India and Nepal owe their dramatic geology to the ongoing collision between the Indian Plate and the Eurasian Plate, which has been pushing up the Himalayas for around 50 million years. As the Indian Plate drives northward at roughly 4-5 centimetres a year, enormous strain accumulates along the Main Himalayan Thrust, releasing some of the planet's most powerful continental earthquakes.
Neither country hosts active volcanoes along the Himalaya, but the seismic hazard is immense: the 1934 Nepal-Bihar earthquake killed over 10,000 people, and the 2015 Gorkha earthquake in Nepal killed nearly 9,000 and toppled historic temples in Kathmandu. In India, the 2001 Bhuj earthquake in Gujarat and the 1950 Assam-Tibet quake rank among the deadliest and largest ever recorded on the subcontinent.