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132-542: The Intermontane Trench was an ancient oceanic trench during the Triassic . The trench was probably 600 to 800 miles (970 to 1,290 km) long, parallel to the west coast of North America . The ocean that the trench was located in was called the Slide Mountain Ocean . This palaeogeography article is a stub . You can help Misplaced Pages by expanding it . Oceanic trench Oceanic trenches are

264-476: A volcanic arc . Much of the fluid trapped in sediments of the subducting slab returns to the surface at the oceanic trench, producing mud volcanoes and cold seeps . These support unique biomes based on chemotrophic microorganisms. There is concern that plastic debris is accumulating in trenches and threatening these communities. There are approximately 50,000 km (31,000 mi) of convergent plate margins worldwide. These are mostly located around

396-457: A difference in buoyancy. An increase in retrograde trench migration (slab rollback) (2–4 cm/yr) is a result of flattened slabs at the 660-km discontinuity where the slab does not penetrate into the lower mantle. This is the case for the Japan, Java and Izu–Bonin trenches. These flattened slabs are only temporarily arrested in the transition zone. The subsequent displacement into the lower mantle

528-607: A feature of the Earth's distinctive plate tectonics . They mark the locations of convergent plate boundaries , along which lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. Oceanic lithosphere moves into trenches at a global rate of about 3 km (1.2 sq mi) per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to and about 200 km (120 mi) from

660-426: A high angle of repose. Over half of all convergent margins are erosive margins. Accretionary margins, such as the southern Peru-Chile, Cascadia, and Aleutians, are associated with moderately to heavily sedimented trenches. As the slab subducts, sediments are "bulldozed" onto the edge of the overriding plate, producing an accretionary wedge or accretionary prism . This builds the overriding plate outwards. Because

792-516: A location is dependent on the season, orientation and bearing with respect to the Sun , and the mass of the mountain. As the Sun is the major contributor to the temperature, it is often directly proportional to the received radiation from the Sun with faces receiving more sunlight having a higher heat buildup. In narrow valleys between steep mountain faces, the weather conditions may differ significantly on both

924-495: A notable increase in the rate of glacier retreat across the region as a result of climate change. The rate of retreat varies across regions depending on the local conditions. Since 1975, a marked increase in the loss of glacial mass from 5–13 Gt/yr to 16–24 Gt/yr has been observed with an estimated 13% overall decrease in glacial coverage in the Himalayas. The resulting climate variations and changes in hydrology could affect

1056-475: A prominent elongated depression of the sea bottom, was first used by Johnstone in his 1923 textbook An Introduction to Oceanography . During the 1920s and 1930s, Felix Andries Vening Meinesz measured gravity over trenches using a newly developed gravimeter that could measure gravity from aboard a submarine. He proposed the tectogene hypothesis to explain the belts of negative gravity anomalies that were found near island arcs. According to this hypothesis,

1188-528: A zone of continental collision. Features analogous to trenches are associated with collision zones . One such feature is the peripheral foreland basin , a sediment-filled foredeep . Examples of peripheral foreland basins include the floodplains of the Ganges River and the Tigris-Euphrates river system . Trenches were not clearly defined until the late 1940s and 1950s. The bathymetry of

1320-824: Is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau . The range has several peaks exceeding an elevation of 8,000 m (26,000 ft) including Mount Everest , the highest mountain on Earth. The mountain range runs for 2,400 km (1,500 mi) as an arc from west-northwest to east-southeast at the northern end of the Indian subcontinent. The Himalayas occupy an area of 595,000 km (230,000 sq mi) across six countries – Afghanistan , Bhutan , China , India , Nepal , and Pakistan . The sovereignty of

1452-716: Is also the source of major streams of the Ganges river system. The Eastern Himalayas form the eastern most stretch of the range and consist of the states of parts of Tibet in China, Sikkim , Assam , Arunachal Pradesh , parts of other North East Indian states and north West Bengal in India, entirety of Bhutan, mountain regions of central and eastern Nepal, and most of the western lowlands in Nepal. The eastern Himalayas broadly consists of two regions–the western Nepal Himalayas and

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1584-518: Is among the highest in the world, at typically around 5,500 m (18,000 ft) while several equatorial mountains such as in New Guinea , the Rwenzoris , and Colombia , have a snow line at 900 m (3,000 ft) lower. As the physical features of mountains are irregular, with broken jagged contours, there can be wide variations in temperature over short distances. The temperature at

1716-479: Is amongst the most affected regions due to climate change . Since the late 20th century, scientists have reported a notable increase in the rate of glacier retreat and changes occurring at a far rapid rate. As per a 2019 assessment, the Himalayan region, which had experienced a temperature rise of 0.1 °C (32.2 °F) per decade was warming at an increased rate of 0.1 °C (32.2 °F) per decade over

1848-476: Is caused by slab pull forces, or the destabilization of the slab from warming and broadening due to thermal diffusion. Slabs that penetrate directly into the lower mantle result in slower slab rollback rates (~1–3 cm/yr) such as the Mariana arc, Tonga arcs. As sediments are subducted at the bottom of trenches, much of their fluid content is expelled and moves back along the subduction décollement to emerge on

1980-422: Is complex, with many thrust ridges. These compete with canyon formation by rivers draining into the trench. Inner trench slopes of erosive margins rarely show thrust ridges. Accretionary prisms grow in two ways. The first is by frontal accretion, in which sediments are scraped off the downgoing plate and emplaced at the front of the accretionary prism. As the accretionary wedge grows, older sediments further from

2112-416: Is determined by the angle of repose of the overriding plate edge. This reflects frequent earthquakes along the trench that prevent oversteepening of the inner slope. As the subducting plate approaches the trench, it bends slightly upwards before beginning its plunge into the depths. As a result, the outer trench slope is bounded by an outer trench high . This is subtle, often only tens of meters high, and

2244-489: Is explained by a change in the density of the subducting plate, such as the arrival of buoyant lithosphere (a continent, arc, ridge, or plateau), a change in the subduction dynamics, or a change in the plate kinematics. The age of the subducting plates does not have any effect on slab rollback. Nearby continental collisions have an effect on slab rollback. Continental collisions induce mantle flow and extrusion of mantle material, which causes stretching and arc-trench rollback. In

