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A Level Geography (OCR) > Coasts (Topic 1) > Flashcards

Coasts (Topic 1) Flashcards

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1
Q

Why can coastal landscapes be viewed as open systems?

A
  • Energy and matter can be transferred from neighbouring systems as an input + transferred to neighbouring systems as an output
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2
Q

What are the components of an open system? (4)

A
  1. Inputs
  2. Outputs
  3. Processes
  4. Stores
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3
Q

What is a state of equilibrium in a system?

A
  • When inputs and outputs are equal
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4
Q

What is dynamic equilibrium in a coastal system?

A
  • When the Eq is disturbed, system goes under self-regulation and changes its form in order to restore the Eq - system produces its own response to the disturbance
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5
Q

What type of feedback is dynamic Eq an example of?

A
  • Negative - an automatic response that restores Eq
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6
Q

What is a sediment cell?

A
  • A stretch of coastline and its associated nearshore area within which the movement of coarse sediment, sand and shingle is largely self-contained
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7
Q

How many large sediment cells are there around England and Wales?

A
  • 11
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8
Q

What are the boundaries of sediment cells determined by?

A
  • Topography and shape of coastline
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9
Q

Why are sediment cells generally regarded as a closed system?

A
  • Suggests that no sediment is transferred from one cell to another - held within the headlands (barriers)
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10
Q

Why, in reality, is it unlikely that sediment cells are completely closed? (2)

A
  1. Variations in wind direction and presence of tidal currents = inevitable that some sediment is transferred between neighbouring cells
  2. Many sub-cells of a smaller scale exist within the major cells
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11
Q

How does wind influence coastal systems?

A
  1. Winds are the source of energy for waves
  2. Wind direction can influence the impact of waves (oblique waves = LSD)
  3. Aeolian processes can erode or transport and deposit sediment
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12
Q

Describe the anatomy of a wave?

A
  1. Crest - highest surface part of the wave
  2. Trough - lowest part
  3. Wave height - vertical distance between trough and crest
  4. Wavelength - horizontal distance between 2 adjacent crests/troughs
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13
Q

What is the difference between swell and storm waves?

A

Swell waves - longer wavelength, wave period of ~20s

Storm waves - short wavelength, greater height and shorter wave period

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14
Q

Describe the process of a breaking wave?

A
  1. Wave move into shallow water
  2. Wave slow down (friction)
  3. Wavelength decreases = successive waves bunch up
  4. Deepest part of wave slows down more than the top
  5. Wave steepens - crest advances ahead of base
  6. When water depth is less than 1.3x wave height, wave topples over and breaks against shore
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15
Q

Describe a constructive wave?

A
  • Low in height, long wavelength, low frequency
  • Break by spilling forwards, strong swash travels a long way up gently sloping beaches
  • Long wavelength = backwash returns to sea before next wave breaks = next swash movement is uninterrupted and thus retains its energy
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16
Q

Describe a destructive wave?

A
  • Greater height, shorter wavelengths and a higher frequency
  • Break by plunging downwards = little forward transfer of energy to move water up the steeply sloping beach as friction slows swash, so wave does not travel far
  • Short wavelength = swash of next wave often slowed by the frictional effects of meeting the returning backwash of the previous wave
  • Swash energy is less than backwash energy
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17
Q

What produces tides?

A
  • The gravitational pull of the moon, and to a lesser extent, the sun
  • The moon pulls water towards it, creating a high tide
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18
Q

What is a spring tide AND what happens during it?

A
  • When the moon, sun and earth = aligned
    = Higher high tides and lower low tides
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19
Q

What is a neap tide AND what happens during?

A
  • Moon and sun at right angles to each other
    = Lower high tides and higher low tides
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20
Q

How does tidal range influence coastal landscapes?

A
  • In enclosed areas (Mediterranean) - tidal range are low and so wave action is restricted to a narrow area of land
  • In areas where coast is funnelled (Servern Estuary) - tidal ranges can be as high as 14m
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21
Q

What is meant by lithology?

A
  • Chemical and physical composition of rocks
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22
Q

How are coastal systems influenced by lithology?

