Coasts Flashcards
(168 cards)
1
Q
How do coastal landscapes vary in the UK?
A
- The UK’s coastline is 31,368km long (including the main islands)
- Tees - exe line is an imaginary North East - South West line (divides the country into low land and upland areas)
- Many are a mixture of high and low energy coastlines
The coast varies greatly
2
Q
Describe the coastline of Western and Northern Britain.
A
- A resistant rock coastline
- Igneous granite, Basalt
-These can withstand frequent storms with little erosion - There is also compacted older sedimentary rock and metamorphic rock
3
Q
What are the features of high energy coastlines?
A
- Rocky coasts are found here
- Stretches of the Atlantic facing coast e.g. Cornwall
- Rate of erosion exceeds the rate of deposition
- Landforms include; headlands, cliffs and wave cut platforms
4
Q
Describe the coastline of Eastern and Southern Britain.
A
- Younger, weaker sedimentary rocks
-Chalks, clays and sandstone - Most of Eastern England is low lying sandy beaches, and coastal plains, and has habitats such as salt marshes, lagoons and mud flats
-e.g the wash which is a coastal plain formed by 4 rivers: Ouse, Nene, Welland and Witham
5
Q
What are the features of low energy coastlines?
A
- Sandy and estuarine coasts
- Waves are less powerful, or where the coast is sheltered from large waves
- Where the rate of deposition exceeds the rate of erosion
6
Q
Describe the inputs of a sediment cell.
A
- Marine (waves, tides and storm surges)
- Atmospheric (weather, solar energy, climate change
- Land (rock type, tectonic activity)
- People (human activity, coastal management)
7
Q
Describe the Processes of a sediment cell.
A
- Weathering
- Deposition
- Mass movement
- Erosion
- Transport
8
Q
Describe the outputs of a sediment cell.
A
- Erosional landforms
- Depositional landforms
- Different types of coasts
9
Q
What is a sediment cell?
A
- Sediment supply is sourced by weathering and erosion
- This is then transported and deposited to produce coastal landforms
- Sediment cells are dynamic, so any change to a component will have an impact on the rest of the system
10
Q
What are some ways you can classify coasts?
A
- Geology - rocky, sandy, concordant, discordant and estuarine coasts
- Level of energy - high/low
- Balance between erosion and deposition - and their features
- Changes in sea level - creating emergent or submergent coasts
11
Q
What is the foreshore?
A
- Area lying between the high water mark and the low water mark
-Seen as most important for marine activity
12
Q
What is the backshore?
A
- Area between the high water mark and the landward limit of marine activity
13
Q
What is the littoral zone?
A
- The area between the land and the sea - stretches into the sea and on the shore
- It is constantly changing because of dynamic interaction between processes
14
Q
What is the inshore?
A
- Area between the low water mark and the point where the waves cease to have influence on the land around them
15
Q
What is the fetch?
A
- Distance of open water over which the wind can blow
16
Q
What is the offshore?
A
- Area beyond point where waves cease to impact the seabed
-activity limited to depostion fo sediments
17
Q
What causes waves?
A
- The stronger the wind is, the longer it blows for, and the longer the fetch
- The larger the wave will be, and the more enrgy it will have
- Frictional drag increases as wind speed increases, making the wave bigger
Waves are a medium through which energy is transferred
18
Q
What is a beach?
A
- A deposit of sand or shingle at the coast
19
Q
What is the crest?
A
- The top of a wave
20
Q
What is the trough?
A
- The lowest point of a wave
21
Q
What is the swash?
A
- The forward movement of a wave up the beach
22
Q
What is the backwash?
A
- The backward movement of water down a beach when a wave has broken
23
Q
What is wave frequency?
A
- Number of wave crests passing one point each second
24
Q
What is the wave orbit?
A
- The shape of the wave - varying between circular and eliptical
- The orbit diameter decreases with depth, to a depth roughly equal to the wavelength
- There is no further movement related to wind energy
-This is the wave base
25
What is a wave period?
## Footnote
What is the wavelength?
