A mountain is a natural rise of the Earth's surface that usually has a "summit" (or "top"). It is usually steeper and taller than a hill. Mountains are often thought of as being a hill of over 600 metres (about 2,000 feet), but this thought is not the same in every country.
Mountains are important to life on Earth, because most rivers begin in mountains and carry water from the mountains down to the sea.
Definition of a mountain[change | change source]
- The highest point of a mountain is called the peak. A mountain's summit is the highest area an individual can reach. A mountain climber will not reach the peak of the mountain but can reach the summit.
- Britannica Student Encyclopedia says that the term "mountain' usually means a rise of over 2,000 feet (610 m)".
- Polytechnic Student Encyclopedia says that the term "mountain' usually means a rise of over 1,000 feet (610 m)".
- The standard height for a mountain in England is 600 metres. In England, it is important to have a legal height because people have the "Right to Roam" in mountains, but they do not have the same right to walk on someone-else's land. Even though mountains are defined by law, many people in England use the word "hill" even when they are talking about a very large mountain such as those in north India.
- In the USA, even though there are many very tall mountains, the name mountain is often given to hills that may be only 100 feet high.
- In Scotland, a mountain that is over 3,000 feet (914.4 m) is sometimes called a "Munro".
- In Australia, Botswana and some other places, the word "mountains" is also used to describe high land that is really a plateau and is flat on top, rather than having peaks.
- In the South Africa, even though there are many very tall mountains, the name mountain is often given to hills that may be only 100 feet high.
Form[change | change source]
The forming of a mountain is called orogeny. Mountains are formed when rock layers are pushed from opposite sides, and they push the crust up. A mountain range is a large group of mountains beside each other. There are three/four ways a mountain may be made:
- volcanic (Volcanos are usually called mountains, but because they are not formed by "orogeny", scientists do not call them "mountains")
Mountain types[change | change source]
There are five main types of mountains:
Some people say there are eight types, as domed mountains can be a plutonic dome or a tectonic dome.
Volcanic mountains[change | change source]
Volcanic mountains are mountains that form when molten rock erupts onto the Earth's surface. They can either form on land or in the ocean. The Cascade Range in Washington, Oregon and northern California is made of volcanoes. Some of the largest volcanoes are on divergent boundaries, which form the mid-ocean ridges. The mid-ocean ridges have big volcanic mountain chains that run through the Atlantic, Pacific and Indian Oceans. The mountains in the mid-ocean ridges can actually grow tall enough to create islands such as Iceland or the Azores.
Other volcanic mountains can form over hot spots, which are pockets of magma beneath the crust that erupt onto Earth's surface. The Hawaiian Islands are actually the tops of really high volcanic islands that have formed over a hot spot on the sea floor. The main Hawaiian island is actually a volcano that is about 9 km above the ocean floor, with a base that is about 160 km wide. Almost 4 km of this island is above sea level.
Dome mountains[change | change source]
Dome mountains, like those in the Black Hills of South Dakota and the Adirondack Mountains of New York, are an unusual domish type of mountain that is formed when molten rock rises through the crust and push up the rock layers above it. This creates a circular dome on the Earth's surface. The molten rock later cools off and forms hardened rock. When the pushed up rocks are worn away, the hardened rock is shown. This hardened rock then wears away in places. When it wears away, it leaves mountains, and they are called dome mountains.
Folded mountains[change | change source]
Folded mountains make up some of the highest mountains in the world. Folded mountains commonly form along boundaries, where 2 continents meet. Some really complex folds are in parts of the Andes, Alps, Himalayas, Appalachians, and Russia's Ural Mountains. These long mountain chains also show lots of signs of folding.
Plateau mountains[change | change source]
Plateau mountains are formed a bit like folded mountains. They are large areas of flat topped rocks that have been lifted high above the crust by continental plates. Most plateaus are near folded mountains.
Fault-block mountains[change | change source]
Fault-block mountains are formed when parts of the Earth's crust has been broken off into large block mountains. They are also formed when two blocks of land rise above or fall down leaving its middle part behind, and when magma pushes up by the lava and forces top layers of rock up with it. Domed mountains, although have broken and move up as a 'chunk'. A fault block mountain is a mountain or range formed as a horst when it was elevated between parallel normal faults. A horst is the raised fault block bound by normal faults.
Height[change | change source]
The height of a mountain is measured as distance above sea level.
Tallest mountains[change | change source]
The highest mountain in the solar system is the Olympus Mons (27 km) on Mars. The highest mountain in the world is Mount Everest (8,848m)which is in Nepal/Tibet in Asia. (The "tallest" mountain in the world is Mauna Loa, in Hawaii. The "height" of a mountain is measured from sea level, but the "tallness" of a mountain is measured from its base, even if under water.) The highest mountain in North America is Mount McKinley (6,194m) in Alaska in the USA. The highest in South America is Aconcagua (6,962m) in Argentina. For Africa, it is Kilimanjaro (5,963m) of Tanzania. In Europe, the highest mountain is in Russia called Elbrus (5,633m). Antarctica's highest mountain is Vinsin Massiff (5,140m). In Oceania, a mountain called Puncak Jaya (5,030m) is the highest there. This particular mountain is in Papua New Guinea / Indonesia.
References[change | change source]
- "Mountain -- Britannica Student Encyclopedia". http://www.britannica.com/ebi/article-9275956?&query=mountain&ct=%22ebi%22Britannica. Retrieved 2007-01-08.
- "Mountain -- Polytechnic Student Encyclopedia". http://www.polytechnic.com/ebi/article-9275956?&query=mountain&ct=%22ebi%22Polytechic. Retrieved 2012-08-08.
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A satellite view of the Alps, a mountain range in Europe.