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Geography AS level Examination Content
Hydraulic action: When the pressure of the water breaks rock particles away from the bed
and the banks
Abrasion: Eroded pieces of rock in the water scrape and rub against the bed and banks, this
removes the material.
Attrition: When rocks in the river smash against each other and break into smaller pieces.
Their edges get rounded.
Corrosion (Solution): The dissolving of rock by chemical processes. Carbon dioxide
dissolves into the water and forms a weak acid which reacts with rocks like limestone and
chalk breaking them down.
Solution: Substances that can dissolve are carried along in the water.
Suspension: Very fine material is whipped by the waters turbulence and carried along in the
Saltation: Larger particles which are too heavy to be carried by suspension so the force of the
river only bounces them along the river bed.
Traction: Very large particles are pushed along the river bed by the force of the water.
This occurs when the river slows down and doesn't have enough energy so it deposits its load.
This decrease in the rivers speed can occur because of:
When the river is forced to slow down e.g narrow secton in the channel.
When the river meets the sea