TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Geography > Weathering
- Weathering is the breaking and decomposition of rocks at/near the earth's surface by physical & chemical processes.
- There are two main types of weathering:
- Chemical Weathering: This involves the decomposition of rocks due to chemical reactions between rock minerals, water and some atmospheric gases such as oxygen and carbon dioxide. The main types of chemical reactions are:
- Hydration: This is the absorption of water by rock minerals.
- Oxidation: This is when oxygen is taken up by a mineral compound.
- Carbonation: this is when hydrogen carbonate ions combine with a mineral to give a soluble compound which can then be carried away in solution.
- Solution: The solution of soluble minerals e.g. limestone in rocks.
- Hydrolisis: The reaction between the hydrogen ions in water and some metal ions.
- Mechanical Weathering:
- Temperature changes causing expansion and contraction of rocks.
- Freezing of water--frost action.
- Wetting and Drying
Factors Influencing the Character and Rate of Weathering
These factors include:
- Climate
- The greater the amount of rainfall the higher the rate of chemical weathering.
- Temperature changes accelerate the rate of mechanical weathering.
- The nature of the parent rock.
- Vegetation cover
- The gradient of the slope
- Time
- Man's activities
Mass Wasting
- Mass wasting is the movement of rock materials under the influence of gravity.
Factors Affecting the Speed of Mass Wasting
- These factors include:
- The nature of the material
- The angle of the slope
- Vegetation cover
- Earthquakes
- Mans activities
Main Types of Mass Wasting
- Soil Creep: This is the downward movement of soil
- Mudflow: When continued heavy rainfall turns the soil into a semi-liquid state.
- Landslide: When large quantities of loosened surface rocks slide down a steep slope.
- Rockfall: When rocks fall off a steep cliff
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