Physical weathering is the disintegration of rock by mechanical processes and therefore depends on the application of force. The applied forces could be:
- Gravitational forces such as overburden pressure, load and shearing stress;
- Expansion forces due to temperature changes, crystal growth or animal activity;
- Water pressures controlled by wetting and drying cycles.
Chemical weathering is the weakening and subsequent breakdown of rocks by chemical reactions. A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/or soil water and other acids.