Mountain

A mountain is a landform that extends above the surrounding terrain in a limited area. A mountain is generally much higher and steeper than a hill, but there is considerable overlap, and usage often depends on local custom. Some authorities define a mountain as a peak with a topographic prominence over an arbitrary value: for example, the Encyclopædia Britannica requires a prominence of 2,000 feet (610 m).

Characteristics

The altitude of mountains means that the tops exist in higher cold layers of the atmosphere. They are consequently often subject to glaciation and erosion through frost action. This produces the classic mountain peak shape. Some mountains have glacial lakes, created by melting glaciers; for example, there are an estimated 3000 in Bhutan.

Related Topics:
Glaciation - Erosion - Peak - Glacial lake - Bhutan

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Sufficiently tall mountains have very different climatic conditions at the top than at the base, and will thus have different life zones at different altitudes on their slopes. The plants and animals of a zone are somewhat isolated when the zones above and below are inhospitable, and many unique species occur on mountainsides as a result. Extreme cases are known as sky islands. Cloud forests are forests on mountain sides which attract moisture from the air, creating a unique ecosystem.

Related Topics:
Life zone - Sky island - Cloud forest - Ecosystem

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Mountains are not generally favored for human habitation; the weather is harsher, less food is available, and there is little level ground suitable for farming. 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 3500 metres. Despite some biological adaptation by peoples who have lived on mountains for hundreds or thousands of years, babies' average birthweight is reduced by 100 grams for every 1000-metre gain in altitude.

Related Topics:
Human - Farming - Oxygen - Acute mountain sickness - Hypoxia - Birthweight

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Most mountains of the world have been left in their natural state, and are today primarily used for recreation. Some mountains are very difficult to climb, and offer spectacular views. Some people therefore enjoy the sport of mountaineering. Mountains are also the site for the sport of downhill skiing. People engaging in these activities often stay at mountain resorts built for the purpose.

Related Topics:
Recreation - Mountaineering - Downhill skiing - Mountain resort

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