A
  • Differences in rock lithology = varying levels of susceptibility to erosion, weathering and mass movements = formation of different coastal formations
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23
Q

What is meant by structure in regards to geology?

A
  • Structure concerns the properties of individual rock types such as jointing, bedding and faulting
  • Also includes the permeability of rocks
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24
Q

What is meant by porous rocks?

A
  • Rocks which contain pores of air spaces between mineral particles, where water is stored
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25
Q

What is meant by permeable?

A
  • A type of rock that is penetrated by water, either through mineral pores or along joints, faults and fissures
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26
Q

How does structure influence coastal landscapes?

A
  1. Important influence on the planform of coasts at regional scale e.g. rock outcrops that run parallel to coast = straight coastlines (concordant)
    - rocks that lie at right angles to the coast create discordant coastlines - more resistant rocks for headlands, weaker rocks for bays
  2. Influence on cliff profiles
    - horizontally bedded/landward dipping = steep vertical cliff profiles
    - strata/seaward dipping = profiles tend to follow the angle of bedding plane
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27
Q

How are ocean currents generated?

A
  • Generated by the Coriolis effect and convection and are set in motion by the movement of winds across the water surface
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28
Q

How do ocean currents influence coastal landscapes?

A
  • Strength of the current = limited impact in terms of geomorphic processes (driven by offshore winds = less effect on coastal landscapes) but the transfer of heat energy = significant- directly affects air temperature, therefore sub-aerial processes
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29
Q

What is terrestrial sediment?

A
  • Sediment from land
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30
Q

What are the main sources of sediment input?

A
  • Rivers - some locations, as much as 90% of coastal sediment comes from rivers
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31
Q

What is the origin of terrestrial sediment?

A
  • Erosion of inland areas by water, wind and ice as well as sub-aerial processes (weathering and mass movement)
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32
Q

What are the other sources of terrestrial sediment

A
  1. Wave erosion
  2. Cliff erosion - increased by rising sea levels and amplified by storm surge events - erosion of weak cliffs in high energy wave environments contributes as much as 70% of the overall material supplied to beaches
  3. LSD
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33
Q

What type of waves bring sediment to the shore from offshore locations and deposit it

A
  • Constructive waves
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34
Q

What also brings sediment to the shore from offshore locations?

A
  1. tides
  2. currents
  3. wind - blows sediment from other locations (exposed sand bars, dunes and beaches along the coast) - material is generally fine sand
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35
Q

What is a way in which sediment equilibrium can be maintained?

A
  • beach nourishment
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36
Q

How can beach nourishment occur?

A
  1. Sediment brought in by a lorry and dumped on the beach before spread by bulldozers
  2. Sand and water can be pumped onshore by pipeline from offshore sources
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37
Q

What is weathering?

A
  • the use of energy to produce physically or chemical altered materials from surface or near surface rocks
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38
Q

The breakdown of rock is largely achieved by which weathering process?

A
  • Physical weathering processes
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39
Q

What doesn’t take place during physical weathering?

A
  • Chemical alterations
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40
Q

How does physical weathering allow for more weathering to take place?

A
  • Increase the exposed surface area of the rock
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41
Q

Why are some physical weathering processes ineffective?

A
  • In many coastal landscapes, the presence of sea results in moderation of temperature, so air temperature may drop below 0, reducing the extent of fluccuations
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42
Q

What are the typical physical weathering processes of coastal environment?

A
  1. Freeze-thaw
  2. Pressure release
  3. Thermal expansion
  4. Salt crystalisation
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43
Q

How does freeze-thaw work?

A
  1. water enters cracks or joints
  2. expands by nearly 10% when freezes
  3. exerts pressure on rock - causing to split into pieces
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44
Q

How does pressure release work?

A
  1. overlying rocks are removed by weathering/erosion
  2. underlying rocks expand and fracture parallel to the surface
  3. significant in exposure of sub-surface rocks
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45
Q

How does thermal expansion work?

A
  1. rocks expand when heated/ contract when cooled
  2. if subject to frequent cycles of temp change, outer layers may crack and flake off
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46
Q

How does salt crystallisation work?

