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Major types of mountains
What is Mountain?
A mountain is part of the earth’s surface that rises abruptly to a greater height, usually above 300 metres from the surrounding level. There are four major types of mountains. These are Fold Mountains, Block Mountains, volcanic mountains, and residual mountains. These mountains are categorised based on the way they were formed.
(a) Fold mountains
Fold Mountains are features formed mainly by the process of folding or wrinkling of the upper parts of the earth’s crust due to compressional forces. Major Fold Mountains in the world include the Himalayas in Asia, the Rockies and Appalachians in North America, and the Andes in South America. Others are the Alps in Europe, the Atlas in North Africa, and Cape ranges in South Africa.
(b) Block mountains
A Block Mountain (horst) is an upland area with a table-like structure bordered by faults on one or both sides. It is formed when tensional or compressional forces in the crust force layers of crustal rocks to break, resulting in central part being uplifted.
Examples of Block Mountains are the Uluguru and Usambara in Tanzania, and Ruwenzori in Uganda (East Africa), the Vosges and Black Forest Mountains in Europe, and Mount Sinai in Asia.
(c) Volcanic mountains
When rocks are under intense heat and pressure in the earth’s crust they melt and form magma. When the magma inside the earth’s crust finds a weak point in the earth’s crust, they erupt and molten rock flows out as lava. When it cools, it forms a cone. Volcanic Mountains are cone-shaped mountains formed from the cooling and solidification of hot molten rock material (lava) from the interior of the Earth during a volcanic eruption.
There are three main types of Volcanic Mountains, depending on the frequency of eruption and the types of lava.
Active volcano mountains are the ones which experience periodic eruptions.
For example, Oldonyo Lengai in Tanzania, Vesuvius in Italy, Nyiragongo in the Democratic Republic of Congo, and Mauna Loa in Hawaii. Volcanic Mountains, which erupted only once in historical times, are referred to as dormant volcanic mountains, since they are no longer active. Examples include Mount Kilimanjaro in Tanzaniab), Mount Ararat in Turkey, Fuji and Mauna Kea in Hawaii. Volcanic Mountains, which have not erupted for a very long time and have not shown any sign of eruption, are known as extinct or dead volcanic mountains. Examples include Mount Rungwe in Tanzania, Mount Kulal in Kenya, and Mount Chimborazo in Ecuador.
(d) Residual
Residual Mountains are formed because of weathering and erosion of weaker rocks of the already existing mountains, leaving behind resistant rocks. The remaining resistant rocks are known as residual mountains or mountains of denudation. Examples of residual mountains include the Sekenke Hills of Singida in Tanzania, the Ahaggar Mountains of Central Sahara and the Adamawa Mountains of Eastern Nigeria.
INTERSECONDARY SCHOOLS EXAMINATION SERIES (ISESE) FORM TWO PRE NATIONAL 2024