2376-492: Is followed by monsoon rains from June to September. The post monsoon season is largely devoid of rain and snow before beginning of cold winters in December-January with intermediate spring before the summer. There are localised wind pressure systems at high altitudes resulting in heavy winds. Due to its high altitude, the range blocks the flow of cold winds from the north into the Indian subcontinent. This causes

2508-603: Is found in the mixed deciduous and conifer forests of the Eastern Himalayas and the Himalayan water shrew are found on the river banks. The forests of the foothills are inhabited by several different primates, including the endangered Gee's golden langur and the Kashmir gray langur , within highly restricted ranges in the east and west of the Himalayas, respectively. The yaks are large domesticated cattle found in

2640-422: Is fully exposed on the ocean bottom. The central Chile segment of the trench is moderately sedimented, with sediments onlapping onto pelagic sediments or ocean basement of the subducting slab, but the trench morphology is still clearly discernible. The southern Chile segment of the trench is fully sedimented, to the point where the outer rise and slope are no longer discernible. Other fully sedimented trenches include

2772-560: Is home to more than a billion people. In 2011, the population in the Himalayan region was estimated to be about 52.8 million with the combined drainage basin of the Himalayan rivers home to nearly 600 million. Of this, 7.96 million (15.1% of the total Himalayan population) live in Eastern Himalayas, 19.22 million in Central Himalayas (36.4%), and 25.59 million reside in Western Himalayas (48.5%). The population of

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2904-614: Is one of the youngest mountain ranges on the planet and consists of uplifted sedimentary and metamorphic rock . According to the modern theory of plate tectonics , it was formed as a result of a continental collision and orogeny along the convergent boundary between the India and Eurasian Plates . During the Jurassic period (201 to 145 mya ), the Tethys Ocean formed the southern border of then existent Eurasian landmass. When

3036-484: Is recorded as tectonic mélanges and duplex structures. Frequent megathrust earthquakes modify the inner slope of the trench by triggering massive landslides. These leave semicircular landslide scarps with slopes of up to 20 degrees on the headwalls and sidewalls. Subduction of seamounts and aseismic ridges into the trench may increase aseismic creep and reduce the severity of earthquakes. Contrariwise, subduction of large amounts of sediments may allow ruptures along

3168-580: Is the lower middle sub-section of the Himalayas. It extends almost along the entire length of the Himalayas and is about 75 km (47 mi) wide. It is mostly composed of rocky surfaces and has an average elevation of 3,700–4,500 m (12,100–14,800 ft). The Greater Himalayas (also known as Himadri ) form the highest section of the Himalayas and extend for about 2,300 km (1,400 mi) from northern Pakistan to northern Arunachal Pradesh in India. The sub-range has an average elevation of more than 6,100 m (20,000 ft) and contains many of

3300-412: Is typically located a few tens of kilometers from the trench axis. On the outer slope itself, where the plate begins to bend downwards into the trench, the upper part of the subducting slab is broken by bending faults that give the outer trench slope a horst and graben topography. The formation of these bending faults is suppressed where oceanic ridges or large seamounts are subducting into the trench, but

3432-515: Is what generates slab rollback. When the deep slab section obstructs the down-going motion of the shallow slab section, slab rollback occurs. The subducting slab undergoes backward sinking due to the negative buoyancy forces causing a retrogradation of the trench hinge along the surface. Upwelling of the mantle around the slab can create favorable conditions for the formation of a back-arc basin. Seismic tomography provides evidence for slab rollback. Results demonstrate high temperature anomalies within

3564-755: The Andaman Sea . The Salween , Mekong , Yangtze , and Yellow Rivers all originate from parts of the Tibetan Plateau, north of the great water divide. These are considered distinct from the Himalayan watershed and are known as circum-Himalayan rivers. The Himalayan region has multiple lakes across various elevations including endorheic freshwater and saline lakes . The geology of the lakes vary across geographies depending on various factors such as altitude, climate, water source, and lithology . Tarns are high altitude mountain lakes situated above 5,500 m (18,000 ft) and are formed primarily by

3696-567: The Bay of Bengal were also formed as a result of the same tectonic processes that formed the Himalayas. The Indian plate continues to be driven horizontally at the Tibetan Plateau at about 67 mm (2.6 in) per year, forcing it to continue to move upwards. About 20 mm (0.79 in) per year is absorbed by thrusting along the Himalaya southern front , which leads to the Himalayas rising by about 5 mm (0.20 in) per year. This makes

3828-663: The Dihang River to the India-Tibet border. The highest peak is the eastern anchor Namcha Barwa at 7,756 m (25,446 ft). The region is the source of many of the tributaries of the Brahmaputra River and consists of major mountain passes such as Nathu La , and Jelep La . Beyond the Dihang valley, the mountains extend as Purvanchal mountain range across the eastern boundary of India. The Himalayan range

3960-490: The Everest . At lower altitudes, the temperature is pleasantly warm during the summers. During winters, the low-pressure weather systems from the west cause heavy snowfall . There are two periods of precipitation with most of the rainfall occurring during the post summer season and moderate amount during the winter storms. The Himalayan range obstructs the path of the south west monsoon winds, causing heavy precipitation on

4092-761: The Indian epic Mahabharata , which is the personification of the Hindu deity Himavan . The mountain range is known as Himālaya in Hindi and Nepali (both written हिमालय ), Himalaya ( ཧི་མ་ལ་ཡ་ ) in Tibetan , Himāliya ( سلسلہ کوہ ہمالیہ ) in Urdu , Himaloy ( হিমালয় ) in Bengali , and Ximalaya ( simplified Chinese : 喜马拉雅 ; traditional Chinese : 喜馬拉雅 ; pinyin : Xǐmǎlāyǎ ) in Chinese . It

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4224-520: The Indian subcontinent and the regions north of the range. The mountains are spread across more than eight degrees of latitude and hence includes a wide range of climatic zones including sub-tropical , temperate , and semi-arid . The climate in a region is determined by factors such as altitude, latitude, and the impact on monsoon. There are generally five seasons: summer, monsoon, autumn or post-monsoon, winter, and spring. The summer in April-May

4356-602: The Kashmir valley . The higher elevations consist of rock fragements and lithosols with very low humus content. The Himalayas and the Central Asian mountain ranges consist of the third-largest deposit of ice and snow in the world, after the Antarctic and Arctic regions. It is often referred to as the "Third Pole" as it encompasses about 15,000 glaciers, which store about 12,000 km (2,900 cu mi) of fresh water. The South Col and Khumbu Glacier in

