Wednesday, 10 February 2016

MOUNTAIN


TOPIC: mountains 
SOURCE: 8TH NCERT

Mountains :
·        Landform is a natural feature of the earth’s surface.
·        The surface of the earth varies from one place to another.
·        The main landforms are; mountains, plateau and plains.
·        There are two processes which lead to formation of different landforms.
·        These processes are; internal process and external process.
Internal Process:
·        The earth beneath your feet is continuously moving.
·         The movement of earth’s surface results in internal process.
·        The internal process results in a portion of the earth’s surface getting elevated or getting sunk.
External Process:
·        Continuous wearing down and rebuilding of the earth’s surface is the result of external process.
Erosion:
·        Removal of materials is called erosion. Erosion results in lowering of the earth’s surface.
·        Erosion is carried out by various agents; like wind and water.
Deposition:
·        Deposition of materials results in rebuild of the earth’s surface. It also results in the surface getting elevated.
·        Wind and water are the main agents of deposition.

Mountains

·        A mountain is the natural elevation of the earth’s surface.
·        A mountain may be narrow at top and broad at the base.
·        The elevation of mountain is considerably more than that of surrounding area.

·        We know that temperature reduces with increase in altitude.
·        Due to this, very high mountains are usually covered with snow.

Glacier:
·        Permanently frozen rivers of ice are called glaciers.
·        Glaciers are found in some of the very high mountains.
Mountain Range:
·        When mountains are arranged in a line, then it is called a mountain range.
·        Some of the mountain systems contain ranges spread over hundreds of kilometers.
Types of Mountains :

There are three types of mountains, viz. fold mountains, block mountains and volcanic mountains.

Fold Mountains:
                  



·        Fold mountains are created through a process called orogeny. An orogenic event takes millions of years to create a fold mountain,
·        When a tectonic plate gets pressure from two sides, it gets folded. Some of its portion becomes elevated and forms the mountains.
·        The depressions form the valleys. The Himalayas, 
·        The Andes and the Alps are examples of Fold Mountain. They are the young mountains of the world and hence they have some of the highest peaks of the world.
·         Highest peaks are found in folded mountains 
·        Folded mountains are the youngest on the surface of the earth
·        fold mountains in India: Himalaya- young fold mountain

Block Mountains: 

·        When large areas are broken and displaced vertically, Block Mountains are formed.
·        In this case, the uplifted blocks are called horsts. 
·        On the other hand, the lowered blocks are called graben.
·        Examples of Block Mountains are; the Rhine Valley and the Vosges mountain in Europe.
·         
Volcanic Mountains:

·         A mountain formed due to volcanic activity is called Volcanic Mountain.
·        Examples of Volcanic Mountains are; Mt. Kilimanjaro and Mt. Fujiyama.

·         Andaman and Nicobar islands in India are the tip of the volcanic mountains which rise from the ocean floor



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