Biological Weathering

                   BIOLOGICAL WEATHERING

          This process of weathering is mainly related to the activities of various organisms. Organisms mainly plants and bacteria, take part in the transformation of rocks at the surface, in the following ways : 

           1) Bio-physical processes

           2) Bio-chemical processes 

1) Bio-physical Processes : 

                     a) Plant - roots, growing between joint blocks and alone minute fractures between mineral grains, exert an expansive force tending to widen those opening and sometimes create new fractures.

                     b) Insects like earth - worm, snail etc. Loosen the soli cover and create suitable conditions for the various external agencies to have their own action on the underlying rocks, which ultimately lead to rock weathering. 

2) Bio-chemical Processes : 

                     a) Sometimes, certain groups of bacteria, algae and mosses break rock - forming Silicates down directly, removing from them elements like silicon, potassium, phosphorus, calcium, magnesium, that they need as nutrients. 

                    b) After the death of animals or plants, with their subsequent decay and degeneration, chemically active substances are produced, which are cable of bringing about rock weathering. For example, humic acid which is formed during decay and degeneration of plant life is capable of bringing about rock weathering effectively, to some extend. 

           Thus in nature the processes of weathering is being carried out by various external agencies.