4488-516: The Kumaon region. The northern extremes of the Great Himalayas in Kashmir and Ladakh receive only 3–6 in (76–152 mm) of rainfall per year. During the winter season, a high pressure system develops over Central Asia, which results in winds flowing towards the Himalayas. However, due to the presence of less water bodies in the Central Asian region, the moisture content is low. As

4620-1272: The Main Frontal Thrust and the Main Boundary Thrust (MBT); the Lesser Himalayan Zone between the MBT and the Main Central Thrust (MCT); the Higher Himalayan Zone beyond the MCT; the Tethyan Zone, separated by the South Tibetan Detachment System; and the Indus-Tsangpo Suture Zone, where the Indian plate is subducted below the Asian plate. The Arakan Yoma highlands in Myanmar and the Andaman and Nicobar Islands in

4752-481: The Mount Everest region are amongst the world's highest glaciers. The Gangotri which is 32 km (20 mi) long and is one of the largest glaciers, is one of the sources of the Ganges . The Himalayan glaciers show considerable variation in the rate of descent. The Khumbu moves about 1 ft (0.30 m) daily compared to certain other glaciers which move about 6 ft (1.8 m) per day. During

4884-454: The Paris agreement , aimed at climate change mitigation and adaptation . The actions are aimed at reducing emissions , increase the usage of renewable energy , and sustainable environmental practices. As the local population increasingly experience the impact of the changes in climate such as variations in temperature and precipitation, and change in vegetation, they are forced to adapt for

5016-738: The Sivalik Hills on the south; the Lower Himalayas ; the Great Himalayas , which is the highest and central range; and the Tibetan Himalayas on the north. The Sivalik Hills form the lowest sub-Himalayan range and extends for about 1,600 km (990 mi) from the Teesta River in the Indian state of Sikkim to northern Pakistan. The name derives from Sanskrit meaning "Belonging to Shiva ", which

5148-542: The Western Himalayas has characteristics of species from Central Asia and Mediterranean region. Fossils of species such as giraffe , and hippopotamus have been found in the foothills, suggesting the presence of African species some time ago. Large mammals such as Indian elephant , and Indian rhinoceros are confined to the densely forested moist ecosystems in the Eastern and Central Himalayas. Many of

5280-473: The Yarlung Tsangpo River . The Himalayas consists of four parallel mountain ranges: the Sivalik Hills on the south; the Lower Himalayas ; the Great Himalayas , which is the highest and central range; and the Tibetan Himalayas on the north. The range varies in width from 350 km (220 mi) in the north-west to 150 km (93 mi) in the south-east. The Himalayan range is one of

5412-517: The Zanskar , Pir Panjal Ranges , and parts of the Sivalik and Great Himalayas. The western anchor Nanga Parbat is the highest point in the region at 8,126 m (26,660 ft). It is also referred Punjab, Kashmir or Himachal Himalyas from west to east locally. The central Himalayas or Kumaon extend for about 320 km (200 mi) along the state of Uttarakhand in northern India from

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5544-631: The last ice age , there was a connected ice stream of glaciers between Kangchenjunga in the east and Nanga Parbat in the west. The glaciers joined with the ice stream network in the Karakoram in the west, the Tibetan inland ice in the north, and came to an end below an elevation of 1,000–2,000 m (3,300–6,600 ft) in the south. While the current valley glaciers of the Himalaya reach at most 20–32 km (12–20 mi) in length, several of

5676-444: The shear stresses at the base of the overriding plate. As slab rollback velocities increase, circular mantle flow velocities also increase, accelerating extension rates. Extension rates are altered when the slab interacts with the discontinuities within the mantle at 410 km and 660 km depth. Slabs can either penetrate directly into the lower mantle , or can be retarded due to the phase transition at 660 km depth creating

5808-410: The 18th century till the independence of the constituent states in the mid 20th century. The long history along with various outside influences have resulted in the mixture of various traditions and existence of wide range of ethnicity in the region. People speak various languages belonging to four principal language families– Indo-European , Tibeto-Burman , Austroasiatic , and Dravidian , with

5940-572: The 1960 descent of the Bathyscaphe Trieste to the bottom of the Challenger Deep. Following Robert S. Dietz ' and Harry Hess ' promulgation of the seafloor spreading hypothesis in the early 1960s and the plate tectonic revolution in the late 1960s, the oceanic trench became an important concept in plate tectonic theory. Oceanic trenches are 50 to 100 kilometers (30 to 60 mi) wide and have an asymmetric V-shape, with

6072-470: The Aleutian trench. In addition to sedimentation from rivers draining into a trench, sedimentation also takes place from landslides on the tectonically steepened inner slope, often driven by megathrust earthquakes . The Reloca Slide of the central Chile trench is an example of this process. Convergent margins are classified as erosive or accretionary, and this has a strong influence on the morphology of

6204-635: The Brahmaputra river system from the Tibetan rivers to the north. There are 19 major rivers in the Himalayas which form part of the two major river systems of Ganges - Brahmaputra , which follow an easterly course and Indus , which follows a north-westerly course. The northern slopes of Gyala Peri and the peaks beyond the Tsangpo drain into the Irrawaddy River , which originates in eastern Tibet and flows south through Myanmar to drain into

6336-626: The Cascadia subduction zone. Sedimentation is largely controlled by whether the trench is near a continental sediment source. The range of sedimentation is well illustrated by the Chilean trench. The north Chile portion of the trench, which lies along the Atacama Desert with its very slow rate of weathering, is sediment-starved, with from 20 to a few hundred meters of sediments on the trench floor. The tectonic morphology of this trench segment

6468-534: The Cayman Trough, which is a pull-apart basin within a transform fault zone, is not an oceanic trench. Trenches, along with volcanic arcs and Wadati–Benioff zones (zones of earthquakes under a volcanic arc) are diagnostic of convergent plate boundaries and their deeper manifestations, subduction zones . Here, two tectonic plates are drifting into each other at a rate of a few millimeters to over 10 centimeters (4 in) per year. At least one of

6600-412: The Earth. The trench asymmetry reflects the different physical mechanisms that determine the inner and outer slope angle. The outer slope angle of the trench is determined by the bending radius of the subducting slab, as determined by its elastic thickness. Since oceanic lithosphere thickens with age, the outer slope angle is ultimately determined by the age of the subducting slab. The inner slope angle

