Himalayan thrust faults
Also called: Main Central Thrust, Main Boundary Thrust, Main Frontal Thrust · Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Beyond NCERT
Meaning
Himalayan thrust faults are huge cracks in the Himalayas. Along each one, a slab of rock has been pushed up and over the rock to its south. They form because India keeps pushing into Asia, and the crust breaks and stacks up like overlapping roof tiles. All of them slope down towards the north. From north to south, the three main ones are:
- Main Central Thrust (MCT): pushed the Greater Himalaya over the Lesser Himalaya.
- Main Boundary Thrust (MBT): pushed the Lesser Himalaya over the Siwaliks.
- Main Frontal Thrust (MFT): pushed the Siwaliks over the plains.
All three branch off one deep fault below called the Main Himalayan Thrust. Each thrust is younger than the one north of it, so the mountain front keeps moving south towards the plains. Sudden slips along these faults cause major Himalayan earthquakes.
Example
The Siwalik hills, at the southern edge of the Himalayas in Uttarakhand, were pushed over the Gangetic plains along the Main Frontal Thrust. In Nepal, the Gorkha earthquake of 2015 happened on the Main Himalayan Thrust.
Don't confuse with
- Indus-Tsangpo Suture Zone: this is the line where two plates (Indian and Eurasian) joined, far to the north. The thrust faults lie further south, inside the crust of the Indian plate itself.