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A mountain is a large landform that rises above the surrounding land in a limited area, usually in the form of a peak.[1] A mountain is generally steeper than a hill. Mountains are formed through tectonic forces or volcanism. These forces can locally raise the surface of the earth. Mountains erode slowly through the action of rivers, weather conditions, and glaciers. A few mountains are isolated summits, but most occur in huge mountain ranges.
High elevations on mountains produce colder climates than at sea level. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction and recreation, such as mountain climbing.
The highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m (29,035 ft) above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m (69,459 ft).

Contents1 Definition2 Geology2.1 Volcanoes2.2 Fold mountains2.3 Block mountains2.4 Erosion3 Climate4 Ecology5 Mountains and humans5.1 Mountain societies and economies5.2 Mountaineering6 Superlatives7 See also8 Notes9 References10 External linksDefinition
Peaks of Mount Kenya
Mount Wilhelm in Papua New GuineaThere is no universally accepted definition of a mountain. Elevation, volume, relief, steepness, spacing and continuity have been used as criteria for defining a mountain.[1] In the Oxford English Dictionary a mountain is defined as "a natural elevation of the earth surface rising more or less abruptly from the surrounding level and attaining an altitude which, relatively to the adjacent elevation, is impressive or notable."[1]
Whether a landform is called a mountain may depend on local usage. Mount Scott outside Lawton, Oklahoma, USA, is only 251 m (823 ft) from its base to its highest point. Whittow's Dictionary of Physical Geography[2] states "Some authorities regard eminences above 600 metres (2,000 ft) as mountains, those below being referred to as hills."
In the United Kingdom and the Republic of Ireland, a mountain is usually defined as any summit at least 2,000 feet (610 m) high,[3] which accords with the official UK government's definition that a mountain, for the purposes of access, is a summit of 2,000 feet (610 m) or higher.[4] In addition, some definitions also include a topographical prominence requirement, typically 100 or 500 feet (30 or 152 m).[5] At one time the U.S. Board on Geographic Names defined a mountain as being 1,000 feet (300 m) or taller,[6] but has abandoned the definition since the 1970s. Any similar landform lower than this height was considered a hill. However, today, the United States Geological Survey (USGS) concludes that these terms do not have technical definitions in the US.[7]
The UN Environmental Programme's definition of "mountainous environment" includes any of the following:[8]
Elevation of at least 2,500 m (8,200 ft);Elevation of at least 1,500 m (4,900 ft), with a slope greater than 2 degrees;Elevation of at least 1,000 m (3,300 ft), with a slope greater than 5 degrees;Elevation of at least 300 m (980 ft), with a 300 m (980 ft) elevation range within 7 km (4.3 mi).Using these definitions, mountains cover 33% of Eurasia, 19% of South America, 24% of North America, and 14% of Africa.[9] As a whole, 24% of the Earth's land mass is mountainous.[10]
GeologyMain articles: Mountain formation and List of mountain typesThere are three main types of mountains: volcanic, fold, and block.[11] All three types are formed from The Walking Dead Season 10 Episode 1 Online Full plate tectonics: when portions of the Earth's crust move, crumple, and dive. Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. Major mountains tend to occur in long linear arcs, indicating The Walking Dead Season 10 Episode 1 Online Free tectonic plate boundaries and activity.
VolcanoesMain article: Volcano
Geological cross-section of Fuji Watch The Walking Dead Season 10 Episode 1 Online volcanoVolcanoes are formed when a plate is pushed below another plate, or at a mid-ocean ridge or hotspot.[12] At a depth of around 100 km, melting occurs in rock above the slab (due to the addition of water), and forms magma that reaches the surface. When the magma reaches the surface, it often builds a volcanic mountain, such as a shield volcano or a stratovolcano.[13] Watch The Walking Dead Season 10 Episode 1 Online Free Examples of volcanoes include Mount Fuji in Japan and Mount Pinatubo in the Philippines. The magma does not have to reach the surface in order to create a mountain: magma that solidifies below ground can still form dome mountains, such as Navajo Mountain in the US.
Fold mountains
Illustration of mountains that developed on a fold that thrusted.Main article: Watch The Walking Dead Season 10 Episode 1 Online Full Fold mountainsFold mountains occur when two plates collide: shortening occurs along thrust faults and the crust is overthickened.[14] Since the less dense continental crust "floats" on the denser mantle rocks beneath, the weight of any crustal material forced upward to form hills, Watch Mr Robot Season 4 Episode 1 Online plateaus or mountains must be balanced by the buoyancy force of a much greater volume forced downward into the mantle. Thus the continental crust is normally much thicker under mountains, compared to lower lying areas.[15] Rock can fold either symmetrically or asymmetrically. The upfolds are anticlines and the downfolds are synclines: in asymmetric folding there may also be recumbent and overturned folds. The Balkan Mountains and the Jura Mountains are examples of fold mountains.
Block mountainsMain article: Block mountainsthe highest summit of PirinPirin Mountain, Bulgaria, part of the fault-block Rila-Rhodope massifBlock mountains are caused by faults in the crust: a plane where rocks have moved past each other. When rocks on one side of a fault rise relative to the other, it can form a mountain.[16] The uplifted blocks are block mountains or horsts. The intervening dropped blocks are termed Watch Mr Robot Season 4 Episode 1 Online Full graben: these can be small or form extensive rift valley systems. This form of landscape can be seen in East Africa, the Vosges, the Basin and Range Province of Western North America and the Rhine valley. These areas often occur when the regional stress is extensional and the crust is thinned.
ErosionMain article: Erosion
The Catskills in Upstate New York represent an eroded plateau.During and following uplift, mountains are subjected to the agents of erosion (water, wind, ice, and gravity) which gradually wear the uplifted area down. Erosion causes the surface of mountains to be younger than the rocks that form the mountains themselves.[17] Glacial processes produce characteristic landforms, such as pyramidal peaks, knife-edge arêtes, and bowl-shaped cirques that can contain lakes. Plateau mountains, such as the Catskills, are formed from the erosion of an uplifted plateau.
In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transport it away to another location (not to be confused with weathering which involves no movement). The Watch Mr Robot Season 4 Episode 1 Online Free particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by its dissolving into a solvent (typically water), followed by the flow away of that solution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
ClimateMain article: Alpine climate
A combination of high latitude and high altitude makes the northern Urals in picture to have climatic conditions that make the ground barren.
Mountains retain snow much longer than lower elevations, pictured "Witches' Mountain" in Poland at the end of MayClimate in the mountains becomes colder at high elevations, due to an interaction between radiation and convection. Sunlight in the visible spectrum hits the ground and heats it. The ground then heats the air at the surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height.[18]
However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This is the process of convection. Mr Robot Season 4 Episode 1 Online FreeConvection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an adiabatic process, which has a characteristic Mr Robot Season 4 Episode 1 Online Full pressure-temperature dependence. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation is known as the adiabatic lapse rate, which is approximately 9.8 °C per kilometre (or 5.4 °F per 1000 feet) of altitude.[18]

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