6732-420: The Himalayan lakes present the danger of a glacial lake outburst flood as they have grown considerably over the last 50 years due to glacial melting. While these lakes support a range of ecosystems and local communities, many of them remain poorly studied in terms of their hydrology and biodiversity. Due to its location and size, the Himalayas acts as a climatic barrier which affects the weather conditions of

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6864-413: The Himalayan region geologically active and the movement of the Indian plate into the Asian plate makes the region seismically active, leading to earthquakes from time to time. The northern slopes of the Himalayas have a thicker soil cover than the southern slopes due to presence of lesser number of rivers and streams. These soils are loamy and are dark brown in colour, and are covered with forests in

6996-591: The Himalayan region including Bhutan, Nepal, Bangladesh, India, and Pakistan are amongst the most vulnerable countries in the Global South due to climate change. The temperature rise increases the incidence of tropical diseases such as malaria , and dengue further north. The extreme weather events might cause physical harm directly and indirectly due to lack of access and contamination of drinking water , pollution , exposure to chemicals, and destruction of crops, and drought . The climate change also impact

7128-630: The Himalayan region occurred in 2000 BCE when Aryans came from Central Asia and progressively settled along the plains to the south. Information on the Aryan culture in the region is found in Hindu literature such as the Vedas , and Puranas . Since the second century BCE, the Silk Road in China was connected to the Indian subcontinent by various routes running along the Himalayan region. The northern side of

7260-433: The Himalayan waters. The extremes of high altitude favor the presence of extremophile organisms, which include various species of insects such as spiders , and mites . The Himalayan fauna include endemic plants and animals and critically endangered or endangered species such as Indian elephant, Indian rhinoceros, musk deer and hangul . There are more than 7,000 endemic plants and 1.9% of global endemic vertebrates in

7392-426: The Himalayas has grown considerably over the last five decades from 19.9 million in 1961 with the annual growth rate (3.31%) more than three times higher than the world average (1.1%) during the same period. The earliest tribes in the Himalayas might have originated from Dravidian people from the south of the Indian subcontinent as evidenced by the presence of Dravidian languages . The major human migration towards

7524-447: The Himalayas reduce by 2 °C (36 °F) for every 300 m (980 ft) increase of altitude. Higher altitudes invariably experience low temperatures. In the Eastern Himalayas, Darjeeling at an altitude of 1,945 m (6,381 ft) has an average minimum temperature of 11 °C (52 °F) during the month of May, while the same has been recorded as −22 °C (−8 °F) at an altitude of 5,000 m (16,000 ft) on

7656-583: The Himalayas was under the influence of various Tibetan kingdoms across history. In the middle ages , the southern side came under the influence of various Rajput kings and later under the Mughal rule . Nepal was ruled by various kingdoms from both the Indian and Tibetan regions, until it was conquered by the Gurkha kingdom in the early 18th century. Most of the southern region came under the British influence in

7788-839: The Indian Himalayas. Pangong Lake spread across India and China is the highest saline lake in the world at an altitude of 4,350 m (14,270 ft) and amongst the largest in the region with a surface area of 700 km (270 sq mi). Spread across 189 km (73 sq mi), Wular Lake is amongst the largest fresh water lakes in Asia. Other large lakes include Tso Moriri , and Tso Kar in Ladakh , Nilnag , and Tarsar Lake , in Jammu and Kashmir , Gurudongmar , Chholhamu , and Tsomgo Lakes in Sikkim , Tilicho , Rara , Phoksundo , and Gokyo Lakes in Nepal. Some of

7920-533: The Makran Trough, where sediments are up to 7.5 kilometers (4.7 mi) thick; the Cascadia subduction zone, which is completed buried by 3 to 4 kilometers (1.9 to 2.5 mi) of sediments; and the northernmost Sumatra subduction zone, which is buried under 6 kilometers (3.7 mi) of sediments. Sediments are sometimes transported along the axis of an oceanic trench. The central Chile trench experiences transport of sediments from source fans along an axial channel. Similar transport of sediments has been documented in

8052-493: The Pacific Ocean, but are also found in the eastern Indian Ocean , with a few shorter convergent margin segments in other parts of the Indian Ocean, in the Atlantic Ocean, and in the Mediterranean. They are found on the oceanward side of island arcs and Andean-type orogens . Globally, there are over 50 major ocean trenches covering an area of 1.9 million km or about 0.5% of the oceans. Trenches are geomorphologically distinct from troughs . Troughs are elongated depressions of

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8184-487: The Sutlej River in the east to the Kali River in the west. The region comprises parts of Sivalik and Great Himalayas. At lower elevations below 2,400 m (7,900 ft), the region has a temperate climate and consists of permanent settlements. At elevations higher than 4,300 m (14,100 ft), permanent snow caps cover the Great Himalayas with the highest peaks being Nanda Devi at 7,817 m (25,646 ft) and Kamet at 7,756 m (25,446 ft). The region

8316-411: The Tethys ocean. The upliftment of the Himalayas occurred gradually and as the Great Himalayas became higher, they became a climatic barrier and blocked the winds, which resulted in lesser precipitation on the upper slopes. The lower slopes continued to be eroded by the rivers, which flowed in the gaps between the mountains and the folded lower Shivalik Hills and the Lesser Himalayas were formed due to

8448-419: The Tibetan Himalayas and the plateau beyond. It also played a role in the formation of Central Asian deserts such as the Taklamakan and Gobi . The monsoon is triggered by the different rates of heating and cooling between the Indian Ocean and Central Asia, which create large differences in the atmospheric pressure prevailing above each. As the Central Asian landmass heats up during the summer compared to

8580-534: The Western Himalayas. The high altitude mountainous areas are mostly barren or, at the most, sparsely sprinkled with stunted bushes. The Himalayas are home to various medicinal plants such as Abies pindrow used to treat bronchitis , Andrachne cordifolia used for snake bites , and Callicarpa arborea used for skin diseases . Nearly a fifth of the plant species in the Himalayas are used for medicinal purposes. Climate change , illegal deforestation , and introduction of non native species have had an effect on

8712-455: The animal species found in the region are unique and endemic or nearly endemic to the region. Other large animal species found in the Himalayas include Asiatic black bear , clouded leopard , and herbivores such as bharal , Himalayan tahr , takin , Himalayan serow , Himalayan musk deer , and Himalayan goral . Animals found at higher altitudes include brown bear , and the elusive snow leopard , which mainly feed on bharal. The red panda

