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. 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
Mount Everest in the
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).
2.2 Fold mountains
2.3 Block mountains
5 Mountains and humans
Mountain societies and economies
7 See also
10 External links
Peaks of Mount Kenya
Mount Wilhelm in Papua New Guinea
There is no universally accepted definition of a mountain. Elevation,
volume, relief, steepness, spacing and continuity have 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
Whether a landform is called a mountain may depend on local usage.
Mount Scott outside
Lawton, Oklahoma is only 251 m (823 ft)
from its base to its highest point. Whittow's Dictionary of Physical
Geography states "Some authorities regard eminences above 600
metres (2,000 ft) as mountains, those below being referred to as
In the United Kingdom and the Republic of Ireland, a mountain is
usually defined as any summit at least 2,000 feet (or 610 metres)
high, whilst the official UK government's definition of
a mountain, for the purposes of access, is a summit of 600 metres or
higher. In addition, some definitions also include a topographical
prominence requirement, typically 100 or 500 feet (30 or
152 m). For a while, the US defined a mountain as being 1,000
feet (300 m) or taller. 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.
The UN Environmental Programme's definition of "mountainous
environment" includes any of the following:
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. As a whole, 24%
of the Earth's land mass is mountainous.
Mountain formation and List of mountain types
There are three main types of mountains: volcanic, fold, and
block. All three types are formed from 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 tectonic plate boundaries and activity.
Main article: Volcano
Geological cross-section of Fuji volcano
Volcanoes are formed when a plate is pushed below another plate, or at
a mid-ocean ridge or hotspot. 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. Examples of volcanoes include
Mount Fuji in
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.
Illustration of mountains that developed on a fold that thrusted.
Main article: Fold mountains
Fold mountains occur when two plates collide: shortening occurs along
thrust faults and the crust is overthickened. Since the less dense
continental crust "floats" on the denser mantle rocks beneath, the
weight of any crustal material forced upward to form hills, 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. 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 Jura
Mountains are an example of fold mountains.
Main article: Block mountains
Upstate New York
Upstate New York represent an eroded plateau.
Block 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. 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
Basin and Range Province
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.
Main article: Erosion
Kitty Ann Mountain 1259 ft is an eroded mountain in the Ramapo
mountain range in
New Jersey and New York
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. 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 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 millimeters, or for thousands of
Main 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
Climate in the mountains becomes colder at high elevations, due 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
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.
Convection comes to equilibrium when a
parcel at 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 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 kilometer (or
5.4 °F per 1000 feet) of altitude.
Note that the presence of water in the atmosphere complicates the
process of convection. Water vapor contains latent heat of
vaporization. As air rises and cools, it eventually becomes saturated
and cannot hold its quantity of water vapor. The water vapor condenses
(forming clouds), and releases heat, which changes the lapse rate from
the dry adiabatic lapse rate to the moist adiabatic lapse rate
(5.5 °C per kilometer or 3 °F per 1000 feet) The
actual lapse rate can vary by altitude and by location.
Therefore, moving up 100 meters on a mountain is roughly
equivalent to moving 80 kilometers (45 miles or 0.75° of
latitude) towards the nearest pole. This relationship is only
approximate, however, since local factors such as proximity to oceans
(such as the Arctic Ocean) can drastically modify the climate. As
the altitude increases, the main form of precipitation becomes snow
and the winds increase.
The effect of the climate on the ecology at an elevation can be
largely captured through a combination of amount of precipitation, and
the biotemperature, as described by
Leslie Holdridge in 1947.
Biotemperature is the mean temperature; all temperatures below
0 °C (32 °F) are considered to be 0 °C. When the
temperature is below 0 °C, plants are dormant, so the exact
temperature is unimportant. The peaks of mountains with permanent snow
can have a biotemperature below 1.5 °C (34.7 °F).
Main article: Montane ecology
An alpine mire in the Swiss Alps
The colder climate on mountains affects the plants and animals
residing on mountains. A particular set of plants and animals tend to
be adapted to a relatively narrow range of climate. Thus, ecosystems
tend to lie along elevation bands of roughly constant climate. This is
called altitudinal zonation. In regions with dry climates, the
tendency of mountains to have higher precipitation as well as lower
temperatures also provides for varying conditions, which enhances
Some plants and animals found in altitudinal zones tend to become
isolated since the conditions above and below a particular zone will
be inhospitable and thus constrain their movements or dispersal. These
isolated ecological systems are known as sky islands.
Altitudinal zones tend to follow a typical pattern. At the highest
elevations, trees cannot grow, and whatever life may be present will
be of the alpine type, resembling tundra. Just below the tree
line, one may find subalpine forests of needleleaf trees, which can
withstand cold, dry conditions. Below that, montane forests grow.
