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Geography > Coasts > Flashcards

Coasts Flashcards

1
Q

Types of erosion

A
  • corrasion / abrasion
  • hydraulic action
  • cavitation
  • wave quarrying
  • solution / corrosion
  • attrition
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2
Q

Definition : corrasion (abrasion)

A
  • type of erosion
    Bits of rock and sediment transported by waves that smash and grind against other rocks and cliffs becoming smoother
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3
Q

Definition : Hydraulic action

A
  • type of erosion
    Air in the cracks on a cliff is compressed from waves crash against it, the pressure breaks apart the rock
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4
Q

Definition: cavitation

A
  • type of erosion
    As waves recede from the cliff the compressed air largely expands exerting more pressure and causing rock to break
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5
Q

Definition: wave quarrying

A
  • type of erosion
    Energy of the waves against a cliff breaks away the rock
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6
Q

Definition: solution/corrosion

A
  • type of erosion and transportation
    Soluble rock (limestone or chalk) dissolved by seawater
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7
Q

Definition: attrition

A
  • type of erosion
    Rocks in the water smashed against each other and become smaller
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8
Q

Definition: suspension

A
  • Type of transportation
    Very fine material is carried in the water
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9
Q

Definition: saltation

A
  • Type of transportation
    Larger particles transported by the force of the water causing them to bounce along the seabed
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10
Q

Definition: traction

A
  • Type of transportation
    Very large particles such as boulders are pushed along the sea bed
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11
Q

Types of transportation

A
  • Solution
  • saltation
  • traction
  • suspension
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12
Q

How do groynes (hard engineering) work

A
  • fences built at right angles to the coast
  • trap beach material transported by longshore drift
  • creates wider beaches which reduces the waves energy preventing erosion
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13
Q

Evaluation of groynes (hard engineering)

A

+ relatively cheap
+ low maintenance

Last around 10-25 years

  • unnatural and can be unattractive
  • only work on the part of the beach they are covering, can increase erosion in other parts of the beach
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14
Q

How do sea walls (hard engineering) work

A
  • reflect waves back into the sea to prevent erosion of the coast
  • can act as a barrier to prevent flooding
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15
Q

Evaluation of sea walls (hard engineering)

A

+ 30-50 years
+ effective in preventing erosion

  • expensive to build and maintain
  • can create a strong backwash which erodes under the wall
  • can be intrusive on a beach
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16
Q

How does rip rap (hard engineering) work

A
  • boulders piled up along the coast
  • absorb wave energy and prevent beach erosion
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17
Q

Evaluation of rip rap (hard engineering)

A

+ fairly cheap
+ easy to maintain

  • can shift in storms
  • can lookout of place with local geology
  • can be a danger to public with children climbing across them
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18
Q

How do revetments (hard engineering) work

A
  • slanting structures built at the bottom of a cliff
  • break up waves and absorb their energy which prevents cliff erosion
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19
Q

Evaluation of revetments (hard engineering)

A

+ cheap to maintain
+ effective and quick
+ last 30-50 years

  • can create a strong backwash which can erode under the wall
  • intrusive and unnatural
  • expensive to build
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20
Q

How does offshore breakwater (hard engineering) work

A
  • Concrete blocks or boulders deposited off the coast
  • Force waves to break offshore
  • Waves energy and erosive power are reduced before they reach the beach
21
Q

Evaluation of offshore breakwaters (hard engineering)

A

+ Keep the beach natural
+ Last between 30 and 50 years
+ Effective in reducing erosion

  • Can be damaged in storms
  • Yearly maintenance and inspection required
22
Q

How do gabions (hard engineering) work

A
  • rock filled cages
  • A wall is usually built at the foot of cliffs
  • Absorb wave energy
23
Q

Evaluation of gabions (hard engineering)

A

+ Cheap
+ Last between 10 and 75 years
+ Strong, stable and good for drainage

  • Unnatural
  • Annually inspection required
24
Q

How do barrages (hard engineering) work

A
  • A dam built to increase the depth of the water
  • Controlled release of the water through turbines
  • Prevents flooding and generates electricity
25
Q

Evaluation of garages (hard engineering)

A

+ Last up to 100 years
+ Nearly 100% effective

  • Very expensive
  • Very man-made could possibly be an eyesore
  • Can disrupt sediment flow, which may cause increased erosion elsewhere
26
Q