8844-411: The area of the Southeast Pacific, there have been several rollback events resulting in the formation of numerous back-arc basins. Interactions with the mantle discontinuities play a significant role in slab rollback. Stagnation at the 660-km discontinuity causes retrograde slab motion due to the suction forces acting at the surface. Slab rollback induces mantle return flow, which causes extension from

8976-405: The belts were zones of downwelling of light crustal rock arising from subcrustal convection currents. The tectogene hypothesis was further developed by Griggs in 1939, using an analogue model based on a pair of rotating drums. Harry Hammond Hess substantially revised the theory based on his geological analysis. World War II in the Pacific led to great improvements of bathymetry, particularly in

9108-425: The bend of the Indus River along the Pakistan-Afghanistan border region in the north-west to the Satlej river basin in India in the south-east. Most of the region lies in the Kashmir territory disputed between India and Pakistan with certain portions of the Indian state of Himachal Pradesh . The Indus forms the division between the Western Himalayas and the Karakoram range to the north. The Western Himalayas include

9240-433: The bending faults cut right across smaller seamounts. Where the subducting slab is only thinly veneered with sediments, the outer slope will often show seafloor spreading ridges oblique to the horst and graben ridges. Trench morphology is strongly modified by the amount of sedimentation in the trench. This varies from practically no sedimentation, as in the Tonga-Kermadec trench, to completely filled with sediments, as with

9372-510: The cold winds from Central Asia , and plays a significant roles in influencing the monsoons . The vast size, varying altitude range, and complex topography of the Himalayas result in a wide range of climates, from humid and subtropical to cold and dry desert conditions. The mountains have profoundly shaped the cultures of South Asia and Tibet . Many Himalayan peaks are considered sacred across various Indian and Tibetan religions such as Hinduism , Buddhism , Jainism , and Bon . Hence,

9504-453: The condensation occurs at higher altitudes in the north, there is more precipitation in the Great Himalayas in the west during the winter rains and the precipitation reduces towards the east. In January, the Kumaon region receives about 3 in (76 mm) of rainfall compared to about 1 in (25 mm) in the Eastern Himalayas. The Himalayan region has a highly sensitive ecosystem and

9636-475: The downwarping of the intermediate lands. Minor streams ran between the faults within the mountains until they joined the major river systems in the plains. Intermediate valleys such as Kashmir and Kathmandu were formed from temporary lakes that were formed during pleistocene , which dried up later. The Himalayan region is made up of five geological zones– the Sub-Himalayan Zone bound by

9768-508: The eastern Assam Himalayas. The Nepal Himalayas forms the centre of the Himalayan curve and extend for 800 km (500 mi) between the Kali and Teesta Rivers . The Great Himalayas in the region form the highest part of the entire Himalayas and consist of many of the eight-thousanders including Everest, Kanchenjunga at 8,586 m (28,169 ft), and Makalu at 8,463 m (27,766 ft). These mountains host large glaciers that form

9900-495: The ecosystem. At higher altitudes, Eastern and Western Himalayan subalpine conifer forests consisting of various conifers occur. Chir pine is the dominant species which occurs at elevations from 800–900 m (2,600–3,000 ft). Other species include Deodar cedar , which grows at altitudes of 1,900–2,700 m (6,200–8,900 ft), blue pine and morinda spruce between 2,200–3,000 m (7,200–9,800 ft). At higher altitudes, alpine shrubs and meadows occur above

10032-426: The existence of back-arc basins . Forces perpendicular to the slab (the portion of the subducting plate within the mantle) are responsible for steepening of the slab and, ultimately, the movement of the hinge and trench at the surface. These forces arise from the negative buoyancy of the slab with respect to the mantle modified by the geometry of the slab itself. The extension in the overriding plate, in response to

10164-417: The flora and fauna of the region. Changes might decrease the territory available for local wildlife and reduction in prey for the predators . This puts the animals in conflict with humans as humans might encroach animal territories and the animals might venture into human habitats for search of food, which might exacerbate the economic loss of the local population. The Himalayan nations are signatories of

10296-521: The flora of the range. The increase in temperature has resulted in shifting of various species to higher elevations, and early flowering and fruiting. Many of the animal species are from the tropics, which have adapted to the various conditions across the Himalayan range. Some of the species of the Eastern Himalayas are similar to those found in East and South East Asia , while the animals of

10428-405: The formation of the Tibetan plateau . During miocene (20 mya), the increasing collision between the plates resulted in the top layer of metamorphic rocks getting peeled, which moved southwards to form nappes with trenches in between. As the mountains received rainfall, the waters flowing down the mountains eroded and steepened the southern slopes. The silt deposited by these rivers and streams in

10560-690: The fundamental plate-tectonic structure is still an oceanic trench. Some troughs look similar to oceanic trenches but possess other tectonic structures. One example is the Lesser Antilles Trough, which is the forearc basin of the Lesser Antilles subduction zone . Also not a trench is the New Caledonia trough, which is an extensional sedimentary basin related to the Tonga-Kermadec subduction zone . Additionally,

10692-462: The inner slope as mud volcanoes and cold seeps . Methane clathrates and gas hydrates also accumulate in the inner slope, and there is concern that their breakdown could contribute to global warming . The fluids released at mud volcanoes and cold seeps are rich in methane and hydrogen sulfide , providing chemical energy for chemotrophic microorganisms that form the base of a unique trench biome . Cold seep communities have been identified in

10824-431: The inner slope of the trench. Erosive margins, such as the northern Peru-Chile, Tonga-Kermadec, and Mariana trenches, correspond to sediment-starved trenches. The subducting slab erodes material from the lower part of the overriding slab, reducing its volume. The edge of the slab experiences subsidence and steepening, with normal faulting. The slope is underlain by relative strong igneous and metamorphic rock, which maintains

10956-514: The inner trench slopes of the western Pacific (especially Japan ), South America, Barbados, the Mediterranean, Makran, and the Sunda trench. These are found at depths as great as 6,000 meters (20,000 ft). The genome of the extremophile Deinococcus from Challenger Deep has sequenced for its ecological insights and potential industrial uses. Because trenches are the lowest points in

