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Coasts & Population & Skills > Coasts > Flashcards

Coasts Flashcards

0
Q

What are the inputs of a coastal system?

A
  • River sediment
  • Sediment from cliff erosion or mass movement
  • Transported by waves from offshore
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1
Q

What is the definition of a Coast?

A

A narrow strip of land where the land meets the sea

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2
Q

What outputs are there in a coastal system?

A

Sediment washed out to sea or deposited further along the sea, usually by longshore drift

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3
Q

What are sediment/littoral cells

A

Lengths of coastline that are pretty much entirely self contained for the movement of sediment

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4
Q

How do sediment cells work?

A

Each one is its own coastal system. Processes going on in one cell don’t affect the movement of sediment in another

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5
Q

How do waves form?

A

When wind blows over the surface of the sea, friction between the wind and the surface gives the water a circular motion

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6
Q

What is the fetch?

A

The maximum distance of sea the wind has blown over when creating the waves. The longer the fetch the more erosion occurs

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7
Q

How are waves with high wave heights created?

A

When there is a high wind speed and long fetch

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8
Q

Why do waves break as they approach the shore?

A

Friction with the sea bed slows the bottom of the waves down. The motion of the water goes from circular to elliptical. The crest rises and then collapses

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9
Q

What are the two types of wave?

A

Constructive and destructive

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10
Q

What are the characteristics of a constructive wave?

A
  • Low frequency (6-8 per minute)
  • Produces a gentle beach gradient
  • Powerful swash weak backwash
  • High deposition
  • Large wavelength
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11
Q

What are the characteristics of destructive waves?

A 
High frequency (10-14 per minute)
Strong backwash weak swash 
Steeper beach profile
High erosion
Short wavelength
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12
Q

What are tides?

A

The periodic rise and fall of the ocean surface

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13
Q

Why do tides change?

A

The gravitational pull of the moon and the sun cause the changes.

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14
Q

What are sub-aerial processes?

A

Coastal processes that are not linked to the action of the sea

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15
Q

What is freeze thaw weathering?

A

Water enters cracks in the rock. If temperatures fall below 0 degrees Celsius the water freezes, cracking it as it expands.

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16
Q

How does wetting and drying of certain rocks cause weathering?

A

Rocks like clay expand when wet, exerting pressure which can break up fragments of rock

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17
Q

What is thermal expansion?

A

When the repeated action of heating and cooling of rock causes them to fracture and shed layers

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18
Q

What is biological weathering?

A

When plant seeds get into cracks and begin to grow. This exerts pressure on the rock, causing them to fracture

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19
Q

What is chemical weathering?

A
  • Hydrolysis is the splitting of materials due to their reactivity with water. •Oxidation is when rocks rust.
  • Corrosion technically is a form of weathering
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20
Q

What is mass movement?

A

Large scale movement of material down slope in response to gravity

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21
Q

Where do rockfalls most commonly occur?

A

Cliffs where there are lots of joints. The joints make it easier for the rock to break up

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22
Q

What is the slowest form of mass movement?

A

Soil creep - when soil is dampened its mass slightly increases, causing it to move downhill

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23
Q

Why does slumping and landslides occur?

A

Water increases the mass of the soil and acts as a lubricant, so material slides down the cliff

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24
Q

What are the four main forms of erosion?

A
  • Abrasion
  • Hydraulic Action
  • Corrosion
  • Attrition
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25
Q

What is abrasion?

A

Waves carrying sand and shingle break on the cliff, the sediment acts like sandpaper, breaking bits off and smoothing surfaces

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26
Q

What is hydraulic action?

A

Waves force air into cracks under high pressure. The cracks grow as this is repeated and rock breaks off it

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27
Q

What is corrosion?

A

Soluble rocks get dissolved by the water

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28
Q

What is attrition?

A

Beach material is knocked together, reducing their size and making them round and smooth

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29
Q

How does the width of a beach affect the rate of erosion?

A

Beaches slow down waves due to the friction between the two, reducing their erosive power. A wide flat beach protects cliffs

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30
Q

What happens if a wave breaks at the base of a cliff?

