Weathering is the gradual wearing and tearing of rocks on the surface of the Earth. The main agents of weathering are temperature, humidity, and precipitation. Weathering is of three types — mechanical, chemical, and biological.
Main characteristics of weathering
- Weathering is the wearing away or the disintegration of rocks.
- This process includes the breaking down and not the removal of rocks from the surface of the Earth.
- One of the most important results of weathering is soil formation.
- Rocks break into stones, pebbles, and eventually fine particles, which get transported by the agents of gradation such as wind and water.
- It depends on climatic conditions. For example, in a dry climate, mechanical weathering is very common.
- The nature of the rock (texture, composition, and hardness) also affects the process of weathering.
Types of Weathering
There are three types of Weathering —mechanical, chemical, and biological Weathering.
Types of Weathering #1
It is also known as physical weathering. The disintegration of rocks without any change in their chemical composition is known as mechanical weathering. Moisture, changes in temperature, frost action, and winds are the main actors of mechanical weathering. This kind of weathering usually occurs in hot deserts because of the wide ranges of temperature. There are four types of mechanical weathering:
Block Disintegration: Rocks disintegrate because of repeated expansion (due to high temperature) and contraction (due to extremely low temperature).
Granular Disintegration: Agents of weathering reduce the rocks made of different minerals to small pieces and fragments.
Exfoliation: Sudden change in temperature may cause cracks and fissures in rocks. Weathering occurs when water percolates in these fissures. The sudden expansion and contraction of rocks result in the peeling of their outer layers or exfoliation.
Frost Action: In regions of a dry climate, the cracks in rocks get filled with water. During the night, the water freezes and expands. When this process is repeated several times, the rock eventually breaks.
Types of Weathering #2
Minerals present in rocks undergo changes because of the action of water, oxygen, and other organic acids. Thus, rocks get decomposed because of chemical weathering. This happens because of chemical reactions which occur in rocks when these agents come into contact with the surface of rocks. There are four types of chemical weathering:
- Minerals present in rocks get dissolved in water. The rate at which the solution of rocks takes place is subject to the chemical composition and the structure of rocks.
- For example, rainwater causes chemical disintegration of gypsum.
- Many rocks contain constituents that have carbon dioxide present in them. When it comes in contact with water, acidic effects on rocks are produced.
- Many rocks such as marble and limestone get dissolved in water. Rainwater converts carbonate into calcium bicarbonate which is soluble and hence dissolves in water.
- Minerals present in rocks react with oxygen present in the atmosphere. Rainwater also involves atmospheric oxygen.
- When rainwater comes into contact with the iron compounds in rocks, iron begins to rust. This may also change the colour of the rocks to red, brown or yellow.
- Minerals present in rocks expand on coming into contact with rainwater.
- The minerals become heavy and begin to break down. Rocks such as feldspar get converted to kaolin.
Types of Weathering #3
Biological weathering is also known as organic weathering. Animals, insects, plants, and humans are the main agents of this type of weathering. This is because all the organic or biological matter is made of oxygen and water which may lead to chemical reactions in rocks, resulting in their decomposition and physical disintegration. Biological weathering occurs in the following ways:
Burrowing animals: such as rodents and moles loosen the ground or surface materials resulting in their physical disintegration. When animals die, their decaying bodies release chemicals that also lead to the disintegration of rocks.
Vegetation: Rocks may disintegrate when the roots of trees reach deep into them. However, trees may also prevent the disintegration of rocks by protecting them from direct exposure to sunlight and wind.
Humans: Humans are the most active agents of physical and chemical weathering. Mining, construction of roads and buildings, agriculture, and dumping of chemicals lead to both physical and chemical disintegration.
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Weathering is the gradual wearing and tearing of rocks on the surface of the Earth. The main agents of weathering are temperature, humidity, and precipitation. Read more