river processes

Question 1

what is erosion

Answer 1

The wearing away of rock and soil by moving water

Question 2

hydraulic action

Answer 2

Water crashes into the river bank forcing air into cracks. The pressure weakens the rock until pieces break off.

Question 3

abrasion

Answer 3

Sediment carried by the river scrapes and grinds the river bed and banks, gradually wearing them away like sandpaper.

Question 4

attrition

Answer 4

Rocks carried by the river collide with each other, breaking into smaller, smoother, rounder pieces.

Question 5

solution

Answer 5

Some rocks such as limestone dissolve in slightly acidic river water.

Question 6

what is transportation

Answer 6

The movement of eroded material downstream.

Question 7

traction

Answer 7

Large rocks roll along the river bed due to the force of the water.

Question 8

saltation

Answer 8

Small pebbles are bounced along the river bed by the current.

Question 9

suspension

Answer 9

Fine particles such as silt and clay are carried within the water.

Question 10

solution

Answer 10

dissolved minerals are transported within the water

Question 11

deposition

Answer 11

When velocity decreases, the river can no longer carry its load, so sediment is deposited, often forming features such as floodplains and deltas.

Question 12

whats a drainage basin

Answer 12

The area of land drained by a river and its tributaries.

Question 13

whats a watershed

Answer 13

The high land separating two drainage basins

Question 14

whats a floodplain- D

Answer 14

an area of land which is covered in water when a river bursts its banks.

River floods during heavy rainfall
Water spreads over land
Velocity decreases
Sediment deposited
Repeated floods build fertile floodplain

Question 15

why are floodplains agriultural land

Answer 15

the area is very fertile because it’s made up of
alluvium

Question 16

whats a levee - D

Answer 16

Raised embankments along the sides of a river channel formed by repeated flood deposition.

Question 17

how is a levee fromed - depositional

Answer 17

When a river floods, water flows out of the channel onto the floodplain.
As the water leaves the channel, velocity rapidly decreases
Heavier sediment is deposited first next to the river banks.
Finer sediment travels further across the floodplain.
Over many floods, layers of sediment build up, forming raised levees.

Question 18

formation of a waterfall - E

Answer 18

1. A layer of hard rock overlies softer rock.
2. The softer rock erodes faster through hydraulic action and abrasion.
3. This creates a step in the river bed, forming a waterfall.
4. Water falling creates a plunge pool which erodes the softer rock further.
5. The har d rock becomes undercut and collapses.
   6.The waterfall retreats upstream, leaving a steep gorge.

Question 19

how is a meander formed

Answer 19

Small bends develop in the river channel.

Faster water flows on the outer bend, causing erosion (river cliff).

Slower water flows on the inner bend, causing deposition (slip-off slope).

Over time the bend becomes larger and more pronounced.

Question 20

Explain How an Oxbow Lake Forms

Answer 20

Meander develops
Erosion narrows neck
River cuts through during flood
Deposition seals old channel
Crescent-shaped oxbow lake remains