Coasts Flashcards
1
Q
Littoral zone
A
The wider coastal zone including adjacent land areas and shallow parts of the sea just offshore
2
Q
Primary coasts
A
Dominated by land based processes such as deposition from rivers or new land from lava flows
3
Q
Secondary coasts
A
Dominated by marine erosion or deposition processes from the sea
4
Q
Emergent coasts
A
Where the coasts are rising relative to sea level eg due to tectonic uplift
5
Q
Submergent coasts
A
Where coasts are being flooded by the sea either due to rising sea levels or subsiding land
6
Q
Low energy coastlines
A
Sheltered coasts with limited fetch and low wind speeds resulting in small waves
7
Q
High energy coastlines
A
Exposed coasts facing prevailing winds with long wave fetches resulting in powerful waves
8
Q
Cliff profile
A
The height and angle of a cliff face as well as it’s features such as wave cut notches or changes in slope angle
9
Q
Dynamic equilibrium
A
The balanced state of a system when inputs and outputs balance over time
10
Q
Short term factors showing the littoral zone is constantly changing
A
Individual waves
Daily tides
Seasonal storms
11
Q
Long term factors showing the littoral zone is constantly changing
A
Changes to sea level
Climate change
12
Q
3 features of a marine erosion dominated cliff
A
Steep face
Active undercutting
Limited cliff base debris
13
Q
3 features of a sub-aerial process dominated cliff
A
Curved slope profile
Lower angle face
Accumulated debris
14
Q
Faults
A
Major fractures that have moved rocks from their original positions
Formed when the pressure to which a rock is subjected exceeds its internal strength causing it to fracture
15
Q
Deformation
A
Folds and dips caused by tectonic activity
16
Q
Strata
A
Different layers with bedding planes
17
Q
Joints
A
Fractures caused either by contraction as sediments dry out or by earth movements during uplift
18
Q
Concordant coastline
A
Rock strata run parallel to the coastline
19
Q
Discordant coastline
A
Different rock strata run at right angles to the coastline
Bands of more and less resistant rock
Headlands and bays
20
Q
Deposition
A
The laying down of sediment carried by wind or water
21
Q
Coastal erosion
A
The process in which cliffs are worn away and transported by the sea
22
Q
Traction
A
Large materials such as boulders are rolled along the sea bed
As they are heavy so waves don’t have enough energy to carry them
23
Q
Saltation
A
Pebbles or small stones are lifted by the sea but dropped when energy is lost.
As a result pebbles are bounced along sea bed
24
Q
Suspension
A
Smaller particles such as sand float in the sea
25
Solution
Particles such as clay are dissolved in the sea and constantly move with water
26
Abrasion
Material is hurled against the cliff by waves wearing away at it
27
Attrition
A pieces of material knock each other they get smaller smoother and more rounded
28
Hydraulic action
Where waves crash into base of cliff forcing air into cracks. This exerts a pressure, cracks grow until rock detatches
29
Solution (erosion)
Soluble particles dissolved by acids in sea water
30
Lithology
The characteristics of the rock including the type, whether it’s permeable or impermeable, how porous it is
31
Isle of Purbeck, Jurassic coast
Resistant Portland limestone lies parallel to the coast
At points where this limestone is weaker erosion causes small coves eg Lulworth cove
32
Igneous rock erosion rate
Very slow
Interlocking crystals make rock strong and resistant
Few joints and therefore limited areas of weakness to exploit
33
Metamorphic rock erosion rate
slow
Crystallised sedimentary rock
Some folds and fractures to exploit
34
Sedimentary erosion rate
Moderate to fast
If cement between layers is weak then it will be weak
Younger rocks are weaker
35
Permeability (lithology)
The ability of water to pass through the rock.
Related to its previousness and porosity.
36
Pervious rocks
Eg limestone
Joints and bedding planes that water can flow through
37
How can groundwater flow weaken rocks
Flows through rocks layers removing binding cement
38
Carbonation
Acidic rainwater slowly dissolved the calcium carbonate in the limestone or chalk creating calcium bicarbonate which is taken away in solution
Calcium carbonate reacts with carbonic acid creating calcium bicarbonate
39
Hydrolysis
Water combines with minerals like granite and the chemical reaction creates salts and clay
Eg in Devon it has created Kaolin (porcelain china clay)
40
Freeze thaw
Water goes into cracks and freezes
This expands and breaks the rock
41
Horizontal bedding plane
1)Erosional processes
2)Main mass movement type
Undercutting by wave action can lead to development of wave cut notches and platforms
Main mass movement=rock fall
42
Sloping bedding plane (towards sea)
1)Weathering
2)Sub aerial processes
Large slabs of rock loosened by weathering slide off easily along bedding planes.
