Gradation
The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation.
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Exogenetic forces constantly work to bring about leveling or the gradation of land.
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They attempt to achieve a condition of balance between erosion and deposition which means a graded position.
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Agents of gradation like rivers, glaciers, winds, sea waves, and groundwater perform their tasks with the help of the triple action of weathering, erosion, and deposition.
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Of these, the first three agents are controlled by climatic conditions. The work of the other two agents of erosion-waves and groundwater is not controlled by climate.
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In the case of waves, it is the location along the interface of lithosphere and hydrosphere — coastal region — that will determine the work of waves, whereas the work of groundwater is determined more by the lithological character of the region.
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The leveling down of elevated portions of the earth’s surface is done by erosion.