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OCR A LEVEL GEOGRAPHY > Coasts > Flashcards

Coasts Flashcards

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1
Q

What is a system?

A

A set of inputs, outputs, stores and flows which are all connected to form a unified system.

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2
Q

Define equilibrium

A

Where inputs are = to outputs

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3
Q

Define dynamic equilibrium?

A

Where the equilibrium is disturbed, the system undergoes self regulation to undo said changes

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4
Q

What are sediment cells?

A

A stretch of coastline and its associated nearshore area which sediment is self contained in. They are closed systems so no sediment will transfer in, or out.

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5
Q

What are the 5 physical factors that work on coastal systems.

A

Winds
Waves
Tides
Currents
Geology

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6
Q

How are waves generated?

A

Is generated by frictional drag from winds moving across the surface of the ocean.

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7
Q

What affects a waves power?

A

Fetch - The distance the wind travels
Wind speed

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8
Q

How do waves break?

A

When the water gets more shallower, the waves come in contact with more friction, which reduces the wave energy, creating an elliptical wave orbit instead of circular creating a higher wave height. The deepest part of the wave slows more than the top part of the wave and then break when the depth is less than 1.3x the height

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9
Q

Define swash and backwash

A

Swash - The movement of water up a beach after a wave has broken
Backwash - The movement of water won a beach after a wave has broken

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10
Q

What are constructive and destructive waves?

A

Constructive - Swash is greater than the backwash so the beach is built up
Destructive waves - Backwash is greater than the swash so beach is destroyed

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11
Q

What is the frequency of both constructive and destructive waves?

A

Constructive = 6-8 per min
Destructive = 12-14 per min

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12
Q

What will the beach profile be like in the winter?

A

Higher wind speeds, means more destructive waves will be present, eroding material off of the beach. This will reduce the beaches gradient making it gentle gradient, and flat.

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13
Q

What will the beach profile be like in the summer?

A

Lower energy waves, means more constructive waves will be present, building up the beach. This will increase the beaches gradient, making it steeper.

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14
Q

How are tides generated?

A

Rise and fall of the sea surface is caused from the gravitational pull of the moon. Moon pulls water towards it giving a high tide. When the moon is aligned with the Earth and the Sun which happens twice per lunar month giving spring tides. When moon and sun are at right angles neap tides arise

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15
Q

Where are tidal ranges the lowest on the Earth?

A

Mediterranean. Which reduces wave action

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16
Q

Where are tidal ranges the highest on the Earth?

A

UK, where the coast is funnelled such as in estuaries, which increases the wave action.

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17
Q

How do tides affect a coasts shape?

A

Determines the wave action, low tidal ranges will have little wave action so therefore landforms of deposition will be present. High tidal ranges will have more wave action, so therefore more landforms of erosion due to more marine erosion and chemical weathering.

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18
Q

What are the two components geology is split into?

A

Lithology - Refers to the physical and chemical composition of rocks
Structure - Properties such as jointing, bedding, permeability and faulting

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19
Q

What is meant by concordant and discordant?

A

Concordant - Where rock outcrops are uniform and lie parallel to the coast
Discordant - Where different rock types lie at right angles to the coast, which create headlands and bays

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20
Q

What are the two types of coastlines?

A

Swash aligned - These coastlines are found near small bodies of ocean or are protected by offshore barriers or islands. The prevailing wind is unable to influence the wind directions and so waves approach the coast parallel to the shore. These build large beaches with possible dunes.

Drift aligned - These coastlines are exposed to a large open ocean, prevailing wind dominates wind direction and waves approach the coastline at an angle. These are associated with longshore drift. These will have beaches that are narrower and may be exposed to higher rates of erosion

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21
Q

What are the 3 types of strata on a coastline?

A

Horizontal - Undercutting by wave action lead to rockfall ; the cliff retreats inland parallel to the coast
Seaward dipping - Undercutting removes base support, which causes landslides and slumping along the bedding plane
Landward dipping - Rocks loosened by erosions and weathering are difficult to dislodge, the slope profile gradually lowers by weathering and mass movement.

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22
Q

How are currents generated?

