Weathering
Introduction
The process of disintegration and decomposition of rocks is known as weathering.
Factors like temperature, pressure, rainfall, frost, wind, plants, animals and human beings are responsible for weathering.
The character of the rock, its chemical composition, hardness, texture, joints, and permeability play an important role in weathering.
The endogenic and exogenic forces causing physical stresses and chemical actions on earth materials and bringing about changes in the configuration of the surface of the earth are known as geomorphic processes.
Diastrophism and volcanism are endogenic geomorphic processes.
Weathering, mass wasting, erosion and deposition are exogenic geomorphic processes.
Any exogenic element of nature (like water, ice, wind, etc.,) capable of acquiring and transporting earth materials can be called a geomorphic agent.
Running water, groundwater, glaciers, wind, waves and currents, etc., are geomorphic agents.
The process of weathering away the earth causes a general lowering and levelling out of the surface is known as denudation and is carried out in four phases:
Weathering
Erosion
Transportation
Deposition
Weathering Types:
Mechanical Weathering
Chemical weathering
Biological Weathering
I. Mechanical weathering
The disintegration of rocks in a mechanical way and without any physical changes is called mechanical weathering.
It is also called physical weathering.
Mechanical weathering is mainly influenced by temperature, frost, wind, and sea waves.
The agents of mechanical weathering are:
1. Temperature
High temperature leads the rocks to expand and low temperature makes them contract.
During the day the rocks expand due to high temperature and at night contraction takes place due to a reduction in temperature.
This is a continuous process that leads to the breaking or disintegration of rocks.
2. Frost
In the cold and frigid regions during night time, due to low-temperature water solidifies into ice, and during the day ice melts.
Continuous freezing and thawing lead to the expansion and contraction of rocks, resulting in the disintegration of rocks.
3. Wind
In the desert, the wind carries sand materials from one region to another and causes friction of particles on the rock surface. This results in the scratching and breaking of rocks.
4. Gravitation
The gravity of the earth makes the huge rocks roll towards the slope.
Rolling rocks strike against each other and break up into pieces.
5. Sea waves
Seawater brushes against the coastal rocks of the sea and causes the breaking of rocks.
The process of Mechanical weathering is in various forms, depending on the type of rock. They are.
1. Block weathering
Due to temperature variation, there is a continuous expansion and contraction in the rocks causing tension and stress. Later these rocks disintegrate into blocks known as block disintegration.
2. Granular disintegration
Rocks consist of several types of minerals and these minerals react differently to heat. As a result, the rocks break into different mineral gains known as granular disintegration.
3. Exfoliation
Due to the heat of the sun. the outer surface of rocks gets heated up, but inside it remains almost cool. This makes the rock expand and crack. The thin layer of rocks peels off, like the peeling of an onion. this process is called exfoliation.
II. Chemical weathering
The disintegration and decomposition of rocks by the chemical process is called chemical weathering.
In this process, secondary and new minerals are developed from the original minerals of the rocks.
The rainwater and atmospheric gases are the main agents of chemical weathering. It is very common in humid regions.
Types of chemical weathering
There are four types of chemical weathering processes. They are,
Oxidation
Carbonation
Hydration
Solution
1. Oxidation
The rainwater with oxygen reacts with rocks containing iron and produces oxides. This chemical reaction is known as oxidation. The common process of rusting iron is an example of oxidation.
2. Carbonation
The rainwater with carbon dioxide becomes a weak carbonic acid and it reacts with calcium carbonate or limestone to form calcium carbonate, which dissolves easily. This process is called carbonation. It is very active in limestone regions.
3. Hydration
The rock minerals take up water, the increased volume creates physical stress within the rock. As a result, certain minerals like feldspar and gypsum are reduced into powder. This process is called Hydration.
4. Solution
The rainwater is able to dissolve some of the soluble minerals, such as rock salt, gypsum, and potash. This process is called a solution.
III. Biological weathering
The disintegration of rocks caused by plants, animals and human beings is called Biological weathering.
1. Plants
The roots of plants grow through soil and in the cracks of rocks to find water and minerals. As the roots grow deep in the rock they widen and disintegrate the rocks. this process is most prominent in thick forests and vegetative regions.
2. Animals
The burrowing animals like rats, rabbits, earthworms, and termites influence the breaking up of rock and make passages resulting in rapid weathering of rocks.
3. Human being
Human beings play an important role in weathering of rocks, through activities like agriculture, mining, quarrying, oil drilling, deforestation, etc.
Importance of weathering
Weathering is an important process in the formation of soil and helps for natural vegetation and agriculture.
The process of weathering produces a new landscape and variety of sceneries.
This process prepares the ground for the work of different agents of denudation.
