Topic3(2)- Coastal Processes

Question 1

Six main ways waves erode coast

Answer 1

1) corrasion (abrasion)
2) hydraulic action
3) cavitation
4) wave quarrying
5) solution (corrosion)
6) Attrition

Question 2

Abrasion (corrasion)

Answer 2

Bits of rock/sediment transported by waves smash and grind against rocks and cliffs, breaking bits off & smoothing surfaces

Question 3

Hydraulic action

Answer 3

Air in cracks in cliffs is compressed when waves crash in. The pressure exerted by compressed air breaks off rock pieces

Question 4

Cavitation

Answer 4

As waves recede, the compressed air expands violently, again exerting pressure on the rock causing pieces to break off

Question 5

Wave quarrying

Answer 5

The energy of a wave as it breaks against a cliff is enough to detach bits of rock

Question 6

Solution (corrosion)

Answer 6

Soluble rocks (limestone n chalk) get gradually dissolved by the seawater

Question 7

Attrition

Answer 7

Bits of rock in water smash against each other and break into smaller bits

Question 8

4 main processes of transportation

Answer 8

1. Solution
2. Suspension
3. Saltation
4. Traction

Question 9

Solution (transportation)

Answer 9

Substances that can be dissolved are carried along in the water e.g limestone in slightly acidic water

Question 10

Suspension

Answer 10

Very fine material, like silt and clay, is whipped up by turbulence (erratic swirling of water) and carried along in water

Question 11

Saltation

Answer 11

Larger particles, such as pebbles, are too heavy to be carried via suspension. Instead the force of water causes them to bounce along sea bed

Question 12

Traction

Answer 12

Very large particles, like boulders, are pushed along sea bed by force of water

Question 13

Longshore drift

Answer 13

1) Swash carries sediment up the beach, parallel to prevailing wind. Backwash carries sediment down beach at right angles to shoreline
2) when theres an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along coastline

Question 14

Deposition and its 2 types

Answer 14

When material being transported is dropped on the coast

1) marine deposition - sediment carried by sea water deposited
2) Aeolian deposition- sediment carried by wind deposited

Question 15

When do Marine and Aeolian deposition happen? And why?

Answer 15

-When the sediment load exceeds the ability of water or wind to carry it
-this can happen due to an increase in sediment load or wind or water flow slows down (less energy)
-

Question 16

2 reasons wind and water slow down:

Answer 16

1) friction increases (shallow water or wind reaches land, friction slows them down)
2) Flow becomes turbulent (encountering of an obstacle- flow becomes rough and speed decreases)

Question 17

What happens to waves if wind slows down

Answer 17

Wave height, speed and energy decrease

Question 18

Sub-aerial weathering

Answer 18

Gradual break down of rock by agents such as ice, salt, plant roots and acids. Weathering weakens cliffs, making them more vulnerable to erosion

Question 19

4 types of Sub-aerial weathering

Answer 19

1) salt weathering
2) freeze-thaw weathering
3) chemical weathering
4) wetting and drying

Question 20

Salt weathering

Answer 20

• caused by saline (salty) water
• saline water enters cracks in rocks at high tide
• as tide goes out, rocks dry and water evaporates, forming salt crystals
• the salt crystals expand as they form, exerting pressure on the rock, causing pieces to fall off

Question 21

Freeze-thaw weathering

Answer 21

• occurs in areas where temperatures fluctuate above and below freezing
• water enters joints and crevices in rocks
• if temp. drops below 0 celcius, water freezes and expands in cracks
• over time, repeated freeze-thaw weakens the rocks and causes pieces to fall off

Question 22

Chemical weathering

Answer 22

• the breakdown of rock by changing its chemical composition
• e.g. Carbon dioxide in atmosphere dissolves in rainwater, forming a weak carbonic acid. This acid reacts with rock which contains calcium carbonate

Question 23

Wetting and drying

Answer 23

• some rocks contain clay

- when clay gets wet, it expands and the pressure causes fragments of rock to break off

Question 24

Mass movement

Answer 24

The shifting of material downhill due to gravity
In coastal areas its most likely to occur when cliffs are undercut by wave action (unsupported overhang causing it to collapse)

Question 25

4 types of mass movement

Answer 25

1) Slides
2) Slumps
3) Rockfalls
4) Mudflows

Question 26

Slides

Answer 26

Material shifts in a straight line

Question 27

Slumps

Answer 27

Material shifts with a rotation

Question 28

Rockfalls

Answer 28

Material breaks up and falls

Question 29

Mudflows

Answer 29

Material flows downslope

Question 30

Factors affecting mass movement

Answer 30

• unconsolidated rocks are prone to collapse as theres little friction between particles to hold them together
• heavy rain, can saturate unconsolidated rock , further reducing friction making it more likely to collapse
• Runoff can erode fine particles and transport them downslope