The Meaning and Types of Weathering
Several naturally-occurring processes influence the world that we see around us, and that's why the terrain and the sea are diverse. Be it because of rains, snow, wind, or sunshine, the rocks break down or disintegrate into smaller units. Such a process, in its elaborate form, is called weathering. The causes of weathering can be the effect of continuous biological, chemical, and physical processes, as seen on rocks, wood, soils, and minerals. Often confused with erosion that occurs with the movement of rocks, soil, minerals via water, gravity, snow, wind, weathering, on the other hand, only occurs in rocks, soil, and minerals that stay in one place.
There are Primarily Three Different Types of Weathering Processes:
There are mainly three types of weathering, which are Mechanical Weathering, Chemical weathering, and Biological Weathering. Below you can find further detail about these types.
Mechanical Weathering: Mechanical weathering is also regarded as physical weathering. The main agent of mechanical weathering is the water, either in liquid form or in solid form.
Chemical Weathering: The type of weathering, that causes the molecular structure of the rocks and soil to change, is called chemical weathering. Oxidation, the salinity of seawater are some of the prominent examples of chemical weathering. Some prominent chemical weathering examples would include oxidation, the salinity of seawater, etc.
Biological Weathering: When the mineral weathering is started or accelerated by the microorganisms present in the soil, it is called biological weathering. As interesting as these types of weathering is, one example would be that of lichens that are found in rocks, causing it to open and be more vulnerable to weathering.
Physical Weathering: Among the most commonly found tangible weathering examples are ice wedging, growing of plant roots in rock cracks.
More often than not students get a little confused between the Erosion and Weathering, and hence if you have such confusion as well, and want to get clarity for the same, then you must follow this link.
The topic of Weathering is of utmost importance for the students in the subject of science. And hence a good explanation of the same is very much required for the students. It is really difficult to define a good explanation exactly, but you can say that, if after going through the explanation, you do not have to go anywhere else for further clarification regarding the topic of weathering, then such explanation can be termed as a good explanation.
If you are not provided with such a good explanation for the topic of weathering. Then you may look at more than one explanation of the same topic, and each time you end up more confused. And this does not only make you believe that the topic of weathering is difficult, but it also lowers your confidence. And hence, Vedantu provides the students such a good explanation of the topic of weathering along with its types, which they can easily understand and comprehend. After going through this explanation of the topic of weathering and its types, you are not going to have any confusion regarding the topic.
Weathering Diagram
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There can be many weathering agents, like water, ice, acids, salts, plants, animals, and timely changes in temperature. There are no rocks present on Earth that are resistant to weathering, and the Grand Canyon in Arizona, USA, is one such example.
Weathering of Rocks
Weathering is often observed as a mechanical, chemical, and biological process. However, the biological processes can come as a combining effect of both physical and chemical processes taking place via a living organism. The processes are:
Physical or Mechanical Weathering
In this type of weathering, the process can also be called disaggregation, where the rocks get disintegrated without undergoing chemical changes in them. Abrasion is one such process in which the clastic rocks get reduced in size, especially seen in the rocks near the shoreline that get washed away due to waves.
However, physical weathering mainly occurs due to the result of extreme temperatures, pressure, frosting, etc. These can be found occurring in areas with lesser soil deposits, low vegetation, and arid regions. In the tundra, physical weathering can occur by continuous melting and freezing of water. In contrast, in hot deserts, the same can occur due to the constant expansion and shrinking of the surface rocks.
Chemical Weathering
The chemical weathering can take place due to changes in rock compositions, as a result of several chemical reactions. Upon slow, gradual, and ongoing process, the rocks surface minerals now develop newer minerals allowing oxidation and hydration to occur subsequently. It is further enhanced by geological agents like water and oxygen that make microbial and plant-root metabolism acids. These occur rampantly in areas having high temperatures (in tropical climates) but are also found across the world. There are different types of chemical weathering:
Carbonation: The removal of rock in the form of acidic rainwater causes chemical weathering. Here the rain that contains dissolved Carbon dioxide can help in the weathering of Celestone.
Hydrolysis: It refers to the acidic water that breaks down rock into clay and several soluble salts.
Oxidation: It refers to the breakdown of rocks with the continuous effect of oxygen and water, thus providing it with a rust-like surface to rocks that are rich in iron constituents.
Biological Weathering
This refers to the weakening and breakdown of rocks under the influence of microorganisms, plants, and animals. It can occur due to the growth of roots that can pressurize rocks, causing them to get weakened and exposed to further weathering. It can also come as a process favoring chemical weathering since the organic acids that get produced by the plant roots can provide the ground for the growth of several microorganisms and help in dissolving the minerals.
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It is also due to the surge in microbial activity that causes the alteration of the natural composition of rocks, making them more susceptible to weathering. In lichen, such symbiotic microbial growth is observed prominently between algae and fungi that release chemicals responsible for breaking down minerals present in the rocks. Such minerals are further consumed by algae and facilitate cracks in rocks, slowly breaking it down as a combined effect of physical and chemical weathering.