A
  1. Solutions of salt seep into pore spaces
  2. Salt precipitates, forming crystals
  3. The growth of these crystals creates stress in rock, causing it to disintegrate
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47
Q

What is the result of chemical weathering?

A
  • the decay of rocks
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48
Q

What do chemical processes produce?

A
  • Weak residues of different materials that may then be easily removed by erosion or transportation processes
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49
Q

What causes most chemical reactions to increase?

A
  • Increasing temperature
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50
Q

Where do higher rates of chemical weathering take place?

A
  • tropical regions
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51
Q

Why is carbonation more effective at lower temperatures?

A
  • As CO2 is more soluble in cold water rather than hot
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52
Q

What are the processes of chemical weathering?

A
  1. oxidation
  2. carbonation
  3. solution
  4. hydrolysis
  5. hydration
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53
Q

What is oxidation?

A
  • When some minerals in rocks react with oxygen, either in the air or water
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54
Q

What is carbonation?

A
  • When rainwater combines with dissolved CO2 from the atmosphere to produce a weak carbonic acid
  • This reacts with the CaCO3 in rocks to produce Calcium Bicarbonate
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55
Q

What is solution?

A
  • Any process by which a mineral dissolves in water
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56
Q

What is hydrolysis?

A
  • A chemical reaction between rock minerals and water
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57
Q

What is hydration?

A
  • When water molecules added to rock minerals create new minerals of a larger volume
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58
Q

What type of processes may biological weathering consist of?

A
  1. Physical actions (growth of plant roots)
  2. Chemical processes (Chelation by organic acids)
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59
Q

What are the processes of biological weathering?

A
  1. Tree roots
  2. Organic acids
60
Q

How does biological weathering by tree roots work?

A
  1. Tree roots grow into cracks/joints in rocks and exert outward pressure
  2. When trees topple, their roots can also exert leverage on rock and soil - this brings them to the surface and exposes them to further weathering
61
Q

What may have a similar effect to tree roots?

A
  • Burrowing animals
62
Q

How does biological weathering by organic acids work?

A
  1. Organic acids (produced during the decomposition of plant and animal litter) causes soil water to become more acidic and react with some minerals (chelation)
  2. Blue-green algae produce a shiny film of iron and manganese oxides on rocks - this breaks down metallic irons in rocks
  3. On shore platforms, molluscs may secrete acids which produce small surface hollows in the rock - rocks more susceptible to types of erosion
63
Q

When does mass movement occur?

A
  • When the forces acting on slope material (gravity) exceed the force trying to keep material on the slope (friction)
64
Q

What are the main processes in mass movement?

A
  1. Rock fall
  2. Rock slides
65
Q

How does rock fall occur?

A
  1. On cliffs of 40* or more, rocks may become detached from the slope by physical weathering processes
  2. These fall to the foot of the cliff under gravity
  3. Wave processes remove this material, or it may accumulate as. a relatively straight, lower angled screen slope
66
Q

What are the types of slides?

A
  1. Linear - movement along a straight line slip plane, such as a fault or a bedding plane between layers of rocks
  2. Rotational - movement taking place along a curved slip plane (also known as slumps)
67
Q

Why do slides occur?

A
  • Undercutting by wave erosion at the base of cliff which removes support for the materials above
68
Q

What type of rocks are slumps common in?

A
  • Weak rocks, such as clay, which also become heavier when wet, adding to the downward force
69
Q

What processes are breaking waves able to erode the coastline with?

A
  1. Abrasion
  2. Attrition
  3. Hydraulic action
  4. Pounding
  5. Solution
70
Q

What is abrasion?

A
  • When waves armed with rock particles scour the coastline - rock rubbing against rock
71
Q

What is attrition?

A
  • When rock particles transported by wave action collide with each other and with coastal rocks and progressively become worn away
72
Q

What is hydraulic action?

A
  • Waves break against a cliff face, and air and water trapped in racks and crevices becomes compressed
  • As the wave pressure is released - air and water suddenly expand and the crack is widened
73
Q

What is pounding?

A
  • When the mass of the breaking wave exerts pressure on the rock causing it to weaken
74
Q

What is solution?

A
  • Dissolving minerals like magnesium carbonate in coastal rock
75
Q

Why is solutions impact limited?

