Figure 8 – Denudational process and their driving forces

The basic reason of these processes is development of stresses in the body of the earth materials. It is this stress that breaks rocks and other earth materials. The shear stresses result in angular displacement or slippage. Stress can be produced by gravitation pull, climatic factors

– thermal gradients, pressure gradients, amount and intensity of precipitation, humidity etc. The density, type and distribution of vegetation also exert influence on exogenic processes. The exogenic geomorphic processes vary from one climatic region to another. These vary within a climatic region also due to location variation in climatic elements.

All the exogenic geomorphic processes are covered under a general term, called denudation which means to strip off. Denudation consists of two kinds of processes – static and mobile. Weathering is a static process while mass movement, erosion and transportation are mobile processes (figure 8).

5.3.1. Weathering

Weathering may be described as the mechanical disintegration or chemical decomposition of rocks in situ by different geomorphic agents at or near the surface of the earth. It changes hard massive rock into finer material. It is the first phase in the denudation process which prepares rock materials for transportation by the agents of erosion and mass movement.

The main factors responsible for weathering are geological – rock structure, climatic, topographic and vegetative. These factors result into activities such as thermal expansion, exfoliation, rock solutions, salt and ice crystallization etc. There are three types of weathering which are described below in detail.