Weathering is the breaking down of rocks in place (in situ) by natural agents. Unlike erosion, weathering does not move the broken material away; it only loosens and decomposes rock where it lies.
Types of weathering
- Physical (mechanical) weathering breaks rock into smaller pieces without changing its chemistry. It includes exfoliation from repeated heating and cooling, pressure release, and frost action in cold regions.
- Chemical weathering changes the minerals in rock through water and gases. It includes carbonation (rainwater with carbon dioxide dissolving limestone), oxidation (rusting of iron minerals) and hydrolysis.
- Biological weathering is caused by living things, such as plant roots widening cracks and burrowing animals or human activity breaking rock.
Key idea
Weathering breaks rock in situ; erosion carries the material away. In Malaysia's hot, wet equatorial climate, high temperatures and heavy rain make chemical weathering the most active type.
Effects of weathering
Example
Carbonation of limestone in Malaysia produces karst landscapes with caves, sinkholes and steep limestone hills such as those in the Kinta Valley.
Weathering forms the parent material for soil, so deep, well-weathered soils develop in the tropics and support Malaysia's rich vegetation and farming. It also weakens slopes by loosening rock, which can lead to landslides during heavy rain, and it slowly shapes distinctive landforms over long periods. Understanding weathering therefore helps engineers judge how safe a slope is before roads or houses are built on it.
Remember
- Weathering is in situ; erosion involves transport.
- Malaysia's climate favours chemical weathering.
- Weathering forms soil, karst features and can trigger landslides.