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GCSE Physical Geography > Rivers > Flashcards

Flashcards in Rivers Deck (51)
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1

What is the river course

The path of the river as it flows downhill

2

Where is the upper course

Closest to the source of the river

3

Where is the lower course

Closest to the mouth of the river

4

How do rivers form channels and valleys

1. The ERODE the landscape
2. They transport the material somewhere where it is deposited
3. The shape depends on whether erosion or deposition has the most impact

5

Upper course properties

- Steep
- V-shaped valley, steep sides
- Narrow, shallow channel

6

Middle course properties

- Medium
- Gently sloping sides
- Wider, deeper channel

7

Lower course properties

- Gentle
- Very wide, almost flat valley
- Very wide, deep channel

8

Vertical erosion

- This DEEPENS the river valley, making it a V-SHAPED valley
- Dominant in the UPPER course of the river

9

Lateral erosion

- This WIDENS the river valley
- Dominant in the MIDDLE and LOWER courses

10

Name the four process of erosion

- Hydraulic action
- Abrasion
- Attrition
- Solution

11

Hydraulic action

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

12

Abrasion

Eroded rocks picked up by the river SCRAPE and RUB against the channel, wearing away.
Most erosion happens by abrasion

13

Attrition

Eroded rocks picked up by the river SMASH into each other breaking into smaller fragments.
The edges are rounded off as they rub together

14

Solution

River water DISSOLVES some type of rocks e.g. chalk and limestone

15

Name the four processes of transportation

- Traction
- Saltation
- Suspension
- Solution

16

Traction

Large particles (like boulders) are PUSHED along the river bed by the water FORCE

17

Saltation

PEBBLE sized particles are BOUNCED along the river bed by the water FORCE

18

Suspension

SOLUBLE materials DISSOLVE in the water and are CARRIED along

19

Solution

River water DISSOLVES some type of rocks e.g. chalk and limestone

20

When does deposition happen and why

- When a river drops eroded material
- Happens when a river slows down (loses velocity)

21

Why do rivers slow down and deposit material

- Volume of water falls
- Amount of eroded material in the water increases
- Water is shallower e.g. inside of a bend
- River reaches the mouth

22

What happens when a river is eroding and depositing material

Meanders and ox-bow lakes

23

Where are meanders found

In the middle and lower courses

24

Formation of a meander

1. The water current flows faster on the outside of the bend, because the river channel is deeper (less friction to slow water down)
2. More erosion on the outside of the bends, forming river cliffs
3. Current is slower on the inside bend (channel is slower) More friction -> Slow water down
4. Eroded material is deposited on the inside of the bend, forming slip-off slopes

25

Formation of an ox-bow lake

1. Water flows in a corkscrew pattern causing lateral erosion. Erosion causes the outside bends to get closer
2. Water flows fastest on the outside and slowest on the inside bends leading to deposition
3. Two meanders will erode coming closer together The river breaks through this land, usually during a flood
4. The river flows the shortest course
5. Deposition eventually cuts of the meander, forming an ox-bow lake

26

Waterfalls and gorges are formed by what

Erosion

27

Formation of a waterfall and a gorges

1. The river flows over the cliff of horizontal bands of soft and hard rock
2. The soft rock is undercut by Hydraulic action and abrasion. A steep drop is created -> waterfall
3. Eventually the soft rock erodes so much that the more resistant rock is left unsupported.
4. This rock will eventually fall, the erode the softer rock by abrasion forming a plunge pool at the base of a cliff
5. Overtime the cliff will retreat backwards and the process repeats forming a gorge

28

Where are waterfalls and gorges found

The upper course of the river

29

How are flood plains and levees formed

By deposition

30

Formation of a flood plain

1. The wide valley floor gets flooded
2. The water slows down on the flood plain and deposits the eroded material that its transporting -> Builds up the flood plain
3. Meanders migrate (move) across the flood plain making it wider
4. Deposition that happens on the slip-of slopes of meanders also build up the flood levees