Biological weathering is where the processes of living organisms, animals and plants, help to weather rocks to aid in the process of erosion. Examples of Biological weathering are tree roots growing and expanding through cracks in the rock, especially those which hold a lot of water within them, and the decomposition of dead animals and plants produces acidic by-products that slowly corrode the rock. These processes can take thousands of years to begin to see any real results.
Biological weathering can be seen to both Chemical and Physical weathering. Another factor that affects the shape of a coastline is mass wasting or mass wastage, which is the geomorphic process by which soil and rock move down slope under the force of gravity. Other factors include the many processes of erosion. These include Quarrying, otherwise known as hydraulic action, Abrasion/Corrasion, Corrosion/Solution and Attrition.Hydraulic action is where the water is thrown at the base of a cliff, for example, by the force of the waves. The shear weight of the water (30 tonnes/ meter squared) slams into the cliff forcing air into small cracks within the cliff, which may be caused by weathering or if the rock is arranged in layers or not, and creates immense pressure that forces the rock apart.
This continuous cycle of the build up of pressure and release of pressure (Dilatation) eventually causes sediments of the cliff to fall off.Abrasion, or Corrasion, happens when rocks and other pieces or sediment carried in suspension in the water is thrown at the cliff, thus braking off pieces of the cliff that can then be used to throw back at the cliff. This is particularly effective on exposed coastlines. Corrosion is when chemicals dissolved within the water, mostly acidic chemicals, decompose the rock changing the chemical structure of the rock allowing the rock to be soluble in water, rather than insoluble in water, so that it can be transported away fro the cliff.Human activity can also have a large effect on the shape of a coastline.
For example the deployment of a groyne can build up the beach in one area, thus increasing that particular coastlines defences, but reducing the defences of the coastline away from it by cutting off the supply of sand transported to that beach by long shore drift, and because of the transportation of sand away form the beach by long shore drift as well. A real place example of this is in Bournemouth, Dorset; a large concrete groyne was constructed to build the beach to attract more tourists to the holiday resorts in the area.This trapped all of the sand that would have been transported by long shore drift away from the beach was built up against the groyne, thus increasing the size of the beach, just as it was constructed to do so. But further down the coastline at a town called Buren-on-sea had all of its sand from the beach taken away by long shore drift, and what would have been the sand that would replace the sand taken away was trapped by the groyne at Bournemouth, and therefore taking the beach away from the town all together.
Since a beach is one of the most effective coastal defences you can have, the coastline was rapidly eroded by the sea. In conclusion, there are many factors affecting the shape of any coastline. These include; the geology of the rock forming the cliff, various processes of weathering (Chemical, Physical and Biological) and mass movement, processes of erosion, human activity and past processes.