A

Earths rotation and convection along with wind across the water surface. Warm currents transfer heat from low latitudes towards to poles so move upwards. Cold ocean currents do the opposite so move towards the equator.

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23
Q

What are 5 sources of sediment?

A

Fluvial deposition - Rocks eroded from the upper course of the river are transported downstream and deposited at the end of the river
Marine erosion - Cliff erosion by waves erodes the cliffs causing mass movement which then is deposited on beaches
Aeolian deposition/ offshore - Wind carries fine particles and deposits them as they loose energy
Longshore drift- This can supply sediment to one coastal area to another
Human- Beach nourishment via rainbowing and dumping of sand

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24
Q

What are 7 geomorphic processes?

A

Erosion
Weathering
Mass movement
Transportation
Deposition
Fluvial processes (Erosion, transportation and deposition in rivers)
Aeolian processes (Erosion, transportation and deposition in wind)

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25
Define weathering
The breakdown of rock in-situ through exposure to the Earths atmosphere, organisms and water.
26
Give 5 mechanical weathering examples.
Freeze thaw - Water enters cracks, freezes and expands exerting pressure up to 2100kg/cm2 when rocks can only withstand a pressure of 500kg/cm2 Pressure release - When overlying rocks are removed by weathering and erosion, the underlying rocks expand and fracture, parallel to the surface. Thermal expansion - During the day the rock heats up and expands, at night it cools and contracts causing cracks. Salt crystallisation - Solutions of salt in sea water enter pore of porous rocks such as chalk and limestone, which then precipitate out and expand up to 300% causing cracks. Wetting and drying - rocks rich in clay expand when wet, and crack when dry.
27
Give 5 chemical weathering examples.
Oxidation - Some minerals such as iron in rocks react with oxygen/water causing it to become soluble under acidic conditions Carbonation - Carbon dioxide dissolves in water creates carbonic acid which is then either reacted with rocks from the ocean or rainwater which will dissolve them depending on their lithology. Solution - Some mineral such as halite are soluble in water and as they dissolve they weaken the structure of the rock Hydrolysis - Is the chemical reaction between minerals in water. Silicates combine with water producing secondary minerals such as clay or feldspars Hydration - Water molecules added to rock minerals to create new minerals of a larger volumes such as anhydrite forming gypsum
28
Give 3 biological weathering examples.
Tree roots grow into cracks and joints and exert outward pressure, causing rock to split Burrows - Similar effects Organic acids - Decay of organic matter release acids that may dissolve a rock
29
What are the 5 mass movements?
Rock fall - Fast change, rain on top or marine erosion undercuts the base of a cliff with horizontal bedding planes causing the rock on top of the undercut to fall and accumulate at the base of the cliff Landslides - Involves a block of rock moving downwards. Frequently occurs during earthquakes or heavy rainfall, which causes rocks to slide down the seaward dipping bedding planes. Is fast Slumping - A slump differs from slides as is curved slip plane rather than straight. Occur in weak and unconsolidated clays which build up in water and causes it to fall. Is also fast Mud flows - Saturated soils and weak rock flows down a slope, materials become mixed. Is sudden and fast but not as fast as others. Soil creep - Slowest, soil gets wet and heavy. Particles rise towards the ground due to wetting or freezing then retreat vertically to the surface causing the movement of the soil
30
What are the 5 types of marine erosion?
Abrasion - Rocks are thrown at the coastline eroding the coastline Attrition - Rocks hit against eachother eroding them Hydraulic action - Waves break against cliff face, and air and water get trapped in cracks and become compressed. When the pressure is released, the air and water expand rapidly and the crack is widened. Pounding - Mass of breaking waves exert pressure on the rock up to 30 tonnes Solution - Involves miners in coastal rock dissolving in sea water, will become more significant with increases of temperature.
31
What are the 4 transport methods?
TSSS Traction - Largest particles slide or roll along the river/sea bed Saltation - Smaller particles bounce along seabed Suspension - Smaller particles suspended in water Solution - Particles dissolved in water
