Types of Weathering

The soil that you use to plant trees in, the sand that you use to make sandcastles at the beach, the clay that you use to make all those pots, are all results of the process of weathering. As kids, you probably have read about the process of how huge rocks and boulders breaks down with time to form sand or soil particles. This whole process is called weathering. There are different types of weathering, namely mechanical weathering or physical weathering and chemical weathering.

Process of Weathering

In lay man's term, weathering is a term in Geology which means or which indicates the 'natural decaying away of the rocks and their minerals and this decaying mainly takes place near the surface of the earth.' The rocks or stones are either broken down by physical forces or by chemical process and sometimes by both the processes. Exposure of these rocks and boulders to water, air or to living organisms, often leads to weathering. Due to weathering, the minerals usually breaks down into small pieces so that they can be easily carried away by water and air and with time, this rock is converted into sand and clay. The time taken for the rock to weather and also the process of weathering, often depends upon the climate or the area where the rock is present.

Weathering Types

There are generally two types (as it has already been mentioned above); physical and chemical weathering. Each of these types have been discussed below.

Physical Weathering/Mechanical Weathering

As the name suggests, physical weathering does not involve the use of chemicals during the whole process of disintegration of rocks. Abrasion is the main process through which the physical weathering takes place. This kind of a weathering takes place mainly in areas where there is little vegetation, places where the temperature fluctuates around 0°C and also those places where the diurnal range of temperature (or the difference in the minimum temperature at night and maximum temperature at day) is high. Physical weathering and chemical weathering goes hand in hand. How? Physical weathering increases the surface area so that chemical weathering can take place. It can take place by the following means:

• Frost Shattering: This process usually takes place in places where the temperature goes above or below the freezing point. The water in the cracks or joints of the rocks, freezes during the night and this whole process of freeze and thaw, leads to the breaking up of the rock into several smaller pieces.
• Crystallization: This process is also known as Haloclasty. This occurs when salt water seeps into the cracks and joints of the rocks and then evaporates leaving behind the salt crystals. These crystals expands as they start heating and thus exerting pressure on the rock. This usually takes place in arid regions.
• Exfoliation: Exfoliation mainly takes place in the desert regions where during the day the temperature goes to more than 40°C and at night the temperature goes below 10°C. Due to the constant change in temperature every day, the rocks and stones starts to expand and contract and this causes stress within the rocks which in turn causes cracks and finally leads to the peeling off, of the top layer of the rocks.
• Release of Pressure: Release of pressure or pressure release occurs due to removal of the top layer of the rocks through erosion. Now since the pressure that was earlier exerted on the rocks is released, the rocks gets a chance to expand, and this causes stress inside the rock which creates cracks and with time, the top layer of the rock breaks away.
• Biological Weathering: Sometimes due to plants and animals, physical weathering might also take place. When the roots of the plants grows into the cracks of the rocks or sometimes during cultivation, the rocks are exposed to the other agents of weathering such as air and water. The animals and worms like earthworms also helps in weathering by making tunnels underground.

Chemical Weathering

As the name suggests, this type of weathering takes place due to the various chemical reactions due to which the minerals present in the rocks starts dissolving thus transforming the whole rock and also changing its physical characteristics. The whole process mainly depends on the warm climate or temperature and also the moisture present in that particular area. The main agents of chemical weathering are usually water, air and rainfall with rainfall being the most important agent. We all know that rainwater contains a small amount of acid in it and when this acidic rainwater mixes with the carbon dioxide in the air, it forms carbonic acid which is mainly responsible for the dissolving of the various minerals in the soil and thus causing weathering. The rocks are not made up of the same minerals, hence, the reaction of the chemicals on each mineral will vary. Some rocks like quartz do not break down due to chemical weathering while some like limestone reacts strongly.

The various types of erosion should not be considered to be the same thing as they are two separate things. So now you know how the soil and sand that you see everyday are formed. It takes time and by time I do not mean one or two years but millions of years.