Beneath the grand Himalayan mountains, scientists have uncovered a remarkable geological phenomenon: the Indian continental plate appears to be tearing itself apart, revealing an unexpected level of geological complexity.
Recent research, presented at the annual meeting of the American Geophysical Union, suggests that tectonic dynamics beneath the Himalayas are more complex than previously thought. This mountain range, the highest in the world, sits atop a unique spot where two continental plates, the Indian and Eurasian, collide. Unlike areas where an oceanic plate slides beneath a continental plate, the collision of these two similarly dense plates presents distinct challenges for understanding to geoscientists.
The collision process between these plates is anything but straightforward. While in some areas the Indian plate appears to slide under the Eurasian plate without sinking deeply into the mantle, a hypothesis known as underplating, other parts seem to follow a different process. Researchers hypothesize that deeper sections of the Indian plate might be undergoing subduction, while the upper parts resist and become wedged against Tibet.
The study has revealed that the Indian plate is deforming and tearing as it subducts, a phenomenon known as delamination. This discovery was made through analyzing the seismic waves that travel through the Earth's crust in this area. Data indicates variations in the depth of the plate, with some parts reaching down to approximately 124 miles (200 kilometers), while others descend only to about 62 miles (100 kilometers), suggesting that the plate is detaching.
Moreover, geochemical studies on the helium variations in regional geothermal springs support these observations. The varied presence of helium-3, typical of mantle rocks, indicates changes in the crust's composition at these locations, corroborating the idea of a plate undergoing fragmentation.
This discovery is not only significant for understanding the geology of the Himalayas but also has implications for assessing seismic risks in the region. Although the connections between these deep crustal deformations and surface stresses remain to be clarified, tear zones could indicate areas with an increased risk of earthquakes.