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geography > Coasts > Flashcards

Coasts Flashcards

1
Q

what is a coast

A

the area where land and sea meet

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2
Q

what is the shoreline

A

the boundary of the land defined by the high water mark on a low-lying coast or the base of a steeply sloping coast

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3
Q

what is the shore

A

the area between the highest and lowest tide points

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4
Q

what are tides

A
  • usually twice a day but vary from coast to coast and with the time of the year
  • the difference between low and high tide is known as the tidal range
  • the tide determines the waves’ height and depth
  • the movement of waves and currents affects coastal features
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5
Q

what does the size of a wave depend on

A

The speed of the wind

The fetch (distance the wind travels)

The amount of time the wind blows (in the same direction)

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6
Q

what are destructive waves (5 features)

A

Destructive waves erode the beach and have:
- a steep wave gradient
- a short wavelength with high height
- a high frequency wave rate of 10-12 per minute
- high energy
- a strong, abrasive backwash that drags material out to sea and forms shingle beaches

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7
Q

what are constructive waves

A

Constructive waves are beach builders and have:
- a long wavelength with low height
- a low-frequency wave rate of 6-8 per minute
- a shallow wave gradient
- low energy
- a stronger swash that carries material up onto the beach and deposits a sandy beach

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8
Q

4 types of erosion

A

Hydraulic Action

Attrition

Corrosion

Abrasion

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9
Q

4 types of transportation

A

Traction

Saltation

Suspension

Solution

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10
Q

process of longshore drift

A

Longshore drift (LSD) is the main process of transportation along the coast

  • waves approach the beach at an angle due to the prevailing wind
  • as the waves break, the swash carries material up the beach at the same angle
  • as the swash dies away, the backwash carries the material down the beach at right angles (90°)
  • the process repeats, transporting material along the beach in a zig-zag movement
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11
Q

process of marine deposition

A

The waves carry sand or shingle as they travel

Backwash carries it away, while swash carries it onto a shore

  • the largest material is deposited along the upper reach of the swash when a constructive wave carries sediment up the beach
  • the backwash loses water and energy as it travels because of the sand’s porosity, resulting in smaller and smaller deposits.
  • when a constructive wave carries sediment up the beach, the largest material is deposited along the upper reach of the swash
  • during a storm, large shingle is thrown above the usual high tide level to form a ridge at the top of the beach called a berm
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12
Q

formation of cliffs and wavecut platforms

A

Cliffs are sloping or steep rocks with different profiles depending on the topography and geology

  • geology and wave attack at the base of the cliff also affect the angle of the cliff face; low-energy waves cause less damage than high-energy ones
  • Many cliffs have a ‘knick-point’ around the high-water mark called the ‘wave-cut notch’, which is where the wave has undercut the rock
  • Abrasion, corrosion and hydraulic action further extend the notch back into the cliff
  • As undercutting continues, the cliff above becomes unsupported and unstable and eventually collapses
  • The backwash of the waves carries away the eroded material, leaving behind a wave-cut platform
  • The process repeats and the cliff continues to retreat, leading to a coastal retreat
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13
Q

formation of headlands and bays

A
  • Found in areas of alternating bands of resistant (hard) and less resistant (soft) rocks running perpendicular to oncoming waves (discordant coastline)
  • Initially, less resistant rock (e.g. clay) is eroded back, forming a bay
  • The more resistant rock (e.g. limestone) is left protruding out to sea as a headland
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14
Q

formation of cave, arch, stack and stump

A
  • Hydraulic action, abrasion, and corrosion take advantage of any weaknesses in the headland
  • As a crack begins to widen, erosion will act to form a cave
  • The cave will become larger and eventually break through the headland to form an arch
  • Due to weathering from above and erosion below, the arch’s foundation continues getting thinner and wider
  • Eventually, the roof of the arch collapses, leaving behind an isolated column of rock called a stack
  • The stack is undercut at the base by wave action and sub-aerial weathering above, until it collapses to form a stump
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15
Q

formation of a spit

A
  • The process that moves sediment is longshore drift
  • Where the coastline changes direction, a shallow, sheltered area allows sediment to be deposited
  • More deposition happens as a result of higher friction
  • Eventually, a spit slowly builds up to sea level and extends in length
  • If the wind changes direction, then the wave pattern alters and results in a hooked end
  • The area behind the spit becomes sheltered
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16
Q

what is a bar

A

A bar is when a spit grows across a bay and joins two headlands together

A bar of sand is formed (sandbar)