32
Name 6 landforms of erosion
Headlands + bays Caves, arches, stacks and stumps Geos Blowholes Marine cliffs Shore platforms
33
What is the case study used for a high energy coast?
Flamborough to Saltburn
34
How do Headlands and bays form?
Bands of soft and hard rock on a discordant coastline are eroded. The soft rock erodes faster and creates a bay leaving hard rock on either side of the bay called headlands.
35
How do caves, arches, stacks and stumps form?
1. Cracks expand and widen due to marine erosional processes 2. Cracks widen creating a cave which deepens from further erosion 3. If two caves are aligned, the waves cut through to form an arch or just erode through original cave 4. This creates an arch, which will weather at the top weakening the support 5. Arch collapses creating a stack 6. The stack gets eroded and a wave cut notch forms, collapses the stack creating a stump
36
How do geos form?
1. Wave action creates faults which erode creating a wave cut notch 2. More erosion making a cave which deepens 3. The top of the cave collapses due to gravity and weathering at the top 4. Creates a ravine in between rock (geo)
37
How do blowholes form?
Form when the bottom of a cliff erodes which is under the water. Continuous hydraulic action causes water to force its way up and comes out in bursts,
38
How do cliffs form?
Vertical cliffs form when the strata is horizontal, marine erosion erodes the base of a cliff creating a wave cut notch. Further erosion causes rock fall making the cliff retreat perpendicular to the shore.
39
How do shore platforms form?
Form when cliffs retreat leaving a platform of rock where the old cliff used to be. Can only have a max of 4 degrees and 500m before the waves erode the platform instead of the cliff.
40
What is wave refraction?
Wave refraction involves waves breaking onto an irregularly shaped coastline, e.g. a headland separated by two bays. Waves drag in the shallow water approaching a headland so the wave becomes high, steep and short. The part of the wave in the deeper water moves forward faster causing the wave to bend.
41
Name 3 headlands and bays
Robin hood bay Filey Bay Slewicks bay
42
What is the fetch and the rate of erosion at Flamborough?
Fetch = 1500km Wave height = 4m Rate = 0.1m/yr on hard rock, 0.8 m/yr on soft rock
43
Name 6 depositional landforms?
Beach Spit Bar Tombolo Marsh Estuary/delta
44
What are the two types of beaches?
Shingle Sand
45
What are 3 factors that affect a beaches morphology?
Wave energy - Higher wave energy, gentle beach profile Sediment size and shape - Higher size sediment, steeper profile due to higher percolation rates reducing the backwash energy Tidal ranges - High tidal range, steeper beach profile
46
What is the angle of repose?
Shows pebbles can support a steeper angle that finer sediments
47
What are berms, cusps and ripples?
Berms = Form on shingle beaches and pebble beaches. Usually related to swash processes associated with high levels of water. At the highest level, the berm is flat (in storm events and spring tides). The bottom part of a berm is called a runnel. Ripples = Smaller feature on a sandy beach. Symmetrical ripples form when the current flows at similar velocities. Creates small wiggly lines on the beach Cusps = Cusps are crescent-shaped indentations that form on beaches of mixed sand and shingle. They are formed where there is a junction between sand and shingle. Once the curving shape is created, swash is concentrated in the small bay that forms in the centre of the cusp. This creates a stronger backwash that removes material down the beach.
48
How are spits formed?
A spit is a long narrow beach of sand or shingle extending from the mainland out to sea. They form when there is a sudden change in direction of coastline and a steady supply of sediment which accumulates in the direction of LSD. The side of the spit at the mainland side is called the proximal end The side of the spit out to sea is called the distal end Compound spits form when waves refract around the end of the spit causing it to recurve or change in wind direction.
49
What is the case study for spit, bars and tombolo's?
Spit - Orford ness, Spurn point Bar - One in Egypt but also Orford Ness Tombolo = Chesil beach, close to Portland
50
How are marshes formed?
1. Flocculation occurs and stick together which help build mudflats 2. Pioneer species that are tolerant to salt water grow and stabilise the mudflat 3. Secondary colonisers grow and out survive pioneer species and stabilise the mudflat even better while it grows 4. As the height increases, to the low neap tide, more plants grow due to the dead first pioneers giving the nutrients. 5. This repeats, but the ecosystems at the terrestrial zone are not affected such as trees
