Gradation and its Types

Gradation is the process of removing unevenness of the land surface and making it a level land. Agents of gradation are running water, wind, glacier, waves, and underground water.

Gradation can be of two types- degradation and aggradation.

Degradation is the process of denudation. It involves weathering, mass wasting and erosion.

Aggradation is also known as deposition. Eroded materials are deposited in the depressions or lowlands and these areas rise up.

Weathering is the process of breaking down or disintegration and decomposition of rocks. Factors affecting weathering are parent rock, nature of ground slope, climatic variations, and vegetative cover.

Different types of weathering are physical weathering, chemical weathering and biological weathering.

Agents of physical weathering are insolation, frost wedging, and pressure release.

Insolation is caused by extremes of hot and cold temperature over a 24 hour period. Effects of insolation are block disintegration, granular disintegration, and exfoliation.

Block disintegration of rocks occurs due to high range of daily temperature in desert areas that results in continuous expansion and contraction of rocks.

Granular disintegration occurs due to the expansion and contraction of minerals of rocks at different rates due to temperature.

Exfoliation refers to peeling off concentric shells of rocks. It occurs in rocks, which are bad conductor of heat.

Frost action or frost wedging is most common in temperate climates.

Rocks deep within the Earth are under great pressure from the surrounding rocks. When the rocks above them are weakened or eroded away, the pressure is released.

Chemical weathering is the decomposition and decaying of rocks due to chemical reactions.

Types of chemical weathering are oxidation, carbonation, hydration, and solution.

Oxidation and reduction occurs when there is a combination of a mineral with oxygen to form oxides or hydroxides.

Carbonation is the reaction of carbonate and bicarbonate ions with rock minerals.

Hydration occurs when the hydrogen of the water dissolve the rocks.

Solution is the process in which some minerals are dissolved in water or acids and leach the soil.

Biological weathering is the decomposition and disintegration of rocks due to organic materials of flora and fauna. Agents of biological weathering are plants and trees, animals and insects, and human activities like construction, mining, deforestation, land cultivation, etc also lead to the disintegration of rocks.

Mass wasting is the downhill movement of weathered rock materials. Factors affecting mass wasting are angle of slope, gravity, water, and human activities.

Types of mass wasting are soil creep, solifluction, mudflow, and earth flow.

Landslides include slumping, rock fall and land slide.

Erosion is the removal and transportation of weathered material through different agents of gradation. It includes the process of scarping, scratching, and grinding of rocks.

The agents of gradation like, river, wind, sea waves, glaciers and groundwater perform the work of erosion, transportation and deposition and build up different landforms.

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