Sandbars can also form offshore due to the action of breaking waves from a beach

17
Q

what is a lagoon

A

A lagoon is where a small body of water is cut off from the sea

A lagoon may form behind a bar or tombolo

Lagoons do not last forever and may fill with sediment and form new land

18
Q

what is a tombolo

A

A tombolo is formed when a spit joins the mainland to an island

Chesil Beach in Dorset is a tombolo, as the mainland is joined to the Isle of Portland

19
Q

formation of a sand dune

A
  • Windblown sand is deposited against an obstruction, such as a pebble or driftwood
  • As more sand particles are caught, the dunes grow in size, forming rows at right angles to the prevailing wind
  • In a process known as succession, vegetation will eventually colonise and fix the ridges of the dunes
20
Q

7 stages of a sand due

A
  • embryo dune
  • fore dune
  • yellow dune
  • grey dune
  • dune slack
  • mature dune
21
Q

conditions required for coral reefs to grow

A
  • temperature: cannot be below 18C but thrive best between 22 - 25C
  • require photosynthesis due to the algae living in the tissue
  • depth of less than 25m so that sunlight can penetrate
  • require salty water
22
Q

3 types of coral reefs

A
  • fringing reef
  • barrier reef
  • atolls
23
Q

4 characteristics of mangroves

A
  • live on the coastline
  • sit in water between 0.5-2.5m high
  • range in size from small shrubs to trees 60m highs
  • the roots have a filteration system with a filter to keep salt out
24
Q

8 coastal opportunities

A
  • Development
  • Nature reserves
  • Swimming and sports
  • Industry
  • Fishing and aquaculture
  • Tourism
  • Agriculture
  • Ports and harbours
25
Q

4 human induced coastal hazards

A
  • urbanisation & transport - damages environment
  • agriculture - loss of ecosystems
  • fisheries - loss of habitats
  • tourism & recreation - pollution and loss of ecosystems
26
Q

3 natural induced coastal hazards

A
  • tropical storms - cause flooding
  • changing sea levels - risk of submersion
  • influence of geology - hard and soft rock could erode
27
Q

what is hard engineering

A

a method of coastal management that involves construction work. usually very expensive

28
Q

what is soft engineering

A

a method of coastal management that involves natural processes on the coastline.

29
Q

3 examples of hard engineering techniques

A
  • rip-rap
  • recurved sea wall
  • groynes
30
Q

what are rip-raps, how does it work and what are the advantages and disadvantages

A
  • resistant boulders placed at the base of the cliff
  • boulders absorb energy from waves, protecting the coastline
    + - looks natural, low maintenance
    —- - can be hazardous, short - so waves can go over it
31
Q

what are recurved sea walls, how does it work and what are the advantages and disadvantages

A
  • seawall built along a section of the coastline
  • recurved structure reflects wave energy back out to sea
    + water goes back to ocean, can be used as a promenade
    — - expensive, ugly, long term construction process
32
Q

what are groynes, how does it work and what are the advantages and disadvantages

A
  • rock or wooden barriers built along the beach and protect the beach from the coastline
  • limits long-shore drift, maintaining the beach and protecting the coastline
    + - cheaper, focuses on limiting long-shore drift
    — - small so cant help much, requires a lot of maintenance
33
Q

2 methods of soft engineering

A
  • beach replenishment
  • cliff regrading
34
Q

what is beach replenishment, how does it work and what are the advantages and disadvantages

A
  • material sprayed onto the beach
  • builds up beach which absorbs wave energy, protecting coastline
    + - natural, cheaper
    — - repetitive process, must be maintained, can deepen sea meaning bigger waves
35
Q

what are cliff regrading, how does it work and what are the advantages and disadvantages

A
  • changing the angle of slope gradient to reduce risk of collapse
  • slows rate of cliff recession so it is more stable
    + - natural, doesnt require materials
    — - doesnt actually stop erosion
36
Q

case study: holderness general facts

A
  • east coast of england
  • extends from flambourough to spurn point
  • most erosion by longshore drift occurs at Hornsea
37
Q

6 holderness management

A
  • Skipsea has gablon cages built by local landowner
  • Hornsea built and repaired groynes at cost of 5.2 million
  • Hornsea raised old seawall
  • Hornsea sand dunes are being planted with trees
  • Withernsea groynes and sea wall built
  • Withernsea wall is protected by rip-rap and beach nourishment - all cost 6.3 million

geography (12 decks)

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