Coasts Flashcards

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1
Q

What is a crest?

A

The top of the wave.

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2
Q

What is a trough?

A

The base of a wave.

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3
Q

What is wave height?

A

The distance from the trough to the crest.

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4
Q

What is wave length?

A

The horizontal distance between two crests.

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5
Q

What is wave frequency?

A

The number of waves breaking per minute.

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6
Q

What is fetch?

A

The distance a wave has travelled.

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7
Q

What is swash?

A

The wave moving up the beach by the energy from the wind.

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8
Q

What is backwash?

A

The wave moving back down the beach under the influence of gravity.

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9
Q

What are the features of a constructive wave?

A

Long wave length, low energy, low wave height, gently sloping, strong swash, weak backwash, transports sediment up the beach and a shallow beach.

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10
Q

What are the features of a destructive wave?

A

Small wave length, high energy, high wave height, steep wave front, weak swash, strong backwash, takes sediment from the beach, plunges onto a steep beach so it doesn’t travel much.

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11
Q

What is weathering?

A

The breaking down of rock by day-day atmospheric changes such as temperature and precipitation.

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12
Q

What are the two types of weathering?

A

Chemical weathering and mechanical weathering.

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13
Q

What are two example of mechanical weathering?

A

Salt weathering and freeze thaw weathering.

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14
Q

What are two examples of chemical weathering?

A

Carbonation and oxidation.

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15
Q

What is salt weathering?

A

Where salt is in rocks when the sea is on it, then it dries and the salt expands, similar to freeze thaw.

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16
Q

What is freeze thaw weathering?

A

When water fills a crack, then the water freezes in the night and the crack is widened as it expands by 9%. This repeats until the size increases of the crack so much the rock falls off making scree.

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17
Q

What is mass movement and what are 3 examples?

A

Mass movement is the downhill movement or rock, soil or mud under the influence of gravity. e.g. slides, falls and slumping.

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18
Q

What is sliding?

A

Material moving downhill that does not lose contact with the slope.

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19
Q

What is falling?

A

Material moving vertically where material does lose contact with the slope.

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20
Q

What is slumping?

A

A curve slip plane where material rotates backwards as it moves downhill.

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21
Q

What are the 4 methods of erosion?

A

Hydraulic action, abrasion, attrition and solution.

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22
Q

What is hydraulic action?

A

The sheer force of waves pounding cliffs. The surge of water compresses air into cracks creating an explosion effect.

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23
Q

What is abrasion?

A

The scratching and scraping of cliff faces as sand and shingle is thrown at a cliff face.

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24
Q

What is attrition?

A

The wearing down of particles as they collide with one another. This leads to smaller and rounder particles.

25
Q

What is solution?

A

The erosion of rock through chemical action as sea water dissolves certain types of rocks.

26
Q

What are the 4 methods of transportation?

A

Traction, saltation, suspension and solution.

27
Q

What is traction?

A

Large pebbles rolled along the sea bed.

28
Q

What is saltation?

A

A bouncing motion of pebbles that are too heavy to be suspended.

29
Q

What is suspension?

A

Particles carried in the water.

30
Q

What is solution?

A

Dissolved sediments often from limestone or chalk.

31
Q

How does longshore drift work?

A

Waves enter at an angle due to prevailing wind, leaving sediment. The backwash returns at a right angle to the beach and it repeats. It causes sediment to be deposited due to the methods of transportation such as traction.

32
Q

What is a discordant coastline?

A

It lets headlands and bays form where there are alternating bands of hard and soft rock. The soft rock erodes quickly and the hard rock erodes slowly in a process known as differential erosion.

33
Q

What is wave refraction?

A

Where waves usually hit the coastline straight on but there are headlands so the waves refract around the headlands leading to erosion of them.

34
Q

What is the order of erosion of a headland?

A

A crack, cave, arch, stack, stump.

35
Q

What is a wave cut platform and how is it formed?

A

It is a rock platform formed by a wave eroding between the HTWM and the LTWM of a cliff. It then makes a wave cut notch leaving an overhang and then the overhang collapses leaving a wave cut platform which is repeated.

36
Q

How is a spit formed?

