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Coasts Flashcards

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1
Q

What is a system

A

A set of interrelated objects compromising of components (stores) and processes (links)

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2
Q

What are the main types of energy in coastal landscapes

A

Kinetic
Potential
Thermal

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3
Q

What are the components of an open system

A

Energy and matter can be transferred from neighbouring system as an input
Energy and matter can be transferred to neighbouring systems as an output

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4
Q

What are the inputs

A

Kinetic energy from wind and waves
Thermal energy from the heat of the sun
Potential energy from the position of material on slopes
Material from marine deposition, weathering, mass movement

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5
Q

What are the outputs

A

Marine and wind erosion from the beach and rock surfaces

Evaporation

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6
Q

What is a throughput

A

It consists of stores (beach, nearshore sediment) and flows (movement of sediment along a beach-LSD)

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7
Q

What is a sediment cell

A

Stretch of coastline and its associated nearshore area

Regard as a closed system but in reality it is unlikely that

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8
Q

How many sediment cells are in the UK and what are they defined by

A

11

Topography and shape of the coastline

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9
Q

What are the physical factors of a landscape

A 
Wind
Waves
Tides
Geology
Currents
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10
Q

How do winds influence landscape

A

Winds drive Waves
Waves drive erosion and sediment transfer
The higher the wind speed and the longer the fetch, the larger the waves and more energy they possess

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11
Q

How do waves work

A

Potential energy above the wave crest

Kinetic energy is the motion of the water within the wave

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12
Q

Amount of energy in a wave formula

A

P=H2T
P = power is kilowatts per metre of wave front
H = wave height in metres
T = time interval between wave crests in second (wave period)
the relationship between wave height and wave energy is non-linear

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13
Q

Compare swell waves and storm waves

A

Swell waves-Long wavelength, wave period of up to 20 seconds

Storm waves-Short wavelength, greater height, shorter wave period

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14
Q

How do waves break

A

When waves moves in to shallow water (half its wavelength) there is friction between water and seafloor
wave slows down
wavelength decreases
wave steepens

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15
Q

What is swash

A

Movement of water up the beach in the same direction as waves travelling up the beach

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16
Q

What is backwash

A

Movement of water back down the beach by gravity perpendicular to the coastline down the steepest gradient

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17
Q

What are constructive waves

A

Low height, long wavelength, low frequency
Spiling waves
Strong swash
Swash is greater than backwash

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18
Q

Destructive waves

A

Greater height, shorter wavelength and higher frequency
Plunging waves
Swash of the next wave is slowed due to returning backwash
Swash is less than backwash

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19
Q

Beach gradient and wave type

A

High-energy waves (often winter months)tend to remove sediment reducing the gradient
Low-energy waves (often summer month) tend to build up the beach face, steepening the profile
Waves steepness is an important factor in this relationship

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20
Q

How are tides formed

A

Formed by the gravitational pull of the moon

Spring tides and neap tides occur twice a lunar month

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21
Q

Geology - Lithology

A

Clays - weak lithology
Basalt - resistant to erosion
Chalk - vulnerable to carbonation

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22
Q

What does jointing, bedding and faulting all affect

A

Permeability and porosity

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23
Q

Why is the angle of dip important for cliffs

A

Landward - dipping strata support cliffs within steep vertical profiles
Seaward - dipping strata support cliffs with profiles which follow the bedding plane

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24
Q

What are rip-currents

A

Caused by tidal motion or by waves breaking at right angle to the shore
Creates cusps - channelling the rip current through a narrow neck

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25
Q

What are terrestrial forms of sediment

A

Rivers are a major source of sediment inout to the coastal sediment budget

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26
Q

What is the origin of terrestrial sediment

A

Erosion carried out by
water
ice
wind

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27
Q

Origin of terrestrial sediments - weathering

A

Decay and disintegration of rock in situ
Mechanical weathering- freeze-thaw, salt crystallisation, wetting and drying
Biological - root action
Chemical weathering - carbonation

28
Q

Origin of terrestrial sediments - Mass movement

A 
Soil creep
Earth flow
Landslides
mudflows
Slumps
Rockfalls
Run-off
29
Q

Sediment form offshore

A

Constructive waves, tides and currents bring sediment to the shore from offshore
Wind can blow sand from other locations

30
Q

Sediment from humans

A

When a coastal budget is in deficit, beach nourishment is one way a sediment equilibrium can be maintained

31
Q

Erosion

A

Abrasion - when waves armed with rock particles scour the coastline
Attrition - when rock particles collide with each other during transportation
Hydraulic action - when waves brake against a cliff face, air and water are forced into crevices. when the wave recedes the pressure is released leading to expansion of the air
Pounding - the mass of the braking wave exerts pressure on the rock causing it to weaken
Solution - dissolving minerals like magnesium carbonate minerals in coastal rock

32
Q

Transportation

A

Solution - minerals which have been dissolved into the mass of moving water
Suspension - small particles of sand, silt and clay can be carried by currents
Saltation - series of irregular movements of material which is too heavy to be carried continuously by suspension
Traction - the largest particles are pushed along the sea floor

33
Q

Deposition in coastal systems

A

Where the rate of sediment accumulation exceeds the rate of removal
When waves slow down immediately after braking
At the top of swash
During the backwash where water percolates in to the beach material
in low-energy environment

34
Q

Cliffs and shore platforms

A

When destructive waves break repeatedly on relative steeply sloping coastlines
Undercutting occurs between HWM and LWM
Forming a wave cut notch
Continued undercutting weakens support of the rock strata above
This eventually collapses
Producing a step profile and a cliff
Cliff retreated parallel to the coast