* Time required for the wave crest at one point to reach a point a wavelength away
## Footnote
The middle of one crest to the middle of the next crest
26
Why do waves break?
* In water, there is little horizontal movement of ocean water
* As the water reaches the coastline, it has increased contact with the shelving sea bed - exerts frictional force on the base of the wave (circular orbit changed to an eliptical orbit)
* As the wave gets closer, the friction grows, so the top of the wave moves faster than the bottom
* Eventually, the crest curves over and creates a breaking wave
27
What are the features of a constructive wave?
* Short amplitude
* Long wavelength
* Low frequency (6-8 waves per min)
* Strong SWASH, weak BACKWASH
* Beach profile with a gently shelving sea floor
28
Whatare the features of a destructive wave?
* High amplitude
* Short wavelength
* High frequency (10-14 waves per min)
* Weak SWASH, strong BACKWASH
* Beach profile with a steeply shelving coastline (storm beach)
29
What is the amplitude?
* Half the wave height
* From the still line to a crest
30
What landforms are created in a wave dominated environment?
* Wave-cut platform
* Cliffs
* Beaches
* Spits
* Deltas
31
What landforms are created in a tide dominated environment?
* Mudflats
* Sand flats
* Salt marshes
* Mangroves
* Deltas
32
What landform is created in awind dominated environment?
* Sand dunes
33
What impacts do waves have on the coastline?
* Coastlines are not uniform, so the depth of water around a coast varies
* Waves are refracted, so energy is concentrated around headlands, but reduced around bays (headlands shelter them)
* Wave energy decreases as water depth decreases
* Refraction is not always fully achieved resulting in logshore drift
34
What is coastal morphology?
* The shape and struture of coastal landscapes, and their features
35
How is the morphology of a coastline determined?
* Lithology - physical characteristics of the rock
* Relief and slope - cliff profiles
* Rock type
* Permeability
36
What makes up the lithology of a coastline?
* Strata
* Bedding planes
* Joints
* Folds
* Faults
* Dips
37
What are strata?
* Layers of rock
38
What are bedding planes?
* Natural breaks in the strata
* Caused by gaps in time during periods of rock formation
| Horizontal cracks
39
What are joints?
* Fractures in the rock
* Caused by contraction of sediments as they dry out, or by earth movement during tectonic uplift
| Vertical cracks
40
What are folds?
* Formed by pressure during tectonic activity which makes rocks buckle and crumple
41
What are faults?
* Formed when the stress/pressure a rock is subjected to exceeds its internal strength
-The fault then slips or moves along the fault plane
42
What are dips?
* The angle rock strata lie at
-It can be a seaward or landward dip
-Cliffs with a seaward dip have a gentler coastline
43
What factors determine a cliff profile?
* Relief is affected by geology
* Relationship between rock type, lithology and rock profiles
* Cliff profiles are subject to marine processes, and sub aerial processes
44
What are some types of chemical weathering?
* Carbonation
-CO2 dissolves in rainwater, forming carbonic acid
-this reacts with the calcium carbonate in limestone, chalk, marble
* Oxidation
-Rocks with metallic elements react with oxygen in air/water and 'rust'
* Hydrolysis
-Combination of water (as a weak acid), reacting with minerals in the rock
45
What are some types of mechanical/physical weathering?
| Physical - Fracture and break down of rocks into fragments
* Freeze-thaw weathering
-Water expands when it freezes
* Salt crystals
-Salt water goes into cracks, and the water evaporates so salt is left behind
-This builds up and applies pressure to the crack
* Wetting and drying
-Water contracts when it is dry, so causes cracks
46
What are some types of biological weathering?
| A form of physical weathering
* Growing plants
-Roots can widen cracks
* Burrowing animals
47
How does geology influence the morphology of a coastline?
* Rocky type can influence permeability
-Affects the rate at which it is eroded, and the features formed
48
What is igneous rock?
* Rocks which have a crystalline structure
* They are resistant and impermeable
* Formed when magma cools
| e.g. granite, basalt, diorite
49
What is sedimentary rock?
