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45-454: Mountain ranges are usually segmented by highlands or mountain passes and valleys . Individual mountains within the same mountain range do not necessarily have the same geologic structure or petrology . They may be a mix of different orogenic expressions and terranes , for example thrust sheets , uplifted blocks , fold mountains, and volcanic landforms resulting in a variety of rock types . Most geologically young mountain ranges on

90-402: A mountainous region, elevated mountainous plateau or high hills . Generally, upland refers to a range of hills, typically from 300 m (980 ft) up to 600 m (2,000 ft), while highland is usually reserved for ranges of low mountains . However, the two terms are interchangeable and also include regions that are transitional between hilly and mountainous terrain. Probably

135-424: A certain proportion of its mass below the surface of the water. If snow falls to the top of the iceberg, the iceberg will sink lower in the water. If a layer of ice melts off the top of the iceberg, the remaining iceberg will rise. Similarly, Earth's lithosphere "floats" in the asthenosphere. When continents collide, the continental crust may thicken at their edges in the collision. It is also very common for one of

180-425: A change in crust loading) provide information on the viscosity of the upper mantle. The basis of the model is Pascal's law , and particularly its consequence that, within a fluid in static equilibrium, the hydrostatic pressure is the same on every point at the same elevation (surface of hydrostatic compensation): h 1 ⋅ρ 1 = h 2 ⋅ρ 2 = h 3 ⋅ρ 3 = ... h n ⋅ρ n For the simplified picture shown,

225-528: A characteristic wave number As the rigid layer becomes weaker, κ {\displaystyle \kappa } approaches infinity, and the behavior approaches the pure hydrostatic balance of the Airy-Heiskanen hypothesis. The depth of compensation (also known as the compensation level , compensation depth , or level of compensation ) is the depth below which the pressure is identical across any horizontal surface. In stable regions, it lies in

270-425: A length of 65,000 kilometres (40,400 mi). The position of mountain ranges influences climate, such as rain or snow. When air masses move up and over mountains, the air cools, producing orographic precipitation (rain or snow). As the air descends on the leeward side, it warms again (following the adiabatic lapse rate ) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect

315-523: A local hydrostatic balance. A third hypothesis, lithospheric flexure , takes into account the rigidity of the Earth's outer shell, the lithosphere . Lithospheric flexure was first invoked in the late 19th century to explain the shorelines uplifted in Scandinavia following the melting of continental glaciers at the end of the last glaciation . It was likewise used by American geologist G. K. Gilbert to explain

360-490: A region, the land may rise to compensate. Therefore, as a mountain range is eroded, the (reduced) range rebounds upwards (to a certain extent) to be eroded further. Some of the rock strata now visible at the ground surface may have spent much of their history at great depths below the surface buried under other strata, to be eventually exposed as those other strata eroded away and the lower layers rebounded upwards. An analogy may be made with an iceberg , which always floats with

405-614: Is 8,848 metres (29,029 ft) high. Mountain ranges outside these two systems include the Arctic Cordillera , Appalachians , Great Dividing Range , East Siberians , Altais , Scandinavians , Qinling , Western Ghats , Vindhyas , Byrrangas , and the Annamite Range . If the definition of a mountain range is stretched to include underwater mountains, then the Ocean Ridge forms the longest continuous mountain system on Earth, with

450-524: Is defined as the Bouger anomaly minus the gravity anomaly due to the subsurface compensation, and is a measure of the local departure from isostatic equilibrium. At the center of a level plateau, it is approximately equal to the free air anomaly . Models such as deep dynamic isostasy (DDI) include such viscous forces and are applicable to a dynamic mantle and lithosphere. Measurements of the rate of isostatic rebound (the return to isostatic equilibrium following

495-685: Is often considered the world's longest mountain system. The Alpide belt stretches 15,000 km across southern Eurasia , from Java in Maritime Southeast Asia to the Iberian Peninsula in Western Europe , including the ranges of the Himalayas , Karakoram , Hindu Kush , Alborz , Caucasus , and the Alps . The Himalayas contain the highest mountains in the world, including Mount Everest , which