A
  • pH of sea is around 7-8, meaning process is of limited significance, unless the water is locally polluted and acidic
  • Even then, only coastal rocks containing significant amounts of soluble minerals are affected by this
76
Q

What are the processes by which waves move material?

A
  1. Traction
  2. Saltation
  3. Suspension
  4. Solution
  5. LSD
77
Q

What is traction?

A
  • Where the largest particles are pushed along the sea floor by the force of flow
78
Q

What is saltation?

A
  • The irregular movements of material that are too heavy to be carried continuously in suspension
79
Q

What is suspension?

A
  • Small particles of sand, silt and clay carried by currents - explains the brown, muddy appearance of some sea water
80
Q

What is solution?

A
  • Minerals dissolving into mass of moving water - remain in solution until evaporated and then precipitated out of solution
81
Q

What is long-shore drift?

A
  • wave approach shore at angle due to dominant wind direction- swash carries particles diagonally up beach, backwash moves them back perpendicular to coastline (influenced by gravity)
82
Q

When does deposition tend to take place in coastal landscape systems?

A
  1. where the rate of sediment accumulation exceeds the rate of removal
  2. when waves slow down immediately after breaking
  3. at the top of the swash, where for a brief moment, the water is no longer moving
  4. during the backwash, when water percolates into the beach material
  5. in low-energy environments, such as those sheltered from winds and waves (e.g. estuaries)
83
Q

What is the settling velocity?

A
  • the velocity at which sediment particles are deposited
84
Q

What is the main source of a rivers sediment load?

A
  • Erosion in the upper catchment
85
Q

How else is sediment derived into river channels?

A
  1. Weathering
  2. Mass movement
86
Q

What are the processes by which rivers carry out erosion?

A
  1. abrasion (or corrasion)
  2. attrition
  3. hydraulic action
  4. pounding
  5. solution (or corrosion)
87
Q

What processes do rivers transport sediment by?

A
  1. traction
  2. saltation
  3. suspension
  4. solution
88
Q

Why do rivers deposit their load?

A
  1. as rivers enter sea, noticeable reduction in velocity, as flowing water from channel enters the relatively static body of the sea
  2. tides & currents may be moving in opposite direction to the river flow, providing a major resistance to its forward movement
89
Q

What does the meeting of salt and fresh water lead to?

A
  • the flocculation of clay particles
90
Q

What is flocculation?

A

fine, light clay material clump together due to electrical charges between them in saline conditions- become heavier and sink to the sea bed

91
Q

What does deflation allow the wind to do?

A
  • Pick up sand particles and move them by deflation
92
Q

Why is dry sand easier for the wind to pick up?

A
  • moisture increases cohesion between particles, helping them stick together
93
Q

How is moving air able to transport minerals?

A
  1. traction
  2. saltation
  3. suspension
94
Q

What usually causes wind speed to fall?

A

surface friction- e.g. inland from vegetation and surface irregularities (much greater than on open sea)

95
Q

How do cliffs form?

A
  1. destructive waves & steeply sloping coastlines = undercutting, forms a wave-cut notch
  2. continued undercutting = weaken support for rock strata above
  3. rock strata eventually collapses, producing a steep profile and a cliff
  4. regular removal of debris at foot of cliff (wave action) ensures that the cliff profile remains relatively steep & that the cliff retreats inland parallel to the coast
96
Q

What are the different types of bedded-strata AND what cliff profiles do them support?

A
  1. landward-dipping strata- steep, near vertical profile- the slope profile is gradually lowered by weathering and mass movement
  2. seaward-dipping strata- profile follows the angle of dip- undercutting by wave action removes support; rock layers loosen and slide into sea along bedding planes
  3. horizontally-bedded strata- steep, near vertical profile; undercutting by wave action = rock fall; cliff retreats inland parallel to the coast
97
Q

How do shore platforms form?

A
  1. undercutting continues; cliff becomes higher; at base, a gently sloping shore platform is cut into the rock
  2. eventually the platform will be so wide that it produces shallow water and small waves
  3. friction from the platform slows down approaching waves = break on the platform rather than the cliff = undercutting slows and eventually ceases (width of approx. 500m before this…)
98
Q

What weathering processes are also important in forming shore platforms?