* Are formed from the accumulation of sediments of other rocks by deposition - these can be lithified
* Jointed sedimentary rocks are permeable - e.g. sandstone and limestone
* Other sedimentary rocks have air spaces between their particles making them porous - e.g. chalk
50
What are metamorphic rocks?
* Existing rocks undergo conditions with extreme temperatures, and pressure
| e.g. schist, slate, marble
51
What are some erosion rates for different types of rocks?
* Glacial till - 1-10m/yr
* Sandstone - 1cm-1m/yr
* Limestone - 1mm-1cm/yr
* Granite - 1mm/yr
52
What factors affect the rate of coastal recession?
* Wave type/energy
* Weathering
* Human activity
* Mass movement
* Geology
* Morphology
53
What is a concordant coastline?
* Rock type runs parallel to the shoreline (in line with)
* Often produces straighter coastlines
54
What is a discordant coastline?
* Rock type runs perpendicular to the sea
* Often produces headlands and bays
55
What is hydraulic action?
* The force of water against the coast
* The waves enter the cracks (faults) in the coastline, and compress the air within
* When the wave retreats, the air in the crack expands, causing a minor explosion
56
What is solution?
* The chemical action of sea water
* The acids in the salt water dissolve rocks on the coast - limestone and chalk are particularly prone to this process
57
What is abrasion?
* The coast is worn down by material carried in the waves
* Waves through these particles against the rock, sometimes at a high velocity
58
What are sub-aerial processes?
* Include weathering and mass movement
* Operate on the cliff face to weaken it and provide material for coastal erosion
59
What is attrition?
* Materials carried by the waves bump into eachother, and so are smoothed and broken down into smaller particles
60
What is differential erosion?
* The altering rate of erosion on soft and hard rock
61
How is a wave-cut platform formed?
* Destructive waves hit the rock face between the high and low water mark
* Waves undercut the rockface forming a wave-cut notch - rock overhangs this notch
* After constant attack by destructive waves, the overhanging rock collapses, forming a wave-cut platform
62
How are caves formed?
* Cracks at the base of the headland become exposed thorugh hydraulic action - they are widened
* Cracks widen further by weathering processes
* Wave refractionmeans destructive waves concentrate their energy on the sides - deepens cave
63
How are arches formed?
* If 2 caves are aligned, waves may cut through the rock in the middle to form an arch
64
How are stacks formed?
* The arch becomes unstable and collapses under its own weight
* This is aided by marine erosion and sub-aerial processes (weathering)
65
How is a stump formed?
* The stack is eroded at its base, creating new wave-cut notches
* Sub-aerial processes continue to weaken the stack from above
* The stack eventually collapses
66
What is longshore drift?
* The process of material being transported along the coastline
67
How does longshore drift work?
* Waves (that carry sediment) approach the coast at an angle - because of prevailing winds, and the gravitational pull of the moon
* This is SWASH
* BACKWASH is the motion of receding waves (carrying sediment) - this always happens at a right angle
68
What is lateral shift?
* The net effect of movement up and down the beach
69
What is suspension?
* Fine particles of silt that hang in the water to be transported
70
What is solution - transportation?
* Minerals dissolve in the water to be transported
71
What is saltation?
* Stones and pebbles bounce along the bed
72
What are tides?
* Tides change the water levels
* Caused by the gravitational forces exerted on the earth by the moon
73
What is traction?
* Rocks and boulders are rolled along the bed by the force of the water
74
What does a high tide mean?
* It will lead to strong tidal currents as the tides rise and fall
* They are usually strong near estuaries and are key in transporting sediment
75
What is tidal range?
* The difference in height between high and low tides
76
What is terminal groyne syndrome?
* The consequence of groynes starving the beach down the coast while building it at another point
77
What is a spit?
| Give an example
* A sand or shingle beach ridge, extending beyond a turn in the coastline (usually greater than 30^o)
| Spurn head, Holderness
78
How is a spit formed?