11088-456: The last ice age , and give rise to some of the world's major rivers such as the Indus , Ganges , and Tsangpo – Brahmaputra . Their combined drainage basin is home to nearly 600 million people including 52.8 million living in the vicinity of the Himalayas. The region is also home to many endorheic lakes. The Himalayas have a major impact on the climate of the Indian subcontinent. It blocks

11220-458: The livelihoods of the people in the Himalayas and the plains below. Despite its greater size, the Himalayas does not form a water divide across its span because of the multiple river systems that cut across the range. While the mountains were formed gradually, the rivers concurrently cut across deeper gorges ranging from 1,500–5,000 m (4,900–16,400 ft) in depth and 10–50 km (6.2–31.1 mi) in width. The actual water divide lies to

11352-590: The lower ranges on the southern slopes speak Indo-European languages. The inhabitants of the Western Himalayas include the Kashmiri people , who speak Kashmiri in the Vale of Kashmir and the Gujjar and Gaddi people , who speak Gujari and Gaddi respectively in the lower altitudes of Jammu and Himachal Pradesh in India. The last two are pastoral and nomadic people, who own flocks of cattle and migrate across

11484-468: The lowlands and grassland meadows in the mid altitudes. The composition and texture of the soils in the Himalayas also vary across regions. In the Eastern Himalayas , the wet soils has a high humus content conducive for growing tea . Podzolic soils occur in the eastern range of the Indus basin between the Indus and Shyok Rivers . The Ladakh region is generally dry with saline soil while fertile alluvial soils occur in select river valleys such as

11616-419: The main valley glaciers were 60–112 km (37–70 mi) long during the ice age. The glacier snowline (the altitude where accumulation and ablation of a glacier are balanced) was about 1,400–1,660 m (4,590–5,450 ft) lower than it is today. Thus, the climate would have been at least 7.0–8.3 °C (12.6–14.9 °F) colder than it is today. Since the late 20th century, scientists have reported

11748-477: The majority of the languages belonging to the first two categories. The Tibetan Himalayas are inhabited by Tibetan people , who speak Tibeto-Burman languages. The Great Himalayas are mostly inhabited by nomadic groups and tribes, with most of the population in Lesser Himalayas , and Shivalik Hills . People towards the Great Himalayas in the north parts mostly speak Tibeto-Burman, while populations in

11880-411: The mantle suggesting subducted material is present in the mantle. Ophiolites are viewed as evidence for such mechanisms as high pressure and temperature rocks are rapidly brought to the surface through the processes of slab rollback, which provides space for the exhumation of ophiolites . Slab rollback is not always a continuous process suggesting an episodic nature. The episodic nature of the rollback

12012-404: The margins. The mountains act as heat islands and heavier mountains absorb and retain more heat than the surroundings, and therefore influences the amount of heat needed to raise the temperature from the winter minimum to the summer maximum. However, soil temperatures mostly remain the same on both the sides of a mountain at altitudes higher than 4,500 m (14,800 ft). Temperatures in

12144-530: The north of the Himalayas with rivers flowing down both the sides of the mountains. Some of the major river systems and their drainage system outdate the formation of the mountains itself. The water divide is formed by the Karakoram and Hindu Kush ranges on the west and the Ladakh Range on the east, separating the Indus system from Central Asia. On the east, Kailas and Nyenchen Tanglha Mountains separate

12276-678: The northwest, which extend into Central Asia . Its western anchor Nanga Parbat lies south of the northernmost bend of the Indus river in Pakistan-administered Kashmir and its eastern anchor Namcha Barwa lies to the west of the great eastern bend of the Yarlung Tsangpo River in Tibet Autonomous Region of China . The Himalayas occupies an area of 595,000 km (230,000 sq mi) across six countries – Afghanistan , Bhutan , China, India , Nepal , and Pakistan . The sovereignty of

12408-436: The number of glacial lakes , some of which may be prone to dangerous floods. The region is expected to encounter continued increase in average annual temperature and 81% of the region's permafrost is projected to be lost by the end of the century. The increased warming and melting of snow is projected to accelerate the regional river flows until 2060 after which it would decline due to reduction in ice caps and glacier mass. As

12540-403: The ocean below, the difference in pressure creates a thermal low . The moist air from the ocean is pushed inwards towards the low pressure system causing the monsoon winds. It results in precipitation along the slopes due to the orographic effect as the air rises along the mountains and condenses. The monsoon begins at the end of May in the eastern fringes of the range and moves upwards towards

12672-544: The ocean floor, there is concern that plastic debris may accumulate in trenches and endanger the fragile trench biomes. Recent measurements, where the salinity and temperature of the water was measured throughout the dive, have uncertainties of about 15 m (49 ft). Older measurements may be off by hundreds of meters. (*) The five deepest trenches in the world Himalayas The Himalayas , or Himalaya ( / ˌ h ɪ m ə ˈ l eɪ . ə , h ɪ ˈ m ɑː l ə j ə / HIM -ə- LAY -ə, hih- MAH -lə-yə )

12804-593: The ocean was poorly known prior to the Challenger expedition of 1872–1876, which took 492 soundings of the deep ocean. At station #225, the expedition discovered Challenger Deep , now known to be the southern end of the Mariana Trench . The laying of transatlantic telegraph cables on the seafloor between the continents during the late 19th and early 20th centuries provided further motivation for improved bathymetry. The term trench , in its modern sense of

12936-415: The overriding plate exerts a force against the subducting plate (FTS). The slab pull force (FSP) is caused by the negative buoyancy of the plate driving the plate to greater depths. The resisting force from the surrounding mantle opposes the slab pull forces. Interactions with the 660-km discontinuity cause a deflection due to the buoyancy at the phase transition (F660). The unique interplay of these forces

13068-477: The past half a century. The average warm days and nights had also increased by 1.2 days and 1.7 nights per decade while the average cold days and nights had declined by 0.5 and 1 respectively. This has also prolonged the length of the growing season by 4.25 days per decade. The climate change might results in erratic rainfall, varying temperatures, and natural disasters like landslides , and floods . The increasing glacier melt had been followed by an increase in

13200-512: The plates is oceanic lithosphere , which plunges under the other plate to be recycled in the Earth's mantle . Trenches are related to, but distinct from, continental collision zones, such as the Himalayas . Unlike in trenches, in continental collision zones continental crust enters a subduction zone. When buoyant continental crust enters a trench, subduction comes to a halt and the area becomes