In the temperate portions of the earth, those forests tend to be
needleleaf trees, while in the tropics, they can be broadleaf trees
growing in a rain forest.
Mountains and humans
See also: List of highest cities in the world
Cerro Rico in Potosí, Bolivia, was in colonial times
an immerse source of wealth for the Spanish administration.
The highest known permanently tolerable altitude is at 5,950 metres
(19,520 ft). At very high altitudes, the decreasing
atmospheric pressure means that less oxygen is available for
breathing, and there is less protection against solar radiation
(UV). Above 8,000 metres (26,000 ft) elevation, there is not
enough oxygen to support human life. This is known as the "death
zone". The summits of
Mount Everest and K2 are in the death zone.
Mountain societies and economies
Mountains are generally less preferable for human habitation than
lowlands, because of harsh weather and little level ground suitable
for agriculture. While 7% of the land area of
Earth is above 2,500
metres (8,200 ft), only 140 million people live above that
altitude and only 20-30 million people above 3,000 metres
(9,800 ft) elevation. About half of mountain dwellers live in
the Andes, Central Asia, and Africa.
With limited access to infrastructure, only a handful of human
communities exist above 4,000 metres (13,000 ft) of elevation.
Many are small and have heavily specialized economies, often relying
on industries such as agriculture, mining, and tourism.[citation
needed] An example of such a specialized town is La Rinconada, Peru, a
gold-mining town and the highest elevation human habitation at 5,100
metres (16,700 ft). A counterexample is El Alto, Bolivia, at
4,150 metres (13,620 ft), which has a highly diverse service and
manufacturing economy and a population of nearly 1 million.
Traditional mountain societies rely on agriculture, with higher risk
of crop failure than at lower elevations. Minerals often occur in
mountains, with mining being an important component of the economics
of some montane societies. More recently, tourism supports mountain
communities, with some intensive development around attractions such
as national parks or ski resorts. About 80% of mountain people
live below the poverty line.
Most of the world's rivers are fed from mountain sources, with snow
acting as a storage mechanism for downstream users. More than half
of humanity depends on mountains for water.
In geopolitics mountains are often seen as preferable "natural
boundaries" between polities.
Mountain climbers ascending Mount Rainier
Mountaineering, mountain climbing, or alpinism is the sport, hobby or
profession of hiking, skiing, and climbing mountains. While
mountaineering began as attempts to reach the highest point of
unclimbed big mountains it has branched into specializations that
address different aspects of the mountain and consists of three areas:
rock-craft, snow-craft and skiing, depending on whether the route
chosen is over rock, snow or ice. All require experience, athletic
ability, and technical knowledge to maintain safety.
Main article: List of highest mountains
Mount Everest, the highest peak on Earth
Chimborazo, Ecuador. The point on Earth's surface farthest from its
Heights of mountains are typically measured above sea level. Using
Mount Everest is the highest mountain on Earth, at 8,848
metres (29,029 ft). There are at least 100 mountains with
heights of over 7,200 metres (23,622 ft) above sea level, all of
which are located in central and southern Asia. The highest mountains
above sea level are generally not the highest above the surrounding
terrain. There is no precise definition of surrounding base, but
Mount Kilimanjaro and
Nanga Parbat are possible candidates
for the tallest mountain on land by this measure. The bases of
mountain islands are below sea level, and given this consideration
Mauna Kea (4,207 m (13,802 ft) above sea level) is the
world's tallest mountain and volcano, rising about 10,203 m
(33,474 ft) from the Pacific
The highest mountains are not generally the most voluminous. Mauna Loa
(4,169 m or 13,678 ft) is the largest mountain on
terms of base area (about 2,000 sq mi or 5,200 km2) and
volume (about 18,000 cu mi or 75,000 km3). Mount
Kilimanjaro is the largest non-shield volcano in terms of both base
area (245 sq mi or 635 km2) and volume
(1,150 cu mi or 4,793 km3).
Mount Logan is the largest
non-volcanic mountain in base area (120 sq mi or
The highest mountains above sea level are also not those with peaks
farthest from the centre of the Earth, because the figure of the Earth
is not spherical.
Sea level closer to the equator is several miles
farther from the centre of the Earth. The summit of Chimborazo,
Ecuador's tallest mountain, is usually considered to be the farthest
point from the Earth's centre, although the southern summit of Peru's
tallest mountain, Huascarán, is another contender. Both have
elevations above sea level more than 2 kilometres (6,600 ft) less
than that of Everest.
Latin names of mountains
List of mountain ranges
List of peaks by prominence
List of ski areas and resorts
Lists of mountains
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Wikimedia Commons has media related to Mountain.
"Mountain". Encyclopædia Britannica. 18 (11th ed.). 1911.
Quotations related to Mountains at Wikiquote
List of landforms
See also: Geographical feature