Describe the Middle Course of the river, (There are four key points)
Medium Gradient. Gently Sloping Valley Sides. Wider Channel. Deeper Channel.
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Describe the Lower Course of the river, (There are four key points)
Gentle Gtadient. Wide, almost Flat Valley Sides, Wide Channel. Deep Channel.
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Define 'VERTICAL EROSION.'
Deepens the river valley (and channel), making it V-Shaped. It's dominant in the Upper Course of the river.
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Define 'LATERAL EROSION.'
This widens the river valley (and channel). It's dominant in the Middle and Lower Courses.
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What are the four processes of Erosion?
Hydraulic Action, Attrition, Abrasion and Solution
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What is 'Hydraulic Action?'
The force of the water breaks rock particles away from the river channel
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What is 'Abrasion?'
Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion.
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Define '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.
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What is 'Solution' in terms of Erosion?
River water dissolves some types of rock.
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What is 'Transportation?'
The movement of eroded material.
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What is 'Traction?'
Large particles like boulders are pushed along the river bed by the force of the water.
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What is 'Saltation?'
Pebble-sized particles are bounced along the river bed by the force of the water.
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Define 'Suspension'.
Small particles like silt and clay are carried along by the water.
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What is 'Solution?' in terms of Transportation?
Soluble materials dissolve in the water and are carried along.
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What is 'DEPOSITION'?
When a river drops the eroded material it's transporting.
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When does Deposition take place?
When a river loses velocity and slows down.
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Why does a river slow down? Give four reasons.
The volume of water in the river falls; the amount of eroded material in the water increases; the water is shallower; the river reaches its mouth.
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At which point in the river do 'Meanders' form?
In their Middle and Lower Courses.
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How are Meanders formed?
Through Erosion and Deposition.
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Why does more Erosion take place on the outside of the bend?
The current is faster on the outside of the bend because the river channel is deeper (there's less friction to slow the water down.) This means that more erosion takes place here.
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What is formed when the outer bend of the river becomes eroded?
RIVER CLIFFS
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Why is the current on the inside of the bend slower?
The river channel is shallower, therefore there is more friction to slow the water down.
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What does a slow current on the inside of the bend mean?
Eroded material is deposited.
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What forms on the inside of the bend when material is deposited?
SLIP-OFF SLOPES
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Describe the formation of an 'OX-BOW LAKE'.
Erosion causes the outside bends to get closer until there is only a small bit of land left between the bends *called the neck*. The river then breaks through this land and the river flows along the shortest course. Deposition cuts off the meander.
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Other cards in this set
Card 2
Front
What are the three sections of a course?
Back
Upper course, Middle Course and Lower Course
Card 3
Front
What are formed when rivers flow downhill?
Back
Card 4
Front
What influences the shape of the valley and channel?
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