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Different mountain types

Different mountain types
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Face of earth is constantly being reshaped by agents of denudation like- running water, rain, frost, sun, wind, glaciers and waves. This modified the...

Face of earth is constantly being reshaped by agents of denudation like- running water, rain, frost, sun, wind, glaciers and waves. This modified the pattern of mountains, plateau and plains. From the origin of earth mountain building movements have taken place, folding and fracturing the earth’s crust. Some of them occurred in pre-Cambrian times between 600-3,500 million years ago. The three most recent such phenomenons are Caledonian, Hercynian and Alpine mountain ranges.

  • The Cadonian are the world’s ancient mountain range raised 320 million years ago. It comprises of mountains of Scandavia and Scotland.
  • Hercynian earth movements about 240 million years ago formed Ural Movements, The Pennines, welsh highlands in Britain, The harz Mountains in Germany, TheAppalachinas in America and high plateau of Siberia and China.
  • Alps, Himalayas, Andes and Rockies are the youngest mountain ranges of earth.

Mountain ranges

Mountains make up a large portion of earth’s surface. Based on their mode of formation they have been divided into following types

Fold Mountains:

Fold Mountains are mountains that form mainly by the effects of folding on layers within the upper part of the Earth's crust. Fold Mountains form when two tectonic plates move together (a convergent plate boundary. They form from sedimentary rocks that accumulate along the margins of continents. When plates and the continents riding on them collide, the accumulated layers of rock may crumple and fold like a tablecloth that is pushed across a table, particularly if there is a mechanically weak layer such as salt.The forces responsible for formation of the Fold Mountains are called orogenic movements. These forces act at tangent to the surface of the earth and are primarily a result of plate tectonics.

Examples include-

  • The Jura Mountains - A series of sub-parallel mountainous ridges that formed by folding over a Triassic evaporitedecollement due to thrust movements in the foreland of the Alps.
  • The 'Simply Folded Belt' of the Zagros mountains - A series of elongated anticlinal domes, mostly formed as detachment folds over underlying thrusts in the foreland of the Zagros collisional belt, generally above a basal decollement that formed in the Neoproterozoic Hormuz evaporite[1]
  • The Akwapim-Togo ranges in Ghana
  • The Ridge-and-Valley Appalachians in the Eastern United States.

Block Mountains:

Block Mountains or Fault Block Mountains are massive in structure. They have very steep slopes. Generally, the topography of the Block Mountains is very smooth. They are usually tucked in the folded zones of some of the most primitive mountains. These folded zones have gradually lost their plastic properties. And as a result, mountain surfaces have been smoothened because of denudations. Tectonic actions continued and eroded these sections.

After breaking, some of the sections rose to new ranges and horsts. The remaining sunk to form depressions and grabens. Due to the repeated actions of orogeny, they formed broad gently sloping folds. These folds were accompanied by faults. There are two types of Block Mountains:

Lifted Block Mountains:

Lifted typeBlock Mountains has two steep sides. Both side scarps are exposed. Sierra Nevada and Teton Mountains in Wyoming (North America) are the best examples of lifted type Block Mountains.

Tilted block Mountains:

Tilted typeBlock Mountains has one gentle slope. The other steep has an exposed scarp. These type of mountains are commonly seen in the Range and Basin region of the western United States, Rhine valley and south-central New England. Level block terrains are commonly seen in northern Europe.

Volcanic Mountains

Volcanoes which are built up for material ejected from fissures in the earth’s crust. The materials include molten lava, volcanic bombs, cinders, ashes, dust and liquid mud. They fall around the vent in successive layers, building up a characteristic volcanic cone. Volcanic mountains are often called mountains of accumulation. They are common in the Circum-Pacific belt.

Examples include

  • Mt. Fuji located in Japan,
  • Mt. Mayon located in Philippines,
  • Mt. Merapi located in Sumatra,
  • Mt. Agung located in Bali and
  • Mt. Catopaxi located in Equador.

Residual Mountains

These are mountains evolved by denundation. Where the general level of the land is lowered by the agents of denundation some very resistant areas may remain and these from residual mountains. These may also evolve from plateaus which have been dissected by rivers into hills and valleys. Here the ridges and peaks are all very similar in height.

Examples include

  • Highlands of Scotland,
  • Highlands of Scandinavia and
  • highlands of Deccan Plateau
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