Coasts Flashcards
Coastal landscapes, erosion and deposition, risks and management
1
Q
Features of high-energy coastlines
A
- Rocky, cliffs
- Found in Atlantic-facing coasts like Cornwall or Scotland
- Rate of erosion exceeds rate of deposition
- Landforms: headlands, cliffs
2
Q
Features of low-energy coastlines
A
- Sandy/estuarine
- Less powerful waves
- East coast like Northumberland and Lincolnshire
- Rate of deposition exceeds rate of erosion
- Landforms: beaches, spits
3
Q
Examples of hard rock
A
- Basalt
- Granite
- Slate
4
Q
Examples of soft rock
A
- Chalk (on the harder side)
- Clay
- Sandstone
5
Q
What is the littoral zone?
A
Zone between the land and the sea
6
Q
Why is it a littoral zone instead of a coastline?
A
Tides and storms constantly change the shape
7
Q
Short-term factors that affect the shape of a coast?
A
Waves, tides and seasonal storms
8
Q
Long-term factors that affect the shape of a coast?
A
Erosion, sea level changes due to climate change
9
Q
Four sections of the littoral zone?
(from land to sea)
A
- Backshore: above the influence of the waves
- Foreshore: inter-tidal or surf zone
- Nearshore: breaker zone
- Offshore: beyond the influence of the waves
10
Q
How can coasts be classified?
A
- Geology
- Wave energy
- Balance between erosion and deposition
- Changes in sea level
11
Q
What is coastal morphology?
A
The shape and form of coastal landscapes and their features
12
Q
What is coastal recession?
A
Another term for coastal erosion
13
Q
What is lithology?
A
The physical characteristics of particular rocks
14
Q
Types of lithology?
A
- Strata
- Bedding planes
- Joints
- Folds
- Faults
- Dips
15
Q
What is strata?
A
Layers of rock
16
Q
What are bedding planes?
A
Horizontal cracks, natural breaks in the strata, caused by gaps in time during rock formation
17
Q
What are joints?
A
Vertical cracks, fractures caused by contraction or sediment drying out
18
Q
What are folds?
A
Formed by pressure during tectonic activity, which makes rocks buckle and crumple
(e.g. Lulworth Crumple)
19
Q
What are faults?
A
Formed when the stress on a rock exceeds its strength, causing it to fracture. The faults then slip along fault planes.
20
Q
What is a dip?
A
Refers to the angle at which the rock strata lie
(horizontally, vertically, dipping towards the sea, dipping inland)
21
Q
What is a concordant coast?
A
Where bands of more and less resistant rock run parallel to the coast.
22
Q
What is a dalmatian coast?
A
Formed as a result of rising sea levels at concordant coasts.
When valleys and ridges run parallel to each other. When the sea rose and the valleys flooded, the tops of ridges remained above the sea creating islands.
23
Q
What is a discordant coast?
A
The geology alternates between bands of more and less resistant rock, which run at right angles to the coast
24
Q
How do headlands affect waves?
A
Force waves to refract or bend. This increases the wave power. This leads to the steepening of cliffs and eventual arches and stacks.
25
How does a wave react in a bay?
Their energy is dissipated and reduced. This leads to the deposition of sediment forming a beach.
26
Example of a discordant coast
Dorset
Coast consists of alternating bands of Portland limestone and greensands.
Greensands erodes quicker than Portland limestone.
27
How do bedding planes affect a cliff profile?
Bedding planes dip inland = steeper cliff profile
Bedding planes dip towards the sea = gentler cliff profile
28
Examples of igneous rock
Basalt
Granite
29
How do igneous rocks form?
From the crystillisation of magma
30
Why are igneous rocks strong?
They contain crystals which increase the strength and reduce the number of weaknesses which would be exploited by physical processes
31
Difference between intrusive and extrusive igneous rocks
Intrusive - formed from magma inside the Earth
Extrusive - formed when magma escapes through vents on the Earth's surface
32
Average rate of erosion for igneous rocks
0.1-0.5cm a year
33
Examples of sedimentary rock
Limestone
Sandstone
Chalk
34
How do sedimentary rocks form?
The build-up, compacting and hardening of sediments into layers over time by lithification
35
How does the age of sedimentary rocks affect how they erode?
