What is Weathering?
Weathering is the breakdown and decay of rock in its original place, without transport. It differs from erosion because the loosened material is not carried away. Three types of weathering often act together. Weathering is important because it provides raw material for soil formation and shapes many landforms, such as karst hills in limestone areas.
Types of Weathering
Physical (mechanical) weathering breaks rock into smaller fragments without changing its chemical make-up. Day-and-night temperature changes cause exfoliation (onion-skin peeling), block disintegration and granular disintegration, while frost action (freeze–thaw) occurs in cold regions. In hot, dry deserts, physical weathering is most active because of the large daily temperature range.
Chemical weathering makes rock decay through reactions with water, oxygen and acids. Carbonation dissolves limestone to form caves, oxidation rusts iron minerals, and hydrolysis turns the feldspar in granite into clay. Chemical weathering is most active in hot, humid regions such as Malaysia.
Biological weathering is caused by living things. Growing plant roots physically prise rocks apart, while acids from organisms such as lichen and from human activity speed up chemical decay.
Remember
Malaysia's hot and humid climate all year round encourages active chemical and biological weathering.
Factors of Weathering
The rate of weathering depends on several factors:
- Temperature and a large daily temperature range.
- High moisture and heavy rainfall.
- Type and structure of rock — jointed rock weathers easily.
- Vegetation and steepness of slope.