51
What is focculatiuon?
A process which solute comes out of solution. Occurs with clays when reacting with salt ions, which form flocs that are heavy enough to be deposited
52
Define settling velocities
Shows the minimum speed that particles of different sizes need to have in order to be deposited.
53
What are 2 ways the bar at Slapton sands (Offord ness) thought to have formed?
1. Spit extended to cover bay connecting the mainland by LSD with no change in depth or secondary wind 2. Onshore movement from glacial deposition (Flandrian transgression). When ice melted it caused higher energy waves due to increase in depth of water and deposited material. We know this because the sediment size changes here where at other bars it doesn't.
54
What can develop in the sheltered part of a spit/compound spit?
Lagoons can form behind these.
55
What is the furthest point called on the spit and the point closest to land called?
The side of the spit at the mainland side is called the proximal end The side of the spit out to sea is called the distal end
56
What is an estuary?
Bodies of water found where a river meets the sea, has brackish water (Salt and fresh water combined) often funnel shaped
57
What are the three components of an estuary?
The inner , central and outer zone
58
What is a delta?
Large areas of sediment found at the mouths of rivers. Sediment is deposited by rivers and tidal currents.
59
What are three factors that allow a delta to form?
Rivers carrying large sediment loads A broad continental shelf Tidal ranges are low
60
What are 3 types of deltas classified on their shape?
Cuspate - Formed in stronger waves pointed toward the sea, triangular, regular and gentle currents from opposite directions. Tooth shaped Arcuate - Sufficient sediment supply, enabling it to grow seaward, wave action allows delta to have smooth ends. Triangle shaped. (IS THE ONE AT THE NILE DELTA) Birds foot - Distributaries are widely spaced and are in a branching system. Looks like a birds feet.
61
What are 3 different types of deltas classified on their influencing factor?
River dominant = Large catchments with rivers discharging into the sea Tide dominant = Tidal range is high sediment deposited perpendicular to the coastline Wave dominant = Deltas that front the open sea and receive high levels of wave energy and have sediment accumulations parallel to the coastline.
62
What are the are the 3 components of a delta?
Upper delta plain = Furthest inland Lower delta plain = In the inter - tidal zone Submerged delta plain = Lies below the mean low water mark
63
What is the case study for deltas?
Nile Delta - Egypt
64
What are the two distributaries called at the Nile delta?
Rosetta Damietta
65
What causes a split in the River nile?
Overloaded with sediment causes bars to for, and levees which grows the delta.
66
What caused the amount of sediment in the delta to decrease?
The Aswan High Dam in 1964, used to be 4.26 Ha/Yr deposited but now decreased due to dam catching sediment.
67
How many m/yr is the Nile delta retreating by and why?
148 m/yr due to the dam reducing the sediment supply, so is in deficit which then makes the waves erode the delta back.
68
What landforms can form in the foreshore and frontal plain?
Frontal = Crescentic and parallel bars, lagoons Foreshore = Saltmarsh
69
What are regressive conditions?
A negative sea level change (Falling sea levels). Emergent landforms are created.
70
What are transgressive conditions?
A positive sea level change (Rising sea levels) Submergent landforms are created.
71
What are eustatic changes?
Global sea level change
72
Why are eustatic changes global?
Because mostly all the oceans and seas are interconnected, as well as the total volume
73
What causes transgressive eustatic change?
Higher temps due to co2 rise causes: Land ice to melt Thermal expansion
74
What causes regressive eustatic change?
Lower temps due to lower in co2: freezing of water on land Thermal contraction
75
What is isostatic change?
Changes in the level of land. Localised
76
What are ways isostatic change can happen?
Weight such as ice can be added/removed which will change the height of the land. Abstraction of water, oil and gas - Tokyo depressed land from ground water extraction Tectonic activity Sea floor spreading
77
What is isostatic rebound (glacial-isostasy)?
Ice melts on land reducing weight on the crus causing it to rise - Is happening in Scotland where land is rising, but in south England is lowering
78
What is glacio-eustasy?
Sea levels rise caused by melting of glaciers and ice sheets