* At the turn, longshore drift current spreads out and loses energy - leading to deposition
* The length of a spit is determined by the existence of secondary currents causing erosion - either the flow of a river, or wave action
79
How do bay head beaches form?
| Give an example
* A swash feature
* Waves break at 90^o to the shoreline and move sediment into a bay where a beach forms
* Due to wave refraction, erosion is concentrated at headlands, and the bay is an area of depostion
| Lulworth cove, dorset
80
What is a tombolo?
| Give an example
* A sand or shingle bar that attaches the coastline to an offshore island
| St Ninians tombolo, Shetland
Chesil beach, Dorset
81
How are tombolos formed?
* Due to wave refraction around an offshore island that creates an area of calm water and deposition between the island and the coast
82
What is a barrier beach/bar?
| Give an example
* A sand or shingle beach connecting two areas of land with a shallow water lagoon behind
| Chesil beach, Dorset
83
How is a barrier beach/bar formed?
* A spit grows so long that it extends across a bay, closing it off
84
What is a cuspate foreland?
| Give an example
* Triangular shaped feature extending out from the shoreline
| Dungeness, Kent
85
What is a cliff, and how can it be formed?
* Vertical or sloping wall of rock
* Result from a number of processes:
-Geological, sub-aerial, marine, human activity
86
How is a cuspate foreland formed?
* There is debate about their formation
-Could be from the growth of two spits from opposing longshore drift directions
87
How can dips be formed?
* Tectonic forces can tilt and deform layers of rock so they dip at an angle
88
What is produced by a seaward dip?
* Gentle cliffs
* They are less stable, because loose material can slide down the bedding planes by mass movement
89
What do landward dipping beds produce?
* Steeper cliffs, but they are more stable
90
What does a vertical dipping bed produce?
* Steep cliffs
91
What does impermeable rock overlaying permeable rock mean?
* Percolation is limited, and the cliffs are more stable
* Mass movement is prevented
| Percolation=the slow movement of fluids through a porous structure
92
What does permeable rock overlaying impermeable rock mean?
* Water may soak into the cliff
* Slope failure is more likely as water builds up between the junction of the two rocks
93
How does latitude affect the coastline?
* In the tropics, low wave energy and high rates of chemical weathering produce low gradient cliffs
* In high latitudes there are low gradients, as the glacial processes produced large amounts of cliff based materials
* Temperate regions tend to have the steepest cliffs
-The rapid removal of debris by high energy waves prevents the build up of material at the base
94
What are sand dunes made of and where are they found?
* Wind blown sand
* They are stabilised by plant succession
* On low energy coastlines e.g. Northumberland
95
What are halophytes and xerophytes?
* Halophyte: a plant that can survive in very salty conditions
* Xerophyte: a plant that can survive in conditions with little water
96
How can depositional features be stabilised?
1. Bare ground is colonised by pioneer species - these bind sand or mud with their roots, and add nutrients when they die/decay
2. Creeping plants with leaves keep moisture in the sand/mud
-These changes allow new species
3. Invaders provide shade and improve the soil
4. As the environment changes, new species colonise until it is stable
5. The final colonisers are trees, in the climax community
97
What is an embryo dune?
* Closest to the sea, and the smallest
* Contain very few species (pioneer species) -e.g. couch grass
98
What is a mobile dune?
* Yellow dunes
* Larger dunes
* Contain marram grass
* Come after embryo dunes
99
What is a semi fixed dune?
* Grey dune
* Have other plants beside marram grass
* Come after yellow dunes
100
What is a fixed dune?
* Come after semi-fixed dunes
* Have almost complete vegetation cover
101
What are dune slacks?
* Areas which develop where the sand becomes eroded, so that the water table is reached
* The sand forms a damp depression, and the area is prone to flooding
* After fixed dunes
102
What is the climax?
* Sand dunes that have developed into scrub or woodland
* Are the oldest and last type of dune
103
What is a salt marsh, and where can they be found?
* Areas of flat silty sediments
* Accumulate around estuaries or lagoons
* Develop in:
-sheltered areas where deposition occurs
-where salt and freshwater meets
-Where there are no strong tides or currents to prevent deposition
104
How do plants help maintain depositional landforms?
