Topic 4 - River Processes And Pressures (set A)✔️

Question 1

Features of a rivers upper course? what type of valley and channel shape is expected?

Answer 1

Has a steep gradient with steep sided V-shaped valleys and narrow, shallow channels

Question 2

Features of a rivers lower course? what type of valley and channel shape is expected?

Answer 2

Has a gentle gradient with very flat, wide valleys and a deep channel

Question 3

Features of a rivers middle course? what type of valley and channel shape is expected?

Answer 3

Has a medium gradient with gentle sloping valley sides and a wider deeper channel

Question 4

What is a rivers course?

Answer 4

The path of the river as it flows downhill - from the source (start) to the mouth (end)

Question 5

Effect of vertical erosion? Where is it dominant?

Answer 5

Deepens the river valley (and channel) making it v-shaped - dominant in the upper course of the river

Question 6

Explain how is vertical erosion caused?

Answer 6

High turbulence causes the rough, angular particles to be scraped along the river bed, causing intense downward erosion

Question 7

Features of lateral erosion?which courses is it most dominant?

Answer 7

Widens the river valley (and channel) during the formation of meanders it is dominant in the middle and lower courses

Question 8

3 features of the river Edens upper course?

Answer 8

• source is in an area of hard, resistant rock
• valley is steep sided, and the channel has a steep gradient due to vertical erosion
• river channel is narrow and shallow - velocity and discharge is low due to friction from rough channel bed

Question 9

4 features of the river Edens lower course?

Answer 9

• valley is very wide and flat
• high velocity due to little friction from the smooth channel sides
• large discharge - joined by other rivers
• river channel is very wide and deep (more then 50m wide)

Question 10

3 features of the river Edens middle course?

Answer 10

• middle parts made from softer, easily eroded rocks like sandstone - results in lateral erosion so river becomes wider
• valley sides become gentler slopes and the gradient of the channel is less steep
• river channel becomes wider and deeper and discharge increases as more streams join main river

Question 11

Explain in depth each stage of how the mechanical weathering ‘ freeze thaw’ shapes valleys?

Answer 11

1) happens when tempertaures alternate above and below 0 degrees

2) water gets into rocks that have cracks - when the water freezes it expands which puts pressure on the rock - when the water thaws it contracts which releases the pressure on the rock

3) repeated freezing and thawing widens the cracks and causes the rocks to break up

Question 12

How does hydraulic action cause erosion?

Answer 12

The force of water breaks rock particles away from the river channel

Question 13

How does abrasion cause erosion?how common is this type of erosion?

Answer 13

Eroded rocks picked up by the river scrape and rub against the channel, wearing it away - most erosion is caused by abrasion

Question 14

Explain how solution causes erosion of sediment?

Answer 14

River water dissolves some types of rock eg chalk

Question 15

Name the four processes of transportation?

Answer 15

• traction
• saltation
• solution
• suspension

Question 16

Explain how traction transports sediment along a river?

Answer 16

Large particles like boulders are pushed along the river bed by the force of the water

Question 17

Explain how saltation transports sediment along a river?

Answer 17

Pebble-sized particles are bounced along the river bed by the force of the water

Question 18

Explain how suspension transports sediment along a river?

Answer 18

Small particles like silt and clay are carried along by the water

Question 19

Explain how solution transports sediment along a river?

Answer 19

Soluble materials dissolve in the water and are carried along

Question 20

Define deposition?what causes it?

Answer 20

Deposition - when a river drops the eroded material its transporting and happens when the river slows down

Question 21

Give three examples of why a river might slow down?

Answer 21

• the volume of water in the river falls
• amount of eroded material in the water increases
• river reaches its mouth

Question 22

Explain in depth how a waterfall is formed? Refer to erosion?

Answer 22

1) river flows over an area of hard rock followed by an area of softer rock
2) softer rock is eroded (by hydraulic action and abrasion) more then the hard rock creating a step
3) water continues to go over the step eroding the softer rock more and more
4) steep drop is eventually created called a water fall

Question 23

Explain in depth how a gorge is created from a waterfall?

Answer 23

1) hard rock is eventually undercut by erosion - it becomes unsupported and collapses
2) collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock (by abrasion) creasing a deep plunge pool
3) over time, more undercutting and collapsing will cause the waterfall to retreat - leaving behind a steep sided gorge

Question 24

What are interlocking spurs?

Answer 24

In the upper course of a river most erosion is verical which creates steep, v-shaped valleys - the rivers are not powerfull enough to erode laterally (sideways) so they wind around the hillsides that stick out in their path - hillsides that interlock with each other (as river winds around them) are interlocking spurs

Question 25

What are meanders?

Answer 25

Large bends developed by rivers in their middle and lower courses in areas where there are both shallow and deep sections in the channel

Question 26

Explain steps 1 and 2 on how a meander forms?

Answer 26

1) current is faster on the outside of the bend because the river channel is deeper (so there’s less friction to slow the water down)

2) so more erosion (abrasion and hydraulic action) takes place on the outside of the bend - which froms river cliffs

Question 27

Explain steps 3 and 4 on how a meander forms?

Answer 27

3) current is slower on the inside of the bend because the river channel is shallower (so there is more friction to slow the water down)

4) so eorded material is deposited on the inside of the bend - forming slip-off slopes

Question 28

Explain in depth how a meander can turn into an ox-bow lake?

Answer 28

1) erosion causes outside bends to get closer - until only a small bit of land is left called the neck

2) river breaks through this land during a flood and the river starts to flow along the shortest course

3) deposition of sediment eventually cuts of the meander - forming an ox-bow lake