The Himalayas (from the Sanskrit words hima, “snow,” and alaya, “abode”), the loftiest mountain system in the world, form the northern limit of India. That great, geologically young mountain arc is about 1,550 miles (2,500 km) long, stretching from the peak of Nanga Parbat (26,660 feet [8,126 metres]) in the Pakistani-administered portion of the Kashmir region to the Namcha Barwa peak in the Tibet Autonomous Region of China. Between those extremes the mountains fall across India, southern Tibet, Nepal, and Bhutan. The width of the system varies between 125 and 250 miles (200 and 400 km).

Within India the Himalayas are divided into three longitudinal belts, called the Outer, Lesser, and Great Himalayas. At each extremity there is a great bend in the system’s alignment, from which a number of lower mountain ranges and hills spread out. Those in the west lie wholly within Pakistan and Afghanistan, while those to the east straddle India’s border with Myanmar (Burma). North of the Himalayas are the Plateau of Tibet and various Trans-Himalayan ranges, only a small part of which, in the Ladakh region of Jammu and Kashmir state (in the Indian-administered portion of Kashmir), are within the territorial limits of India. Because of the continued subduction of the Indian peninsula against the Eurasian Plate,

the Himalayas and the associated eastern ranges remain tectonically active. As a result, the mountains are still rising, and earthquakes—often accompanied by landslides—are common. Several since 1900 have been devastating, including one in 1934 in what is now Bihar state that killed more than 10,000 people. In 2001 another tremor (the Bhuj earthquake), farther from the mountains, in Gujarat state, was less powerful but caused extensive damage, taking the lives of more than 20,000 people and leaving more than 500,000 homeless.

Still others—notably the 2005 quake in Pakistani-administered Kashmir and the 2015 temblor in Nepal—principally affected those regions but also caused widespread damage and hundreds of deaths in adjacent parts of India. The relatively high frequency and wide distribution of earthquakes likewise have generated controversies about the safety and advisability of several hydroelectric and irrigation projects.