That is the Mohorovicic Discontinuity, or last stop for solid ground...so to speak...before the semi-liquid/molten layers of the Mantle.
Below continents, the Moho is usually found about 21 miles down from the surface. But at the Tibetan Plateau, where the crust is particularly thick, the Moho is found 40 miles down; at the western part of the plateau, it dives as far as 50.9 miles deep.
This has also given them a great look at what is happening where the two plates are in conflict right there.
They found that the pressure of the Indian plate pressing into the Eurasian plate buckles the crust, forcing it to climb up (creating the Himalaya mountains) or dive down (becoming the base of the thick Tibetan Plateau). This pattern matches records made by GPS devices that measure the movement of the Earth in the region, Shin said.