A

It is formed due to longshore drift and then a change in direction of the coastline, causing the sediment to deposit in the sea. It then builds up due to it being sheltered and causes a spit to form. A secondary wind could cause the spit to form a hook on the end and behind spits, salt marshes form.

37
Q

What is a bar?

A

It is formed due to longshore drift carrying sediment from a headland to another so it forms a bar. It leaves a lagoon in the bay as well.

38
Q

What are the dunes?

A

An embryo dune, a yellow dune, a grey dune and the wasting dunes.

39
Q

What is an embryo dune?

A

It is 90% bare sand, dry and salty, pioneer species are the ones that go here, and they have to be salt tolerant(halophytic) and drought tolerant(xerophytic). These are the smallest dunes.

40
Q

What is a yellow dune?

A

It is 60% bare sand, conditions are improving, more biodiversity, taller as plant trap more sand.

41
Q

What is a grey dune?

A

They are 10% sand, high vegetation cover, conditions are improving, more soil with more nutrients, more biodiversity, the tallest dune as it has the most plant.

42
Q

What is a wasting dune?

A

Almost 100% vegetation, after the water table making a slack, better conditions, high biodiversity, lower in height due to distance from beach.

43
Q

What is hard engineering?

A

Hard engineering interferes with nature, providing a physical barrier against the force of the waves.

44
Q

What is a sea wall?

A

They provide a barrier between the sea and the land, placed at the back of the beach. As the energy of the wave reflect it reduces the next waves power due to the curved wall. However it is expensive.

45
Q

What is a groyne?

A

Wooden/stone structures built at right angles, they trap sediment from longshore drift, even more effective with beach nourishment however they are unattractive and will cause terminal groyne syndrome.

46
Q

What is rock armour?

A

Mae up of lots of large boulders, they deflect the waves as they are sloped however they are expensive, imported and can be moved by storms.

47
Q

What are gabions?

A

Steel wire-mesh cages filled with smaller rocks, they reduce the risk of landslides and are not attractive and are expensive.

48
Q

What is soft engineering?

A

Using natural materials and unlike hard engineering, works with natural processes. Less expensive but less effective.

49
Q

What is beach nourishment?

A

The adding of sand to a beach so fewer waves reach the back of the beach. Could also do beach recycling which is renewing sad from down drift area and releasing it into updrift.

50
Q

What is beach reprofiling?

A

Winter storms renewing material so you get diggers to shove the sand from near the sea and put it by the back. It looks shoddy.

51
Q

What is dune regenaration?

A

The artificial creation of sand dunes or restoration of existing dunes. Fences can be used to trap the sand and marram grass can be planted to stabilise it or create a barrier.

52
Q

Why was management needed at Lyme Regis?

A

To stop the coast eroding as the town is built on unstable cliffs that are eroding due to powerful waves. Sea waves have been breached at many times as well.

53
Q

What was phase 1 of the Lyme Regis regenaration?

A

It was in 1990, and a new sea wall and promenade was established east of the river Lyme. In 2003/4 £1.4 million emergency money was given to stabilise the cliffs.

54
Q

What was phase 2 of the Lyme Regis regeneration?

A

It was in 2005 to 2007, and it was improvements to the sea front costing £22 million. Construction of sea walls and promenades. There was also a creation of a sand and shingle beach to absorb wave energy along an extension of rock armour at the Cobb to absorb wave energy.

55
Q

What was phase 3 of the Lyme Regis regeneration?

A

It wasn’t undertaken, but there was an initial plan to prevent landslips and erosion to the west of the Cobb, but in the end the costs outweighed the benefits.

56
Q

What was phase 4 of the Lyme Regis regeneration?

A

It was in 2013-15 and focused on the coast, east of the town. £20 million was spent on 390m of new sea wall and extensive nailing, piping and drainage to protect 480 homes.

57
Q

What were the benefits of the Lyme Regis scheme?

A

It increased visitor numbers and seafront businesses are thriving, it brings in around 15000 visitors in the summer, new defences are effective and the new harbour is better protected.

58
Q

What are the drawbacks of the Lyme Regis scheme?

A

Visitors could lead to conflicts with locals, new defences could ruin the scenery, it could interfere with natural processes and it prevents landslides that could reveal important fossils.