* They dissipate wind energy - this leads to more depostion and less erosion
* When plants die and decompose they give organic matter which can:
-Help retain moisture and water
-Add nutrients so other species can colonise
* Their roots can bind and hold sediment, and help retain moisture
105
How do salt marshes form?
* As mud flats develop, halophytes e.g. eel grass begin to colonise and stabilise them
* Halophytes e.g. cordgrass help slow down tidl flow and trap more mud and silt
* As sediment accumulates, the surface becomes drier and different plants colonise e.g. sea asters
* Creeks divide up the marshes
106
What is solifluction?
* Occurs in areas of permafrost - the top layer of soil thaws in the warmer summer, but the layer below stays frozen.
* The surface layer becomes saturated as frost melts and flows over the subsoil and rock below
* Movement is 5cm to 1m per year
107
What is earth/mudflow?
- Heavy rain causes a reduction in friction and the earth turns into mud and flows slowly over the bedrock
108
What is soil creep?
* Individual particles of soil moving downhill
* It is the slowest form of mass movement, but it is almost continuous
109
What is rock slide?
- Rocks that are jointed or have bedding planes parallel to the slope are susceptible to landslides
- Increase in water can reduce friction and make this easier
- The underlying rock which slabs slide over is called the slip plane
110
What is rock fall?
- Occurs when mechanical weathering breaks large chunks of the cliff away
- The cliff has to be at an angle of 40 degrees or more
- Material that breaks off is called scree
111
What is the difference between sliding and slumping?
- Slumping is a rotational movement
112
What type of mass movement occurred?
| Holbeck hall case study
- Slumping, as there was rotational movement and the cliff was saturated
- This led to a mud/debris flow
| In Holderness in North Yorkshire, under a large cliff
113
When do slumps occur?
- In saturated conditions
- On moderate to steep slopes
- When clays or sand are overlying more resistant or impermeable rock like limestone or granite
- Terraced cliffs can be formed if it is repeated
114
What were the antecedent conditions?
| Holbeck hall case study
* There was 140mm of rain in the two months before the slide happened
* There were issues with the drainage of the slope which led to a water pressure build up
115
What is emergence?
- The impact of a fall in sea level - marine regression
116
What is a eustatic change?
- Global scale sea level change caused by a change in the volume of water in the ocean
117
What is an isostatic change?
- Local scale sea level change caused by a change in the level of the land relative to the level of the sea
118
What is the rock type here?
| Holbeck hall case study
* The cliff is made up of permeable rocks - glacial till (sandy and silty clay) - such as sandstone
119
What is submergence?
- The impact of a rise in sea level - marine transgression
120
What are three examples of isostatic changes?
- Tectonic uplift
- Glacial compression/decompression
- Sediment accumulation
121
What are three examples of eustatic changes?
- Sea floor spreading
- Climate change
- Glaciers
122
What is tectonic uplift?
- The movement of tectonic plates
- For example, when mountains are forming, the plates are being pushed upwards - as the land rises, it seems as though the sea levels are falling
123
What is sediment accumulation?
* The weight of the sediment load causes the land to subside, making it seem as though sea levels have risen
124
What is glacial compression/decompression?
* The weight of land ice (glaciers) pushes the land downwards - isostatic subsidence - making it seem as though sea levels have risen
* When the ice melts, there is no longer the weight of the glaciers on the land, so it starts to lift again - isostatic recovery/rebound - making it seem as thoigh sea levels have fallen
125
How does climate change lead to a eustatic change?
- Climate change and global warming mean that the temperature of the water increases
- As the temp increases, the particles gain more kinetic energy, and therefore expand causing sea levels to rise
- Thermal expansion
- An increase in global temps, also means more land base ice melts
126
How does sea floor spreading cause a change in sea level?
* As new rock is formed, the size of the basin increases, making it seem as though the volume of water has decreased
* Sea floor spreading relates to continental drift - if two continents collide, there is also an increase in the size of the basin as there is a reduction of area of continental crust
127
How do glaciers create eustatic changes?