Sub aerial processes have a greater influence than marine processes leading to shelling cliffs
43
Sloping bedding plane (away from sea)
Rocks loosened by weathering and wave action are difficult to dislodge
Slope profile lowered by mass movement and weathering
Cliff face is rugged and uneven
44
Marram grass
Helps stabilise the unconsolidated sediment of the dunes and encourages other plants to grow there as well so helping plant succession
45
Ways vegetation helps stabilise unconsolidated sediment
1)roots of plants bind sediment particles together so harder to erode
2)When submerged plants provide protective layer sonnet exposed to moving water
3)Protect sediment from wind erosion by reducing wind speed due to friction
46
What does geological structure of rock include
Strata
Bedding planes
Joints
Folds
Faults
Dip of the strata
47
Joints
Vertical cracks
48
Bedding planes
Horizontal cracks
49
Dip of the strata
Angle at which rock strata lie
50
Concordant
Bands of more resistant and less resistant rock parallel to coast
51
Discordant
Bands of more resistant and less resistant rock perpendicular to coast
52
Halophyte
Tolerate salt water around roots, tolerate being submerged in water or salt spray from the sea.
53
Xerophyte
Tolerate very dry conditions, like on sand dunes where sandy soil has very little water due to drainage
54
What factors affect size of wave
Fetch: stretch of ocean over which wind blows
Longer fetch -> larger wave
Wind speed
Duration of wind
55
Rockfall
Occur when there is erosion at the base of cliffs creating overhang
Rock type must be resistant. As unconsolidated cliffs slump too quickly to allow overhangs to form.
Rock fragments fall due to gravity
56
Slumping
Occurs in weak unconsolidated cliffs
These cliffs have little strength and are vulnerable to slip planes developing
Rainwater enters cliff increasing weight of soil and lubricating slip plane
Material slides along slip plane
57
How are wave cut platforms formed
Horizontal bedding planes
Wave cut notch forms due to hydraulic action and abrasion
Notch increases in size
Wave cut platform forms when rockfall happens
58
Longshore drift
Swash deposits material on the beach at 45 degrees
Backwash pulls material off beach at 90 degrees
This repeats moving sediment along the coastline
59
How do spits form
-Sand or shingle beach ridge extending beyond a turn in the coastline
-Longshore drift current spreads out and loses energy leading to deposition
-Length of spit is determined by existence of secondary currents causing erosion
-Flow of river or wave action limits its length
60
Detailed example of a spit
Spurn Head, Holderness coast
3.5 miles long
Grows 10cm a year
61
Recurved spits
-A spit whose end is curved landward into a bay/inlet
-Seaward end curved landward into shallower water
-“Hook” may be made more pronounced by waves from a secondary direction to prevailing wind
62
Example of a recurved spit
East Head West Wittering
63
Tombolos
Sand/shingle bar that connects coastline to offshore island
64
How are tombolos formed
-Spit/bar grows due to LSD joining island
-Formed due to wave refraction around island around island
-Area of calm water created
-Opposing Longshore currents may play a role
65
Example of a tombolo
Chesil beach Dorset
-Swash aligned
-Faces SW
66
How are beaches formed
Occur in littoral zone between low and high tide
Constructive waves with strong Swash and weak backwash allow a net increase of material
Longshore drift moves material along shoreline
67
Barrier beaches
-Sand or shingle beach connects 2 areas of land with a shallow water lagoon behind
-Occurs when a spit grows so long that it extends across a bay closing it off
68
Examples of barrier beaches
Many are found along Eastern Seaboard of the USA
Scapton, Devon
69
Offshore bars
-Raised area of seabed that is found offshore
-Form adjacent to coastline
-Formed in areas with high levels of sediment and shallow water
-Form when sediment is transported on and off a beach
70
Cuspate forelands
Roughly triangular shaped features extending out from shoreline
One hypothesis is due to growth of 2 spits from opposing longshore drift directions
71
Yellow dunes
Mobile dunes
Marram grass/Lyme grass/Sandcouch
72
Grey dunes
Less salt tolerant plants
Sea buckthorn, Dewberry
More organic matter and humus in soil
73
Fixed grey dunes
hawthorn
Oaks
Maple
Ash
Climax species
74
Dynamic equilibrium
The balance of all the factors affecting the coastal system. If there is a change to one factor the system will respond and there will be consequent changes
75
Sources of Flamborough head sediment cell
-Deposition from river Humber
-Rockfall from cliffs
-Soft boulder clay
-Chalk from Flamborough head
76
Transfers in Flamborough Head sediment cell
Longshore drift along Bridlington bay
-going southwards
-large waves from north east
-Increased erosion
77
How is the Flamborough Head sediment cell being disrupted?
