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Thursday, March 27, 2014 SCE 3110 1

Mountains

A mountain is a landform that rises high above the surrounding terrain in alimited area. They are made from rocks and earth. Generally, mountains are

higher than 600 meters. Those less than 600 meters are called hills.

Mountains exist on every continent and even beneath our great oceans.

Some of the highest mountains are at the bottom of the sea.

Hawaii is at the top of a volcanic mountain in the Pacific Ocean. More than half

the mountain is below water.

The largest range of mountains is in the Atlantic Ocean.

Mountains cover one-fifth of the earths land surface, and occur in 75

percent of the worlds countries.

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Mountain ranges are long chains or groups of mountains. Ranges are usually

1,000 or more miles long.

The Rocky Mountains and the Himalayan Mountains are examples of

mountain ranges.

A group of mountain ranges is called a mountain system. For example, the

mountain systems of the United States include the Rockies and the

Appalachians.

Mountains are home to approximately one-tenth of the worlds people.

More than half of the worlds fresh water originates in mountains, and all the

world's major rivers are fed from mountain sources.

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Mountains receive more rainfall than low lying areas because the

temperature on top of mountains is lower than the temperature at sea

level.

Winds carry moist air over the land. When air reaches the mountain, it rises

because the mountains are in the way. As the air rises, it cools, and because

cool air can carry less moisture than warm air, there is usually precipitation

(rain).

The climate on a mountain varies depending on what altitude (how high)

you are up a mountain. At the foothills (near the bottom) there may be a

tropical climate, whilst the peaks (the very top of mountains) may be

covered in ice. The uppermost level of mountains is often bare rock andsnow. Tibet and the Himalayas and other mountain ranges such as the

Rocky Mountains or the Andes are good examples of this.

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We can often see snow on the top of mountains all year round, because

the temperature at the top of mountains is lower than at the bottom. The

higher the place is above sea level the colder it will be.

Some mountains reach higher than the clouds. At this altitude the

extreme cold and high winds cause blizzards (severe storm characterized

by extreme cold, strong winds, and a heavy snowfall).

Mountains make it possible for snow to be found at the equator.

Generally the climate on mountains get progressively colder with

increased altitude. Air pressure decreases with altitude. As a result of the

reduced air pressure, rising air expands and cools. The cooler the

temperature the less evaporation there is, meaning that there is more

moisture in the air.

Blizzard: a severe snowstorm with strong winds and poor visibility. For a

snowstorm to be classified as a blizzard, winds must exceed 56 km/35 mi per hour

and the temperature must be -7C/20F or lower.

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Because of the rapid changes in altitude and temperature along a mountain

slope, multiple ecological zones are stacked upon one another sometimes

ranging from dense tropical jungles to glacial ice within a few kilometers.

Mountains can affect the climate of nearby lands. In some areas, mountainsblock rain, so that one side of a mountain range may be rainy and the other

side may be a desert (padang pasir).

Much of airborne moisture (moisture that carried along by movements of

air) falls as rain on the windward side of mountains. This often means that

the land on the other side of the mountain (the leeward side) gets far less

rainan effect called a "rain shadow"which often produces a desert.

The higher the mountain, the more pronounced the rain shadow effect is

and the less likely rain will fall on the leeward side.

By the time the air gets to the leeward side of the mountain it has already lost

some of its moisture.

Many of the deserts of the world are formed because of the lack of moisture

blocked by the mountains. The Gobi desert is located behind the Himalaya

mountain range in Asia.

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Mountains are formed by slow but gigantic movements of the earth's crust

(the outer layer of the Earth).

The Earth's crust is made up of 6 huge slabs called plates, which fittogether like a jigsaw puzzle. When two slabs of the earth's crust smash

into each other the land can be pushed upwards, forming mountains.

Many of the greatest mountain ranges of the world have formed because

of enormous (unusually large or great in size) collisions between

continents.

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Sometimes the crust has folded and buckled, sometimes it breaks into

huge blocks. In both cases, great areas of land are lifted upwards to form

mountains.

Other mountains are formed by the earth's crust rising into a dome, or by

volcanic activity when the crust cracks open.

There are five basic kinds of mountains:

Fold Mountains (Folded Mountains)

Fault-block Mountains (Block Mountains)

Dome Mountains

Volcanic Mountains

Plateau Mountains

These different types of mountain names not only distinguish the physical

characteristics of the mountains, but also how they were formed.

Types of Mountains

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Fold Mountains

Fold mountains are the most common type of mountain. The worlds

largest mountain ranges are fold mountains. These ranges were formed

over millions of years.

Fold mountains are formed when two plates collide head on, and their

edges crumbled, much the same way as a piece of paper folds when

pushed together.

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The upward folds are known as anticlines, and the downward folds are synclines.

Examples of fold mountains include:

Himalayan Mountains in Asia

the Alps in Europethe Andes in South America

the Rockies in North America

the Urals in Russia

The Himalayan Mountains were formed when India crashed into Asia and pushed

up the tallest mountain range on the continents.

In South America, the Andes Mountains were formed by the collision of the South

American continental plate and the oceanic Pacific plate.

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Fault-block Mountains

These mountains form when faults or cracks in the earth's crust force some

materials or blocks of rock up and others down.

Instead of the earth folding over, the earth's crust fractures (pulls apart). It breaksup into blocks or chunks. Sometimes these blocks of rock move up and down, as

they move apart and blocks of rock end up being stacked on one another.

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Often fault-block mountains have a steep front side and a sloping back side.

Examples of fault-block mountains include:the Sierra Nevada mountains in North America

the Harz Mountains in Germany

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Dome Mountains

Dome mountains are the result of a great amount of melted rock (magna) pushingits way up under the earth crust. Without actually erupting onto the surface, the

magma pushes up overlaying rock layers. At some point, the magma cools and

forms hardened rock. The uplifted area created by rising magma is called a dome

because of looking like the top half of a sphere (ball). The rock layers over the

hardened magma are warped upward to form the dome. But the rock layers of the

surrounding area remain flat.

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As the dome is higher than its surroundings, erosion by wind and rain occurs

from the top. This results in a circular mountain range. Domes that have

been worn away in places form many separate peaks called Dome

Mountains.

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Plateau Mountains (Erosion Mountains)

Plateau mountains are not formed by internal activity. Instead, these mountains are

formed by erosion. Plateaus are large flat areas that have been pushed above sea

level by forces within the Earth, or have been formed by layers of lava. The

dictionary describes these as large areas of high levels of flat land, over 600 meters

above sea level.

Plateau mountains are often found near folded mountains. As years pass, streams

and rivers erode valleys through the plateau, leaving mountains standing between

the valleys.

The mountains in New Zealand are examples of plateau mountains

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1.09 Mountains