- During glacial periods, more of the earths water is stored on land, so the volume of water in the sea decreases
- During interglacial periods, the glaciers melt so there is an increased volume of water in the sea, so sea levels rise
128
What is evidence that glaciers melting causes sea level changes?
* If the two main ice caps (Greenland and Antarctica melted), then the oceans would rise by 66 metres
129
What is some evidence for thermal expansion?
- From 1880 to 2012 , average global temperatures rose by 0.85C - in this time, sea levels rose by 21cm
- In the future, thermal expansion will play the most significant role in causing sea levels to rise
130
What is some general evidence that sea levels have changed?
- Scientists estimate that by 2100, average sea levels will rise between 30cm and 1m
- 1993-2010, sea levels rose by an average of 3.2mm, but they are rising much faster now
131
When was the last ice age?
- 18,000 years ago
- Ice covered about 30% of the land in the world
- In Britain, ice was up to 3km thick
132
What impact did the last ice age have on sea levels?
- Then, the sea level was at least 120m lower than it is today (lots of water was stored as ice)
133
Where can isostatic changes be seen?
* Since the last ice age, Scotland has been rising due to isostatic rebound
* Due to this, there is isostatic subsidence in the south of England
134
What is a ria?
- A submerged river valley
- e.g. Kingsbridge, Devon
- They are part of the lower course, where flood plains may be completely drowned
135
Describe what a ria looks like.
- Plan view - winding profile
- Cross section - quite shallow, becoming increasingly deep towards the middle (where the original river channel is)
- Long profile - quite even, with water at a fairly uniform depth
136
What is a fjord?
- A submerged glacial valley
- e.g. Lisefjord, Norway
- Very steep sides, and the water is very deep
137
Describe what a fjord looks like.
- Plan view - Straight profile, the glacier has cut off any interlocking spurs
- Cross section - steep valley sides (V-shaped), water is uniformally deep
- Long profile - have a shallower section at the seaward end
138
What is a raised beach?
| An emergent landform
- Areas of former wave cut platforms, and their beachesleft at a higher level than present sea level due to changes
- Found at a distance inland from the present coastline
- e.g. Little Gruinard, in NW Scotland
139
Why is the Maldives at risk to sea level rises?
| Where is the maldives?
- The highest point in the country is 2.3m above sea level
- A rise of 50cm by 2100 would mean the Maldives losing 77% of its land area
- Areas above sea level would become vulnerable to storm surges and erosion
- It has a population of 400,000 spread across 1200 islands
| The indian ocean
140
What is an example of tectonic uplift?
- Turakirae head, New Zealand
- Tectonic uplift from a major earthquake
141
What is an abandoned cliff line?
| An emergent landform
- Cliffs with wave cut notches, caves, arches and stacks (behind the raised beach) - due to marine erosion when sea levels were higher
142
What are the environmental impacts of sea level rise?
| Kiribati case study - the most at risk island to sea level rise
* 200m of marine transgression (land has dissapeared on one of the islands)
* Pollution, waste disposal and poor sanitation (lots of waste is brought by tides)
* King tides (extreme high tides) used to be non-existent
*
143
What are the social impacts of sea level rise?
| Kiribati case study - the most at risk island to sea level rise
* People are losing their homes and farmland
* Strain on water infrastructure
* Many have had to relocate - mass migration causes overcrowding and other problems
* Loss of tradition, culture and a connection with homeland
144
What is Kiribati doing to manage this?
| Kiribati case study - the most at risk island to sea level rise
- Building concrete and stone sea walls
- Planting mangroves (affordable and effective)
- Reduced tuna fishing to cut carbon emissions
- Migration with dignity - people sent for job training in Australia
145
How much have sea levels risen by?
| Kiribati case study - the most at risk island to sea level rise
* By 2050, the islands will see an additional 6-12 inches of water
* Since 1993, sea levels have risen at an average of 3.2mm per year
146
What are the economic impacts of sea level rise?
| Kiribati case study - the most at risk island to sea level rise
- Reduced tuna fishing, so money is no longer made from this
147
What is a dalmation coastline?
| Give an example.
