Rivers
- Created by: vampette
- Created on: 12-04-14 08:37
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- Rivers
- Long profile of a river
- Upper course
- Steep gradient
- V-shaped valley, steep sides, narrow, shallow channel
- Steep gradient
- Middle course
- Medium gradient
- Gently sloping valley sides, wider deeper channel
- Medium gradient
- Lower course
- Gently gradient
- Very wide, almost flat valley, very wide, deep channel.
- Gently gradient
- Upper course
- Erosion can be vertical or lateral- both types happen at the same time but one is more dominant at different point along the river
- Vertical eroion
- This deepens the river valley (and channel), making it V-shaped. it's dominant in the upper course of the river
- Lateral erosion
- This widens the river valley (and channel). It's dominant in the middle and lower course.
- Vertical eroion
- There are four processes of erosion
- Hydraulic action
- the force of the water breaks rock particle away from the river channel
- Abrasion
- Eroded rocks picked up by the river scrape and rub against the channel, wearing it away.
- Attrition
- Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together.
- Solution
- River water dissolves some types of rock, e.g. chalk and limestone
- Hydraulic action
- Transportation is the movement of eroded material
- Traction
- Large particles like boulders are pushed along the river bed by the force of the water
- Saltation
- Pebble-sized particles are bounced along the river bed by the force of the water
- Suspension
- Small particles like silt and clay are carried along by the water
- Solution
- Soluble material are dissolved in the water and carried along.
- Traction
- Deposition is when a river drops eroded material
- It happens when a river slows down (loses velocity)
- reasons why a river loses velocity and deposits material:
- The water is shallower, e.g. on the inside of a bend
- The amount of eroded material in the water increases
- The river reaches its mouth
- The volume of water in the river falls
- reasons why a river loses velocity and deposits material:
- It happens when a river slows down (loses velocity)
- Long profile of a river
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