Weathering| Class 11 Geography Notes

Weathering is the process of breaking down rocks, minerals, and other materials on the Earth’s surface. It is a natural process that is caused by a variety of factors, including wind, water, ice, temperature changes, and plants and animals. Weathering can occur in a variety of different environments, from deserts to mountains to oceans. Weathering is an important process because it helps to create soil, which is essential for plant growth. It also helps to shape the Earth’s surface by breaking down rocks and creating new landforms. Weathering can also have a negative impact on human activities, such as by causing erosion and damage to buildings and infrastructure.

Weathering is the action of elements of weather and climate over the earth’s materials. Several processes within weathering act either individually or together to affect the earth’s materials to reduce them to a fragmental state.

Weathering: Definition

Weathering is defined as the mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate. As very little or no motion of materials takes place in weathering, it is an in-situ or on-site process. Weathering processes are conditioned by many complex geological, climatic, topographic, and vegetative factors. Climate is of particular importance. Not only do weathering processes differ from climate to climate, but also the depth of the weathering mantle.

There are three major groups of weathering processes :

(i) Chemical;

(ii) Physical or mechanical;

(iii) Biological weathering processes.

Very rarely does any one of these processes ever operate completely by itself, but quite often a dominance of one process can be seen.

• A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/or soil water and other acids.
• Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions. Over and above the carbon dioxide present in the air, decomposition of plants and animals increases the quantity of carbon dioxide underground.
• These chemical reactions on various minerals are very similar to the chemical reactions in a laboratory.

Physical or mechanical weathering processes depend on some applied forces. The applied forces could be:

(i) gravitational forces such as overburden pressure, load and shearing stress;

(ii) expansion forces due to temperature changes, crystal growth or animal activity;

(iii) water pressures controlled by wetting and drying cycles.

Most of the physical weathering processes are caused by thermal expansion and pressure release. These processes are small and slow but can cause great damage to the rocks because of the continued fatigue the rocks suffer due to the repetition of contraction and expansion.

• Biological weathering is the contribution to or removal of minerals and ions from the weathering environment and physical changes due to the growth or movement of organisms.
• Burrowing and wedging by organisms like earthworms, termites, rodents etc., help in exposing the new surfaces to chemical attack and assist in the penetration of moisture and air.
• Human beings by disturbing vegetation, ploughing and cultivating soils, also help in mixing and creating new contacts between air, water and minerals in the earth’s materials.
• Decaying plant and animal matter helps in the production of humic, carbonic and other acids which enhance decay and solubility of some elements.
• Plant roots exert tremendous pressure on the earth’s materials mechanically breaking them apart.

People Also View:

• What is weathering? Types, Process, Examples
• Significance of Weathering

What do you mean by the term “Weathering”?

Weathering is defined as the mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate. Weathering is the action of elements of weather and climate over the earth’s materials.

What are the different processes of Weathering?

The different processes of weathering are : Chemical Activity ; Physical Activity and Biological Activity.

What do you mean by “Physical Processes” in weathering?

Physical or mechanical weathering processes depend on some applied forces. The applied forces could be:

(i) gravitational forces such as overburden pressure, load and shearing stress;

(ii) expansion forces due to temperature changes, crystal growth or animal activity;

(iii) water pressures controlled by wetting and drying cycles.

What is Salt Weathering?

Salts in rocks expand due to thermal action, hydration and crystallisation. Many salts like calcium, sodium, magnesium, potassium and barium have a tendency to expand. Expansion of these salts depends on temperature and their thermal properties.

Mention the significance of Weathering.

The significance of weathering are as follows:Weathering processes are responsible for breaking down the rocks into smaller fragments and preparing the way for formation of not only regolith and soils, but also erosion and mass movements. Biomes and biodiversity is basically a result of forests (vegetation) and forests depend upon the depth of weathering mantles.