Explain the work of a river as an agent of erosion. (any three points)
Answers
Answer:
In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location[1] (not to be confused with weathering which involves no movement). This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, animals, and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolic) erosion, zoogenic erosion, and anthropogenic erosion.[2] The particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by its dissolving into a solvent (typically water), followed by the flow away of that solution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
Answer
There are four main processes of erosion that occur in rivers. These are:
hydraulic action;
abrasion / corrasion;
attrition; and
corrosion
Description
hydraulic action
The pressure of water breaks away rock particles from the river bed and banks. The force of the water hits river banks and then pushes water into cracks.
abrasion/corrosion
The sediment carried by a river scours the bed and banks. Where depressions exist in the channel floor the river can cause pebbles to spin around and turn hollows into potholes.
attritionEroded rocks collide and break into smaller fragments. The edges of these rocks become smoother and more rounded. Attrition makes the particles of rock smaller. It does not erode the bed and bank.
corrosion
Transportation of material in a river begins when friction is overcome. Material that has been loosened by erosion may be then transported along the river.