Definition : weathering

A

The breakdown of rocks in situ (where it is originally found / lands on the cliff)

27
Q

Definition : sub aerial processes

A

Land based processes which alter the shape of the coastline, combination of weathering and mass movement

28
Q

Biological weathering

A
  • break up of rocks by organic activity
  • thin plant roots grow in small cracks in the cliff face
  • as the plant grows the cracks widen causing rock to break off
  • water running through any decaying vegetation in rocks becomes acidic causing chemical weathering
  • birds and animals dig burrows into cliffs breaking off rock
29
Q

Mechanical weathering

A

Freeze thaw : water enters the cracks in the rocks and freezes which expands the crack, process repeats until the rock eventually breaks

Salt crystallisation : when salt water evaporates it leaves behind crystals which expands over time in the cracks of the rock causes pieces to break off

Wetting and drying : rocks rich in clay expand when they are wet and contract when they are dry, this causes them to crack and break

30
Q

Chemical weathering

A

Carbonation : carbon dioxide in the atmosphere dissolves in rainwater forming a weak carbonic acid, the acid rain reacts with rocks causing them to rock

Oxidation : reaction of oxygen with rock minerals e.g. iron reacts with o2 leaving the rock vulnerable to break

Solution : dissolving of rock minerals

31
Q

Definition : mass movement

A

Downhill movement of material under the influence of gravity

32
Q

Soil creep (mass movement)

A
  • Movement of individual particles downhill
  • extremely slow process
  • cannot be seen but may be shown by a build up of particles near a tree or building
33
Q

Mudflows (mass movement)

A
  • earth and mud flowing downhill over weak bedrock
  • quite rapid
34
Q

Landslide (mass movement)

A
  • block of rock moving down the side of a cliff
  • triggered by earthquakes or heavy rainfall
35
Q

Rockfall (mass movement)

A
  • collapse or breaking away of rock fragments at a cliffs face
  • triggered by mechanical weathering or earthquakes
  • sediment at the bottom of the cliff is gradually removed by the sea
36
Q

Landslip or slump (mass movement)

A
  • movement of material on a cliff where the slide surface is curved
  • occurs on weak clays or sand
37
Q

Run off (mass movement)

A
  • when overland flow occurs down a slope of cliff face small particles are moved to the coastline
38
Q

Solifluction (mass movement)

A
  • similar to soil creep but specific to cold environments
  • in summer the surface layer of soil thaws out and becomes saturated
  • the sodden soil and vegetation is moved slowly downhill
39
Q

How does beach nourishment (soft engineering) work

A

Addition of sand and pebbles to a beach to make it higher protecting it from wave erosion

40
Q

Evaluation of beach nourishment

A

+ natural beach
+ relatively cheap
+ increases tourism

  • constant maintenance due to natural processes
  • only lasts 2-10 years
  • does not end erosion
41
Q

How does cliff regrading / drainage (soft engineering) work

A
  • reduces the angle of the cliff to stabilise it
42
Q

Evaluation of cliff regrading and drainage (soft engineering)

A

+ can be effective where other methods don’t work e.g. On loose rock
+ cost effective
+ natural

  • can dry out and lead to collapse
43
Q

How does dune stabilisation (soft engineering) work

A

Marram grass can be planted to stabilise the dunes or areas can be fenced off

44
Q

Evaluation of dune stabilisation (soft engineering)

A

+ natural environment
+ provides habitats
+ cheap and sustainable

  • time consuming
  • people may respond negatively to areas being shut off
  • may need to constantly replant
45
Q

How does land use management (soft engineering) work

A
  • important for dune management
  • wooden pathways may be by built to stop cyclists or the public walking on dunes
46
Q

Evaluation of land use management (soft engineering)

A

+ can be cheap depending on size and structure
+ can fit in with the areas

  • only lasts 3 to 5 years
  • can destroy the land underneath
47
Q

How does managed retreat (soft engineering) work

A
  • allow low lying coastal areas to be flooded by the sea
48
Q

Evaluation of managed retreat (soft engineering)

A

+ relatively cheap (depends on area)
+ land reverts back to original state
+ creates habitats

  • agricultural land is lost
  • farmers or landowners need to be compensated

Geography (5 decks)

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