A

Most of the energy of the waves is transferred to the cliffs, causing the most erosion. Waves that break further offshore erode much less

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31
Q

How is material moved along a Coast?

A

Longshore drift

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32
Q

How does longshore drift work?

A

Swash carries sediment up the beach in the direction of the prevailing wind. The backwash carries sediment back down the beach at right angles. When the prevailing wind is at an angle to the backwash, sediment is moved along the beach.

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33
Q

How do wave cut platforms form?

A
  1. Erosion at the high water mark forms notches in the cliff.
  2. These continue to be eroded, forming caves.
  3. The rock above becomes unstable and collapses
  4. This continues to happen and the cliff retreats, leaving a wave cut platform
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34
Q

What is the name of a coastline where the rock type is perpendicular to the coastline?

A

Discordant coastline

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35
Q

How do headlands and bays form?

A

When there are bands of soft and hard rock on a discordant coastline. The soft rock is easily eroded, forming bays. The more resistant rock takes longer to erode, forming headlands

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36
Q

What happens when faults are eroded on a headland?

A
  1. They increase in size, forming caves
  2. Caves on both sides of a headland may join up, forming an arch
  3. Arches can collapse forming stacks
  4. As the base of a stack is eroded it can collapse forming a stump
37
Q

Why are shingle beaches steep and narrow?

A

Waves easily flow through the coarse shingle. This decreases the backwash erosion so sediment remains on the beach

38
Q

Why are sand beaches wide and flat?

A

Small particles are evenly distributed, making it harder for water to percolate into the sand. This increases backwash erosion and the amount of sediment removed from the beach

39
Q

What are berms and how do they form?

A

They are ridges of sand and pebbles. They’re formed by deposition of coarse material at the limit of the swash

40
Q

What are runnels?

A

Grooves in the sand running parallel to the shore. They’re formed by backwash draining into the sea

41
Q

What are cusps?

A

Crescent shaped depressions in the sand

42
Q

How do spits form?

A
  1. Longshore drift continues to deposit material across the river mouth, leaving a bank of sand and shingle in the sea
  2. If the dominant wind changes the spit may begin to curve, several of these curves may develop over time
  3. The area behind is sheltered from waves, so mudflats and salt marshes develop
43
Q

What are bars?

A

When a spit joins two headlands together, across a bay or river mouth

44
Q

What is the area behind a bar in a bay called?

A

A lagoon

45
Q

How are sand dunes formed?

A

When sand deposited by longshore drift is moved up the beach by wind

46
Q

How does the sand remain stable in a sand dune?

A

They are colonised by plants and grasses like marram grass. It holds the sand together, allowing more sand to accumulate here

47
Q

How do mudflats develop?

A

Silt and mud are deposited by the river or the tide

48
Q

How do mudflats become salt marshes?

A

The mudflats are colonised by vegetation that can survive high salt levels and be submerged in water for long periods of time. Over time more mud and silt builds up creating marshes

49
Q

By how many mm are sea levels rising?

A

2mm

50
Q

What are the two types of sea level change?

A

Eustatic and Isostatic

51
Q

What is Eustatic sea level change?

A

Sea level change when there is a change in volume of water in the sea or a change in shape of the sea bed. This usually happens on a global scale

52
Q

How do tectonics affect Eustatic sea level change?

A

Tectonic movements alter the shape of the ocean basins, a decrease in volume would cause sea level rise

53
Q

What happens to sea levels when the temperature of the climate increases?

A

Ice sheets melt, which increases sea level. Water expands when it’s heated which increases sea levels

54
Q

What happens if the temperature of the climate decreases?

A

Increases the volume of water in glaciers, reducing volume of water in the sea, which decreases sea level

55
Q

What is Isostatic sea level change?

A

Vertical movements of the land relative to the sea.
•Downward movement of land causes sea level rise
•Upward movement of land causes sea levels to fall

56
Q

How does land compress?

A
  • Accumulation of ice sheets causes the land beneath to fall, rising sea levels
  • Sediment at a river mouth
57
Q

How does land up lift?

