The geology of the Himalayas is a record of the most dramatic and visible creations of the immense mountain range formed by plate tectonic forces and sculpted by weathering and erosion. The Himalayas, which stretch over 2400 km between the Namcha Barwa syntaxis at the eastern end of the mountain range and the Nanga Parbat syntaxis at the western end, are the result of an ongoing orogeny — the collision of the continental crust of two tectonic plates, namely, the Indian Plate thrusting into the Eurasian Plate. The Himalaya-Tibet region supplies fresh water for more than one-fifth of the world population, and accounts for a quarter of the global sedimentary budget. Topographically, the belt has many superlatives: the highest rate of uplift, the highest relief, among the highest erosion rates at 2–12 mm/yr, the source of some of the greatest rivers and the highest concentration of glaciers outside of the polar regions. This last feature earned the Himalaya its name, originating from the Sanskrit for "the abode of the snow".
The geology of Nepal is dominated by the Himalaya, the highest, youngest and a very highly active mountain range. Himalaya is a type locality for the study of on-going continent-continent collision tectonics. The Himalayan arc extends about 2,400 km (1,500 mi) from Nanga Parbat by the Indus River in northern Pakistan eastward to Namche Barwa by the gorge of the Tsangpo-Brahmaputra in eastern Tibet. About 800 km (500 mi) of this extent is in Nepal; the remainder includes Bhutan and parts of Pakistan, India, and China.
Thrust tectonics or contractional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the shortening and thickening of the crust or lithosphere. It is one of the three main types of tectonic regime, the others being extensional tectonics and strike-slip tectonics. These match the three types of plate boundary, convergent (thrust), divergent (extensional) and transform (strike-slip). There are two main types of thrust tectonics, thin-skinned and thick-skinned, depending on whether or not basement rocks are involved in the deformation. The principle geological environments where thrust tectonics is observed are zones of continental collision, restraining bends on strike-slip faults and as part of detached fault systems on some passive margins.
The 1999 Chamoli earthquake occurred on 29 March in the Chamoli district in the Indian state of Uttar Pradesh. Approximately 103 people died in the earthquake.
The 1975 Kinnaur earthquake occurred in the early afternoon of 19 January. It had a magnitude of 6.8 on the surface wave magnitude scale and a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale, causing extensive damage in Himachal Pradesh, in northern India. Its epicentre was in Kinnaur district in the southeastern part of Himachal Pradesh and caused 47 casualties. Landslides, rock falls and avalanches caused major damage to the Hindustan-Tibet Road. The earthquake affected many monasteries and buildings in the state and led to an extensive restoration work in the late 1970s and early 1980s in Himachal Pradesh. The Spiti and Parachu valleys in particular suffered the greatest damage being on the north–south Kaurik-Chango fault, causing damage to landmarks such as Key Monastery and Tabo Monastery.
The South Tibetan Detachment is one of the major faults in the Himalaya Mountains.
The Karakoram fault is an oblique-slip fault system in the Himalayan region across India and Asia. The slip along the fault accommodates radial expansion of the Himalayan arc, northward indentation of the Pamir Mountains, and eastward lateral extrusion of the Tibetan plateau. Current plate motions suggest that the convergence between the Indian Plate and the Eurasian Plate is around 44±5 mm per year in the western Himalaya-Pamir region and approximately 50±2 mm per year in the eastern Himalayan region.
The Main Central Thrust is a major geological fault where the Indian Plate has pushed under the Eurasian Plate along the Himalaya. The fault slopes down to the north and is exposed on the surface in a NW-SE direction (strike). It is a thrust fault that continues along 2900 km of the Himalaya mountain belt.
