of fish.
In that sense, it is a horizontal break and not a vertical one, as is often the case in divergent plates, such as Africa and Iceland.
The breakup of the Indian plate
The rupture of the Indian plate was discovered after reviewing seismic waves from 94 seismological stations in Asia and identifying that this structure, on the one hand, is about 200 kilometers deep and, on the other hand, only about 100 km.
“We did not know that the continents could move in such a way and that, for solid Earth science, is very important,” said Douwe van Hinsbergen, a geodynamicist at the University of Utrecht (Netherlands) and one of the authors of the research.
The findings were presented at the American Geophysical Union conference in San Francisco last December and were led by institutions from the United States and China.