-Mappleton village intense erosion
-2m a year
-£2000000 spent on rock groynes and revetments
-Due to this there has been more erosion further south
-No beach to protect cliffs so sea reaches base of cliffs causing erosion
78
Isostatic change
A LOCAL rise or fall in LAND level
79
Eustatic change
Rise or fall in WATER LEVEL.
This is a GLOBAL change.
80
Post glacial isostatic adjustment
Refers to uplift of land following removal of the weight of ice sheets
81
How do sea levels change day to day?
-High/low tides alter local sea level every few hours
-Atmospheric air pressure influenced sea level (low pressure=slight rise)
-Winds can push water towards coast
82
How much have sea levels risen by since last glacial period (ice age)
120m
83
Eustatic fall in sea level
During glacial periods when ice sheets form on land in high latitudes, water evaporated from the sea is locked up on land as ice to sea levels fall.
84
Isostatic fall
Weight of ice sheets causes earths coast to sag. When they melt the island surface slowly rebounds upward over 1000s of years. This lifts land out of sea
85
Eustatic rise in sea level
At end of glacial period melting ice sheets return water to sea causing level to rise globally
86
Isostatic rise
Lands can sink due to deposition of sediment (accretion)
87
Raised beach + example
A former beach that is now above the high tide line
Rounded boulders and pebbles present
Fife Scotland
88
Fossil cliff + example
Best vertical slopes initially formed by marine processes but can now be found further inland
Land can be stressed downwards from post glacial adjustments, subsidence and accretion
Ayrshire 10m high
89
Rias + example
Drowned river valley
Caused by sea level rise flooding
Kingsbridge estuary Devon 500 to 1000m wide creeks
90
Fjords + example
Deeper than adjacent sea
Submerged lip at seaward end
Post glacial isostatic adjustment slowly raises land out of sea
91
Barrier islands + example
Offshore sediment bars.
Formed as lines of coastal sand dunes. Dunes are not eroded so become islands
Florida USA
92
Dalmation coasts + example
Concordant coasts where sea has flooded landscape brewing long bays and parallel hilly islands
Croatia
93
What effect does past and present tectonic activity have on sea level change?
Example
-Can lead to subsidence causing land to sink
-Oceanic plates sink
Turakirea head NZ shoreline has raised several metres by major earthquakes
94
Eccentricity cycle
Earths orbit
95
Obliquity cycle
Earths tilt
96
Precession
A gradual change or wobble of earths axis
97
Human reasons for spatial variations along the coast
-Coastal defences can cause starvation of sediment further south.
-Groynes interrupt longshore drift
Example: Hornsea
Hornsea groynes caused sediment starvation is mappleton so increased erosion
98
Physical reasons for spatial variations along coast
Example
-Variations in cliff height
-Variations in rock resistance
-Mass movement susceptibility
-Debris from previous erosion
Example
Flamborough head shelters area south of it reducing impact of waves
Also has resistant chalk
99
Ords
Deep hollows on the beach running parallel to the cliff at the base
100
What influence do ords have
-Concentrate erosion in particular locations
-By allowing waves to directly attack the cliff with little energy dissipation
101
Skipsea: Economic impacts of sea level rise
-10 caravan patches a year lost
-Property values declining
-No compensation for homeowners
-Loss of tourism revenue
102
Social impacts of sea level rise in Skipsea
-Displacement of residents
-Stress over lost caravans/homes
103
What’s needed for a storm surge to happen?
-Area of low pressure
-Strong winds around it
-High tides around the coast
104
What physical factors make Bangladesh prone to flooding?
