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Major Landforms - Work of Water

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Major Landforms - Work of Water - Lesson Summary

The process involved in the creation of the various landforms on earth i.e. mountains, plains and plateaus are endogenic and exogenic. The endogenic forces like earthquakes and volcanic eruptions bring about rapid change and even mass destruction. 

The Exogenic forces involve weathering, erosion and deposition. Weathering and erosion are two processes, constantly working together, wearing away the earth’s surface and lowering it.

The process of weathering involves breakdown of rocks and soils on the earth’s surface through direct contact with atmospheric conditions, and agents like water, ice and wind while erosion involves the loosening and carrying away of rocks and debris formed by weathering. The eroded material is carried away by agents i.e. water, ice and wind and deposited at other locations.

This results in the rebuilding of the earth’s surface at the new location. Water is the most powerful agent of erosion. Waterfalls, are a result of erosion by rivers.

Waterfalls are formed when the river water tumbles at a steep angle over erosion-resistant rocks or the side of a steep valley.

Flowing down from the mountains, rivers enter plains. A river never flows straight but in twists and turns, forming large bends. These bends are called meanders. The water of a river continuously erodes and deposits sediments along the sides of these meanders. This way the ends of the meander loop come close with time.

At a point, the ends of the meander loop meet and it gets cut off from the river forming a lake. Such a lake formed from the erosion and deposition along the meanders of a river is called an ox-bow lake.

When a river overflows it floods the areas around it depositing layers of fine soil and other types of sediment along the banks of the river. The areas subject to recurring floods get deposits which gradually spread over to build flat, fertile plains, called flood plains. The raised banks of such flood plains are called levees.

The speed of the river decreases owing to the flat land and it starts breaking up into distributaries and depositing the sediments. At some point, the speed of the river water becomes so low that it is not able to the sediments further. The river hence, starts depositing the sediments.

The deposition of sediments forms a mouth at the end of each distributary of the river which collects to form a delta.

The sea water in the form of waves carries on the task of erosion and deposition. As the sea waves keep striking at the rocks, they develop cracks which with time increase in size and width, gradually forming sea caves.

As water keeps eroding these caves, the cavities increase in size until only the roof is left from the original rock, resulting in the formation of a sea arch. Further erosion results in the destruction of the roof also, leaving only the walls of the original cave called stacks.

Where the sea waves encounter erosion-resistant rocks parallel to the coast, sea cliffs are formed. Sea waves continuously transport and deposit sediments along the shores and with time, these deposits form beaches.

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