A
  1. solution
  2. freeze-thaw
  3. salt crystallisation
99
Q

How do marine organisms accelerate weathering when the platform is exposed at low tide? [3]

A
  1. at night, algae release CO2 (photosynthesis not happening)
  2. mixes with sea water = more acidic
  3. results in higher rates of chemical weathering
100
Q

Why are these features worse developed if the tidal range is more than 4m? [2]

A
  1. erosion is spread over a wider area of the platform
  2. water is at its high & low tide positions for shorter time

= platform tends to be more uniform and more steeply sloping

101
Q

What type of coastline is it if different rock outcrops lie perpendicular to the coastline?

A
  • Discordant
102
Q

Why do bays and headlands form?

A
  • weaker rocks are eroded more rapidly to form bays; more resistant rocks remain as headlands
103
Q

What determines the width of a bay?

A

the width of the band of weaker rock

104
Q

What determines the depth of a bay?

A

depend on the differential rates of erosion between the more resistant and weaker rocks

105
Q

What type of coastline is it if rock types lie parallel to the coastline?

A
  • concordant
106
Q

What happens if the more resistant rock lies on the seaward side?

A

protects any weaker rocks inland from erosion- resultant coastline is relatively straight and even

107
Q

How can small bays or coves still be eroded in a concordant, resistant coastline?

A

at points of weakness, such as fault lines

108
Q

What is an example of a concordant and discordant coastline?

A

Isle of Purbeck, Dorset

east-facing coast is discordant

south-facing coast is concordant

109
Q

What is wave refraction?

A

the change of direction of wave fronts as they enter shallow water so that they approach parallel to the shoreline

110
Q

What causes wave refraction to take place?

A

when waves approach an irregularly shaped coastline

111
Q

What happens when waves approach a coastline with bays and headlands?

A

headlands: wave energy focussed on headland, erosion concentrated there

bays: orthagonals diverge and energy is dissipated, leading to deposition

112
Q

What is a geo?

A

a narrow, steep-sided inlet

113
Q

How do geos form? [4 steps)

A
  1. waves attack the coastline
  2. lines of weakness in coastlines (i.e. joints and faults) are eroded more rapidly by wave action (i.e. hydraulic action and abrasion) weakening the rock strata
  3. a tunnel-like cave is created
  4. cave is enlarged by continuing erosion- leads to collapse of the roof of the cave
114
Q

What is an example of a geo?

A

Huntsman’s Leap, Pembrokeshire

35m deep & eroded along a large joint in the carboniferous limestone

115
Q

How do blowholes form? [5 steps]

A
  1. waves attack the coastline
  2. lines of weakness in coastlines (i.e. joints and faults) are eroded more rapidly by wave action (i.e. hydraulic action and abrasion) weakening the rock strata
  3. a tunnel-like cave is created
  4. part of the roof of the cave collapse along master joint, which may form a vertical shaft that reaches the cliff top
  5. during stormy conditions, larger waves may force spray out of blowholes as plumes of white, aerated water
116
Q

What may geos and blowholes also be associated with AND an example?

A

Mining shafts

e.g. Trevone, Cornwall (25m deep blowhole)

117
Q

How do caves, arches, stacks and stumps form? [5 steps]

A
  1. wave refraction = energy of wave focussed on side of a headland
  2. points of weakness (i.e. joints or faults) exploited (hydraulic action & abrasion) = formation of a cave in location between high and low tide (where wave attack concentrated)
  3. cave enlarges so that extends to other side of the headland/meets another cave in process = formation of arch
  4. continued erosion widens arch & weakens support (aided by weathering processes)- arch collapses, leaving an isolated stack separate from the headland
  5. further erosion at the base of the stack causes it to collapse further, leaving a flat, small portion of the original stack as a stump (may only be visible at low tide)
118
Q

What is an example of the sequence of cave, arch, stack and stump?

A

Old Harry Rocks, Isle of Purbeck

119
Q

What do beaches represent?

A

the accumulation of material deposited between the lowest tides and the highest storm waves

120
Q

What are the main source of beach material? [3]

A
  1. cliff erosion (5%)
  2. offshore (5%)
  3. rivers (up to 90%)
121
Q

What type of beaches does sand produce?