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540-592: Is the Central Highlands area, which covers most of the central-western parts of the state. Many of these areas are highly elevated alpine regions. The Ozarks cover nearly 120,000 square kilometres (46,000 sq mi), making it the most extensive highland region between the Appalachians and Rockies. This region contains some of the oldest rocks in North America. The spine of the mountains stretches across

585-445: Is the acceleration due to gravity, and P ( x ) {\displaystyle P(x)} is the load on the ocean crust. The parameter D is the flexural rigidity , defined as where E is Young's modulus , σ {\displaystyle \sigma } is Poisson's ratio , and T c {\displaystyle T_{c}} is the thickness of the lithosphere. Solutions to this equation have

630-470: The Baltic Sea and Hudson Bay . As the ice retreats, the load on the lithosphere and asthenosphere is reduced and they rebound back towards their equilibrium levels. In this way, it is possible to find former sea cliffs and associated wave-cut platforms hundreds of metres above present-day sea level . The rebound movements are so slow that the uplift caused by the ending of the last glacial period

675-470: The Hawaiian Islands . Although Earth is a dynamic system that responds to loads in many different ways, isostasy describes the important limiting case in which crust and mantle are in static equilibrium . Certain areas (such as the Himalayas and other convergent margins) are not in isostatic equilibrium and are not well described by isostatic models. The general term isostasy was coined in 1882 by

720-592: The Mithrim Montes and Doom Mons on Titan, and Tenzing Montes and Hillary Montes on Pluto. Some terrestrial planets other than Earth also exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars . Jupiter's moon Io has mountain ranges formed from tectonic processes including the Boösaule , Dorian, Hi'iaka and Euboea Montes . Highland Highlands or uplands are areas of high elevation such as

765-681: The Moon . Isostasy Isostasy (Greek ísos 'equal', stásis 'standstill') or isostatic equilibrium is the state of gravitational equilibrium between Earth 's crust (or lithosphere ) and mantle such that the crust "floats" at an elevation that depends on its thickness and density. This concept is invoked to explain how different topographic heights can exist at Earth's surface. Although originally defined in terms of continental crust and mantle, it has subsequently been interpreted in terms of lithosphere and asthenosphere , particularly with respect to oceanic island volcanoes , such as

810-638: The United States (notably Western North Carolina ), highveld , used in South Africa and Roof of the World , used for Tibet . The central Afghan highlands are in the center of Afghanistan , mostly located between 2,000 and 3,000 m above sea level. They have a very cold winter, and a short and cool summer. These highlands have mountain pastures during summer ( sardsīr ), watered by many small streams and rivers. There are also pastures available during winter in

855-510: The American geologist Clarence Dutton . In the 17th and 18th centuries, French geodesists (for example, Jean Picard ) attempted to determine the shape of the Earth (the geoid ) by measuring the length of a degree of latitude at different latitudes ( arc measurement ). A party working in Ecuador was aware that its plumb lines , used to determine the vertical direction, would be deflected by

900-725: The Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide belt . The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera , the Aleutian Range , on through Kamchatka Peninsula , Japan , Taiwan , the Philippines , Papua New Guinea , to New Zealand . The Andes is 7,000 kilometres (4,350 mi) long and

945-547: The Pratt hypothesis as overlying regions of unusually low density in the upper mantle. This reflects thermal expansion from the higher temperatures present under the ridges. In the Basin and Range Province of western North America, the isostatic anomaly is small except near the Pacific coast, indicating that the region is generally near isostatic equilibrium. However, the depth to the base of

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990-1083: The United Kingdom include the Southern Uplands in Scotland, the Pennines , North York Moors , Dartmoor and Exmoor in England , and the Cambrian Mountains in Wales . Many countries and regions also have areas referred to as highlands . These include parts of Afghanistan , Tibet , Ethiopia , Canada , Kenya , Eritrea , Yemen , Ghana , Nigeria , Papua New Guinea , Syria , Turkey and Cantabria . Similar terms used in other countries include high country , used in New Zealand , New South Wales , Victoria , Tasmania and Southern Queensland in Australia , and parts of

