River processes Flashcards
What are the 4 main forms of river erosion?
Hydraulic action
Abrasion
Attrition
Solution
What is hydraulic action?
The force of the river against the banks cause air to be trapped in cracks. The pressure weakens the banks and gradually wears it away
What is abrasion?
Rocks carried along by the river wear down the river bed and banks
What is attrition?
Rocks being carried by the river smash together and break into smaller, smoother and rounder particles
What is solution?
Soluble particles are dissolved into the river
What are 4 different transport processes?
Solution
Suspension
Saltation
Traction
What is solution (transport)?
minerals are dissolved in the water and carried along in solution
What is saltation?
Small pebbles and stones are bounced along the river bed
What is suspension?
Fine light material is carried along in the water
What is traction?
Large boulders and rocks are rolled along the river bed?
What happens when energy levels are very high?
Large rocks and boulders can be transported. Energy levels are higher near a rivers source, where the valley is narrow. Energy levels rise even higher in flooding.
What happens when energy levels are low?
Small particles can be transported. Energy levels are lowest when velocity drops as a river enters a lake or sea (at mouth)
What is deposition?
When a river loses energy, it will drop some of the material it is carrying.
When does deposition take place?
When a river enters an area of shallow water or when the volume of water decreases.
Where does deposition usually happen?
Towards the end of a river’s journey, at the mouth