A

entle gradient (usually less than 5*)- small particle size means that it becomes compact when wet, allowing little percolation during backwash

= little energy lost to

122
Q

What is a salt marsh?

A

Vegetated areas of deposited silts and clays, regularly flooded by water - the UK has 45,500 ha of salt marsh.

123
Q

Explain the formation of a salt marsh (6)

A
  1. Low-energy environment required - e.g. landward side of a spit.
  2. Daily inundation (2x per day) - driven by tides -> salt tolerant plant species (i.e. eelgrass and spartina) trap sediment = increased height - sediment (10cm per year) from rivers and flocculation.
  3. Marsh increases in height = shorter period of daily submergence & less saline conditions (reeds etc) // lower marsh = high salinity, turbid water, long submergence (species diversity = poor).
  4. At high parts of marsh, low-energy, slack water present for 2-3 hours = high deposition rates.
  5. Small, steep-sided channels, or creeks = drain marsh at low tide/routes for water to enter as tide rises -> between creeks = saltpans (trap water when tide falls).
124
Q

What physical factors affect changes in global temperature and the volume of water in oceans?

A
  1. Variations in Earth’s orbit around the sun
  2. Variations in the tilt of the Earth’s axis
  3. Variations in the energy produced by the sun
  4. Major Volcanic eruptions
125
Q

What is the milankovitch cycle?

A
  • It describes the collective effects of hange in the Earth’s movements on its climate over thousands of years
126
Q

What physical factors are part of the Milankovitch cycle? (3)

A
  1. Variations in Earth’s orbit around the Sun.
  2. Variations in the tilt of the Earth’s axis.
  3. Variations in energy produced by the Sun
127
Q

What periods does the Milankovitch cycle drive? (2)

A
  1. Glacial period
  2. Inter-glacial period
128
Q

What is meant by eustatic?

A

A global change in sea level resulting from an actual fall or rise in the level of the sea.

Glacial periods = eustatic sea level fall (more ice = less water).

Interglacial periods = eustatic sea level rise (more ice melt = more water).

129
Q

What is meant by isostatic?

A

Local changes in sea level resulting from the land rising or falling relative to the sea.

130
Q

How does a decrease in global temperature impact sea levels? (2)

A
  1. Leads to more snow = snow turns to ice = water stored in solid form rather than being returned to ocean store as liquid = eustatic sea level fall.
  2. Lower temps = water molecules contract = increased density (and reduced volume)- est. that 1*C fall in mean global temp = sea level fall by approx. 2m.
131
Q

8-mark question structure (3 parts) - Emergent landforms

A
  1. Past
    -Interglacial
    -Glacial
  2. Present day interglacial
  3. Future modifications
    -Warmer = eustatic sea level rise Stormier (waves = more erosive power)
    -Chemical weathering
    -Vant Hoff’s Law (10*C increase = 2.5x faster chemical reactions)
    -Biological weathering (vegetation & marine organisms- e.g. limpets and whelks)
132
Q

What is an abandoned cliff?

A

Sea level used to be at base of cliff, but due to eustatic sea level fall, sea level is now below cliff, so marine processes not dominant.

133
Q

Describe the formation of an abandoned cliff (3)

A
  1. Past
    -Interglacial: eustatic sea level rise = marine erosion is dominant process (hydraulic action & abrasion & pounding).
    -Glacial: eustatic sea level fall = sub-aerial processes dominant (i.e. physical/biological weathering).
  2. Present
    -Eustatic sea level rise (but still 20m lower than when cliff formed) although some eustatic rise = marine erosion becoming more dominant- but not all areas.
    -Warmer temps = increased chemical weathering processes.
  3. Future
    -Increased marine erosion (eustatic sea level rise).
    -Stormier conditions = waves more erosive force.
    -Increased chemical weathering (increasing temps).
    -Further altercations to cliffs.
134
Q

What is a raised beach?

A

Areas of former shore platforms that are left at a higher level than the present sea level. They are often found a distance inland from the present coastline.