Recently formed rocks = more susceptible to erosion and weathering and erode faster
Older rocks = More resistant to erosion therefore takes longer
36
Average rate of erosion for sedimentary rocks
2-6cm a year
37
Examples of metamorphic rock
Slate
Marble
38
How are metamorphic rocks formed?
A change in the structure of igneous/sedimentary rocks caused by variations in heat and pressure (process called metamorphosis)
39
How is marble formed (marble = metamorphic)
Limestone changing structure due to the re-crystillisation of calcite
40
How do metamorphic rocks erode?
They are resistant to erosion
41
2 types of plants that can grow in sand dunes
Xerophytes - Can withstand periods of dry weather
Halophytes - Can withstand high concentrations of salt from seawater
42
What does a sand dune need to form?
- Continuous supply of sand
- Powerful winds to transport sand
- Obstacles to trap the sand like plants
43
Order of sand dune succession
1. Embryo dunes
2. Fore dunes
3. Yellow dunes
4. Grey dunes
5. Dune slack
1-3 = mobile dunes
4-5 = fixed dunes
44
Examples of plants that typically colonise embryo and fore dunes and their features
- Sea rocket
- Sea crouch
Features:
- Long roots
- Salt tolerant
45
Example of a plant that typically colonises yellow dunes and its features
Marram grass
Features:
- Long roots
- Salt tolerant
46
Example of a plant that typically colonises grey dunes
Heathers
47
Features of destructive waves?
- Cause erosional processes
- High frequency (10-15 waves per min)
- Steep and high
- Circular motion causes the wave to 'plunge' and travel a shorter distance along the beach
- Swash less powerful than backwash
48
Features of constructive waves?
- Low frequency (6-9 waves a min)
- Long and low
- Form gently sloping beaches
- Deposit material
- Swash less powerful than backwash
- Elliptical motion causes the wave to 'spill' and break out further along the beach
49
What is attrition?
Pieces of bedload (material carried in water) hit against each other. This causes them to break and become smaller and more rounded.
50
What is corrosion?
A chemical reaction between the sea water (which is a weak acid) and susceptible rocks like limestone
51
What is hydraulic power?
Causes the breakdown of cliffs due to the force of the water being compressed into cracks in the rock, putting pressure on them to eventually break.
52
What is abrasion?
Where pieces of rock are picked up by waves and hit against the bed, beach or cliff. They wear away over time.
53
How are wave-cut notches formed?
Destructive waves erode the base of a cliff through abrasion
54
Why does a wave-cut notch collapse?
Continued erosion of the wave-cut notch causes the rock above it to become less and less stable until it eventually collapses and the material is washed away
55
How is a wave-cut platform formed?
After multiple collapsing events leading to the cliff retreating, what is left behind is called a wave-cut platform
56
How do the erosional processes lead to the formation of coastal landforms (e.g. caves, arches)?
1. Destructive waves erode weaknesses in the headlands through corrosion and hydraulic action
2. When weaknesses in the rock widen, abrasion becomes more important
3. Over time these processes form coastal landforms
57
How is a cave formed?
Erosion attacks weakness in the headland. When the crack widens into a small, hollowed out area, a cave has formed
58
What coastal landforms are caused by headland erosion?
- Cave
- Arch
- Stack
- Stump
59
Example of an arch
Durdle Door on the Dorset coast
60
How are arches created?
When caves are eroded through the headland, an arch is created
61
How are stacks formed?
When the top of an arch collapses due to gravity, a column called a stack is left behind
62
How are stumps formed?
Continued erosion and weathering causes the stack to breakdown, forming a stump. During high tide, stumps can become submerged. Eventually, the stump will erode and nothing will be left.
63
What is isostatic change?
- Refers to the level of the land
- During an ice age, the weight of the ice forces the land to sink
- When the ice age is finished, the melting ice causes the land to rebound back up
64
4 factors that contribute to sea level change
- Isostatic change
- Tectonic change
- Eustatic change
- Climate change
65
How does tectonic change affect sea levels?
- Causes land to either rise or sink at the boundaries where tectonic plates meet
- A sudden change in the movement of a plate can lead to a rise or fall of the sea bed, causing a change in sea level
- Earthquakes can also trigger tsunamis
66
What is eustatic change?
The rising and falling of sea levels caused by ice ages
67
How does eustatic change affect sea levels?
