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GCSE Geography > Coasts > Flashcards

Coasts Flashcards

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1
Q

What is fetch?

A
  • The length of water over which a given wind has blown
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2
Q

What are the characteristics of a destructive wave?

A
  • They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
  • They occur when wave energy is high and the wave has travelled over a long fetch.
  • They tend to erode the coast.
  • They have a stronger backwash than swash.
  • They have a short wave length and are high and steep.
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3
Q

What are the characteristics of a constructive wave?

A
  • They are created in calm weather and are less powerful than destructive waves.
  • They break on the shore and deposit material, building up beaches.
  • They have a swash that is stronger than the backwash.
  • They have a long wavelength, and are low in height.
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4
Q

What is hydraulic action?

A
  • The force of waves hitting the cliffs and forcing pockets of air into cracks and crevices.
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5
Q

What is abrasion?

A
  • Caused by waves picking up stones and hurling them at cliffs and so wearing them away
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6
Q

What is corosion?

A
  • Dissolving of rocks by the acid in sea water
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7
Q

What is attrition?

A
  • A process whereby the material carried by the waves carried by the waves becomes rounded and smaller over time as it collides with other material.
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8
Q

What is longshore drift?

A
  • Longshore drift is caused by the oblique wave angles that create a near shore current.
  • The zigzag pattern is because when a wave breaks, the swash carries material up the beach at the same angle as that which the wave approached the shore.
  • As the swash dies away, the backwash and any material carried by it returns straight down the beach, at right angles to the waterline, as a result of gravity.
  • Constructive waves
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9
Q

What is weathering?

A
  • The breakdown of rocks which is caused by freeze-thaw and the growth of salt crystals, by acid rain and by the growth of vegetation roots
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10
Q

What is erosion?

A
  • The wearing away of rocks by wind and rain
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11
Q

What is mass movement?

A
  • The removal of cliff-face material under the influence of gravity in the form of rock falls, slumping an landslides.
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12
Q

When is deposition likely to occur?

A
  • When waves enter an area of shallow water.
  • When waves enter a sheltered area, eg a cove or bay.
  • When there is little wind.
  • When there is a good supply of material.
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13
Q

What is a concordant coastline?

A
  • Occurs where the bands of differing rock types run parallel to the coast.
  • The outer hard rock (e.g. granite) provides a protective barrier to erosion of the softer rocks (e.g. clays) further inland.
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14
Q

What is a discordant coastline?

A
  • Occurs where bands of differing rock type run perpendicular to the coast.
  • E.g. Dorset coastline running north from the Portland limestone of Durlston Head
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15
Q

How does a cave form?

A
  • Occur when waves force their way into cracks in the cliff face.
  • The water contains sand and other materials that grind away at the rock until the cracks become a cave.
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16
Q

How does an arch form?

A
  • If the cave is enlarged and extends back through to the other side of the headland.
17
Q

How does a stack form?

A
  • The arch will gradually become bigger until it can no longer support the top of the arch.
  • When the arch collapses, it leaves the headland on one side and a stack on the other.
18
Q

How are wave-cut notches formed?

A
  • When destructive waves repeatdely break at cliffs that rise steeply from the sea and this leads to the cliffs being undercut at the base.
19
Q

How are wave-cut platforms formed?

A
  • Undercutting weakens the rock above the notch and it eventually collapses.
  • Thus the cliff face retreats but its cliff face is maintained.
20
Q

What is a spit?

A
  • An extended stretch of beach material that projects out to sea and is joined to the mainland at one end.
21
Q

How is a spit formed?

A
  1. Longshore drift moves material along the coastline.
  2. A spit forms when the material is deposited.
  3. Over time, the spit grows and develops a hook if wind direction changes further out.
  4. Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.
22
Q

What is a tombolo?

A
  • A spit connecting an island to the mainland.
  • An example of a tombolo is Chesil Beach, which connects the Isle of Portland to the mainland of the Dorset coast.
23
Q

What is a bar?

A
  • A ridge of sand that blocks off a bay or river mouth.
24
Q

How does Marram Grass help stop erosional processes?

