What is a Mountain?

Translated from Zedler's Universal-Lexikon, 1733: 

"Mountain is being called part of the Earth inasmuch as it is elevated over the ground to a substantial height. It is reasonable  therefore to ask which the reasons are that have led to such great creations and what their use might be."

Translated from Brockhaus Bilder-Conversations-Lexikon for the German People, 1841:  

„Mountain are being called, in general, all considerable elevations of the earth surface, the lesser significant ones, however, hills or heights. The usual shape of mountains is like a cone, i.e. they rise from a large base more or less steeply and likewise fall off from their highest point, the apex or summit, which, if appearing thick and rounded off, is called knoll, if peculiarly shaped, also horn, needle, etc. The flanks that are formed through this are called slopes.”  

A mountain is a landform that extends above the surrounding terrain in a limited area. A mountain is generally 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 a defined value: for example, the Encyclopædia Britannica requires a prominence of 610 m (2,000 ft).  

24% of the Earth's land mass is mountainous; 1 in 10 people live in mountainous regions. All the world's major rivers are fed from mountain sources, and more than half of humanity depends on mountains for water.   

The adjective montane is used to describe mountainous areas and the things associated with them. 

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.   

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.   

Mountains are not generally favoured 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 3,500 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 1,000-metre gain in altitude.   

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. 

Geology  

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 upwards, 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 topography. The major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Mountain creation tends to occur in discrete periods, each referred to as an orogeny. The orogeny may last millions of years, and the uplifted region is being eroded away, producing valley-and-peak topography, even while the uplift is taking place. Two types of mountain are formed depending on how the rock reacts to the tectonic forces – block mountains or fold mountains.   

The compressional forces in continental collisions may cause the compressed region to thicken, so the upper surface is forced upwards. In order to balance the weight, much of the compressed rock is forced downwards, producing deep "mountain roots". Mountains therefore form downwards as well as upwards (isostasy). However, in some continental collisions part of one continent may simply override part of the other, 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. 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, e.g. the Rhine valley. In the context of this book series: Grand Ballon d’Alsace.   

Where rock does not fault it folds, 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. In the context of this book series: Crêt de la Neige.  

Local definitions  

In the United States, a mountain is 1,000 feet or more in height from base to summit. A hill is 500 to 999 feet. A discernible hill that is less than 500 feet high is a knoll. A series of knolls constitutes a rolling plain. A plain is generally considered flat if it has no significant prominences (e.g., "hills" less than 20 feet high, though the range of height varies for a plain to be considered flat).   

In the United Kingdom the Department for Environment, Food and Rural Affairs defines mountain as all land over 600 m. This is a close metric equivalent of 2,000 ft (which is 609.6 metres).  

Department for Environment, Food and Rural Affairs

 

ACCESS TO THE OPEN COUNTRYSIDE
IN ENGLAND AND WALES

SECTION 3: A NEW STATUTORY RIGHT OF ACCESS

SECTION 3a: THE LAND AFFECTED