In ice age = water stored in the form of ice so sea levels fall
After ice age = ice melts and sea levels rise
68
What is a submergent coastline?
When sea levels rise and land stays the same height
69
What is an emergent coastline?
When sea levels fall exposing more land
70
What is a ria?
A flooded valley formed when sea levels rise, often creating an estuary
71
What is a fjord?
A flooded valley formed when a glacier erodes vertically, creating a u-shape
72
Example of a fjord?
Lysefjord in Norway
73
Features formed at submergent coastlines
- Rias
- Fjords
- Dalmatian coasts
74
What are raised beaches/fossil cliffs?
- Caused by isostatic rebound; following an ice age the land rebounds
- This causes the original height of the land to increase
- This leaves behind beaches and cliffs higher than their original position
75
Example of a raised beach/fossil cliff?
Fife, Scotland
76
What type of coastline causes raised beaches/fossil cliffs to form?
Emergent coastlines
77
How much have average sea levels increased 1901-2010
0.19m
(using data from the IPCC)
78
Why has climate change caused sea levels to rise?
The melting of glaciers and ice sheets in places like Greenland and the Arctic
79
Higher sea levels cause higher tides. Why is this bad?
- Higher frequency of coastal flooding
- Removes more material from beaches, leaving cliffs less protected
80
Evidence to show global warming
Between 1983 and 2012, the Northern Hemisphere experienced the warmest 30 years of the last 1,400 years
81
What gases have predominantly caused global warming?
Anthropogenic greenhouse gas (GHG)
82
Why have the levels of greenhouse gases increased in recent centuries?
Industrialisation
83
How will an increased number of storms (caused by climate change) influence the coast?
- Creates more high energy, destructive waves
- Increased energy of sea means more material can be transported longer distance = some areas more vulnerable to erosion
- Frequency of storm surges increases. When combined with sea level rise, these surges will reach further inland and cause more damage.
84
What is dredging?
The removal of sediment from the sea bed for use in construction
85
How does dredging increase the rate of coastal recession?
Causes the depth of the ocean to increase
This increases the occurrence of destructive waves because they can maintain their energy further towards shoreline
86
How does a long period of rainfall increase the rate of coastal recession?
Weakens rock, and in turn, leads to the mass movement of material.
87
How does hard engineering disrupt sediment cells?
By disrupting one area of the coast, further along the coast may be starved of sediment supply, which can then result in the destruction of beaches
88
Example of a place where dredging occurs
Dredging on the coast of California has affected the supply of sediment to the Santa Barbara littoral cell
89
Why is the rate of coastal recession greater in winter than summer?
In the winter there is more stormy weather, which is linked with higher tides and greater wave fetch
90
How can wind direction influence the rate of coastal erosion?
Winds control the movement of waves and a dominant wind direction causes powerful waves to attack the coastline. This happens because the wave has often travelled a long distance.
91
Example of a place where wind direction has affected its rate of coastal erosion
The south-westerly wind directing waves across the Atlantic towards Land's End in Cornwall
92
Difference between anticyclones and depressions
Anticyclones = areas of high pressure
Depressions = areas of low pressure
93
How does the pressure of the a weather belt affect coastal erosion?
High pressure belts make calmer weather, leading to less coastal erosion.
Low pressure belts cause unsettled weather conditions.
94
Why does coastal recession increase during high tide?
Waves can reach further towards the shore
95
Why is the removal of mangroves bad?
Mangroves help to defend against coastal erosion as their roots strengthen the soil
96
Example of a place that is threatened by the removal of mangroves?
The Maldives
97
How do mangroves protect against coastal erosion?
As well as strengthening the soil, the trees dissipate the wave's energy before it reaches land
98
Why do many people choose to live near dangerous coastlines?
Either for recreation (beautiful scenery, good nightlife, etc) or for employment
99
Why is Bangladesh at risk from rising sea levels?
Bangladesh is very low-lying so storm surges in the Bay of Bengal will cause lots of damage
100
Why has climate change increased the chances of storm surges?
Rising global temperatures are causing oceans to warm, triggering low-pressure systems and increased stormy weather
101
Storm surge definition
A rising of the sea as a result of wind and atmospheric pressure changes associated with a storm
102
How do sea walls work to protect the coast?
