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
Mars at 21,171 m (69,459 ft).
* 1 Definition
* 2 Geology
* 2.1 Volcanoes
* 3 Climate
* 4 Ecology
* 5 In society
* 6 Superlatives
* 7 See also
* 8 Notes
* 9 References
* 10 External links
Swiss Alps Peaks of
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 hills."
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
UN Environmental Programme
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
Jeff Davis Peak seen from the glacier-carved summit of Wheeler Peak ,
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.
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.
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.
Block mountains The
Catskills in Upstate New York
represent an eroded plateau .
Block mountains are caused by faults in the crust: a seam where rocks
can move 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
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.
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.
Alpine climate A mountain in
Carbon County, Utah
Valley of the Ten Peaks ,
Climate on mountains become 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 height.
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 curve. 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
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).
Montane ecology An alpine mire in the
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 .
Mountain climbers ascending
Mount Rainier The summit of
Ben Nevis , the British Isles' highest, has a memorial
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.
The decreasing atmospheric pressure with increasing elevation means
that less oxygen is available for breathing, and there is less
protection against solar radiation (UV ). Due to decreasing oxygen,
the highest known permanent habitation in the world is at 5,100 metres
(16,700 ft), while the highest known permanently tolerable altitude is
at 5,950 metres (19,520 ft). 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.
About half of mountain dwellers live in the
Andes , Central
Africa . 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.
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.
List of highest mountains The
Zugspitze , the
highest mountain in
Maat Mons of Venus (22.5x
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 Ocean
The highest mountains are not generally the most voluminous. Mauna
Loa (4,169 m or 13,678 ft) is the largest mountain on
Earth in 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 311 km2).
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
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 mountain ranges
List of peaks by prominence
List of ski areas and resorts
Lists of mountains
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