COASTAL SYSTEMS AND LANDSCAPES CGP - Coastal Processes

Question 1

What are the two types of processes that affect the coast?

Answer 1

Marine processes caused by the sea. Sub-aerial processes aren’t directly caused by the sea.

Question 2

Six main ways waves erode the coastline

Answer 2

Corrasion/abrasion
Hydraulic action
Cavitation
Wave quarrying
Solution/corrosion
Attrition

Question 3

Corrasion/abrasion (erosion)

Answer 3

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

Question 4

Hydraulic action (erosion)

Answer 4

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

Question 5

Cavitation (erosion)

Answer 5

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

Question 6

Wave quarrying (erosion)

Answer 6

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

Question 7

Solution/corrosion (erosion)

Answer 7

Soluble rocks (e.g.limestone, chalk) get gradually dissolved by the seawater.

Question 8

Attrition (corrosion)

Answer 8

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

Question 9

Transportation

Answer 9

The process of eroded material being moved.

Question 10

What transports eroded material?

Answer 10

Energy provided by waves, tides and currents.

Question 11

Four main processes of transportation

Answer 11

Solution
Saltation
Suspension
Traction

Question 12

Solution (transportation)

Answer 12

Substances that can dissolve are carried along in the water. E.g. limestone is dissolved into water that slightly acidic.

Question 13

Suspension (transportation)

Answer 13

Very fine material, such as silt and clay particles, is whipped up by turbulence (erratic swirling of water) and carried along in the water. Most eroded material is transported this way.

Question 14

Saltation (transportation)

Answer 14

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

Question 15

Traction (transportation)

Answer 15

Very large particles, e.g. boulders, are pushed along the sea bed by the force of the water.

Question 16

What is longshore/littoral drift?

Answer 16

The process of sediment being transported along the shore in the direction of the prevailing wind.

Question 17

Describe longshore drift

Answer 17

Swash carrels sediment (e.g. shingles, pebbles) up the beach, parallel to the prevailing wind. Backwash carries sediment back down the beach, at right angles to the shoreline. When there’s angle between prevailing wind and shoreline, a few rounds of swash and backwash move the sediment along the shoreline.

Question 18

Deposition is when…

Answer 18

…material being transported is dropped on the coast.

Question 19

Marine deposition

Answer 19

When sediment carried by seawater is deposited

Question 20

Aeolian deposition

Answer 20

When sediment carried by wind is deposited

Question 21

When does both marine and aeolian deposition happen? Why?

Answer 21

When the sediment load exceeds the ability of the water or wind to carry it. Can be because sediment load increases (e.g. if there is landslide), or because wind or water flows slows down (so it has less energy).

Question 22

Why do wind and water slow down?

Answer 22

Friction increases or flow becomes turbulent

Question 23

Friction increases (deposition)

Answer 23

If waves enter shallow water or wind reaches land, friction between the water/wind and ground surface increases, which slows down the wind or water.

Question 24

Flow becomes turbulent (deposition)

Answer 24

If water or wind encounters an obstacle (e.g. a current moving in the opposite direction, or n area of vegetation), flow becomes rougher and overall speed decreases.

Question 25

What happens if wind drops?

Answer 25

Wave height, speed and energy will decrease.

Question 26

Sub-aerial weathering

Answer 26

The gradual break down of rock by agents such as ice, salt, plant roots and acids.

Question 27

What does weathering do to cliffs?

Answer 27

Weakens cliffs and makes them more vulnerable to erosion.

Question 28

What are the five types of weathering?

Answer 28

Salt weathering
Freeze-thaw weathering
Chemical weathering
Wetting and drying
Biological weathering

Question 29

What is salt weathering caused by? How does it occur?

Answer 29

Saline (salty) water. Saline water enters pores or cracks in rocks at high tide. As tide goes out the rocks dry and the water evaporates, forming salt crystals. As salt crystals form they expand, exerting pressure on the rock - causing pieces to fall off.

Question 30

Where does freeze-thaw weathering occur?

Answer 30

In areas where temperatures fluctuate above and below freezing.

Question 31

How does freeze-thaw weathering occur?

Answer 31

Water enters joints and crevices in rocks. If temperature drops below 0 degrees C, water in cracks freezes and expands. Over time, repeated freeze-thaw action weakens the rocks and causes pieces to fall off.

Question 32

Wetting and drying weathering

Answer 32

Some rocks contain clay. When clay gets wet, it expands and the pressure caused by this breaks fragments off the rock.

Question 33

What is chemical weathering and example.

Answer 33

The breakdown of rock by changing its chemical composition. E.g. carbon dioxide in atmosphere dissolves in rainwater, forming weak carbonic acid. This acid reacts with rock that contains calcium carbonate - e.g. Carboniferous limestone, so the rocks are gradually dissolved.

Question 34

Biological weathering and example

Answer 34

Weathering caused by biological organisms e.g. plants, animals, bacteria. E.g. plant roots growing into cracks in the rock and widening them can also cause rocks to break.

Question 35

What is mass movement?

Answer 35

The shifting of material downhill due to gravity.

Question 36

When is mass movement most likely to occur in coastal areas?

Answer 36

When cliffs are undercut by wave action - this causes an unsupported overhang, which is likely to collapse.

Question 37

Types of mass movement

Answer 37

Slides
Slumps
Rockfall
Mudflow
Soil creep

Question 38

Slides (mass movement)

Answer 38

Material shifts in a straight line.

Question 39

Slumps (mass movement)

Answer 39

Material shifts with a rotation

Question 40

Rockfalls (mass movement)

Answer 40

Material breaks up and falls

Question 41

Mudflows

Answer 41

Material flows downslops

Question 42

Soil creep (mass movement)

Answer 42

Material moves gradually downwards

Question 43

What are unconsolidated rocks (e.g.) prone to and why?

Answer 43

E.g. clay. Prone to collapse as there’s little friction between particles to hold them together.

Question 44

What can heavy rain do to unconsolidated rock and what does this result in?

Answer 44

Can saturate unconsolidated rock, further reducing friction and making it more likely to collapse.

Question 45

How is runoff related to mass movement?

Answer 45

Runoff (flow of water overland) can erode fine particles (e.g. sand and silt) and transport them downslope.

Question 46

Unconsolidated rock

Answer 46

Minerals or sediments in the form of loose particles, such as sand or gravel.