135
Q

Describe the formation of a raised beach (3)

A
  1. Past
    -Interglacial: 3*C warmer than today = eustatic sea level rise (+20m than today) = marine erosion dominant (hydraulic action, abrasion) at base of cliffs = undercutting & retreat (mass movement- rock fall) = formation of wave cut platform.
    -Glacial: eustatic sea level fall = marine erosion less dominant = sub-aerial processes (i.e. biological, physical- e.g. freeze thaw).
  2. Present
    -Eustatic sea level rise (but still 20m lower than when cliff formed) although some eustatic rise = marine erosion becoming more dominant- but not all areas.
    -Warmer temps = increased chemical weathering processes.
  3. Future
    -Increased marine erosion (eustatic sea level rise).
    -Stormier conditions = waves more erosive force.
    -Increased chemical weathering (increasing temps).
    -Further altercations to raised beaches.
136
Q

What is a marine terrace?

A

Much larger landscape features than raised beaches (which are smaller/more localised at base of relic cliffs). Terraces do not necessarily have cliffs above them.

137
Q

Describe the formation of a marine terrace

A

Formation essentially same as raised beaches- marine erosion during previous period of higher sea level.

138
Q

How does an increase in global temperature impact sea levels?

A
  1. Higher temps = higher rates of melting of ice stored on land in ice sheets, ice caps and valley glaciers = global increase in volume of water in the ocean store (consequent rise in sea level).
  2. Water molecules expand = increase in volume- e.g. 1*C rise in mean global temps = sea level rise of approx. 2m.
139
Q

What period does the Flandrian Transgression cover?

A

12,000 years ago (end of last glacial period) to present day.

140
Q

What has occurred in the Flandrian Transgression?

A

Temperatures & sea levels have risen to their present level.

141
Q

8-mark question structure (3) - Submerging landscapes

A
  1. Past - glacial
  2. Present - interglacial
  3. Future - warming climate
142
Q

What is a ria?

A

A ria is a submerged river valley, formed as sea level rises.

143
Q

Describe the formation of a ria (3)

A
  1. Past (glacial)
    -Eustatic sea level fall due to more water stored in ice = coastline further out to sea.
  2. Present (inter-glacial)
    -Eustatic sea level rise (Flandrian Transgression) = floods plains/mouth of river inundated.
    -Valley sides remain exposed.
  3. Future
    -Eustatic sea level rise = flooding/increased depth.
    -More erosive power of water.
    -More weathering occurs on valleys = create an even more gently sloping valley.
144
Q

What is a shingle beach?

A

Accumulation of sediment- in form of beach, tombolo, bar (e.g. Chesil beach- tombolo, Slapton- onshore bar).

145
Q

Describe the formation of a shingle beach (3)

A
  1. Past (glacial)
    -New land emerged (sea moved further out from the coast than we see today) = ‘new land’. Sediment accumulates on new land = sediment build up.
  2. Present (inter-glacial)
    -Flandrian Transgression = rapid sea level rise = sediment is pushed up with the sea level (due to sea level having a lot of energy due to increased depth) = more/larger sediment being pushed up beach (larger sediment than we would see today = how we know), able to be picked up and deposited at coastline.
  3. Future
    -Increased sea levels (onshore bars/tombolo being breached) waves have more kinetic energy and stormier conditions/shingle is being sorted = moving in direction of the prevailing wind.
146
Q

What is a fjord?

A

A submerged glacial valley.

147
Q

Describe the formation of a fjord (3)

A
  1. Past (glacial)
    -Glaciers have huge erosive powers (heavy and ice has a huge force) = able to carve out valleys (break through interlocking spurs). Form at top of mountains which then slowly move down due to gravity.
  2. Present (inter-glacial)
    -Rapid sea level rise (Flandrian Transgression) = glacial valley inundated with sea water- very deep (1,000m) = high marine erosion (but water not breach valleys as steep).
  3. Future
    -Widening/deepening of fjord (sea level rise continue)- marine erosion increase (stormier conditions/deeper water)- banks change profile (more gentle) due to sub-aerial processes (weathering)- warmer temperatures = more biological/chemical weathering (Vant Hoff) = gentler sloping sides.

A Level Geography (OCR) (4 decks)

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