[Physics Class Notes] on Weathering Pdf for Exam

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. 

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, 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

 

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. 

 

 

 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.