Geography: Understanding Weathering

Learning objective:

 By the end of this Chapter, you must be able to describe what is weathering and distinguish the different types of weathering and how weathering occurs in each element.

 What is weathering 

Weathering is the breaking down of rocks and minerals on the surface of the earth due the exposure of atmospheric condition, element of weathering includes, flowing and running water, Ice, plant roots, acid, animals and change in temperature. Once the rock has been broken down the process called erosion transports the bit of rocks and minerals away, no rock on earth is hard enough to resist the force of weathering.

Three Types of weathering 

1. Mechanical or Physical weathering- This type of weathering which is caused mainly due temperature difference and is particularly noticeable in areas that are hot during the day and very cold at night. The constant heating and cooling of the surface rocks causes them to expand during the day and contrast at night. This puts the top few centimeters under great stress: cracks appear which deepens and eventually causes the outer layer of the rock to peel and expose the layer underneath causing the rock to break.

The video below explains mechanical or physical weathering in details 

2.Chemical weathering - Is the result of rocks undergoing a chemical change. This type of weathering is mostly rapid in a warm, moist regions, where rocks have already been broken up by mechanical weathering, example chemical weathering includes 

•  Oxidation This involves the reaction of minerals with oxygen, typically from the atmosphere or rainwater. Iron-bearing minerals, like olivine and pyroxene, can oxidize to form iron oxides (such as rust). For instance, the reddish color of many rocks is due to the presence of iron oxides resulting from oxidation. and
•  Carbonation: This process occurs when carbon dioxide (CO2) in the atmosphere dissolves in water to form carbonic acid. This acid reacts with minerals like calcite in limestone or marble, leading to the dissolution of these rocks. An example of carbonation is the formation of caves in limestone regions, where the rock dissolves over time due to acidic rainwater.

Picture below shows how weathering occurs as a result of acid rain 

3. Biological weathering -Is the process of rock breakdown that is caused by living organisms. Here are some keyways biological weathering occurs

• Root Expansion: Plant roots can grow into cracks and crevices in rocks. As the roots expand, they exert pressure on the rock, causing it to crack and break apart. This process can also contribute to the formation of soil.
• Organic Acids: Many plants, fungi, and lichens produce organic acids as part of their metabolic processes. These acids can dissolve minerals in rocks, promoting chemical weathering. For example, lichens on rocks release acids that slowly break down the rock surface.
• Animal Activity: Animals, including insects, burrowing mammals, and even birds, can contribute to biological weathering. For instance, burrowing animals can expose deeper layers of rock to the surface, increasing their susceptibility to weathering processes. Earthworms and other soil-dwelling organisms can mix and move soil, enhancing weathering through mechanical disruption and organic acid production.

below is video explaining the overview of weathering 

Conclusion 

In conclusion, weathering is a fundamental geological process that breaks down rocks and minerals at or near the Earth's surface, shaping landscapes and contributing to soil formation. Understanding weathering helps us to comprehend Earth's dynamic systems, predict geological changes, and manage natural resources effectively.

References 

Price, D. G. (1995). Weathering and weathering processes. Quarterly Journal of Engineering Geology and Hydrogeology, 28(3), 243-252.

Bland, W. J., & Rolls, D. (2016). Weathering: an introduction to the scientific principles. Routledge.

Hoffland, E., Kuyper, T. W., Wallander & van Breemen, N. (2004). The role of fungi in weathering. Frontiers in Ecology and the Environment, 2(5), 258-264.