Mountain range
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A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain.[1] Other definitions may include a mountain system which is a group of mountain ranges exhibiting certain unifying features, such as similarity in form, structure, and alignment, and presumably originating from the same general causes; esp. a series of ranges belonging to an orogenic belt.[1] A mountain system or system of mountain ranges sometimes is used to combine several geological features that are geographically (regionally) related.
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.
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[edit] Major ranges
Considering underwater topography, the Ocean Ridges of the world form the longest mountain systems on Earth. Above sea level major mountain systems are chiefly arranged in two regions; the Pacific Ring of Fire and the Alpide Belt. The first includes the mountains of the western coast of the Americas, Kamatchaka, Japan, Taiwan, the Philippines, as well as parts of Indonesia and Papua New Guinea. The Alpide Belt runs from Indonesia to the Alps including the Himalayas and other European and Asian ranges. Above sea level the Andes is usually considered the world's longest mountain system; it is 7,000 kilometres (4,300 mi) in length. The Himalaya Range contains the highest mountains on the Earth's surface, the highest of which is Mount Everest. The world's longest mountain system is known as Ocean Ridge, which is a chain of mountains that runs on the seafloor of five oceans around the world; it has a length of 65,000 kilometres (40,400 mi), and the total length of the system is 80,000 kilometres (49,700 mi). The Andes is the world's longest mountain system on the surface of a continent; it is 7,000 kilometres (4,300 mi) in length. To clarify, the Andes is the world's largest chain of mountains above sea level. The Arctic Cordillera is the world's northernmost mountain system and contains the highest point in eastern North America.
[edit] Divisions and categories
The mountain systems of the earth are characterized by a tree structure, that is, many mountain ranges have sub-ranges within them. It can be thought of as a parent-child relationship. For example, the Appalachian Mountains range is the parent of other ranges it comprises, some of which are the White Mountains and the Blue Ridge Mountains. The White Mountains are a child of the Appalachians, and there are also children of the Whites, including the Sandwich Range and the Presidential Range. Further, the Presidential Range can be broken up into the Northern Presidential Range and Southern Presidential Range.
[edit] Climate
The position of mountains 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 (in accordance with the adiabatic lapse rate) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect the leeward side of a range.
[edit] Erosion
Mountain ranges are constantly subjected to erosional forces which work to tear them down. Erosion is at work while the mountains are being uplifted and long after until the mountains are reduced to low hills and plains. The rugged topography of a mountain range is the product of erosion. The basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock.
The early Cenozoic uplift of the Rocky Mountains of Colorado provide 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.[2] This mass of rock 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.
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