The Himalayan foreland basin is an active collisional foreland basin system in South Asia. Uplift and loading of the Eurasian Plate on to the Indian Plate resulted in the flexure (bending) of the Indian Plate, and the creation of a depression adjacent to the Himalayan mountain belt. This depression was filled with sediment eroded from the Himalaya, that lithified and produced a sedimentary basin ~3 to >7 km deep. The foreland basin spans approximately 2,000 kilometres (1,200 mi) in length and 450 kilometres (280 mi) in width. From west to east the foreland basin stretches across five countries: Pakistan, India, Nepal, Bangladesh, and Bhutan.
Pre-collisional Himalaya is the arrangement of the Himalayan rock units before mountain-building processes resulted in the collision of Asia and India. The collision began in the Cenozoic and it is a type locality of a continental-continental collision. The reconstruction of the initial configuration of the rock units and the relationship between them is highly controversial, and major concerns relate to the arrangements of the different rock units in three dimensions. Several models have been advanced to explain the possible arrangements and petrogenesis of the rock units.
The geology of Himachal Pradesh is dominated by Precambrian rocks that were assembled and deformed during the India-Asia collision and the subsequent Himalayan orogeny. The Northern Indian State Himachal Pradesh is located in the Western Himalaya. It has a rugged terrain, with elevation ranging from 320m to 6975m. Rock materials in the region are largely from the Indian craton, and their ages range from the Paleoproterozoic to the present day. It is generally agreed that the Indian craton collided with Asia 50-60 million years ago (Ma). Rock sequences were thrust and folded immensely during the collision. The area has also been shaped by focused orographic precipitation, glaciation and rapid erosion.
The Main Himalayan Thrust (MHT) is a décollement under the Himalaya Range. This thrust fault follows a NW-SE strike, reminiscent of an arc, and gently dips about 10 degrees towards the north, beneath the region. It is the largest active continental megathrust fault in the world.
The 2021 Assam earthquake struck 11 km away from Dhekiajuli, Assam, India at 07:51 (IST) on April 28, 2021 with a moment magnitude of 6.0 at 34.0 km (21.1 mi) depth. The quake struck with an epicenter 140 km north of the main city of Guwahati. It resulted in two fatalities and at least 12 injuries.
The 1555 Kashmir earthquake occurred at around midnight in the month of Ashvin in the Hindu calendar, or September in the Gregorian calendar, although the exact day of occurrence is not known. The earthquake seriously impacted the Kashmir Valley in present-day Pakistan and northwestern India. A moment magnitude (Mw ) of 7.6 to 8.0 and Modified Mercalli intensity of XII (Extreme) has been estimated for the earthquake. Thought to be one of the most destructive in the Kashmir Valley, the earthquake caused serious widespread damage and ground effects, killing an estimated 600–60,000 individuals.
The 1885 Kashmir earthquake, also known as the Baramulla earthquake occurred on 30 May in Srinagar. It had an estimated moment magnitude of Mw 6.3–6.8 and maximum Medvedev–Sponheuer–Karnik scale intensity of VIII (Damaging). At least 3,081 people died and severe damage resulted.
The 1803 Garhwal earthquake occurred in the early morning of September 1 at 01:30 local time. The estimated 7.8-magnitude-earthquake had an epicenter in the Garhwal Himalaya near Uttarkashi, British India. Major damage occurred in the Himalaya and Indo-Gangetic Plain, with the loss of between 200 and 300 lives. It is among the largest Himalaya earthquakes of the 19th-century, caused by thrust faulting.
The 1980 Nepal earthquake devastated the Nepal–India border region on the evening of July 29. The epicenter of the 6.6 earthquake was located in Nepal, northwest of Khaptad National Park. At least 200 people died and 5,600 were injured in the disaster. Extensive damage occurred on both sides of the border, amounting to 245 million USD.
Bhutan was struck by a major earthquake on 4 May 1714. It had an estimated magnitude of about 8.1 and caused shaking that reached IX (Violent) on the Modified Mercalli intensity scale. It is thought to have been caused by rupture of the Bhutan part of the Main Frontal Thrust. Damage was reported from west central Bhutan and northeast India. The earthquake resulted in "many fatalities".
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
