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geography a-level coasts > COASTS THEORY > Flashcards

COASTS THEORY Flashcards

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1
Q

What is freeze-thaw? (Mechanical weathering)

A

Water enters crack in rocks, water freezes overnight + expands by approx. 10% in volume. Increase in pressure causing more cracks to develop. Process is repeated and cracks grow, wakening cliff.

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2
Q

What is salt crystallisation? (Mechanical weathering)

A

Seawater evaporates, salt left behind. Salt crystals grow over time, exerting pressure on rock, forcing cracks to widen.

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3
Q

What is carbonation? (Chemical weathering)

A

Rainwater absorbs CO2 from air to create weak carbonic acid. Reacts with calcium carbonate in rocks to form calcium bicarbonate which can then be easily dissolved. Acid rain reacts with limestone to form calcium bicarbonate which is then easily dissolved allowing erosion.

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4
Q

What is oxidation? (Chemical weathering)

A

Minerals exposed to air through cracks + fissures, mineral becomes oxidised increasing its volume, causing rock to crumble

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5
Q

What is solution? (Chemical weathering)

A

Rock minerals such as rock salt are dissolved

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6
Q

What is mass movement?

A

Movement of material down a slope under influence of gravity

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7
Q

What are the different types of mass movement?

A

creeps, flows, slides and falls

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8
Q

What is soil creep (mass movement)?

A

Slowest but most continuous form of mass movement involving movement of soil particles downhill. Particles rise + fall due to wetting + freezing, causing soil to move down slope. Leads to formation of shallow terracettes.

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9
Q

What is solifluction (mass movement)?

A

Occurs mainly in periglacial environments where land is frozen. Top layers thaw during summer (but lower layers stay frozen due to permafrost) surface layers flow over frozen layer.

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10
Q

What are mudflows (mass movement)?

A

Increase in water content of soil = reduction in friction, leading to earth and mud to flow over underlying bedrock. Water can get trapped w/in rock increasing pore water pressure, forcing rock particles apart + weakening slope.

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11
Q

What is rock fall (mass movement)?

A

Occurs on sloped cliffs when exposed to mechanical weathering. Leads to scree (rock fragments) building up at base of slope.

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12
Q

What are landslides (mass movement)?

A

Heavy rainfall leads to water between joints + bedding planes which can reduce friction and lead to landslide. Occurs when block of intact rock moves down cliff face v quickly along flat slope.

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13
Q

What are slumps (mass movement)?

A

Slope is curved, thus occur in weak + unconsolidated clay + sand areas. Build up in pore water pressure leads to land to collapse under own weight. Can create scarred/terraced appearance to cliff face.

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14
Q

What is runoff (mass movement)?

A

when heavy rain washes material from the surface of a cliff over the edge and down onto the shore.

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15
Q

What causes waves?

A

Wind blows over the surface of the sea. As wind drags over water surface, friction causes disturbance and waves form

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16
Q

What movement do waves follow?

A

Waves follow an orbital movement

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17
Q

What controls wave energy?

A

force of wind + its direction, duration of wind, fetch - the longer the fetch, the more energy wave has

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18
Q

what are the three types of breaking wave?

A

spilling - waves break on to gently sloping beaches, water flows gently forward as waves breaks
plunging - steep waves breaking on to steep beaches ; water falls vertically downwards
surging - low-angle waves breaking on to steep beaches; wave slides forward

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19
Q

constructive waves features:

A
  • build beaches
  • are product of distant weather systems
  • have longer wavelengths , lower height + are less frequent
  • swash is bigger than backwash so add to beach materials
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20
Q

destructive waves features:

A
  • have shorter wavelength, greater height + are more frequent
  • backwash is greater than swash so sediment dragged offshore
  • create steeper beach profile, though over time will flatten beach as material is drawn backwards
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21
Q

How are tides created?

A

tides are produced by gravitational pull of moon + sun - as moon orbits Earth, high tides follow it

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22
Q

When do the highest tides occur?

A

when the moon + sun are aligned, when gravitational pull is at its strongest

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23
Q

What is tidal range?

A

Difference between water level at high tide + low tide

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24
Q

When are tidal ranges low?

A

Are low in enclosed seas - wave action is restricted to narrow area of land

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25
Q

When are tidal ranges high?

A

Are higher in places where coast is funnelled, eg estuaries

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26
Q

What is lithology?

A

Physical + chemical composition of rocks

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27
Q

Is carboniferous limestone permeable or impermeable?

A

Carboniferous limestone is permeable bc of many joints

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28
Q

What makes a rock have a strong lithology?