79
How does thermal expansion effect the sea level change?
As the sea surface temperature rises, the density of sea water decreases - water volume increases and sea levels rise.
80
What are emergent landforms the result of?
Regressive conditions
81
What are two emergent landforms?
Raised beaches Abandoned cliffs
82
What is the case study for a raised beach?
Isle of Portland formed 125,000 years ago
83
How are emergent landforms modified?
Landforms no longer affected by wave processes, so continue to be modified by weathering and mass movements.
84
By how much does the sea level rise with a 1 degree of warming?
2m
85
What are three submergent landforms?
Rias Fjords
86
What are the two case studies for rias?
Salcombe in Devon Kingsbridge estuary in Cornwall
87
What is the Flandrian transgression?
The most recent eustatic change caused by the melting of ice caps
88
What is the cross section of a ria like
Relatively shallow water on the river banks, and increase in deepness in the centre. The exposed sides are gently sloping
89
How are rias formed?
The lower course of a river is submerged in transgressive eustatic change.
90
What are fjords?
Submerged glacial valleys
91
How are fjords formed?
Glaciers bulldoze through inland spurs of a river causing a v - shaped valley. When the glaciers melt, it floods the valley creating a fjord
92
What is the case study used for fjords?
Sogne Fjord - Norway 200km long
93
What is the cross section of a fjord like?
V- Shaped valley, with steep sides cliff like valley sides, water is uniformly deep up to 100m
94
What is an example of a shingle beach?
Chesil beach
95
How are shingle beaches formed?
When sea levels fall, large areas of new land emerge and sediment accumulates on the surface deposited by waves. As the sea level rose at the end of the Flandrian transgression, wave action pushed the sediment onshore at the base of the cliffs, on forming tombolo's and bars such as a Chesil beach
96
How are submergent landforms modified?
Wave processes act on the sides of rias and fjords. Sub - aerial processes affecting valley sides, will increase erosion when sea levels rise. Shingle beaches are modified by LSD and storm events
97
What are examples of hard engineering?
Sea wall Gabions Rock wall Rip Rap Groynes
98
What are examples of soft engineering?
Managed retreat Beach replenishments Rainbowing Dumping
99
What is the case study used for coastal management?
Sandbanks dorset
100
Why is sandbanks being eroded?
Due to lithology, soft sandstone, complex ocean currents large fetch, SW prevailing wind
101
What are 6 reasons for protecting sandbanks and Poole harbour
High value commercial properties Residential properties The beach - Tourism Protection and shelter Entrance to poole harbour - Blocked due to LSD Climate change - Rising sea levels
102
What are two methods that are being used to protect sandbanks and Poole harbour?
Hold the line using groynes Managed retreat Both successful
103
What is the case study used for mining sand and its consquences?
Mangwhai - Pakiri coastline of new Zealand
104
Why was sand being mined in New Zealand?
Used for glass, concrete, fill and beach nourishment
105
What problems did the sand mining in New Zealand cause?
Causes beaches to be in deficit which will cause further/rapid beach erosion Mines are now ceased.
106
How are bars formed?
Same as a spit, but extends and grows across a bay connecting two land masses.
107
How are tombolos formed?
Same as a spit, but form and connect mainland to an island.
108
What was a period of regressive ecstatic change
Riss glaciation
109
What is the sediment budget?
The balance between changes in the volume of sediment held within the system and the volume of sediment entering or leaving the system In surplus when inputs > outputs In deficit when outputs > inputs In equilibrium when inputs = outputs
110
How has sand dredging affected the Mangawhai- Pakiri coastline?
as the sediment cell is closed current rates of sand extraction are unsustainable - beaches starved of sediment are wider, flatter and less effective are absorbing wave energy - higher waves erode beaches and make spits and dunes vulnerable - loss of vegetation makes them susceptible to wind erosion . 1978 storms caused one 28m breach at the base of mangawhai spit - this and a second breach caused the sedimentation of Mangawhai-Pakiri's harbour - shallow water threatened the waterfront community with flooding - dredging and groyne construction on the spit has helped restore some equilibrium.
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OCR A LEVEL GEOGRAPHY (7 decks)

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