1035-403: The balancing of lithospheric columns gives: where ρ m {\displaystyle \rho _{m}} is the density of the mantle (ca. 3,300 kg m ), ρ c {\displaystyle \rho _{c}} is the density of the crust (ca. 2,750 kg m ) and ρ w {\displaystyle \rho _{w}} is the density of

1080-646: The best-known area officially or unofficially referred to as highlands in the Anglosphere is the Scottish Highlands in northern Scotland , the mountainous region north and west of the Highland Boundary Fault . The Highland council area is a local government area in the Scottish Highlands and Britain's largest local government area. Other highland or upland areas reaching 400 m or higher in

1125-418: The crust does not strongly correlate with the height of the terrain. This provides evidence (via the Pratt hypothesis) that the upper mantle in this region is inhomogeneous, with significant lateral variations in density. The formation of ice sheets can cause Earth's surface to sink. Conversely, isostatic post-glacial rebound is observed in areas once covered by ice sheets that have now melted, such as around

1170-448: The deep crust, but in active regions, it may lie below the base of the lithosphere. In the Pratt model, it is the depth below which all rock has the same density; above this depth, density is lower where topographic elevation is greater. When large amounts of sediment are deposited on a particular region, the immense weight of the new sediment may cause the crust below to sink. Similarly, when large amounts of material are eroded away from

1215-406: The deformation of the rigid crust. These elastic forces can transmit buoyant forces across a large region of deformation to a more concentrated load. Perfect isostatic equilibrium is possible only if mantle material is in rest. However, thermal convection is present in the mantle. This introduces viscous forces that are not accounted for the static theory of isostacy. The isostatic anomaly or IA

1260-411: The depth of the mountain belt roots (b 1 ) is calculated as follows: where ρ m {\displaystyle \rho _{m}} is the density of the mantle (ca. 3,300 kg m ) and ρ c {\displaystyle \rho _{c}} is the density of the crust (ca. 2,750 kg m ). Thus, generally: In the case of negative topography (a marine basin),

1305-629: The endemic vertebrates are restricted to this ecoregion. The highlands of Iceland cover about 40% of the country and are mostly inhospitable to humans. They are generally considered to be any land above 500 m. The mountainous natural region of the Thai highlands is found in Northern Thailand. The Cameron Highlands is a highland area and hill station in Northern Malaysia. Shillong in India in

1350-403: The flexural rigidity of the lithosphere approaches zero. For example, the vertical displacement z of a region of ocean crust would be described by the differential equation where ρ m {\displaystyle \rho _{m}} and ρ w {\displaystyle \rho _{w}} are the densities of the aesthenosphere and ocean water, g

1395-449: The gravitational attraction of the nearby Andes Mountains . However, the deflection was less than expected, which was attributed to the mountains having low-density roots that compensated for the mass of the mountains. In other words, the low-density mountain roots provided the buoyancy to support the weight of the mountains above the surrounding terrain. Similar observations in the 19th century by British surveyors in India showed that this

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1440-593: The island of New Guinea, forming the densely populated highlands of Papua New Guinea , and the Highland Papua , Indonesia . The Central Highlands of Sri Lanka are rain forests, where the elevation reaches 2,500 m (8,200 ft) above sea level. The Sri Lanka montane rain forests represent the montane and submontane moist forests above 1,000 m (3,300 ft) in the central highlands and in the Knuckles mountain range . Half of Sri Lanka's endemic flowering plants and 51 percent of

1485-451: The leeward side of a range. As a consequence, large mountain ranges, such as the Andes, compartmentalize continents into distinct climate regions . Mountain ranges are constantly subjected to erosional forces which work to tear them down. The basins adjacent to an eroding mountain range are then filled with sediments that are buried and turned into sedimentary rock . Erosion is at work while

