Which Himalayan tectonic feature marks the boundary between the Higher Himalaya and the Lesser Himalaya?

The Main Central Thrust marks the boundary between the Higher Himalaya and the Lesser Himalaya.

The Main Central Thrust, usually abbreviated MCT, is a major geological fault system running through the Himalayan mountain belt. It developed as the Indian Plate was pushed beneath and against the Eurasian Plate, compressing, folding and uplifting rocks over millions of years.

The Higher Himalaya contains many of the range’s tallest, largely crystalline mountain massifs. South of it, the Lesser Himalaya consists of generally lower but still rugged ranges with different rock units and geological histories. The MCT helps geologists distinguish these broad structural zones.

The MCT is not the same as the Main Boundary Thrust or the Himalayan Frontal Thrust. Those are separate major structures farther south in the Himalayan tectonic sequence. Together, these thrust systems record the continuing collision that still produces earthquakes and raises the mountains.