-Low lying. 0 to 3m above sea level
-Delta funnel shape
-Deforestation of coastal mangroves
-Floodplains of 3 major rivers incl Ganges
105
Cyclone Sidr
-Heavy rain
-223 km/h winds
-$1.7 billion
-Contaminated drinking water
-Electricity and comms knocked out
-10000 deaths
106
Economic costs of coastal recession
-Housing eg 24 homes at risk Skipsea
-Businesses
-Loss of tourism
-Infrastructure
107
Social costs of coastal recession
-Impacts on health eg stress
-Relocation separates people
-Loss of livelihood
-Loss of amenity areas eg beaches
108
What is ICZM
Integrated coastal zone management
Entire coastal zone is managed.
Ecosystems, resources, human activity
Recognises importance of zone to livelihoods
Involves all stakeholders
109
Policy options of shoreline management plans
No active intervention
Managed realignment
Hold the line
Advance the line
110
Example of a good ICZM
Blackwater Estuary Essex
Wildlife trust bought Abbots Hall Farm for market price
Paths and waterways for measure
5 breaches created in sea wall to form salt marshes
111
Impacts of storm Xaver North Sea in England
100 000 homes lost power
Severe flooding Hull, Skegness, Whitby, Rhyl
2500 coastal homes flooded
-15 deaths
112
Physical factors North Sea storm xaver
Sea gets shallower and narrower towards south
Increases height of storm surge
113
Explain marsh succession
Starts with pioneer species: cordgrass and eelgrass
Sediment builds up decreasing salinity so less salt tolerant plants can grow
This causes a vegetation succession resulting in climax communities
114
Explain sand dune succession
Vegetation stabilises the sand dunes
Starts with embryo(mobile), then yellow(mobile), then grey (fixed)
As it develops soil fertility increases
Embryo-pioneer
Yellow- marram grass
Grey dunes -oak and hawthorn
115
Define plant succession
The way that vegetation on a sandy coastline changes over time from pioneer plants to climax communities
116
Name 3 types of mass movement
Slumping
Rockfall
Landslides
117
What is the difference between slumping and landslides?
Slumping involves a rotational movement of sediment along a curved surface
Landslides involve linear movement along a flat slip plane
118
Define flocculation and gravity settling (deposition types)
Flocculation: sand particles clump together due to chemical processes and are added to the sea floor in shallow areas
Gravity settling: sand particles clump together and fall to floor due to gravity
119
Name examples of emergent and submergent coasts
Emergent: raised beach, fossil cliffs
Submergent: Dalmatian coast, Ria Fjord
120
What are the physical causes of coastal recession?
Marine processes: wave type, tides, submerging coasts
Geology: Resistance of rock and lithology
Sub aerial processes
121
How are policies for SMPs decided?
Coastal defence evaluation
Is the defence….
Appropriate for physical processes
Environmentally acceptable
Feasible to build
Economically viable
Sustainable
122
Groynes explanation and positives and negatives
Barriers on a beach at right angles to the coast to slow LSD. They widen a beach so it can reflect wave energy
Good:
Maintains size of beach
Less expensive
Bad:
£1000/m
May hinder people walking
Sediment starvation
123
Sea walls explanation and positives and negatives
Concrete walls to absorb and reflect wave energy.
Good:
Effective
Bad:
£5000/m
Reduced sediment supply
Ugly
124
Rip rap explanation and positives and negatives
Boulders that are resistant that dissipate wave energy
Good:
Long lasting and flexible
Cheap £50/m^3
Some backshore erosion
125
Dune stabilisation explanation and positives and negatives
Adding vegetation to dunes, fencing them off etc
Good:
Looks natural
Provides ecosystem
Bad:
£1000/m to replant
Fenced off
Storms undo
126
Beach nourishment explanation and positives and negatives
Replacing beach sediment that’s been eroded
Good:
Looks natural
£10/m^3
Bad:
Constant replacement work may reduce tourism
127
How does the sediment cell concept contribute to understanding of coastal systems?
Can track movement of sediment - this informs decisions in where to add/reinforce defences
Demonstrates dynamic equilibrium
128
How do sediment cells demonstrate dynamic equilibrium?
Negative feedback maintains equilibrium - eg wave causes rockfall which protects cliff base from further erosion
Positive feedback increases the change until a new equilibrium is reached
129
Where can granite coasts be found in the UK?
Cornwall
130
Example of a landward dip of the strata?
Filey Bay in North Yorkshire
Jurassic rocks overlaying weaker clays and shales
131
Example of a wave cut platform
Kimmeridge bay in Dorset
This has visible notches and ridges showing past positions of coastal retreat
132
What are the characteristics of a drift aligned beach?
Spit
Smoother sediment which becomes finer as you go down the beach due to LSD and attrition occurring more to those bits of sand