They are made out of hard concrete that deflects waves. They are often curved to dissipate the wave's energy and refract it back towards the sea.
103
What are the benefits and costs of sea walls?
Benefits:
- Long-term as concrete needs little maintenance
Costs:
- They create a strong backwash that can undercut the wall
- They are expensive to build and maintain
104
What are offshore breakwaters?
Rocks placed in a parallel line to the shore
105
What are the benefits and costs of offshore breakwaters?
Benefits:
- Provide calm conditions behind the breakwater so the beach can be used recreationally
Costs:
- Can cause wave patterns to change
- Expensive to install
106
What is rip rap and how does it protect the coast?
A pile of boulders often placed in front of sea walls to dissipate the wave's energy.
107
What are the benefits and costs of rip rap?
Benefits:
- Long-lasting
- Relatively cheap
Costs:
- Provide a hazard for people accessing the beach
- Gaps between the rocks still allows for some erosion
108
What are revetments and how do they protect the coast?
Angled walls placed just offshore to assist in breaking down the force of the waves to reduce their ability to erode the coastline.
109
What are the benefits and costs of revetments?
Benefits:
- More cost-effective than a sea wall
Costs:
- Often require regular maintenance
- Can create access problems to the beach
110
What are groynes and how do they protect the coast?
Stone or wooden fences that stick out at 90 degrees from the coast. They stop material being transported through longshore drift.
111
What are the benefits and costs of groynes?
Benefits:
- They create wider beaches, which slows down waves and reduces their energy
- Relatively cheap
Costs:
- Beaches further down the coast get narrower (terminal groyne syndrome) so more erosion takes place
112
Cost of groynes
£150-250 per metre
113
Cost of a sea wall
£3,000-10,000 per metre
114
Cost of rip rap
£1,300-6,000 per metre
115
Example of groynes
Hornsea
116
Example of revetments
Hornsea
117
Example of a sea wall
Scarborough
118
Example of an offshore breakwater
Ulrome - Skipsea
119
Example of rip rap
Scarborough
120
What does ICMZ stand for?
Integrated Coastal Management Zone
121
Why is the ICZM method used in coastal management?
- Holistic approach (considers ALL factors)
- Considers economic, social and environmental factors
- Careful consideration of the most effective and sustainable way to manage a coastline
122
When was ICZM created?
1992 by world leaders at the Earth Summit
123
What are the factors considered using ICZM?
- The risk to buildings
- Impact on local economy
- Impact of coastal recession and flooding on the natural environment
124
What are the benefits of ICZM?
- Promotes environmental conservation
- Promotes efficient use of resources to reduce unnecessary costs
- Tries to reduce the potential loss to all stakeholders that rely on the coast for their livelihood.
125
What is a shoreline management plan (SMP)?
- Each sediment cell (there are 11 in the UK) has one
- 4 key management approaches
- Each coastline is carefully considered to determine which SMP is most appropriate
126
4 SMP management approaches
- No active intervention
- Strategic realignment
- Hold the existing defences
- Advance the line
127
SMP approach:
No active intervention
No management used along this coastline with physical processes allowed to work naturally
128
SMP approach:
Strategic realignment
Physical processes are allowed to work naturally, with monitoring and intervention only when necessary
129
SMP approach:
Hold the existing defences
Maintaining existing defences to make sure they continue to be effective
130
SMP approach:
Advance the line
The construction of new engineering techniques to protect the coastline from further recession
131
What is a cost-benefit analysis used to determine?
The economic value of a coastline and if intervention is needed to protect the surrounding land
132
What is an environmental impact analysis used to determine?
To assess the short and long-term implications of using management strategies on the environment
133
Population of Happisburgh
1,400
134
Location of Happisburgh
Norfolk Coast
135
Name of the group aiming to protect Happisburgh's coastline
Coastal Concern Action Group (CCAG)
136
How fast is Happisburgh eroding?
Approx 0.9m a year
137
Why did the rate of erosion at Happisburgh increase in the '90s?
The wooden defences began to fail
138
What shoreline management plan is in place at Happisburgh?
No active intervention
139
What are the CCAG group campaigning to change the Happisburgh shoreline management plan to?
Managed realignment
140
What hard engineering strategy is in place at Happisburgh?
Rip-rap (since 2012)
141
Why is the local government not installing coastal defences at Happisburgh?
