Coasts

Question 0

What is attrition?

Answer 0

The rocks and stones which the sea erodes from the cliff are broken down as they bump against each other as they are thrown against a cliff.

Question 1

What are the two types of waves?

Answer 1

Constructive and destructive

Question 2

What is abrasion/corrasion?

Answer 2

The sea hurls pebbles against a cliff, chipping and grinding it down.

Question 3

What is solution?

Answer 3

The sea water may react with chemicals and minerals in some rocks and they can be dissolved.

Question 4

What is hydraulic action?

Answer 4

Powerful waves lash the cliffs forcing air into tiny cracks. The pressure weakens the rock and forces it to break up.

Question 5

What is a destructive wave?

Answer 5

A strong, tall, high frequency, short wavelength wave with a circular orbit and a stronger backwash than swash.

Question 6

What is a constructive wave?

Answer 6

A gentle wave with low height, a long wavelength, low frequency, elliptical orbit and a stronger swash than backwash.

Question 7

What is swash?

Answer 7

The movement of water up the beach.

Question 8

What is backwash?

Answer 8

The movement of water back down the beach.

Question 9

What is fetch?

Answer 9

The length of water over which the wind has blown. The longer the fetch, the larger the wave is likely to be.

Question 10

What is prevailing wind?

Answer 10

The predominant wind direction.

Question 11

What three processes does the sea carry out?

Answer 11

• it erodes the land.
• it transports the eroded material.
• it deposits the material at another given location.

Question 12

What is chemical weathering?

Answer 12

The decomposition of rocks caused by a chemical change within a rock.

Question 13

What is the difference between weathering and erosion?

Answer 13

Weathering ensures the objects will stay in the same place where as erosion means the object is eroded and removed from it’s place of origin.

Question 14

When are bays formed?

Answer 14

A bay is formed when there is an area of less resistant rock next to areas of more resistant rock. The soft rock is eroded by hydraulic action to form a bay.

Question 15

How are headlands formed?

Answer 15

Headlands are formed when the sea attacks a section of Coast with alternating bands of soft and hard rock. The bands of soft rock are eroded more quickly by the waves than the hard rock. This leaves a section of hard rock jutting out into the sea and this is known as a headland.

Question 16

What is the name for the bands of rock?

Answer 16

Strata.

Question 17

How is a cave formed?

Answer 17

Powerful waves smash against the rock forcing air into the tiny cracks and eroding it. This continues as well as waves hurling pebbles against the cliff eroding it further. A cave is formed.

Question 18

How is an arch formed?

Answer 18

A fault in the headland had been expanded by hydraulic action. The fault becomes a wave cut notch, which is expanded into a cave by abrasion and more hydraulic action. Eventually by some corrosion, abrasion and more hydraulic action the cave is eroded through the headland and becomes an arch.

Question 19

How is a stack formed?

Answer 19

The arch eventually breaks and a stack forms, this is due to weathering.

Question 20

How is a stump formed?

Answer 20

When a stack is eroded and affected by weathering it becomes a stump.

Question 21

How is a wave cut platform formed?

Answer 21

Between high and low tide rocks are hurled at the base of a cliff. This is called corrasion. This creates a wave cut notch, the cliff has been undercut. The top of the cliff becomes unstable. This overhand will collapse into the sea providing more material for corrosion. The cliff has now retreated. This process of corrasion will continue. Because there is no corrosion below low tide a rock platform is left called a wave cut platform.

Question 22

What are the four processes of transportation of material?

Answer 22

Traction - when rocks roll along the bottom of the sea.
Saltation - when small pieces of rock bounce along the sea bed.
Suspension - when tiny material floats around in the sea.
Solution - when material is dissolve in the water.

Question 23

How does longshore drift happen?

Answer 23

Beach material moves at the angle of the prevailing wind. It the wind blows the wave at a right angle to the shore sand and pebbles are washed up and down the beach. However if the wind blows so that waves come in at a sharp angle to the coast, the swash carries the pebbles at an angle across the beach. When the backwash moves by gravity back down the beach the pebbles end up in a different position. This process is repeated and pebbles gradually shift along the beach.

Question 24

How is a spit formed?

Answer 24

Eroded material is carried up the coastline and deposited in the direction of the prevailing wind. The material builds upwards by longshore drift forming a spit. A spit is an area of sand or pebbles that extends out into the sea. Occasionally a strong wind blows from a different direction. Some material will be pushed inland causing the end of the spit to become hook shaped.

Question 25

What is soft engineering defences?

Answer 25

Using natural environments to reduce the energy of waves.

Question 26

What are hard engineering defences?

Answer 26

Using built techniques to reduce damage caused by waves.

Question 27

Beach nourishment

Answer 27

Last 1-10 years | £10 per metre squares

Question 28

Sea walls

Answer 28

Lasts up to 100 years | £3000 per metre squared

Question 29

Gabions

Answer 29

Lasts 100 years for rock, 60 years for cage. | £50 per metre squared

Question 30

Rip rap

Answer 30

Lasts 50-100 years | £3000 per metre squared

Question 31

Groynes

Answer 31

Lasts 30 years £1000 per km squared Ugly

Question 32

Revetments

Answer 32

Lasts 30-40 years £1000-2000 per km squared Ugly

Question 33

Offshore breakwater

Answer 33

Lasts 50-100 years | £3,000,000 per km squared

Question 34

Which is the best coastal defence?

Answer 34

I think that overall beach nourishment is the best coastal defence. Although it needs to be replaced more frequently that other defences it is much cheaper. It is an efficient defence and the visual impact is low. The beach will not be ruined as it is simply adding sand or sediment. It would not discontinue any tourism like other defences, for example revetments or groynes. It is also beneficial to beaches with excess sediment as this is where the sand is taken from. All of the other defences are far more expensive. For example revetments are £1000-2000 and they only last 30-40 years. They are also ugly unlike beach nourishment.

Question 35

Name 3 factors that will affect the rate of erosion on a coastline.

Answer 35

Human activity: Coastal defences will slow erosion. Geology: some rocks like limestone are easier to erode. Wave speed and size: a larger, faster wave will erode a coastline more quickly.