A

Rocks (eg basalt, granite) made of dense interlocking crystals + are v resistant to erosion

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29
Q

What are the various sediment sources?

A

Rivers, sea bed, erosion of coastline, transported material, human activity (beach nourishment)

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30
Q

What is scree?

A

Collections of loose rock at base of slope

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31
Q

What is regolith?

A

Collective name for all of material produced by weathering

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32
Q

What is abrasion (corrasion)?

A

material carried by waves used as ammunition to wear away rocks on cliff or wave-cut platform - material is thrown or rubbed against it repeatedly

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33
Q

What is suspension?

A

Form of transporation - process by which very small particles held in water

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34
Q

What is traction?

A

Form of transportation - large stones + pebbles rolled along sea bed + across beach

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35
Q

What is fluvial erosion?

A

material eroded + transported in coastal areas by runoff

36
Q

What kind of environments does deposition occur in?

A

deposition occurs in low-energy environments

37
Q

What is flocculation?

A

Particles carried by a river join together on contact with the salt in sea water, increasing particles’ weight, causing them to be more readily deposited.

38
Q

How do sand dunes form on beaches?

A

Sand is deposited on beach + dries out, can be blown further inland by aeolian erosion to form sand dunes at back of beach

39
Q

How are extensive areas of mudflats created as a result of deposition?

A

In river estuary, mud + silt can build up in sheltered water to create salt marsh; fresh water of river meets salt water of sea, causing flocculation of suspended material to occur, creating extensive areas of mudflats

40
Q

What is wave refraction?

A

Wave refraction = erosion concentrated on headlands causes erosion, whereas in bays waves spread over a wider area + their energy is dissipated causing more deposition

41
Q

What is pleistocene?

A

Pleistocene is a geological time period stretching from 2 million years before present (BP) to 10,000 years BP

42
Q

How much lower were temperatures in the early Pleistocene?

A

during early Pleistocene (100,000 years ago), temps were 7 degrees C lower than today

43
Q

Why were sea levels different in the Pleistocene period?

A

much water locked into ice caps + glaciers, + sea levels fell to approx. 85m lower than at present

44
Q

What are the emergent coastal landform formations?

A

‘abandoned’ cliffs, raised marine terraces, raised beaches

45
Q

‘abandoned’ cliffs

A

are no longer being eroded, are isolated from sea, + have ‘fossil’ features, such as former caves + stacks

46
Q

raised marine terraces

A

some are ‘stepped’, each step representing standstill in sea level fall

47
Q

raised beaches

A

common on coast of western Scotland, series of raised sandy + pebble areas exist well above sea level

48
Q

If not by wave processes, what are emergent landforms affected by?

A

emergent landforms are no longer affected by wave processes - but are modified by weathering and mass movement

49
Q

As global temperatures rise due to climate change, sea levels rise and thus emergent landforms…

A

are likely to be re-submerged

50
Q

What happened in the period known as the Flandrian Transgression and why?

A
  • towards the end of Pleistocene period, sea level began to rise to present - total rise of 90m
  • this was bc of increase in global temps, hence more melting of ice caps and glaciers
51
Q

How to rising sea levels affect rias and fjords?

A

water depth in rias and fjords will increase, leading to more erosion

52
Q

How do rising sea levels affect shingle beaches?

A

shingle beaches will be more affected by storm events

53
Q

What are the characteristics of rias (submerged river valleys)?

A
  • submerged, winding river valleys w long fingers of water stretching inland, including their tributary valleys
  • widest + deepest nearer sea, becoming progressively narrower + shallower inland
  • tidal changes reveal extensive areas of mudflats
54
Q

What are the characteristics of fjords (submerged glacial valleys)?

A
  • submerged, straight, glaciated valleys, w right-angled tributary valleys
  • have shallower area at mouth where glacial ice thinned as reached sea + hence lost erosional power have typical steep-sided + deep (over 1000m) cross-profile associated w glacial troughs
  • can stretch many km inland
55
Q

What are characteristics of shingle beaches?

A
  • are features of both fall and rise of past sea levels
  • when sea level fell, sediment from land was deposited by rivers on newly exposed land
  • sea levels rose again, sediment pushed landward, forming large shingle beaches eg. Chesil Beach, Dorset
56
Q

Inputs can include…

A

kinetic energy from winds + waves, thermal energy from heat of Sun + potential energy from position of material on slopes as well as material from marine deposition, weathering + mass movement

57
Q

outputs can include…

A

marine + wind erosion from beaches + rock surfaces + evaporation

58
Q

throughputs (stores + processes) consist of…

A

stores, including beach + nearshore sediment accumulations + flows such as movement of sediment along a beach by longshore drift

59
Q

equilibrium

A

a steady state where inputs = outputs

60
Q

dynamic equilibrium and what kind of feedback is this?

