Himalayas
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"Himalaya" redirects here. For other uses, see Himalaya (disambiguation).
| Himalayas | |
| Range | |
 The north face of Mount Everest as seen from the path to the base camp in Tibet Autonomous Region,People's Republic of China. | |
| Countries |  Bhutan,  People's Republic of China,  India,  Nepal,  Pakistan,  Burma,  Afghanistan |
|---|---|
| Highest point | Mount Everest |
| - elevation | 8,848 m (29,029 ft) |
| - coordinates | 27°59′17″N 86°55′31″E |
The Himalaya Range (Sanskrit: literally, "abode of snow", Sanskrit: Devanagari: हिमालय, IPA: /hɪˈmɑːləj(ə)/), the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau. By extension, it is also the name of a massive mountain system that includes the Karakoram, the Hindu Kush, and other, lesser, ranges that extend out from the Pamir Knot.
Together, the Himalayan mountain system is the planet's highest, and home to the world's highest peaks, the Eight-thousanders, which include Mount Everest and K2. To comprehend the enormous scale of this mountain range, consider that Aconcagua, in the Andes, at 6,962 metres (22,841 ft) is the highest peak outside Asia, whereas the Himalayan system includes over 100 mountains exceeding 7,200 m (23,622 ft).[1]
Some of the world's major rivers, the Ganges, Indus,Brahmaputra, Yangtze, Mekong, Salween, Red River (Asia), Xunjiang, Chao Phraya, Irrawaddy River, Amu Darya, Syr Darya, Tarim River and Yellow River, rise in the Himalayas, and their combined drainage basin is home to some 3 billion people (almost half of Earth's population) in Afghanistan, Bangladesh, Bhutan, People's Republic of China, India, Nepal,Burma, Cambodia, Tajikistan, Uzbekistan, Turkmenistan, Kazakhstan, Kyrgyzstan, Thailand, Laos,Vietnam, Malaysia and Pakistan.
The Himalayas have profoundly shaped the cultures of South Asia; many Himalayan peaks are sacred in Hinduism, Buddhism and Sikhism. The main Himalaya range runs west to east, from the Indus river valley to the Brahmaputra river valley, forming an arc 2,400 km (1,491 mi) long, which varies in width from 400 km (249 mi) in the western Kashmir-Xinjiang region to 150 km (93 mi) in the easternTibet-Arunachal Pradesh region. The range consists of three coextensive sub-ranges, with the northernmost, and highest, known as the Great or Inner Himalayas.
Ecology
The flora and fauna of the Himalayas vary with climate, rainfall, altitude, and soils. The climate ranges from tropical at the base of the mountains to permanent ice and snow at the highest elevations. The amount of yearly rainfall increases from west to east along the front of the range. This diversity of climate, altitude, rainfall and soil conditions generates a variety of distinct plant and animal communities.
Lowland forests
On the Indo-Gangetic plain at the base of the mountains, an alluvial plain drained by the Indus and Ganges-Brahmaputra river systems, vegetation varies from west to east with rainfall. The xericNorthwestern thorn scrub forests occupy the plains of Pakistan and the Indian Punjab. Further east lie the Upper Gangetic plains moist deciduous forests of Uttarakhand and Uttar Pradesh and Lower Gangetic plains moist deciduous forests of Bihar and West Bengal. These are monsoon forests, with drought-deciduous trees that lose their leaves during the dry season. The moister Brahmaputra Valley semi-evergreen forests occupy the plains of Assam.
The Terai belt
Above the alluvial plain lies the Terai strip, a seasonally marshy zone of sand and clay soils. The Terai has higher rainfall than the plains, and the downward-rushing rivers of the Himalaya slow down and spread out in the flatter Terai zone, depositing fertile silt during the monsoon season and receding in the dry season. The Terai has a high water table due to groundwater percolating down from the adjacent zone. The central part of the Terai belt is occupied by the Terai-Duar savanna and grasslands, a mosaic of grasslands, savannas, deciduous and evergreen forests that includes some of the world's tallest grasslands. The grasslands of the Terai belt are home to the Indian rhinoceros(Rhinoceros unicornis).
Bhabhar belt
Above the Terai belt is an upland zone known as the Bhabhar, a zone of porous and rocky soils made up of debris washed down from the higher ranges. The Bhabhar and the lower Shiwalik ranges have a subtropical climate. The Himalayan subtropical pine forests occupy the western end of the subtropical belt, with forests dominated by Chir Pine (Pinus roxburghii). The central part of the range is home to the Himalayan subtropical broadleaf forests, dominated by the sal tree (Shorea robusta). They are at the foot of the Himalayas where the Himalayan streams descend on to the plains.
