A mountain is a large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. The adjective montane is used to describe mountainous areas and things associated with them. The study of mountains is Orology.
Exogeology deals with planetary mountains, which in that branch of science are usually called montes (singular - mons). The highest mountain on earth is the Mount Everest (elevation 8,848 m). The highest known mountain in the Solar System is Olympus Mons on the planet Mars (elevation 21,171 m).
There is no universally-accepted definition of mountain. Elevation, volume, relief, steepness, spacing and continuity has been used as criteria for defining a mountain. 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."
In the United States, the following points of measurement have been used and taught in geography classes:
Other definitions of "mountain" include:
High mountains, as well as those located close to the Earth's poles, reach into the colder layers of the atmosphere. They are consequently subject to glaciation, and erosion through frost action. Such processes produce the peak shape. Some of these mountains have glacial lakes, created by melting glaciers; for example, there are an estimated 3,000 glacial lakes in Bhutan. Mountains can be eroded and weathered, altering their characteristics over time.
Tall mountains have different climatic conditions at the top than at the base, and will thus have different life zones at different altitudes. The flora and fauna found in these zones tend to become isolated since the conditions above and below a particular zone will be inhospitable to those organisms. These isolated ecological systems are known as sky islands and/or microclimates. Alpine forests are forests on mountain sides.
Mountains are colder than lower ground, because the Sun heats Earth from the ground up. The Sun's radiation travels through the atmosphere to the ground, where Earth absorbs the heat. Air closest to the Earth's surface is, in general, warmest (see lapse rate for details). Air temperature normally drops 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) for each 300 meters (1000 ft) of altitude.
Mountains are generally less preferable for human habitation than lowlands; the weather is often harsher, and there is little level ground suitable for agriculture. At very high altitudes, there is less oxygen in the air and less protection against solar radiation (UV). Acute mountain sickness (caused by hypoxia - a lack of oxygen in the blood) affects over half of lowlanders who spend more than a few hours above 3,500 meters (11,483 ft).
Many mountains and mountain ranges throughout the world have been left in their natural state, and are today primarily used for recreation, while others are used for logging, mining, grazing, or see little use. Some mountains offer spectacular views from their summits, while others are densely wooded. Summit accessibility is affected by height, steepness, latitude, terrain, weather. Roads, lifts, or tramways affect accessibility. Hiking, backpacking, mountaineering, rock climbing, ice climbing, downhill skiing, and snowboarding are recreational activities enjoyed on mountains. Mountains that support heavy recreational use (especially downhill skiing) are often the locations of mountain resorts.
Mountains can be characterized in several ways. Some mountains are volcanoes and can be characterized by the type of lava and eruptive history. Other mountains are shaped by glacial processes and can be characterized by their shape. Finally, many mountains can be characterized by the type of rock that make up their composition.
A mountain is usually produced by the movement of lithospheric plates, either orogenic movement or epeirogenic movement. The 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. The absolute heights of features termed mountains and hills vary greatly according to an area's terrain. The major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Two types of mountain are formed depending on how the rock reacts to the tectonic forces - block mountains or fold mountains.
Compressional forces in continental collisions may cause the compressed region to thicken, so the upper surface is forced upward. In order to balance the weight of the earth surface, much of the compressed rock is forced downward, producing deep "mountain roots" [see the Book of "Earth", Press and Siever page.413]. Mountains therefore form downward as well as upward (see isostasy). However, in some continental collisions part of one continent may simply override part of the others, crumpling in the process.
Some isolated mountains were produced by volcanoes, including many apparently small islands that reach a great height above the ocean floor.
Block mountains are created when large areas are widely broken up by faults creating large vertical displacements. This occurrence is fairly common. The uplifted blocks are block mountains or horsts. The intervening dropped blocks are termed 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.
The mid-ocean ridges are often referred to as undersea mountain ranges due to their bathymetric prominence.
Rock that does not fault may 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 Jura mountains are an example of folding. Over time, erosion can bring about an inversion of relief: the soft upthrust rock is worn away so the anticlines are actually lower than the tougher, more compressed rock of the synclines
Mountain Wikipedia
Undersea mountains march into the abyss BBC - December 6, 2011
Startling new images from the depths of the Pacific Ocean reveal one of Earth's most violent processes: the destruction of massive underwater mountains. The pictures were created by sonar in waters up to 6km (4mi) deep. They expose how tectonic action is dragging giant volcanoes into a chasm in the seabed. The volcanoes are strung across several thousand kilometres of ocean floor and are moving westward on the Pacific tectonic plate at up to 6cm per year. The extraordinary scene was captured along the Tonga Trench during a research expedition last summer.
World's highest webcam brings Everest to Internet PhysOrg - October 6, 2011
The world's highest webcam has been installed in the Nepalese Himalayas, beaming live images of Mount Everest back to scientists studying the effects of climate change on the planet's tallest peak.
New insights on the origin of the Rocky Mountains PhysOrg - March 1, 2011
The formation of the Rocky Mountains in Colorado has always puzzled scientists. Some 600 miles inland and far removed from the nearest tectonic plate, the only comparable inland mountain range is the Himalaya, which scientists deduced were formed by the collision of the Indian plate with the Eurasian plate.
Marine scientists unveil the mystery of life on undersea mountains PhysOrg - September 20, 2010
They challenge the mountain ranges of the Alps, the Andes and the Himalayas in size yet surprisingly little is known about seamounts, the vast mountains hidden under the world's oceans. Now in a special issue of Marine Ecology scientists uncover the mystery of life on these submerged mountain ranges and reveal why these under studied ecosystems are under threat.
Earth's highest coastal mountain on the move PhysOrg - September 20, 2010
The Earth's highest coastal mountain, Colombia's Sierra Nevada de Santa Marta, moved north from Peru and rotated to form a new basin.
Search for frozen camera may reveal who climbed Everest first PhysOrg - January 29, 2010
An Everest historian believes he may have pinpointed the last resting place of mountaineer Andrew Irvine, who died on a mission to climb Mount Everest in 1924, almost 30 years before the successful climb of Sir Edmund Hillary and Tenzing Norgay.
Data to expose 'ghost mountains' BBC - December 19, 2009
New Study Turns Up the Heat on Soot's Role in Himalayan Warming PhysOrg - December 14, 2009
Black Soot Might Be Main Culprit of Melting Himalayas Live Science - December 14, 2009
Snow at Highest Elevations No Longer Pure Live Science - December 10, 2009
Andes mountains: White, but not pure PhysOrg - December 7, 2009
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