They do not believe it is cost effective
(i.e. more money spent protecting the coast than the village is worth)
142
What waves are eroding Happisburgh?
Destructive ones from the North Sea
143
What is hydraulic action?
The force of the waves crashing against the cliff compress air in cracks which breaks up the rock
144
What is abrasion?
Waves carrying beach material throw it against the cliff wearing it away
145
What is longshore drift?
The process of sediment moving along a beach through swash and backwash
146
What causes the direction of swash?
Prevailing wind
147
What causes the direction of backwash?
Gravity
148
What is a spit?
Long fingers of sand which stick out from the coastline and are slightly curved
149
How is a spit formed?
When the coast changes direction at an estuary, longshore drift continues to deposit sand
150
Where are salt marshes often found?
Behind spits
151
Why do spits usually not meet the other side of the coast?
The river has energy to move the sediment
152
What is a bar?
When a spit grows across a bay
153
What is a lagoon?
An area of water found behind a bar
154
How are beaches formed?
Constructive waves depositing material
155
Which beach is steeper - sand or shingle?
Shingle = steeper
Sand = gentle slope
156
What is a tombolo?
When a spit stretches across the mainland to join an offshore island
157
What are cuspate forelands?
When two spits eventually meet and sediment is trapped, causing new land to form
158
What are the 3 parts of a sediment cell?
Sources = sediment generated
Transfers = sediment moves along coast
Sinks = sediment deposited
159
What is a sediment cell?
A closed system which describes the movement of sediment around a coast
160
How many sediment cells are there in the UK?
11
161
Sediment cell: sources
- Subaerial processes
- Erosional processes
- Sediment from rivers
162
Sediment cell: transfers
- Longshore drift
- Winds
- Tides
163
Sediment cell: sinks
Depositional landforms, for example:
- Spits
- Bars
- Beaches
164
3 types of weathering
- Biological
- Mechanical
- Chemical
165
What is weathering?
The breakdown of rocks where they are
166
What is biological weathering?
When rocks are broken down by living things
167
Examples of biological weathering
- Plant roots
- Algae can release chemicals
- Animals scrap and secrete acid on the rock
168
What is mechanical weathering?
When rocks are broken down without their chemical composition being changed
169
What is the main type of mechanical weathering?
Salt weathering
170
What is the process of salt weathering?
- Seawater gets into cracks in rocks
- Salt crystals form when the sea water evaporates
- Crystals expand and put pressure on the rock until it breaks
171
What is chemical weathering?
When rocks are broken down because their chemical composition changes
172
What is the main type of chemical weathering?
Carbonation
173
What is the process of carbonation?
- Takes place when it is warm and wet
- Carbon dioxide dissolves in rain making a weak carbonic acid
- Acidic rainwater attacks rocks which contain calcium carbonate
174
2 types of sub-aerial processes
Weathering
Mass movement
175
What is mass movement?
When rocks and loose material slide down slopes
176
When does mass movement occur?
When gravity overcomes the force supporting the material
177
Mass movement:
Rockfall
When material breaks apart due to erosion/weathering and falls down the slope
178
Mass movement:
Slides
When material moves down the slope in a straight line
179
Mass movement:
Slumps
When material moves down the slope with a rotation
180
What causes slumps to move with a rotation?
A mixture of heavy rainfall and erosional processes
181
When do slumps usually occur?
When unstable permeable rock overlays more stable impermeable rock
182
How do people in developed countries suffer economically from coastal recession?
If their house is at risk, it can be difficult to get any insurance and/or sell the house, so they lose their house and often get no compensation
183
What rail line was damaged by heavy storms in 2014?
South-west rail line
184
How long was the south-west railway line shut for?
2 months
185
What was the estimated economic cost from the shutting of the south-west railway line?
£1.2bn
186
What industries were disrupted by the closure of the south-west railway line?
Fishing, tourism
187
What developed country is at risk from rising sea levels?
Australia
188
If sea levels continue to rise, how much $ worth of infrastructure is Australia expected to lose?
$216bn
189
How many islands are included in the Maldives?
Over 1,000
190
What industry does the Maldives rely on?
Tourism
191
What developing country is at risk from rising sea levels?
Maldives
192
How has coastal flooding affected the Maldives?
- