The Himalaya is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau. It is home to the world's highest mountain peaks such as Mount Everest and Kanchenjunga. Etymologically Himalaya means "abode of snow" in Sanskrit ( from hima "snow", and aalaya "abode"). The correct name for the range is Himalaya, though the plural Himalayas is often used.

The Himalaya stretch across five nations — Pakistan, India, China, Bhutan and Nepal. It is the source of two of the world's major river systems — the Indus Basin and the Ganga-Brahmaputra Basin. An estimated 750 million people live in the watershed area of the Himalayan rivers, which also includes Bangladesh.

Geography

The Himalayan range runs for about 2400 km, from Nanga Parbat in the west to Namche Barwa in the east. The width varies between 250-300 km. The Himalayan range comprises three parallel ranges, arranged by elevation and geological age.

The youngest of the three is called the Sub-Himalayan range (Siwalik hills in India) and has an elevation of about 1200 m. This range is made up of erosion material from the rising Himalaya. Running parallel to this is the Lower Himalayan range, which has an elevation between 2000 — 5000 m. A number of Indian hill stations such as Shimla, Nainital and Darjeeling are located here. The northernmost range is called the Higher Himalaya and is also the oldest of the three. It has an elevation of more than 6000 m and contains a large number of the world's highest peaks including the three highest - Mount Everest, K2 and Kanchenjunga.

Vegetation across the Himalayan range varies with climate and altitude. While the sub-Himalayan range exhibits deciduous forests, the vegetation graduates to temperate forests, conifers and tundra in the Higher Himalayan range, before giving way to a permanent snow line in the topmost regions. The far eastern Himalaya also have evergreen rainforests.

The Indian states of Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Sikkim and Arunachal Pradesh lie mostly in the Himalayas.

Origins and growth

Main article: Geology of the Himalaya

The Himalaya are among the youngest mountain ranges on the planet. According to the modern theory of plate tectonics, their formation is a result of a continental collision or orogeny along the convergent boundary between the Indo-Australian Plate and the Eurasian Plate. The collision began in the Upper Cretaceous period about 70 million years ago, when the north-moving Indo-Australian Plate, moving at about 15 cm/year, collided with the Eurasian Plate. By about 25 million years ago this fast moving Indo-Australian plate had completely closed the Tethys Ocean, whose existence has been determined by sedimentary rocks settled on the ocean floor and the volcanoes that fringed its edges. Since these sediments were light, they crumpled into mountain ranges rather than sinking to the floor. The Indo-Australian plate continues to be driven horizontally below the Tibetan plateau, which forces the plateau to move upwards. The Arakan Yoma highlands in Myanmar and the Andaman and Nicobar Islands in the Bay of Bengal were also formed as a result of this collision.

The Indo-Australian plate is still moving at about 2 cm/year, and over the next 10 million years it will travel more than 180 km into Tibet. This leads to the Himalaya rising by about 5 mm/year, making them geologically active. The movement of the Indian plate into the Asian plate also makes this region seismically active, leading to earthquakes from time to time.

Glaciers and river systems

The Himalayan range encompasses a very large number of glaciers, notable among which is the Siachen glacier, the largest in the world outside the polar region. Some of the other more famous glaciers include the Gangotri and Yamunotri (Uttaranchal), Nubra, Biafo and Baltoro (Karakoram region), Zemu (Sikkim) and Khumbu glaciers (Mount Everest region).

The higher regions of the Himalaya are snowbound throughout the year in spite of their proximity to the tropics, and they form the sources for several large perennial rivers, most of which combine into two large river systems:

• The western rivers combine into the Indus Basin, of which the Indus River is the largest. The Indus begins in Tibet at the confluence of Sengge and Gar rivers and flows southwest through Pakistan to the Arabian Sea. It is fed by the Jhelum, the Chenab, the Ravi, the Beas, and the Sutlej rivers, among others.
• Most of the other Himalayan rivers drain the Ganga-Brahmaputra Basin. Its two main rivers are the Ganges and the Brahmaputra. The Ganga originates as the Bhagirathi from the Gangotri glacier and flows southeast through the plains of northern India, fed by the Alaknanda and the Yamuna among other tributaries. The Brahmaputra originates as the Tsangpo in western Tibet, and flows east through Tibet and west through the plains of Assam. The Ganga and the Brahmaputra meet in Bangladesh, and drain into the Bay of Bengal through the world's largest river delta.

The eastern-most Himalayan rivers feed the Irrawaddy, which originates in eastern Tibet and flows south through Myanmar to drain into the Andaman Sea.

The Salween, Mekong, the Chang Jiang and the Huang He all originate from parts of the Tibetan plateau that are geologically distinct from the Himalaya mountains, and are therefore not considered true Himalayan rivers. Some geologists refer to all the rivers collectively as the circum-Himalayan rivers ^{[1] (http://www.cosis.net/abstracts/EAE03/13617/EAE03-J-13617.pdf)}.

