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- The exogenic processes derive their energy from atmosphere determined by the ultimate energy from the sun and also the gradients created by tectonic factors processes and their respective driving forces.
- Temperature and precipitation are the two important climatic elements that control various processes.
- All the exogenic geomorphic processes are covered under a general term, denudation. The word ‘denude’ means to strip off or to uncover.
- Weathering, mass wasting/movements, erosion and transportation are included in denudation
- Gravitational force acts upon all earth materials having a sloping surface and tend to produce movement of matter in down slope direction. Force applied per unit area is called stress.
- Stress is produced in a solid by pushing or pulling. This induces deformation.
- Forces acting along the faces of earth materials are shear stresses (separating forces).
- It is this stress that breaks rocks and other earth materials.
- The shear stresses result in angular displacement or slippage.
- Molecular stresses that may be caused by a number of factors amongst which temperature changes, crystallisation and melting are the most common
- Chemical processes normally lead to loosening of bonds between grains, dissolving of soluble minerals or cementing materials
- Thus, the basic reason that leads to weathering, mass movements, and erosion is development of stresses in the body of the earth materials.
- Different types of rocks with differences in their structure offer varying resistances to various geomorphic processes
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