13332-603: The precipitation is projected to increase concurrently, the annual river flows would be largely unaffected for the Eastern Himalayan rivers fed by monsoons, but would reduce the flows in the Western Himalayan rivers. Almost a billion people live on either side of the mountain and are prone to impact of the climate change. This includes the people who live in the mountains, who are more vulnerable due to temperature variations and other biota. Countries in

13464-469: The range in the Kashmir region is disputed among India, Pakistan, and China. It is bordered by the Karakoram and Hindu Kush ranges on the northwest, Tibetan Plateau in the north, and by the Indo-Gangetic Plain in the south. Its western anchor Nanga Parbat lies south of the northernmost bend of the Indus river and its eastern anchor Namcha Barwa lies to the west of the great bend of

13596-517: The range in the Kashmir region is disputed amongst India, Pakistan, and China. The range varies in width from 350 km (220 mi) in the north-west to 150 km (93 mi) in the south-east. The range has several peaks exceeding an elevation of 8,000 m (26,000 ft) including Mount Everest , the highest mountain on Earth at 8,848 m (29,029 ft). The Himalayas consist of four parallel mountain ranges from south to north:

13728-1034: The region  tropical and subtropical , temperate , coniferous , and grasslands . Tropical and subtropical broadleaf forests are mostly constricted to the high temperature and humid regions in Eastern and Central Himalayas , and pockets of Kashmir in the west. There are about 4,000 species of Angiosperms with major vegetation include Dipterocarpus , and Ceylon ironwood on porous soils at elevations below 2,400 m (7,900 ft) and oak , and Indian horse chestnut on lithosol between 1,100–1,700 m (3,600–5,600 ft). Himalayan subtropical pine forests with Himalayan screw pine trees occur above 4,000 m (13,000 ft) and Alder , and bamboo are found on terrains with higher gradient. Temperate forest occur at altitudes between 1,400–3,400 m (4,600–11,200 ft) while moving from south-east to north-west towards higher latitude. Eastern and Western Himalayan broadleaf forests consisting of sal trees dominate

13860-777: The region. More than 800 species of birds have been recorded with a large number of species restricted to the Eastern Himalayas. Amongst the bird species found include magpies such as black-rumped magpie and blue magpie , titmice , choughs , whistling thrushes , and redstarts . Raptors include bearded vulture , black-eared kite , and Himalayan griffon . Snow partridge and Cornish chough are found at altitudes above 5,700 m (18,700 ft). The Himalayan lakes also serve as breeding grounds for species such as black-necked crane and bar-headed goose . There are multiple species of reptiles including Japalura lizards, blind snakes , and insects such as butterflies . Several fresh water fish such as Glyptothorax are found in

13992-500: The region. As of 2022 , there are 575 protected areas established by the nations in the Himalayan-Hindu Kush region, which account for 40% of the land area and 8.5% of the global protected area. There are also four biodiversity hotspots , 12 ecoregions , 348 key biodiversity areas, and six UNESCO World Heritage Sites in the region. The Himalayan region with the associated Indo-Gangetic Plain and Tibetan plateau

14124-494: The same. The Himalayan region belongs to the Indomalayan realm . The flora and fauna of the Himalayas vary broadly across regions depending on the climate and geology. The Himalayas are home to multiple biodiversity hotspots, and is home to an estimated 35,000+ species of plants and 200+ species of animals. An average of 35 new species have been found every year since 1998. There are four types of vegetation found in

14256-593: The same. This has led to increased awareness on the impact of climate change, and adaptations such as change in crop cycles , introduction of drought resistant crops, and plantation of new trees. This has also led to the construction of more dams , canals , and other water structures, to prevent flooding and aid in agriculture. New plantations on barren lands to prevent landslides, and construction of fire lines made of litter and mud to prevent forest fires have been undertaken. However, lack of funding, awareness, access to technology, and government policy are barriers for

14388-525: The sea floor with steep sides and flat bottoms, while trenches are characterized by a V-shaped profile. Trenches that are partially infilled are sometimes described as troughs, for example the Makran Trough. Some trenches are completely buried and lack bathymetric expression as in the Cascadia subduction zone , which is completely filled with sediments. Despite their appearance, in these instances

14520-416: The sediments lack strength, their angle of repose is gentler than the rock making up the inner slope of erosive margin trenches. The inner slope is underlain by imbricated thrust sheets of sediments. The inner slope topography is roughened by localized mass wasting . Cascadia has practically no bathymetric expression of the outer rise and trench, due to complete sediment filling, but the inner trench slope

14652-413: The slopes and the plains below. The effect of Himalayas on the hydroclimate impacts millions in the plains as the variability in monsoon rainfall is the main factor behind wet and dry years. As the Himalayas force the monsoon winds to give up most of the moisture before ascending up, the winds became dry once its reaches the north of the mountains. This results in the dry and windy cold desert climate in

14784-451: The slopes based on seasons. Various ethnic people such as Ladakhi , Balti , and Dard live on the north of the Great Himalayas along the Indus basin in the Kashmir and Ladakh regions spread across India, Pakistan, and China. The Dard speak Dard , which is part of Indo-European languages, while the Balti and Lakadkhi people speak Balti , and Ladakhi , which are part of Tibeto-Burman. In

14916-417: The snow-melt of the glaciers. The lower altitude lakes are replenished by a combination of rains, underground springs, and streams. Large lakes in the Himalayan basin were formed in the holocene period, when water pooled in the faults and the water supply was subsequently cut off. There are more than 4500 high altitude lakes of which about 12 large lakes contribute to more than 75% of the total lake area in

15048-409: The source of various rivers of the Ganges - Brahmaputra river system. The high altitude regions are uninhabitable with few mountain passes inbetween that serve as crossovers with the human settlements in the lower valleys. The Assam Himalaya forms the eastern most sub-section that extends eastward for 720 km (450 mi) from the Indian state of Sikkim through Bhutan and north-east India past

15180-444: The steeper slope (8 to 20 degrees) on the inner (overriding) side of the trench and the gentler slope (around 5 degrees) on the outer (subducting) side of the trench. The bottom of the trench marks the boundary between the subducting and overriding plates, known as the basal plate boundary shear or the subduction décollement . The depth of the trench depends on the starting depth of the oceanic lithosphere as it begins its plunge into