* A submergent landform
* Made up of offshore islands and coastal inlets running parallel to the coastline
-The offshore islands are often long and narrow, seperated from the coast by narrow sea channels
| Dalmatia in croatia
148
How are dalmation coastlines formed?
* They are produced on a concordant coastline
* Valleys are created on the coastline that are parallel to the sea, so when the sea level rises, there are parts of the land that remain above the water (new islands are created)
149
What is a haff coastline?
| Give an example.
* An emergent landform
* Long ridges of sediment with sand dunes on top
* There are lagoons created between the ridges and the shore
-A lagoon is a haff, it is formed between the land and the bar formed from material deposition
| Along the southern Baltic coastline
150
How are haff coastlines formed?
* Stretches of the coastline have been exposed by decreasing sea levels, or isostatic rebound
* They are features of a low energy coastline - sediment is deposited by constructive waves
151
What is the Purbeck coast also known as?
| Purbeck coast case study
- The jurassic coast
152
What landforms can be found along the coast?
| Purbeck coast case study
- Headlands and bays
- Coves
- Arches, stacks and stumps
153
What rock types are found on the coast (order from newest to oldest)?
| Purbeck coast case study
- Chalk limestone - 97
- Greensand (sandstone) - 125
- Wealden beds (sandstone clay) - 140
- Purbeck beds (limestone mud) - 147
- Portland stone (limestone) - 150
| Number in millions of years
154
What rock type is found at swanage bay?
| Purbeck coast case study
* Has some unconsolidated wealden clay
* This can be easily eroded
* On a discordant coastline, so a bay is formed
155
How was durlston head formed?
| Purbeck coast case study
* Portland and purbeck limestone
* On a discordant coastline
* Steep cliffs have been created, as well as peveril point
-The limestone is jointed (created lines of weakness) that can be more easily eroded in places
156
How was stair hole created?
| Purbeck coast case study
- The sea eroded through the limestone and clays to create a small cove
- The lulworth crumple (limestone folding) can be seen here
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How was warbarrow bay created?
| Purbeck coast case study
- Less resistant clay was eroded by the sea to expose the layers of chalk behind - now form the cliffs of the bay
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How was lulworth cove created?
| Purbeck coast case study
- The sea gradually eroded the resistant limestone at the entrance
- Then there was rapid erosion of the less-resistant clays behind, so a cove was formed
159
How was durdle door created?
| Purbeck coast case study
- The sea eroded the harder limestone, and then the softer stone after
160
What landforms can be found here?
| Holderness coast case study
* Arch, stack
* Wave cut platform
* Spit
161
What is the geology of the coast?
| Holderness coast case study
- Consists of chalk and boulder clay
- Formed from glacial till
162
How does the geology affect the coastline?
| Holderness coast case study
- It is very rapidly eroding
- At an average rate of 1.8m per year
- The rock can be easily saturated, causing slides and slumping
- At the foot, fine clay is removed by waves, so there is little left to form beaches and protect the cliffs from winter storms and high tides
163
What are the waves like here?
| Holderness coast case study
- The dominant waves are from the NE direction (largest fetch)
- There are mainly destructive waves
- Longshore drift carries material eroded south
164
How does the weather here affect the coast?
| Holderness coast case study
- Winter storms produce stronger waves and higher sea levels
- Rain saturates the rock more
165
How is spurn head (the spit) created?
| Holderness coast case study
- Sediments are brought here by longshore drift
- The low energy environement next to the estuary allows the spit to form
166
What has the humber estuary done?
| Holderness coast case study
- It has helped the wind, tides and river processes to develop dunes, mudflats and salt marshes (behind the spit)
167
How was flamborough head created?
| Holderness coast case study
- The rock here is resistant chalk, and forms a headland
- Horizontal bedding planes assist in the development of wave cut platforms
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What are the human factors affecting the coast?
| Holderness coast case study
* Increased urbanisation can speed up/cause slumping
* Interfering with natural process e.g. terminal groyne syndrome starves beaches down the coast of sediment, making them more prone to erosion
-Groynes at Hornsea and Mappleton, starve Great cowden of sediment
* Global warming leads to sea level rise and more storms
