Weathering is the process of deterioration of rock, soils, minerals, etc. This occurs when they are in contact with water, atmospheric gases, and biological organisms. Further, water, ice, snow, wind, waves, and gravity are the forms that transport the weathered materials.
During the weathering of rocks or minerals are dissolved with the changes made in the environment by the water, ice, acids, salts, winds, plants, an animal, variations in temperature, etc. This process cannot be resisted by even one of the hardest materials such as rock on the earth.
On the other hand, erosion is the process of transporting this material or any other from one location to another. It is not the same as weathering.
When we consider the rock, there is a process of transformation of the fresh rock to the soil that takes millions of years. The following steps can be observed in this material transformation process.
- Fresh Rock
- Slightly Weathered Rock
- Completely Weathered Rock
- Soil
These are the formation we identified in the rock. Completely weathered rock can be identified as soil.
Factors Control Rate of Weathering
As discussed previously, there are many factors affecting the deterioration of hard rock into fine soil particles. Out of those, some of them are significant and while others support the process moderately.
The following factors are related to weathering of rock.
- Mineralogy and structure of the bedrock. Chemical resistance, water solubility, etc. considerable impact on the rate. Further, rock structure which represents its scale and formation has considerable influence.
- Weather condition in the surrounding area influences the weathering of exposed rock whereas underneath rock has less impact. Hot weather with high temperatures and high rainfall areas are more susceptible to weathering compared to cold and dry areas.
- Soil cover of the surface rock increase the rate of rock weathering. Rainwater will be collected in the soil, and it reacts with the rock minerals to transform. Vegetation, bacteria, etc. contain in the soil from the acidic environment increases the rate of wreathing.
- Duration of the rock exposed to the adverse environment that causes the weathering. With more exposure to adverse conditions, the rate would be higher.
Different Types of Weathering
Mainly there are three processes in weathering.
- Mechanical Weathering
- Chemical Weathering
- Biological Weathering
Let’s discuss each type in detail.
Mechanical Weathering
Mechanical weathering is also known as Physical Weathering, and it is a type of weathering that occurs with a change in environmental conditions.
This is the process of rock disintegrating from the parent rock without a chemical reaction. It occurs due to the mechanical process.
Physical weathering is the process of separating rock into small fragments due to the expansions and contractions caused by variations in temperature. Exposure the aggressive weather conditions, cause a high rate of weathering.
Mechanical weathering and chemical wreathing are interconnected processes. The cracks formed in the rock by the physical weathering facilitate the ground for the chemical weathering.
There are two types of physical breakdowns in the rock.
- Freeze-thaw wreathing
- Thermal Fracturing
Freeze-Thaw Wreathing
The cracks in the rock filled with the water and when the temperature drops, water becomes ice. This causes an increase in the volume within the cack. During this process, the crack will be widened, and rock fragments will form.
With the increase in the temperature, ice will become water and it will transport the broken small rock fragments.
This weathering process is also called Frost Weathering or Cryofractuing.
Thermal Fracturing
Thermal stresses developed in the rock due to the changes in the rock temperature causing cracks. When the temperature rises, it tends to expand and when it drops rock tends to shrink. The occurrence of this process over a long time weakens the rock and leads to wreathing.
These types of wreathing are more common in areas where there is high temperature. During the daytime temperature increased and at the night it lowered considerably. This causes the crack and weakens the rock.
Chemical Wreathing
Chemical weathering is a process of converting rock into soil by the process of a chemical reaction. In these types of weathering processes, the molecular structure of the rock is.
Their process could be identified in the rock chemical weathering.
- Converting silicate in the rock to clay
- Dissolving the rock
- Formation oxides or Oxidation
The important chemical for weathering is water, oxygen, carbon dioxide, and other chemicals that react with a rock to change its structure.
Carbon dioxide in the atmosphere or the soil combines with the water in the carbonation process. It produces carbonic acid which is not that strong acid. However, it can dissolve the rock. Carbonic acid can dissolve the limestone with seep through the cracks. This would be considered carbonation weathering.
Biological Weathering
Biological weathering is different types of weathering that occur with the help of nature.
Biological weathering can be caused by plants, animals, etc.
The plant can grow on the rock and its roots can slowly penetrate the smaller cracks in the rock. With time, the crack would widen and as a result rock fragments could form.
Further, the biological weathering of rock is connected with chemical wreathing. The roots and the organic matter in the soil forms organic acids that can weather the rock.