A

when equilibrium is disturbed + the system adjusts to the change + restores the equilibrium. this is an example of negative feedback.

61
Q

topography

A

arrangement of the natural + artificial physical features of an area

62
Q

what physical factors affect coastlines?

A

Who Would Teach Geography Correctly?

Wind, waves, tides geology, currents

63
Q

swell waves

A

formed in open oceans eg the Atlantic - have long wavelength, low height + wave period of up to 20 seconds - can travel 1000km a day

64
Q

storm waves

A

locally generated - typically have short wavelength, greater height + shorter wave period

65
Q

what happens after a wave has broken?

A

water moves up the beach as swash, driven by the transfer of energy when the wave breaks. the speed of the water movement gradually slows down due to increasing frictional drag + the uphill gradient of the beach

66
Q

relationship between high energy waves + beach gradient

A

high energy waves, often occurring during winter months, tend to remove material from the top of the beach + transport it to the offshore zone, reducing beach gradient

67
Q

relationship between low energy waves + beach gradient

A

low energy waves, often occurring in summer months, build up the beach face, steeping the profile.

68
Q

wave scouring

A

waves breaking at the base of cliffs swirl around the base + result in the removal of loose rock

69
Q

How does the Gulf Stream (main ocean current) affect the UK and what is it?

A

The Gulf Stream is a warm ocean current in the North Atlantic flowing from the Gulf of Mexico, northeast along the US coast, from there to the British Isles. The Gulf of Mexico has higher air temperatures than Britain as it is closer to the equator. This keeps Britain warmer than its latitude suggests it should be

70
Q

What does Vant Hoff’s Law state and how does this relate to weathering and climate change?

A

Vant Hoff’s Law states that a 10 dgrs C increase leads to a 2.5x increase in rate of chemical reaction. With temperatures rising due to climate change, chemical weathering will thus become more erosive according to Vant Hoff’s Law

71
Q

Hydrolysis (Chemical Weathering)

A

Chemical reaction between rock minerals (silicates) and water

72
Q

hydration (chemical weathering)

A

water molecules added to rock minerals create new minerals. this causes surface flaking in many rocks, partly bc minerals expand as they take on water

73
Q

organic acids (biological weathering)

A

organic acids produced during decomposition of plant + animal waste cause soil water to become more acidic. this causes a reaction w some minerals in a process called chelation

74
Q

deflation

A

erosion by wind of loose material from flat areas of dry, un cemented sediments

75
Q

what are eustatic changes?

A

changes in volume of water in global ocean store due to variations in global changes

76
Q

What is the UK av. temperature today?

A

14 dgrs C

77
Q

How long ago was the Tyrrhenian Inter-Glacial Period and temp + sea level

A

130,000 years ago - 3 dgrs C higher than today, sea level 20m higher than today

78
Q

How long ago was the Riss Glacial Period + temp + sea level

A

108,000 years ago - 7 dgrs C lower than today, sea level 83m lower than today (in storage ice)

79
Q

marine regression

A

when there is a fall in relative sea level + land once covered by the sea is revealed; coastline is said to ‘advance’

80
Q

what are submergent landforms?

A

landforms formed as sea level falls due to a warming climate

81
Q

Ria example

A

Solva Harbour, Pembrokeshire, Wales
- Solva Ria was eroded between 2-4 mil. years ago. At end of ice-age, meltwater from glaciers cut deep into the rocks forming a U-shaped valley. Valley was later flooded as sea-levels rose, forming the ria

82
Q

Fjord example

A

Sognefjord, Norway

- Sognefjord is largest + deepest fjord in Norway. Fjord itself is 200km long + has max. depth of 1.3km

83
Q

Shingle beach example

A

Chesil Beach, Dorset

- Beach contains around 100 million tonnes of shingle

84
Q

marine transgression

A

when there is a rise in relative sea level + sea flows over the land to cover it; the coastline is said to ‘retreat’

85
Q

what are the Milankovitch cycles

A

Over the past 2 million years, climate has oscillated (swung) between periods of warm climate (glacials) and periods of cooler climate (interglacials). Changes in the shape of earth’s orbit help explain these changes. These are known as ‘Milankovitch cycles’.

geography a-level coasts (7 decks)

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