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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