Rivers are the most widespread natural agent on this planet earth.
Rivers are the greatest agent of denudation.
The work of river is both destructive and constructive.
It is destructive as it erodes material from one place and transports the materials to another place.
It is constructive as it deposits the carried out materials and creates new landforms.
Erosion and transportation in rivers go on simultaneously by some processes.
Let’s discuss the erosional work of river.
Corrasion or abrasion
Abrasion occurs when pebbles grind along the river bank and bed in the sand papering effect.
So this is the mechanical grinding of the river’s load against the bank and bed of the river.
River’s load is the material transported by the river.
The load of the river is known as the erosional tool of the river.
This process of abrasion slowly wears and tears the bed and the sides away.
This kind of lateral and vertical erosion is called Corrasion.
Vertical erosion is downward erosion and lateral erosion is sideward erosion.
Hydraulic action
Hydraulic action involves the breakdown of rocks of the bank and bed due to the impact of water currents.
This is the sheer power of water as it smashed against the river banks.
The pressure of water causes cracks in the river banks.
Air traps in the cracks of the river bank and bed.
And ultimately causes the rock to break apart.
Solution
Some amount of oxygen and carbon dioxide found in all water in nature.
The presence of oxygen and carbon dioxide in water increases the solubility of rocks and minerals.
Solution is the chemical action of water on soluble rocks.
In this process soluble materials are removed from the parent rocks and are mixed with the river water.
For example, calcium carbonate in limestone is a very soluble mineral.
And it can easily dissolve and removed in solution.
Revision
Rivers are the greatest agent of denudation. The work of river is both destructive and constructive.
The erosional work of river is lead by three main processes- i. Corrasion or abrasion ii. Hydraulic action iii. Solution
Abrasion is the mechanical grinding of river’s load against the bank and bed of the river. This kind of lateral and vertical erosion is called Corrasion.
Hydraulic action involves the breakdown of rocks of the bank and bed due to the impact of water currents.
In solution process soluble materials are removed from the parent rocks and are mixed with the river water. For example, calcium carbonates.