Shiwalik Hills
Also called Churia or Margalla Hills, Sivalik Hills is an intermittent outermost range of foothills extending across the Himalayan region through Pakistan, India, Nepal and Bhutan. This region consists of many sub-ranges. Summits are generally 600 to 1,200 metres (2,000 to 3,900 ft). Steeper southern slopes form along a fault zone called Himalayan Frontal Thrust (HFT); northern slopes are gentler. Permeable conglomerates and other rocks allow rainwater to percolate downslope into the Bhabhar and Terai, supporting only scrubby forests upslope. The Himalayan subtropical pine and broadleaf forests continue here.
Inner Terai or Dun Valleys
The Inner Terai valleys are open valleys north of Shiwalik Hills or nestled between Shiwalik subranges. Examples include Dehra Dun in India and Chitwan in Nepal. Himalayan subtropical broadleaf forests grow here.
Lesser Himalaya
Also called Mahabharat Range, the Lesser Himalayas is a prominent range 2,000 to 3,000 metres (6,600 to 9,800 ft) high formed along the Main Boundary Thrust fault zone, with a steep southern face and gentler northern slopes. They are nearly continuous except for river gorges, where rivers from to the north gather like candelabra in a handful of places to break through the range.
At these elevations and above the biogeography of the Himalayas is generally divided by the Kali Gandaki Gorge in central Nepal, one of the deepest canyons in the world.
At the middle elevations of the range, the subtropical forests yield to a belt of temperate broadleaf and mixed forests growing between 1,500 and 3,000 metres (4,900 and 9,800 ft), with the western Himalayan broadleaf forests to the west of the Gandaki River, and the eastern Himalayan broadleaf forests to the east. The western broadleaf forests stretch from the Kashmir Valley, across Himachal Pradesh and Uttarakhand, and through western Nepal. The eastern broadleaf forests stretch across eastern Nepal, through Sikkim and Bhutan, and through much of Arunachal Pradesh.
Midlands
This 'hilly' region (Pahad), averaging about 1,000 metres (3,300 ft) immediately north of the Mahabharat Range, rises over about 100 kilometres (330,000 ft) to about 4,000 metres (13,000 ft) at the Main Central Thrust fault zone, where the Greater Himalaya begin.
Above the broadleaf forests, between 3,000 and 4,000 metres (9,800 and 13,000 ft), are temperate coniferous forests, likewise split by the Gandaki River. The western Himalayan subalpine conifer forests are found below treeline in northern Pakistan, Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and western Nepal. The eastern Himalayan subalpine conifer forests are found in eastern Nepal, Sikkim, Bhutan, and Arunachal Pradesh. Along the border between Arunachal Pradesh and Tibet, the eastern subalpine conifer forests mix with the northeastern Himalayan subalpine conifer forests. East Himalayan Fir, West Himalayan Spruce, and Himalayan Hemlock are some important trees of these forests. Rhododendrons are exceptionally diverse here, with over 60 species recorded in the northeastern Himalayan subalpine conifer forests.
Greater Himalaya
North of the Main Central Thrust, the highest ranges rise abruptly as much as 4,000 metres (13,000 ft) into the realm of perpetual snow and ice. As the Himalayan system becomes wider from east to west, the number of parallel high ranges increases. For example, the Kagmara and Kanjiroba ranges both reach well over 6,000 metres (20,000 ft) north of the Dhaulagiri Himalaya in central Nepal.
Montane grasslands and shrublands grow above treeline. The northwestern Himalayan alpine shrub and meadows are found in the high elevations of northern Pakistan, Jammu and Kashmir, and Himachal Pradesh. To the east, the western Himalayan alpine shrub and meadows cover extensive areas along the Tibetan border with Uttarakhand and western Nepal. The eastern Himalayan alpine shrub and meadows grow above the eastern and northeastern subalpine conifer forests, along the Tibetan border with eastern Nepal, Sikkim, Bhutan, and Arunachal Pradesh. The shrublands are composed of junipers as well as a wide variety of rhododendrons. They also possess a remarkable variety of wildflowers: Valley of Flowers National Park in the western Himalayan alpine shrub and meadows contains hundreds of species. The upper limit of the grasslands increases from west to east, rising from 3,500 metres (11,500 ft) to 5,500 metres (18,000 ft). The grasslands are the summer habitat of the endangered snow leopard (Uncia uncia).
Trans-Himalaya
The watershed between rivers flowing south into the Ganges or Indus and rivers flowing north into the Brahmaputra or mainstem Indus that flow around the ends of the entire range often follows somewhat lower, less rugged mountains tens of kilometers north of the highest ranges. South-flowing rivers form valleys in this region, often semi-arid due to rainshadow effects. These valleys hold some of the highest permanent villages on earth.
Origins and growth
Main article: Geology of the Himalaya
The Himalayas are among the youngest mountain ranges on the planet and consist mostly of uplifted sedimentaryand metamorphic rock. According to the modern theory ofplate 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. This is referred to as a fold mountain.
