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Geography > Coasts > Flashcards

Coasts Flashcards

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1
Q

What causes waves

A

When wind blows across the sea friction between the wind and water surface causes waves

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2
Q

What does the size of a wave depend on

A

Strength of the wind
How long the wind blows for
The length of water the wind blows over - called the fetch

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3
Q

Why does a wave break

A

As a wave approaches a beach it slows this is the result of friction between the water and the beach causing a wave to break

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4
Q

Characteristics of destructive waves

A 
Erode the most creating a steep beach
High in proportion to their length
The backwash is much stronger than their smash so the sediment is carried back out to sea
Frequent 
Common in winter
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5
Q

Characteristics of constructive waves

A

Build beaches
Each wave is low
As wave breaks it carries material up the beach in its swash
Backwash is weaker so sediment is deposited with the swash building up a beach
Common in summer

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6
Q

What is weathering

A

Weathering is the disintegration or decay of rocks in their original place or close to the ground surface

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7
Q

What are the three types of weathering

A

Mechanical weathering
Chemical weathering
Biological weathering

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8
Q

What is mechanical weathering and the two types of mechanical or physical weathering

A

Disintegration of rocks without any chemical changes taking place often resulting in angular rock fragments called scree.
Freeze thaw and exfoliation

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9
Q

What does freeze thaw involve

A

Water collecting in crocks or holes in the rock
The water freezes and expands by approx 9% which stresses the rock and widens any cracks
Temperature rises and ice thaws the water seeps deeper and the cycle repeats until rock breaks

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10
Q

What is exfoliation

A

In areas of large temperature variation

Heating and cooling of rock causes the rock to expand and contact leading to the outer layer of rock flaking off

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11
Q

What is chemical weathering

A

Affects rocks made of calcium carbonate as rain falls it dissolved CO2 to produce a weak acid called carbonic acid. When rain falls on rock the acid dissolved a calcium carbonate to form calcium hydrogen carbonate which is soluble. Overtime this is dissolved away

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12
Q

What is biological weathering

A

Involves the actions of plants and animals. Plant roots are effective at growing and expanding in cracks in the rocks. Animals such as rabbit burrow into weaker rocks such as sand

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13
Q

What is mass movement and what are some examples

A

The downhill movement of material under the influence of gravity usually classified according to speed of movement and moisture. Rockfalls, mudflows, rotational slip, landslide

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14
Q

What is hydraulic action in relation to coast

A

Water is forced into cracks in the rock as waves strike the cliff air pockets in the cracks are compressed and then expand blasting the cracks apart

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15
Q

When does longshore drift operate

A

When waves approach the coastline at an angle

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16
Q

How does longshore drift occur

A

When waves approach coast at an angle the swash pushes sediment up the beach at this angle. The backwash then drags the material down the beach at 90*c due to gravity, this produces a zig zag movement of sediment along the beach. Smaller sediment carried the farthest

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17
Q

When and why does coastal deposition take place

A

In areas where the flow of the water slows down, sediment can’t be carried or roll so it had to be deposited. Mostly occurs in bays where the energy of the waves is reduced on entering the bay as the waves are refracted so beaches occur in bays.

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18
Q

What is a headland

A

A point of high land that juts out into the sea

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19
Q

What is a bay

A

A broad coastal inlet that often had a beach

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20
Q

What two ways can rock strata be arranged along coastlines

A

If the layers are parallel to the coast it is concordant

If the layers are perpendicular it is discordant

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21
Q

How do coves form

A

On a concordant coastline. First layer is hard rock and behind it is soft rock so water erodes a small bit of the resistant rock creating a gap then the water can erode the soft rock behind it more creating a cove where the sea can flow into.

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22
Q

How do wave cut platforms form

A

Wave breaks against cliff and wave takes “bite” out of cliff forming a wave cut notch. A long period of time and Notch gets deeper and overhanging cliff can’t be supported so it falls into the sea. Cliff line gradually retreats and in its place will be a gently sloping platform called a wave cut platform and overtime it may get covered in sand and shingle

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23
Q

Explain the stages of eroding the headland

A

Hydraulic action in weaknesses in the rock causing it to erode and over time small caves may form. These caves get wider until they join to form an arch. This arch erodes more leading to the roof collapsing and a stack to be formed. Overtime this will become a stump.

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24
Q

How do waves refract

A

Once they enter bays they refract to mirror the shape of the coastline creating converging waves eroding the headland and diverging waves in the bays. Waves enter shallower water and wave refraction causes the waves to spread out and reduce the wave energy in the bay.

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25
Q

What are beaches and how are they formed

A

Accumulations of sand and shingle found where deposition occurs at the coat. Often in sheltered bays .

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26
Q

What is a spit

A

A narrow finger of sand and shingle jutting out into the sea from the land

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27
Q

How does a spit form

A

As sediment is transported along the coast by longshore drift it becomes deposited at a point where the coastline changes or where a river estuary occurs. As more sediment is deposited it just out into the sea more. End of the spit is often affected by the waves approaching from different directions and spit becomes curbed. Behind the spit land is formed which is soon colonised with plants and salt marshes form.