A
  • Absorbs the waves energy and by the time it reaches the coastline, the erosional impact has reduced by a factor of five.
  • This form of defence is very common on the Lincolnshire Coastline where Marram Grass has been planted to deter coastal erosion.
25
Q

How are mangroves helpful?

A
  • Mangroves provide a barrier of interlocking roots and trunks which greatly reduce the power of the waves as the roots will absorb that power and greatly reduce its eroding ability, thus providing a useful barrier to protect the land.
26
Q

How can mangroves have a negative knock on effect?

A
  • This occurred in Nigeria where mangroves were imported from Singapore.
  • The Nipa Palm - the imported, exotic mangrove became an invasive species and took over the nutrients of the natural, native organisms.
  • This resulted in the total takeover and replacement of the native species of trees in the Nigerian mangrove swamp.
27
Q

What are emergent coastlines?

A
  • Emergent coastlines form as a result of a fall in sea level.
  • This may be as a result of greater ice storage, but they also form as a result of isostatic recovery.
  • Raised beaches and wave cut platforms
28
Q

What are submergent coastlines?

A
  • Submergent coastlines form as a result of sea level rise.
  • The current period of sea level rise, caused by melting ice sheets and thermal expansion of the ocean is called eustatic change.
29
Q

What landforms are found in submergent coastlines?

A
  • Fjords - found in Norwary, Iceland and Greenalnd
  • Fjards - found in Sweden and Denmark
30
Q
  • What are the potential impacts caused by construction on the coastline?
A
  • Damage to the natural life on the coast including marine habitats
  • Increased stress on the rock of the coastline
  • Changed wave patterns and a range of secondary factors such as faster erosions rates
  • A potential decline in tourism
  • Increased pollution
  • Loss of further sea life.
31
Q

How have increased pollution levels affected the coast?

A
  • According to the IPCC, the increase in carbon dioxide concentration has lowered global ocean surface pH by 0.1 units since 1750.
  • Global mean sea surface temperatures have risen about 0.6°C since 1950 with associated atmospheric warming in coastal areas.
  • These oceanic changes can have knock on affects on the coastal ecosystem.
32
Q

How has Brazil’s ecoystem been damaged in recent years?

A
  • Guanabara Bay, in Brazil, where there is heavy ship traffic involved in trade and tourism in the area.
  • Its attractive scenery attract even more tourists to Rio and its diverse ecosystem has been damaged in recent time by urbanisation, deforestation and 3 oil spills.
33
Q

What are the advantages and disadvantages of a sea wall?

A

Advantages

  • Effective defence against erosion and
    flooding.
  • Have a long lifespan of 75 years.
  • Socially reassuring to tourists.

Disadvantages

  • Reflected energy picks up sediment, which
    then is used in ‘scouring’ and can
    undermine the sea wall.
  • Very expensive
    £2000+ per metre.
  • Other areas left
    exposed.
34
Q

What are the advantages and disadvantages to groynes?

A

Advantages

  • Limit longshore drift
  • Build up beaches.
  • Very efficient in trapping sediment.

Disadvantages

  • Sediment input lower down coastline is
    reduced
  • Limiting protection offered to
    cliffs lower down coast.
  • Rapid cliff erosion
    can occur.
    • For example, Barton on Sea.
      Lifespan of 25 years
35
Q

At what rate does the Holderness coastline retreat?

A
  • Rate of one to two metres every year.
36
Q

Why does the Holderness coastline erode so quickly?

A
  • Strong prevailing winds creating longshore drift that moves material south along the coastline.
  • The cliffs are made of a soft boulder clay. It will therefore erode quickly, especially when saturated.
    • Glacial deposits
37
Q

What techniques have been used to defend Mappleton?

A
  • A coastal management scheme costing £2 million was introduced involving two types of hard engineering - placing rock armour along the base of the cliff and building two rock groynes.
  • The rock groynes have stopped beach material being moved south from Mappleton along the coast.
  • However, this has increased erosion south of Mappleton. Benefits in one area might have a negative effect on another.

GCSE Geography (6 decks)

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