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Geography > Coasts > Flashcards

Coasts Flashcards

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0
Q

What is attrition?

A

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.

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1
Q

What are the two types of waves?

A

Constructive and destructive

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2
Q

What is abrasion/corrasion?

A

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

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3
Q

What is solution?

A

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

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4
Q

What is hydraulic action?

A

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

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5
Q

What is a destructive wave?

A

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

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6
Q

What is a constructive wave?

A

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

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7
Q

What is swash?

A

The movement of water up the beach.

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8
Q

What is backwash?

A

The movement of water back down the beach.

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9
Q

What is fetch?

A

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

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10
Q

What is prevailing wind?

A

The predominant wind direction.

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11
Q

What three processes does the sea carry out?

A
  • it erodes the land.
  • it transports the eroded material.
  • it deposits the material at another given location.
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12
Q

What is chemical weathering?

A

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

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13
Q

What is the difference between weathering and erosion?

A

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.

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14
Q

When are bays formed?

A

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.

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15
Q

How are headlands formed?

A

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.

16
Q

What is the name for the bands of rock?

A

Strata.

17
Q

How is a cave formed?

A

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.

18
Q

How is an arch formed?

A

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.

19
Q

How is a stack formed?

A

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

20
Q

How is a stump formed?

A

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

21
Q

How is a wave cut platform formed?

A

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.

22
Q

What are the four processes of transportation of material?

A

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.

23
Q

How does longshore drift happen?

A

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.

24
Q

How is a spit formed?

A

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.

25
Q

What is soft engineering defences?

A

Using natural environments to reduce the energy of waves.

26
Q

What are hard engineering defences?

A

Using built techniques to reduce damage caused by waves.

27
Q

Beach nourishment

A

Last 1-10 years

£10 per metre squares

28
Q

Sea walls

A

Lasts up to 100 years

£3000 per metre squared

29
Q

Gabions

A

Lasts 100 years for rock, 60 years for cage.

£50 per metre squared

30
Q

Rip rap

A

Lasts 50-100 years

£3000 per metre squared

31
Q

Groynes

A

Lasts 30 years
£1000 per km squared
Ugly

32
Q

Revetments

A

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

33
Q

Offshore breakwater

A

Lasts 50-100 years

£3,000,000 per km squared

34
Q

Which is the best coastal defence?

A

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.

35
Q

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

A

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.

Geography (3 decks)

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