Lakes

The Himalaya region is dotted with hundreds of lakes. Most lakes are found at altitudes of less than 5,000 m, with the size of the lakes diminishing with altitude. The largest lake is the Pangong t'so, which is spread across the border between India and Tibet. It is situated at an altitude of 4,600 m, and is 8 km wide and nearly 134 km long. The highest lake is the Gurudogmar in North Sikkim 5,370 m (17,600 feet).

The mountain lakes are known as tarns if they are caused by glacial activity. Tarns are found mostly in the upper reaches of the Himalaya, above 5,500 metres.

Impact on climate

The Himalaya has a profound effect on the climate of the Indian subcontinent and the Tibetan plateau. It prevents frigid, dry Arctic winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents. It also forms a barrier for the monsoon winds, keeping them from traveling northwards, and causing heavy rainfall in the Terai region. The Himalaya are also believed to play an important part in the formation of Central Asian deserts such as the Taklamakan and Gobi deserts.

Due to the mountain ranges, the western disturbances which appear from Iran during winter are prevented from travelling any further, resulting in snow in Kashmir and rainfall for parts of Punjab and northern India. Despite being a barrier to the cold northernly winter winds, the Brahmaputra valley receives part of the frigid winds, thus lowering the temperature in the northeast Indian states and Bangladesh. These winds also cause the North East monsoon during this season for these parts.

Mountain passes

The rugged terrain means there are few routes over the Himalaya.

• Gangtok in Sikkim to Lhasa in Tibet via the Nathula Pass and Jelepla Passes (offshoots of the ancient Silk Route).
• Bhadgaon in Nepal to Nyalam in Tibet.
• Rohtang Pass in Himachal Pradesh, India
• The road from Srinigar in Kashmir via Leh to Tibet is now less used because of the troubles in the region.

Impact on politics and culture

The Himalaya, due to its large size and expanse, has been a natural barrier to the movement of people for a long time. In particular, this has prevented intermingling of people from the Indian subcontinent with people from China and Mongolia, causing significantly different languages and customs between these regions. The Himalaya has also hindered trade routes and prevented military expeditions across its expanse. For instance, Genghis Khan could not expand his empire south of the Himalayas into the subcontinent.

Himal

Himal is Nepalese for "range" and is used to name the various regions of the Himalaya. In Nepal, these are as follows:

• Annapurna Himal
• Ganesh Himal
• Khumbu Himal
• Langtang Himal
• Manang Himal
• Rolwaling Himal

Notable peaks

Religion and mythology

Several places in the Himalaya are of religious significance in Hinduism and Buddhism. In Hinduism, the Himalaya have also been personified as the god Himavat, the father of Shiva's consort, Parvati.

• Haridwar, the place where the river Ganges enters the plains.
• Badrinath, a temple dedicated to Vishnu.
• Kedarnath, where one of the 12 Jyothirlingas is located.
• Deoprayag, where the Alaknanda and Bhagirathi merge to form the Ganges.
• Rishikesh, has a temple of Lakshmana.
• Mount Kailash, a 6,718 m high peak which is considered to be the abode of the Hindu god Shiva and is also venerated by Buddhists. Lake Manasarowar lies at the base of Mount Kailash, and is the source of the Brahmaputra.
• Amarnath, has a natural Shivalinga of ice which forms for a few weeks each year. Thousands of people visit this cave during these few weeks.
• A number of Tibetan Buddhist sites are situated in the Himalaya, including the residence of the Dalai Lama.
• The Yeti is one of the most famous creatures in cryptozoology. It is a large primate-like creature that is supposed to live in the Himalaya. Most mainstream scientists and experts consider current evidence of the Yeti's existence unpersuasive, and the result of hoaxes, legend or misidentification of mundane creatures.
• Shambhala is a mystical city in Buddhism with various legends associated with it. While some legends consider it to be a real city where secret Buddhist doctrines are being preserved, other legends believe that the city does not physically exist and can only be reached in the mental realm.

Himalaya in fiction

• Shangri-La is a fictional utopia situated somewhere in the Himalaya, based on the legendary Shambhala. It is described in the novel Lost Horizon, written by the British writer James Hilton in 1933.
• The Hollywood movie Vertical Limit (2000), is set in the K2 peak of the Himalaya.

Further reading

• Michael Palin, Himalaya, Weidenfeld Nicolson Illustrated (2004) [ISBN 0297843710]
• John Hunt, Ascent of Everest, Hodder & Stoughton (1956) [ISBN 0898863619]
• Everest, the IMAX movie (1998), [ISBN 0788814931]

External links

• The making of the Himalaya and major tectonic subdivisions (http://comp1.geol.unibas.ch/zanskar/CHAPITRE2/page23.html)
• Geology of the Himalayan mountains (http://jan.ucc.nau.edu/~wittke/Tibet/Himalaya.html)
• Birth of the Himalaya (http://www.pbs.org/wgbh/nova/everest/earth/birth.html)
• Some notes on the formation of the Himalaya (http://snobear.colorado.edu/Markw/Mountains/03/week11.html)