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 per year, collided with theEurasian Plate. About 50 million years ago, this fast moving Indo-Australian plate had completely closed theTethys Ocean, the existence of which has been determined by sedimentary rocks settled on the ocean floor, and thevolcanoes 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 Yomahighlands 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 67 mm per year, and over the next 10 million years it will travel about 1,500 km into Asia. About 20 mm per year of the India-Asia convergence is absorbed by thrustingalong the Himalaya southern front. This leads to the Himalayas rising by about 5 mm per year, making them geologically active. The movement of the Indian plate into the Asian plate also makes this regionseismically active, leading to earthquakes from time to time.
Glaciers and river systems
The Himalayan range encompasses about 15,000 glaciers, which store about 12,000 km3 of freshwater. The 70 km-long Siachen Glacier at the India-Pakistan border is the second longest glacier in the world outside the polar region. Some of the other more famous glaciers include the Gangotri andYamunotri (Uttarakhand), Nubra, Biafo and Baltoro (Karakoram region), Zemu (Sikkim) and Khumbuglaciers (Mount Everest region).
The higher regions of the Himalayas 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 India and then 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 Ganges-Brahmaputra Basin. Its two main rivers are theGanges and the Brahmaputra and the Yamuna, among other tributaries. The Brahmaputra originates as the Yarlung Tsangpo River in western Tibet, and flows east through Tibet and west through the plains of Assam. The Ganges and the Brahmaputra meet in Bangladesh, and drain into the Bay of Bengal through the world's largest river delta.[2]
The eastern-most Himalayan rivers feed the Ayeyarwady River, which originates in eastern Tibet and flows south through Myanmar to drain into the Andaman Sea.
The Salween, Mekong, Yangtze and the Huang He (Yellow River) 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.[3] In recent years, scientists have monitored a notable increase in the rate of glacier retreatacross the region as a result of global climate change.[4] Although the effect of this will not be known for many years, it potentially could mean disaster for the hundreds of millions of people who rely on the glaciers to feed the rivers of northern India during the dry seasons.[5]
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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.Pangong Tso, which is spread across the border between India and China, and Yamdrok Tso, located in central Tibet, are amongst the largest with a surface area of (700 km²), respectively (638 km²). Other notable lakes include Gurudogmar lake in North Sikkim, Tsongmo lake, near the Indo-China border in Sikkim, and Tilicho lake in Nepal in the Annapurna massif.
The mountain lakes are known to geographers astarns if they are caused by glacial activity. Tarns are found mostly in the upper reaches of the Himalaya, above 5,500 metres.[6]
Impact on climate
The Himalayas have a profound effect on the climateof the Indian subcontinent and the Tibetan plateau. They prevent frigid, dry Arctic winds 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 themonsoon winds, keeping them from traveling northwards, and causing heavy rainfall in the Terairegion. The Himalayas are also believed to play an important part in the formation of Central Asiandeserts, such as the Taklamakan and Gobi.
The mountain ranges also prevent western winter disturbances in Iran from traveling further, resulting in snow in Kashmir and rainfall for parts of Punjaband 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 North East India and Bangladesh.
The Himalayas, which are often called "The Roof of the World", contain the greatest area of glaciers and permafrost outside of the poles. Ten of Asia’s largest rivers flow from here, and more than a billion people’s livelihoods depend on them. To complicate matters, temperatures are rising more rapidly here than the global average. In Nepal, the temperature has risen 0.6 degree C over the last decade, whereas the global warming has been around 0.7 degree C over the last hundred years.[7]
Mountain passes
The rugged terrain makes few routes through the mountains possible. Some of these routes include:
- Banihal is an important pass connecting the hill areas of Jammu to the Kashmir Valley.
- Zoji La lies between the vale of Kashmir and theKargil district, and is the only Western entrance to the highlands of Ladakh.
- Rohtang Pass in Himachal Pradesh, India.
- Mohan Pass is the principal pass in the Siwalik Hills, the southern most and geologically youngest foothills running parallel to the main Himalayas in Sikkim.
- Kora La at 4,594 metres (15,072 ft) elevation on the Nepal-Tibet border at the upper end ofMustang. The Kali Gandaki Gorge (a graben),[citation needed] transects the main Himalaya and Transhimalayan ranges. Kora La is the lowest pass through both ranges between K2 and Everest, but some 300 metres (980 ft) higher than Nathula and Jelepla passes further east between Sikkim and Tibet.
- Arniko Rajmarg/Friendship Highway route from Kathmandu, Nepal crossing into Tibet at Kodari/Zhangmu, to Nyalam, Lalung-La pass (5,050m/16,570'), Tingri, Xêgar, Lakpa La pass (5,250m/17,225'), to Lhatse on the Yarlung Tsangpo/Brahmaputra River about 460 road kilometers west of Lhasa.
- Gangtok in Sikkim to Lhasa in Tibet, via the Nathula Pass and Jelepla Passes (offshoots of the ancient Silk Road).
Impact on politics and culture
It should be noted that almost half of the humans andlivestock of India live on one-third of the landscape within 500 km of the Himalayan range.[citation needed]
The Himalayas, due to their large size and expanse, have been a natural barrier to the movement of people for tens of thousands of years. 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 Himalayas have 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.
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