The Himalayan Frontier and South Asian Climate

The Himalaya forms an arc roughly 2,400 kilometers long, running from Nanga Parbat in Pakistan-administered territory in the west to Namcha Barwa near the China-India border in the east, produced and continually renewed by the ongoing convergence of the Indian and Eurasian plates. Geologists divide the range into parallel belts running its length — the low outer Sub-Himalaya (or Siwalik Hills), the Lesser Himalaya, the high Greater Himalaya carrying the range's tallest peaks, and the arid Tethys Himalaya beyond — reflecting successive stages of crustal thickening and uplift. The plate convergence that built the range, still occurring today at a few centimeters per year, also makes the Himalayan frontier one of the most seismically hazardous regions on Earth; the 2015 Gorkha earthquake in Nepal, of moment magnitude 7.8, killed nearly 9,000 people and damaged or destroyed hundreds of thousands of homes, a stark reminder that the mountains are a live tectonic system rather than a static backdrop.