Class 6 Geography
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.
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.
Population at Mountains: Because of steep slopes, less amount of land is available for farming on mountains. This is also difficult to build houses on steep slopes. Hence, less number of people lives on the 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.
There are three types of mountains, viz. fold mountains, block mountains and volcanic mountains.
Fig: Fold Mountain
Fold Mountains: 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. The Aravali is also an example of Fold Mountain. Because of constant erosion, the Aravali has considerably worn down.
Fig: Block 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.
A plateau is a flat and elevated land. A plateau is at higher elevation than the surrounding areas. A plateau may have one or more sides with steep slopes. A plateau can be young or old. The height of plateau can be from a few hundred meters to several thousand meters.
Examples: The Deccan Plateau (India) is one of the oldest plateaus in the world. Other examples of plateau are; the East African Plateau in Kenya, Tanzania and Uganda and the Western Plateau in Australia. The Tibet plateau is the highest plateau in the world and its elevation is between 4,000 to 6,000 m above sea level.
Plains are flat lands and are generally not more than 200 m above mean sea level. Some plains are extremely level, while others may be slightly rolling and undulating.
Formation of Plains: Plains are usually formed by rivers and their tributaries. When a river flows down a mountain, it erodes the mountain. The river carries forward the eroded material. Then the river deposits the load in its valley. The load consists of stones, sand and silt. Plains are formed from these deposits.
Copyright © excellup 2014