15312-477: The subducting oceanic lithosphere is much younger, the depth of the Peru-Chile trench is around 7 to 8 kilometers (4.3 to 5.0 mi). Though narrow, oceanic trenches are remarkably long and continuous, forming the largest linear depressions on earth. An individual trench can be thousands of kilometers long. Most trenches are convex towards the subducting slab, which is attributed to the spherical geometry of

15444-416: The subduction décollement to propagate for great distances to produce megathrust earthquakes. Trenches seem positionally stable over time, but scientists believe that some trenches—particularly those associated with subduction zones where two oceanic plates converge—move backward into the subducting plate. This is called trench rollback or hinge retreat (also hinge rollback ) and is one explanation for

15576-399: The subsequent subhorizontal mantle flow from the displacement of the slab, can result in formation of a back-arc basin. Several forces are involved in the process of slab rollback. Two forces acting against each other at the interface of the two subducting plates exert forces against one another. The subducting plate exerts a bending force (FPB) that supplies pressure during subduction, while

15708-525: The summits of several peaks in the region such as Gangkhar Puensum , Machapuchare , and Kailash have been off-limits to climbers. The name of the range is derived from the Sanskrit word Himālay ( हिमालय ) meaning 'abode of snow'. It is a combination of the words him ( हिम ) meaning 'frost/cold' and ālay ( आलय ) meaning 'dwelling/house'. The name of the range is mentioned as Himavat ( Sanskrit : हिमवत्) in older literature such as

15840-584: The super-continent Gondwana broke up nearly 180 mya, the Indo-Australian plate slowly drifted northwards towards Eurasia for 130-140 million years. The Indian Plate broke up with the Australian Plate about 100 mya. The Tethys ocean constricted as the Indian plate moved gradually upward. As both the plates were made of continental crusts , which were less denser than oceanic crusts , the increased compressive forces resulted in folding of

15972-612: The trees. The Eastern Himalayan alpine shrub and meadows extend between 3,200–4,200 m (10,500–13,800 ft) and the Western Himalayan alpine shrub and meadows occur at altitudes of 3,600–4,500 m (11,800–14,800 ft). Major vegetation include Juniperus , Rhododendron on rocky terrain facing the Sun, various flowering plants at high elevations, and mosses , and lichens in humid, shaded areas. Interspersed Grasslands occur at certain regions, with thorns and semi-desert vegetation at low precipitation areas in

16104-455: The trench become increasingly lithified , and faults and other structural features are steepened by rotation towards the trench. The other mechanism for accretionary prism growth is underplating (also known as basal accretion ) of subducted sediments, together with some oceanic crust , along the shallow parts of the subduction decollement. The Franciscan Group of California is interpreted as an ancient accretionary prism in which underplating

16236-513: The trench, the angle at which the slab plunges, and the amount of sedimentation in the trench. Both starting depth and subduction angle are greater for older oceanic lithosphere, which is reflected in the deep trenches of the western Pacific. Here the bottoms of the Marianas and the Tonga–Kermadec trenches are up to 10–11 kilometers (6.2–6.8 mi) below sea level. In the eastern Pacific, where

16368-592: The tropical zone to extend farther north in South Asia than anywhere else in the world. The temperatures are more pronounced in the Brahmaputra valley in the eastern section as it lies at a lower latitude and due to the latent heat of the forced air from the Bay of Bengal which condenses before moving past the Namcha Barwa , the eastern anchor of the Himalayas. Due to this, the permanent snow line

16500-543: The trough between the Himalayas and the Deccan plateau formed the Indo-Gangetic Plain . About 0.6 mya in the pleistocene period, the Himalayas rose higher and became the highest mountains on Earth. In the northern Great Himalayas , new gneiss and granite formations emerged on crystalline rocks that gave rise to the higher peaks. The summit of Mount Everest is made of unmetamorphosed marine ordovician limestone with fossil trilobites , crinoids , and ostracods from

16632-542: The underlying rock bed. The thrust faults created between the folds resulted in granite and basalt rocks from the Earth's mantle protruding through the crust . During the paleogene period (about 50 mya), the Indian plate collided with the Eurasian plate after it completely closed the Tethys ocean gap. The Indian plate continued to subduct under the Eurasian plate over the next 30 million years that resulted in

16764-460: The west in June and July. There is heavy precipitation in the east which reduces progressively towards the west as the air becomes drier. Cherrapunji in Eastern Himalayas is one of the wettest places on Earth with an annual precipitation of 428 in (10,900 mm). The average annual rainfall varies from 120 in (3,000 mm) in the Eastern Himalayas to about 120 in (3,000 mm) in

16896-429: The western Pacific. In light of these new measurements, the linear nature of the deeps became clear. There was a rapid growth of deep sea research efforts, especially the widespread use of echosounders in the 1950s and 1960s. These efforts confirmed the morphological utility of the term "trench." Important trenches were identified, sampled, and mapped via sonar. The early phase of trench exploration reached its peak with

17028-481: The world's tallest peaks, including Everest. It is mainly composed of granite rocks. The Tibetan Himalayas (also known as Tethys ) form the northern most sub-range of the Himalayas in Tibet . Longitudinally, the range is broadly divided into three regions– western , central , and eastern . The Western Himalayas form the westernmost section of the range and extend for about 560 km (350 mi) from

17160-524: The youngest mountain ranges on Earth and is made up of uplifted sedimentary and metamorphic rocks. It was formed more than 10 mya due to the subduction of the Indian tectonic plate with the Eurasian Plate along the convergent boundary . Due to the continuous movement of the Indian plate, the Himalayas keep rising every year, making them geologically and seismically active. The mountains consist of large glaciers , which are remnants of

17292-475: Was mentioned as Himmaleh in western literature such as Emily Dickinson 's poetry and Henry David Thoreau 's essays. The Himalayas run as an arc for 2,400 km (1,500 mi) from west-northwest to east-southeast at the northern end of the Indian subcontinent , separating the Indo-Gangetic Plains from the Tibetan Plateau . It is bordered by the Karakoram and Hindu Kush ranges on

17424-534: Was originally used to denote the 320 km (200 mi) stretch from Haridwar to the Beas River . The range is about 16 km (9.9 mi) wide on average and the elevation ranges from 900–1,200 m (3,000–3,900 ft). It rises along the Indo-Gangetic Plain and is often separated from the higher northern sub-ranges by valleys. The eastern portion of the range is called Churia Range in Nepal. The Lower or Lesser Himalaya (also known as Himachal )

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