The weathered material has now reached the river (or glacier). Moving water, ice and wind use this material for the
various processes of erosion, using them as tools to wear away the bedrock; the tools themselves get worn away as well.
Erosion is the wearing away of rock surfaces and rock fragments by moving water, air
or ice. It is therefore not the same as weathering, although they do work hand in hand.
The amount of water (the discharge) and the speed of the current govern the amount of load that can be carried
(size and weight). Most erosion occurs during floods.
In a river, erosion is carried out by
- hydraulic action:
action of water alone
- cavitation:
implosion of water-vapour bubbles causing shock waves
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- corrosion:
chemical wearing away of rock
- corrasion:
mechanical wearing away of rock by
- abrasion of rock surfaces
- attrition of the fragments
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The processes of erosion are most easily demonstrated through pot-holing action and the formation of waterfalls.
Waterfalls generally erode back in the same way, although they have various origins:
resistant rock
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rejuvenation
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effect of faulting
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hanging valley
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Geopix Study Guide "Erosion"
- gives a full image of each of these, and other, examples;
- describes the main processes of erosion;
- describes the main types of waterfalls;
- suggests how to answer exam questions on this topic.
The Study Guide contains the following pages:
'Erosion' is part of the Geopix Weathering and Erosion Study Guide CD.
To order this CD go to the Geopix Online Store