1530-536: The mountains are being uplifted until the mountains are reduced to low hills and plains. The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet (3,000 m) of mostly Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east. This mass of rock

1575-563: The neighboring warm lowlands ( garmsīr ), which makes the region ideal for seasonal transhumance . The highlands in Australia are often above the elevation of 500 m. These areas often receive snowfall in winter. Most of the highlands lead up to large alpine or sub-alpine mountainous regions such as the Australian Alps , Snowy Mountains , Great Dividing Range , Northern Tablelands and Blue Mountains . The most mountainous region of Tasmania

1620-474: The plates to be underthrust beneath the other plate. The result is that the crust in the collision zone becomes as much as 80 kilometers (50 mi) thick, versus 40 kilometers (25 mi) for average continental crust. As noted above , the Airy hypothesis predicts that the resulting mountain roots will be about five times deeper than the height of the mountains, or 32 km versus 8 km. In other words, most of

1665-568: The rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System, including the Moon , are often isolated and formed mainly by processes such as impacts, though there are examples of mountain ranges (or "Montes") somewhat similar to those on Earth. Saturn 's moon Titan and Pluto , in particular, exhibit large mountain ranges in chains composed mainly of ices rather than rock. Examples include

1710-525: The state of Meghalaya is a hill station that is surrounded by highlands. Officers of the British Raj referred to Shillong as "The Scotland of the East". Highland continents —or terrae —are areas of topographically unstable terrain , with high peaks and valleys. They resemble highlands on Earth , but the term is applied to much larger areas on other planets. They can be found on Mercury , Venus , Mars , and

1755-434: The thickened crust moves downwards rather than up, just as most of an iceberg is below the surface of the water. However, convergent plate margins are tectonically highly active, and their surface features are partially supported by dynamic horizontal stresses, so that they are not in complete isostatic equilibrium. These regions show the highest isostatic anomalies on the Earth's surface. Mid-ocean ridges are explained by

1800-408: The thickness of the crust. This hypothesis was suggested to explain how large topographic loads such as seamounts (e.g. Hawaiian Islands ) could be compensated by regional rather than local displacement of the lithosphere. This is the more general solution for lithospheric flexure , as it approaches the locally compensated models above as the load becomes much larger than a flexural wavelength or

1845-556: The uplifted shorelines of Lake Bonneville . The concept was further developed in the 1950s by the Dutch geodesist Vening Meinesz . Three principal models of isostasy are used: Airy and Pratt isostasy are statements of buoyancy, but flexural isostasy is a statement of buoyancy when deflecting a sheet of finite elastic strength. In other words, the Airy and Pratt models are purely hydrostatic, taking no account of material strength, while flexural isostacy takes into account elastic forces from

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1890-401: The water (ca. 1,000 kg m ). Thus, generally: For the simplified model shown the new density is given by: ρ 1 = ρ c c h 1 + c {\displaystyle \rho _{1}=\rho _{c}{\frac {c}{h_{1}+c}}} , where h 1 {\displaystyle h_{1}} is the height of the mountain and c

1935-526: The word 'isostasy' in 1889 to describe this general phenomenon. However, two hypotheses to explain the phenomenon had by then already been proposed, in 1855, one by George Airy and the other by John Henry Pratt . The Airy hypothesis was later refined by the Finnish geodesist Veikko Aleksanteri Heiskanen and the Pratt hypothesis by the American geodesist John Fillmore Hayford . Both the Airy-Heiskanen and Pratt-Hayford hypotheses assume that isostacy reflects

1980-498: Was a widespread phenomenon in mountainous areas. It was later found that the difference between the measured local gravitational field and what was expected for the altitude and local terrain (the Bouguer anomaly ) is positive over ocean basins and negative over high continental areas. This shows that the low elevation of ocean basins and high elevation of continents is also compensated at depth. The American geologist Clarence Dutton use

2025-456: Was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive,

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