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28
Q

How is a bar formed

A

Longshore drift may cause a spit to grow across a bay trapping fresh water lake or a lagoon behind and this spit across a bay is a lagoon

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29
Q

What is the coast shaped by

A

Weathering
Erosion
Mass movement
Transportation

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30
Q

What are the causes of sea level rise

A

Global warming
Thermal expansion - the sea absorbing more heat from the atmosphere
Ice on land melts
The level of the land

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31
Q

How do storm surges occur

A

Twice a day sea levels rise at high tide and fall at low tide. A few times a year when sun and moon are aligned there are Spring tides which are expectationally high. Large waves and Spring tides the sea will be even higher. If an area of low pressure including an intense depression or a hurricane off the coast a storm surge may follow combing this with Spring tide would be devastating.

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32
Q

Case study for rising sea level

A

East anglia

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33
Q

What are the impacts of sea level rise on east anglia

A
  • threaten coastal settlements like overstrand
  • current sea defences will need strengthening which is expensive
  • 22% of EA salt marshes could be lost by 2050
  • when storm surge happened 300 people died
  • Norfolk boards brings £5 million from tourists but rising sea would flood this destroying economy
  • agricultural land (the fens) at risk
  • Thames barrier protecting
34
Q

Information about the Thames flood barrier

A

Cost £594 million
Raised on average 4-6 times a year to prevent flooding in central London
Rising sea could shorten its life span
In 15 years the rate of global sea level rise has doubled to 3.1mm a year
Need replaced in 30-50 years
Protects £80 billion worth of buildings and capital infrastructure

35
Q

Why do cliff collapse

A

Base of cliff attacked by erosion making it steeper
Weathering weakens rocks
Heavy rain saturates permeable rock
Rainwater erode the cliff as it runs down
Permeable rock + water = heavy
Buildings on top make it heavy and unstable

36
Q

What is a case study for cliff collapse

A

Holbeck hall

37
Q

What are the facts about Holbeck hall

A

Section of cliff supporting the Holbeck hall hotel slumped into the sea
Cracks at the surface of the clay let rain seep into the cliff
Heavy rain added additional weight and made cliff slippy and unstable
Waves undercutting base of cliff
Large crack opened up parallel to the coast and rotational slide occurred and large section of cliff slumped into sea

38
Q

What has been done since Holbeck halls cliff collapse to hell

A

Scarborough district council has since stabilised the cliff and founders extensive cliff defences

39
Q

What are the impacts of cliff collapse

A
  • home owners lose their homes, insurance impossible and value of land falls
  • rapid cliff collapses are dangerous for people at top of cliff and on beach
  • roads and infrastructures destroyed
  • many people say erosion makes area unattractive
40
Q

What can help stop cliff collapse

A
  • make slopes where landslide occurs flatter
  • plant salt and erosion resistant vegetation
  • insert drainage pipes into cliff
  • put rock armour at the base of the cliff
  • put sheets of strong plastic called geotextile (let’s water through) into cliff face and pack with clay
41
Q

Why does the coastal zone need to be managed

A

To maintain a balance between the forces of nature and the demands of people, the coastal zone is under threat from cliff collapse, flooding and rising sea levels

42
Q

What are the four strategies councils choose between when they make decisions on how to manage the coast

A 
Hold the line (use sea defences to stop erosion and keep the coast where it is, expensive)
Advance the line (use sea defences to move the coast further into the sea, very expensive)
Strategic retreat (let the coast erode and move people away)
Do nothing (let nature take its course)
43
Q

What are some examples of hard engineering strategies for the coast

A

Groynes
Sea walls
Rock armour (RIP rap)

44
Q

What are some examples of soft engineering strategies st the coast

A

Beach nourishment
Dune regeneration
Marsh creation

45
Q

How do groynes work

A

The best defence is a wide sandy beach. If a groyne is built it helps trap sand by stopping longshore drift so builds up the beach so water has longer to travel before it reaches the cliff and erodes it.

46
Q

What are a disadvantage to groynes

A

Sediment is prevented from reaching other places further down the coast so beaches else where disappear
Expensive to install and maintain, looks bad

47
Q

How do sea walls work

A

A concrete or rock barrier placed at the foot of the cliffs or st the top of s beach that are usually 3-5 pm high. The curved face reflects the waves back into the sea to stop undercutting of the cliff.

48
Q

What is a disadvantage to sea walls

A

Expensive and in the future may need to be built even higher
Can prevent access to the beach
Obtrusive and unnatural to look st

49
Q

How does rock armour work

A

Piles of large boulders dumped at the foot of a cliff the rock forced waves to break and absorbs their energy protecting the cliffs

50
Q

What is a disadvantage to rock armour

A

Usually brought in by barge to the coast
Very expensive to transport
Don’t fit in with local geology

51
Q

Advantages to sea wall

A

Effective at stopping the sea

Often had a walkway for people to walk along

52
Q

Advantages to groynes

A

Reduced erosion
Bigger beach means more tourist potential for the coast
Good for people interested in fishing
Not too expensive

