There are 2 major types of soil weathering. Weathering can be defined as the process by which the rocks would be broken down into sediments, soils and clays at the surface of Earth. This process would affect the rocks in place and there would be no involvement of transport. This is how the soil weathering is distinguished from the soil erosion. More generally, the weathering process would begin with uplift of Earth’s crust by the tectonic forces. The process of weathering is considered as an integral part in the development of soil. The timeline for the weathering process would vary from a number of decades to millions of years depending upon the factors of soil formation.
Types of Soil Weathering are as follows:
Physical or Mechanical Types of Soil Weathering:
These types of soil weathering are the processes that would cause the disintegration of rocks without any chemical change. Abrasion is the primary process in physical/mechanical types of soil weathering by which the particles would be reduced in sizes. The physical weathering would mainly occur due to the changes in temperature and pressure.
• Thermal Stresses: These types of soil weathering are also known as insolation weathering. These result from expansion and contraction of rocks that are caused by the changes in temperature. The thermal stresses are the significant mechanisms in deserts. Though the changes in temperature are the primary drivers, moisture could enhance the thermal expansion in rocks.
These types of soil weathering could be further classified into 2 major types:
• Thermal Shock
• Thermal Fatigue
• Frost Weathering: These processes are common in mountain areas where the temperature would be around the freezing point of water. Freeze included types of soil weathering would occur more generally in environments where one could see a lot of moisture and where the temperatures would often oscillate above and below the freezing point of water. The process of frost weathering include:
• Frost shattering
• Frost wedging
• Freeze-thaw weathering
• Pressure Releases: In these types of soil weathering, the overlying materials would be removed by the processes of erosion and hence, the underlying rocks would expand and fracture. In due course of time, the sheets of the rocks would break away along the fractures. This process is known as mechanical exfoliation.
These are the types of soil weathering that are resulting from the chemical reactions between the rock minerals and the external agents. Chemical weathering has the tendency to change the composition of rocks. This is a gradual and ongoing process. The major types of chemical weathering are:
• Dissolution: This type of chemical weathering is more common in the areas where more amount of limestone is present. The acidic waters would dissolve limestone thereby allowing the entry of additional waters.
• Oxidation: This type of chemical reaction would occur to all the iron-bearing silicates. The common reacting minerals are: hematite and limonite.
• Hydrolysis: This is a chemical reaction which would affect silicate and carbonate minerals. In these reactions, pure water would ionize and react with silicate minerals.