Geography - River Processes

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Erosion

There are 4 types of erosion:

1 - Hydraulic Action; The force of the river can cause air to get into the crevises of the rocks, the pressure weakens the rock and pieces gradually fall away.

2 - Abraison; Rocks that have been carried by the flow of the river waear down the river bed.

3 - Attrition; Rocks that have been carried by the flow of the river smash together and break into smaller, smoother and rounder particles.

4 - Solution; Soluble particles are dissolved into the river water.

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Transport

There are 4 types of transport:

1 - Solution; Minerals are dissolved and carried in the river water.

2 - Suspension; Fine material which is also light is carried along in the river water.

3 - Saltation; Small pebbles and stones are bounced along the river bed.

4 - Traction; Large rocks and boulders are rolled along the river bed.

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Conditionals

Traction only occurs when energy levels are high. At the source, energy levels are usually higher because it's course is steep and it's valley is narrow. Energy levels rise even higher at times of spate.

Only Suspension and Solution occur when energy levels are low. At the mouth, energy levels are usually lower because it's course is gentle and it's valley is flat. Usually occurs when entering a sea or lake.

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Deposition

When a river loses energy it drops some of the material that it's carrying.

Deposition may take place in a shallow area or when the volume of water decreases, e.g: after a flood or during a drought.

Deposition is more likely to occur at the mouth of a river.

Deposition at the mouth of a river may form a Delta such as the Missisippi Delta.

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