A

When ice melts the pressure on the land is released, so land is allowed to rise

58
Q

What are rias?

A

River valleys that are submerged by a rise in sea level. The lower course and its floodplain are drowned, leaving the higher ground above

59
Q

What is a fjord?

A

They are submerged glaciated valleys with steep cliff-like valley sides.

60
Q

How do fjords form?

A

Glaciers eroded below sea level, creating the valleys. The glaciers melted and the valleys flooded

61
Q

How do Dalmatian coastlines form?

A

Valleys that run parallel to the coastline are submerged when sea level rises. This leaves islands that were previously areas of high land

62
Q

What are landforms of emergence?

A

When sea levels fall, revealing features previously submerged by water

63
Q

How do raised beaches form?

A

Former wave cut platforms and their beaches are revealed when the sea level falls

64
Q

What are relict cliffs?

A

Cliffs that appear raised by sea level fall slowly get covered by vegetation. They often feature wave cut notches, caves, arches and stacks

65
Q

What is the aim of coastal management?

A

To protect homes, business and the environment from erosion and flooding

66
Q

What is the cost benefit analysis?

A

Choosing where to place defences by evaluating their benefit

67
Q

What is holing the line?

A

Maintaining the existing coastal defences

68
Q

What is advancing the line?

A

Building new defences further out to sea than the existing line of defence

69
Q

What is doing nothing?

A

Build no coastal defences and allow nature to do what it wishes

70
Q

What is retreating the line?

A

Build no defences but move people away from the coast

71
Q

What are hard engineering methods?

A

Defences that involve the engineering and construction of structures

72
Q

How do sea walls work?

A

The wall reflects waves back out to sea preventing erosion, it acts as a barrier to prevent flooding also

73
Q

What are the disadvantages of sea walls?

A

They are expensive, creates strong backwash which erodes under the wall

74
Q

How do revetments work?

A

Revetments are slanted structures built at the foot of cliffs. When waves break against them their energy is absorbed by the revetments rather than the cliff

75
Q

How do Gabion boxes and riprap work?

A

They absorb energy at the foot of a cliff, preventing erosion

76
Q

What are groynes and how do they work?

A

They are fences built perpendicular to the coastline. They trap material transported by longshore drift, creating wider beaches - which Absorb the energy of waves

77
Q

What are offshore breakwaters?

A

Concrete blocks or boulders built out to sea which cause waves to break before they reach the coastline

78
Q

What are tidal barriers?

A

They are built across river estuaries, they contain retractable floodgates that can be raised to prevent flooding from storm surges

79
Q

How does coastal management affect areas further downdrift?

A

They protect the area where they are built but can make it worse further downdrift. Groynes trap sediment, reducing sediment in other areas, leaving them susceptible to erosion

80
Q

What is a main problem with hard engineering options?

A

They are often ugly and spoil the landscape

82
Q

What are soft engineering defences?

A

Working with natural process to protect the coast

83
Q

What is beach stabilisation?

A

Reducing the slope of a beach’s and planting vegetation and old tree trunks to stabilise the sand and maintain wide beaches

84
Q

What is dune regeneration?

A

When sand dunes are created or restored to maintain the barrier between land and sea

85
Q

What is land use management?

A

Managing environments to protect certain parts, eg wooden walkways to protect sand dunes

86
Q

How can the creation of marshland reduce erosion?

A

By planting appropriate vegetation a marsh can be created which reduces the speed of waves and absorbs the erosive energy

87
Q

What is coastal realignment (managed realignment)?

A

Breaching a sea wall and allowing the sea to flood the land behind. Over time vegetation will colonise the land behind and become marshland

88
Q

Why are soft engineering methods more sustainable?

A

They have a lower environmental impact and a lower cost

89
Q

Why must management strategies think about the future?

A
  • Rising sea levels make storms more frequent and severe

* Improve sustainability

90
Q

What is the integrated coastal zone management?

A

The process of trying to come up with an integrated, sustainable management plan.

91
Q

What is beach nourishment?

A

Where sand and shingle are added to beaches from elsewhere, creating wise beaches which reduce erosion

Coasts & Population & Skills (5 decks)

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