Rivers (Geography)

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What is the watershed?
An area of highland forming the edge of the river basin.
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What is the source?
Where a river begins.
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What is the mouth?
Where the river meets the sea.
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What is the confluence?
A point at which two rivers meet.
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What is a tributary?
A small river/stream that joins a large river.
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What happens to the river valley as it moves downstream?
The sides become less steep. Gradient decreases. It changes shape from a V to a U.
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What happens to the river channel as you move downstream?
It become wider and deeper when joined by other streams.
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What are four processes of erosion?
Corrasion. Attrition. Solution. Hydraulic action.
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When is the erosion rate highest?
In times of flood.
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What is weathering?
The breaking down of material in situe.
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What is erosion?
The removal and further break down of material.
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What is solution?
H2O dissolves soluble minerals from banks and bed- helps to break them up.
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What is attrition?
Rocks and stones knock together and wear each other away.
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What is hydraulic action?
In a fast flowing river H2O is forced into cracks in banks and overtime breaks them up.
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What is chemical weathering?
Weak acids in rain react with certain rocks.
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What is physical weathering?
The H2O in cracks expands when frozen and breaks the bank up.
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What is biological weathering?
Action of plants or animals on land. The plant's roots breaks up soil and burrowing animals do also.
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What is mass movement?
Material moves down slope due to gravity.
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What is 'soil creep'?
H20 in soil is pulled slowly down slope along with soil. Soil appears rippled (terracettes)
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What is slumping?
It is common on river banks. A large area of land moves down a slope and leaves a curved surface. Rocks absorb H2O and become saturated and weak.
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What do you find at the upper course of the river?
Waterfalls, V-shaped valleys, interlocking spurs.
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What type of erosion takes place in the upper course of the river?
Vertical erosion.
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What do you find in the middle course of the river?
Meander bends.
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What type of erosion occurs in the middle course?
Lateral erosion.
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What do you find in the lower course of the river?
Flood plains. Levees. Ox-bow lakes. Deltas.
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What type of erosion occurs in the lower course?
Deposition.
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What are the characteristics of the upper course of the river Tees?
It is steep (V-shaped) Shallow. The source is 600m above sea level. 2000ml rain a year forms rivulettes.
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How are V-shaped valleys formed?
Vertical erosion in river channel results in steep sided valley. Valley sides are weakened over time by continued vertical erosion. Mass movement of materials down the valley sides creates a V-shape. This material is taken away by the river.
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How are interlocking spurs created?
When the river flows from side to side around resistant rocky outcrops.
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How are waterfalls created?
Rapids form when soft rock erodes hard rock. Plunge pools formed as H2O erodes soft rock through attrition and H A. Plunge pool is made bigger by further erosion. Over hang collapses and process continues. Gorge is formed.
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What are the characteristics of the middle course?
It is deeper- joined by other tributaries and faster- less contact with bed and banks.
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What are meanders?
Are a result of lateral erosion and small floodplains.
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How are meanders created?
Deposition occurs on the inside of bends due to slower current producing slip off slope. Erosion on the outside occurs because the current is faster- a river cliff is formed.
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What are the characteristics of the lower course?
Low gradients. Wide channels. Deep channel. Strong current.
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How are ox-bow lakes formed?
1. meander neck is wide so river flows round. 2. meander neck narrows due to erosion. 3. River cuts though neck at time of flood. 4. New channel is formed. Deposition cuts off old bend.
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What is a floodplain?
A low flat area of land surrounding a river. Its formed by deposition after flood. Its made wider when meanders erode the edges.
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How are levees made?
1. when river floods water loses energy and drops material. 2. water level decreases so material stays above ground. 3. Sediment builds up after a number of floods & heavier material is dropped first.
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What are the physical causes of flooding?
Rapid thaw/ rainfall (rivers cant cope & ground cant soak up) Impermeable rocks mean water cant be soaked up. Flat land means water cant flow away. River beds become silted and smaller.
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What are the human causes of flooding?
Towns obstruct moving water. Dams burst causing excess water. Vegetation is removed so water has no interception.
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Other cards in this set

Card 2

Front

What is the source?

Back

Where a river begins.

Card 3

Front

What is the mouth?

Back

Preview of the front of card 3

Card 4

Front

What is the confluence?

Back

Preview of the front of card 4

Card 5

Front

What is a tributary?

Back

Preview of the front of card 5
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