July 15, 2014

Moutains- Formation, Types and Examples- Geography for UPSC IAS Exams

What are mountains & how are they formed?
A mountain is a geological landform that rises above the surrounding land. Mountains result from the collision and friction between tectonic plants in the Earth's crust, or between sub-plates, components of the plates. Tectonic plates move very slowly. It can take millions and millions of years for mountains to form. The Himalayan mountains began forming this way about 55 million years ago. The Himalayan mountain range has 30 of the world’s tallest mountains, including Mount Everest, which soars 29,035 feet in the air.

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Types of mountains:
Mountains can be classified into five different basic types based on the cause that formed the mountain, type of rocks, shape and placement on land.

Fold Mountains (Folded Mountains): These are the most common types of mountains. These are formed when two continental tectonic plates collide and their edges crumble to form mountains. Folded mountains are the product of two intercontinental (continent-continent) plate collisions. The crust is uplifted forming folds on top of the other. Vast mountain ranges stretching across thousands of kilometers are Fold Mountains. The Rocky Mountains in North America, the Alps in Europe, the Andes in South America, the Urals in Russia and the Himalayan Mountains in Asia are examples of Fold Mountains.

The Fold Mountains are of two types:

New or Young Fold Mountains - The Alps, the Himalayas, the Circum-Pacific oceanic mountains, etc., are worth mentioning. The main characteristics of these mountains are the complex folding of the rocks, faulting, Volcanic, activities, cordillera form, the erosion and weathering caused by running water, ice, winds, etc., the existence of glacier-capped high peaks, etc.

Old Fold Mountains - These mountains were folded in very ancient times. They were, then, subjected to denudation and uplift, many faults were formed and the layers of the rock were wrapped. Many mountains exist as relics, due to erosion. The presence of monad rocks, accordant summits, sculptured domes, the irregular forms of peaks, relics plateaus, etc., are some of the important characteristics of these mountains.

Fault-block Mountains (Block Mountains): Fault block mountains are formed as a result of a combination of tension(tensional stress) and uplift forces.  The stretching and cracking of the crust gives the mountains their appearance and name. They are bounded by high‐angle normal faults, and usually form a series of horsts and grabens. Broad crustal uplift (possibly a result of subduction stresses or mantle upwelling) can stretch and break the crust, creating fault zones along which the blocks move or slide. Uneven tectonic uplift can tilt the blocks.

Dome Mountains: Dome mountains are rounded isolated structures that are usually not associated with mountain belts as they occur in generally flat regions.

Volcanic Mountains: These mountains are the accumulations of large amounts of volcanic lavas and pyroclastic material around the volcanic vent, such as seamounts and stratovolcanoes. The Hawaiian and Aleutian Islands are volcanic mountains.

Relict or Residual Mountains - The mountains which are subjected to weathering and erosion for a long time, are lowered down and are called Relief or Residual mountains. The mountains of the Western Ghats, the Aravalli Mountain and the Parasnath mountain of Bihar belong to this type.

Lacolith Mountains - The outrushing magma forms the fissures, the crust of the earth at a place into a dome, mountains formed in such a way are called Lacolith Mountains.

Types of Mountains with Examples
Block Mountain
Ruwenzori Mountain range in Central Africa, Black forest, Vosges, bohemian massif and the Sierra Nevada in the south-western USA.
Fold Mountains
Himalayas, Aravalli, Appalachians, Alps, Rockies, Andes.
Relict Mountains
Aravalli, Rajmahal, Nilgiris, Satpuras, Western Ghats.
Dome Mountain
Henry mountain, USA


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