Small rodents and other animals that live in burrows can dig up rocks and make them vulnerable to intense weathering because of the sudden exposure to sunlight, air, wind, and water.
Humanity and Weathering
There are many ways in which humans facilitate the weathering process and cause it to occur faster than natural methods. An example of it would be due to distinct air pollutants that get into the atmosphere because the burning of fossil fuels can increase the overall composition of nitrogen oxide and sulfur dioxide in the air. Such chemicals can form acidic compounds upon reacting with sunlight and atmospheric moisture that falls on the surface as acid rains.
Acid rains are primarily responsible for weathering limestone, marble, and are often seen on gravestones, making the writings illegible.
An Overview of the Weathering and its Types
The dissolving of the rocks and minerals or the process of breaking down of the rocks and minerals on the surface of the Earth is called Weathering. There are many agents due to which the process of weathering becomes possible such as ice, water, acids, salts, animals, plants, and also the changes in the temperature.
After the breaking down of the rock, the material which is leftover combines with the organic material, and the soil gets created. Many landscapes of the earth have formed because of the combination of the weathering process and the process of erosion, and also re-deposition.
FAQs on Weathering
1. What is meant by weathering in the context of the CBSE syllabus for 2025-26?
In line with the NCERT curriculum, weathering is defined as the natural process of breaking down or dissolving rocks and minerals on the Earth's surface. It is an in-situ process, meaning the rock material is altered without being moved from its original location. The primary agents causing this breakdown include water, ice, acids, salts, plants, animals, and significant changes in temperature.
2. What are the three main types of weathering? Explain each with an example.
The three principal types of weathering are Mechanical, Chemical, and Biological. Each process breaks down rocks differently:
- Mechanical Weathering: This process, also known as physical weathering, disintegrates rocks without changing their chemical composition. An example is frost wedging, where water seeps into rock cracks, freezes, expands, and breaks the rock apart.
- Chemical Weathering: This involves the decomposition of rocks through chemical reactions, altering the rock's molecular structure. A common example is oxidation, where iron in rocks reacts with oxygen to form rust, weakening the rock.
- Biological Weathering: This is the weakening and breakdown of rocks by living organisms. For instance, a plant's roots can grow into a rock's fissures, exerting pressure and eventually splitting the rock.
3. What is the key difference between weathering and erosion?
The key difference is that weathering is the process of breaking down rocks where they are, while erosion is the process that moves the broken pieces (sediments) away. Weathering breaks it, and erosion takes it. For example, acid rain dissolving limestone is weathering. The subsequent washing away of the dissolved material by a river is erosion.
4. How do agents like water and temperature cause physical weathering?
Water and temperature are powerful agents of physical weathering. They work together in processes like frost action (or freeze-thaw), where water enters rock cracks, freezes and expands by about 9%, creating immense pressure that widens the cracks and eventually shatters the rock. Temperature changes alone cause thermal stress; the outer layers of a rock expand when heated and contract when cooled, causing them to peel away over time, a process known as exfoliation.
5. Explain the process of chemical weathering through oxidation and carbonation.
Chemical weathering alters rocks at a molecular level. Key processes include:
- Oxidation: This is the reaction of oxygen with minerals, especially those containing iron. It is essentially the 'rusting' of rocks. This reaction forms iron oxides, which are weaker than the original mineral, making the rock crumble easily.
- Carbonation: This occurs when carbon dioxide from the air dissolves in rainwater to form a weak carbonic acid. This acidic water is highly effective at dissolving rocks containing calcium carbonate, such as limestone and chalk, carving out caves and other karst landscapes.
6. How is biological weathering considered a combination of physical and chemical processes?
Biological weathering often acts as a bridge between physical and chemical processes. Physically, the roots of trees can grow into rock fractures, exerting pressure that breaks the rock apart. Chemically, organisms like lichens and bacteria produce acidic compounds that can dissolve rock minerals. Therefore, biological agents can both physically wedge rocks open and chemically alter their composition, demonstrating aspects of both weathering types.
7. What is the importance of weathering in the formation of soil?
Weathering is the foundational step in soil formation. It breaks down the solid bedrock into smaller particles, creating a layer of loose material called regolith. This regolith is the parent material of soil. Over time, organic matter from decaying plants and animals mixes with these mineral particles, and with the help of water and air, it develops into fertile soil, which is essential for supporting plant life and ecosystems.
8. How can human activities, such as burning fossil fuels, accelerate weathering?
Human activities significantly accelerate weathering, primarily through pollution. The burning of fossil fuels releases sulphur dioxide (SO₂) and nitrogen oxides (NOx) into the atmosphere. These gases react with water, oxygen, and sunlight to form sulphuric and nitric acid, which fall to the Earth as acid rain. Acid rain is a potent agent of chemical weathering, rapidly dissolving statues, buildings, and natural rock formations much faster than natural processes would.