53
Q

Advantages of rock armour

A

Easy to build
Looks more natural
Relevantly cheap and easy to maintain

54
Q

How much do sea walls cost

A

Up to £6m per km

55
Q

How much do groynes cost

A

£10,000 each

56
Q

How much does rock armour cost

A

£1000-£4000 per metre

57
Q

What are the characteristics of soft engineering on the coast

A
  • no large artificial structures
  • STIO erosion by stabilising beaches and cliffs and reducing wave energy
  • cheaper
  • less intrusive
  • sustainable
58
Q

How does beach nourishment work

A

The addition of sand or shingle to an existing beach to make it higher or broader, sand is usually obtained locally so it blends

59
Q

How does dune regeneration work

A

Sand dunes are effective buffer to the sea yet they are easily damaged and destroyed so marram grass can be planted to stabilise the dunes

60
Q

How does marsh creation work

A

E.g managed retreat allowing low lying coastal areas to become salt marshes

61
Q

How expensive is beach nourishment, dune regeneration SND marsh creation

A

£3000 per metre
£2000 per 100m
£5000-£10,000 per hectare

62
Q

Advantages of beach nourishment

A

Relatively cheap and easy to maintain
Blends in well with existing beach
Increases tourist potential

63
Q

What are the disadvantages go beach nourishment

A

Needs constant maintanence unless structures are built to retain the beach like groynes

64
Q

Advantages of dune regeneration

A

Maintains a natural costal environment that is popular with people and wild life
Relatively cheap

65
Q

Disadvantages of dune regeneration

A

Time consuming to plant marram grass and fence off areas
People don’t always follow the rules
Land damaged by storms

66
Q

What is an advantage to marsh creation

A

Cheap option compared with maintaining expensive sea defences that might only protect low value land
Habitat for wildlife

67
Q

Disadvantages of marsh creation

A

Land will be lost as it is flooded by sea water

Farmers or land owners will need to be compensated

68
Q

What can managed retreat involve

A
  • carrying out no repairs to sea defences
  • abandoning the coast to the forces of nature
  • allowing the tide to invade the land forming salt marshes
  • leaving mashes as wildlife habitats
69
Q

What does holistic management take into account

A
  • needs of different groups of people
  • economic cost and benefits of different strategies today and in the future
  • envionment, both on land and in sea
70
Q

Why are some places not protected because of holistic management

A
  • too expensive as value of land doesn’t justify the cost
  • cause erosion somewhere else
  • seen as more sustainable
  • might be better for the environment to let s salt marsh be created
71
Q

Case study for coastal management

A

The holderness coast ,Mappleton town

72
Q

Facts about the holderness coast

A
  • made of soft easily eroded Boulder clay
  • 29 villages have been lost in the past 1000 years
  • coast is exposed and the waves have a long fetch over the North Sea
  • cliffs with little beach protection
  • heavy rain makes cliff top instantly and liable to slumping
73
Q

Facts about Mappleton

A

£2 million spent on a costal protection scheme for s village of 100 people because it would of been expensive to find a new road link.
Blocks of granite imprint from Norway for the bottom the cliff
2 groynes to trap beach material and protect

74
Q

What are holderness councils views on Mappleton

A

only have £4 million so spending a lot of money is hard to justify. Maybe they should let it disappear

75
Q

What are the ministry of agriculture S views on coastal protection in Mappleton

A

Moving towards a policy of managed retreat.

There are food surpluses in the EU so we don’t need every bit of land so we should let some disappear to help

76
Q

What does farmers living just south of Mappleton think of the coastal protection

A

Their farm is at great risk from the sea than ever because of the coastal protection as it increases erosion due to them being south of the groyne

77
Q

What is a sand dune environment characterised by

A
  • large area exposed between high and low tides
  • a prevailing onshore wind
  • a large supply of fine sand
  • extremely arid
  • large amounts of salt spray
  • alkaline conditions
78
Q

How do sand dunes form

A

The sand dries and onshore winds pick up sand and transport it inland but some sand may become trapped by seaweed and driftwood and this continues to build up to create an embryo dune. Plants start to colonise and are this process continues more dunes are created in front of that one creating multiple dunes

79
Q

What are the six stages of sand dunes

A

Embryo dune - sand and some marram grass
Foredunes - marram grass, sea rocket
Yellow dune - 80% plant still covered in marram
Grey dune - more sheltered less acidic. Red fescue, gorse
Dune slack - water loving plants like willow, moss and reeds
Mature dune - trees: birch, alder, oak

80
Q

What is the case study for sand dune ecosystem

A

Studland Heath

81
Q

Key facts about studland

A

On a summer day up to 25,000 people visit
Come to visit the beach but some for the sand dunes and nature reserve
Numbers of visitors increasing so are the problems

82
Q

What are the strategies to manage st studland

A
  • enlarge car parks to increase capacity to 800
  • build a visitor centre with shops, cafes and info points
  • increase number of toilets and services for disabled
  • closed some paths and fenced off parts of the sand dunes
  • planted marram grass
  • placed litter bins on paths
  • placed fire beaters and water hydrants on heather and gorse Heath
  • educating people using information boards and leaflets

Geography (5 decks)

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