35
Q

Shore platforms

A

Often deeply directed by abrasion our to the large amount of rock debris that is dragged across the surface
Reach a maximum length of 500M

36
Q

What is a Disconcordant coastline

A

Form due to the bands of rock with differing resistance to erosion
These bands of rocks will be perpendicular to the coastline
The width of the bay is determined by the width of the weaker rock

37
Q

What is a concordant coastline

A

Rocks are lying parallel to the coastline

38
Q

What is wave refraction

A

The waves is slowed down by the shallow water of the headland
The waves in the bay speed up as they are not slowed down
Waves refract around the headland

39
Q

What is a geo and blowhole

A

Geo are narrow steep-sided inlets, weak points are eroded more rapidly by hydraulic action, they form a tunnel like cave running at right angles to the cliff line
Blowhole is when part of the roof of a tunnel like cave collapses and forms a vertical shaft that reaches the cliff top

40
Q

Caves, arches, stacks and stumps

A

Cracks at the base of a headland become exposed through hydraulic action, the crack widens, other processes such as salt crystallisation widen it eventually becoming a wave cut notch, more weathering becomes a cave, as a result of wave refraction the waves concentrate their energy on the sides, a hole all the way through is eventually made forming an arch, over time this becomes unstable and collapses under its own weight and forms a stack, eventually due to further weathering the stack collapses forming an arch

41
Q

What is a sand beach

A 
Less than 5 degrees
Small particles means it becomes compact when wet
Little percolation during backwash
Little energy lost to friction
material is carried back down the beach
Forming ridges and runnels
42
Q

What is a shingle beach

A

Mix of pebbles and small to medium cobbles

Steeper beaches due to swash greater than backwash

43
Q

What is a storm beach

A

At the back of the beach, Very strong swash during storm conditions may deposit larger material, forming a storm beach or a ridge

44
Q

what is a berm

A

Small ridges that develop at the position of the mean high tide mark resulting from deposition at the top of the swash

45
Q

What is a beach cusp

A

Cusps are semi-circular depressions, they are smaller and more temporary features by a collection of waves reaching the same point

46
Q

Seasonal changes to the beach profile

A

High - energy destructive waves remove sediment offshore and create flatter beaches (summer)
winter is the opposite

47
Q

What is a spit

A

Long narrow beaches of sand or shingle that are attached to the land at one end and extend across a bay, estuary or indentation on a coastline
Form as a result of LSD
The end of the spit becomes recurved
Behind the spit deposition will occur as wave energy is reduced
Silt and mud are deposited
Eventually salt tolerant plants colonise
Slat marsh develops

48
Q

What is an onshore bar

A

Develop when a spit develops across and indentation until it joins into the land at the other end forming a brackish lagoon on the landward side

49
Q

What is a tombolo

A

Beaches which connect the mainland to an offshore bar

Spit continued the grow seaward to join the mainland to an island

50
Q

Salt marsh

A

Feature of low - energy environments, vegetated areas of silt and clay
Vegetation helps stabilise the sediment
The higher the marsh becomes the les saline it is
Flocculation is an important process
Shallow gradient

51
Q

Delta

A

large areas of sediment found at the mouth of rivers
deposited by rivers and tidal action
branching network of distributaries
Overloaded with sediment, deposition in the channel occurs, this splits the channel and reduces the energy allowing further deposition, these channels are lined with levees

52
Q

Cuspate delta

A

Appointed extension of coastline

53
Q

Arcuate delta

A

Sufficient sediment supply is available for the delta to grow seawards

54
Q

birds foot delta

A

Distributaries build out from the coast in a branching pattern
River sediment supply exceeding the rates of removal by waves and currents

55
Q

What is eustatic change

A

Changes in volume of water in the global ocean stores

56
Q

What is isostatic changes

A

Local

relative sea level changes

57
Q

Isostatic changes in britain

A

Changes in the land
Scotland is rebounding
SE coast is sinking

Relative changes to the sea level
Scotland - sea level fall
SE coast - sea level is rising

58
Q

Physical factors that can affect changes in global temperatures

A

Milankovitch cycles
Solar output
Atmosphere composition

59
Q

Climate change and sea level

A

A decrease in global temperature leads to more precipitation falling in the form of snow
Eventually this snow turns to ice and so water is stored on land
As a result, there is a reduction in the amount of water in the ocean and a worldwide fall in sea level

60
Q

Riss glacial period

A

108000 years ago
7 degrees cooler than today
Sea level was about 83 m lower than the present day

61
Q

Wurm glacial period

A

25000 years ago
9 degrees cooler than today
sea level was 90m lowwer

62
Q

Emergent landforms

A

Landforms are shaped by wave processes during times of high sea level
These become exposed when sea level falls
These features are often found well inland, some distance from the present coastline

63
Q

Raised beaches

A

Are areas of former shore platforms that were left at a higher level than the present sea level
they are often found a distance inland rom the present coastline

64
Q

modification on landforms

A

After they emerged they are no longer affected by wave action
the continued to be altered by mass movement and weathering

65
Q

Rias

A

Submerged river valleys
The lowest part of the river course and the floodplains may be completely drowned
The sides of the valleys and the middle and upper parts of the rivers course may still be exposed

66
Q

Formation of Rias

A

Typically underlain with alluvial deposits
These were buried in channels that were eroded by rivers the flowed down to the lowest sea levels during the Pleistocene glacial periods
During the interglacial periods, when sea level rose further deposition would have occurred as the rivers has less surplus energy for erosion
The river valleys then became infilled during the Flandrain Transgression

67
Q

Fjord

A

Submerged glacial valleys

They have steep cliff - like, valley sides and he water is uniformly deep - reaching over 1000 m

Geography Coasts (5 decks)

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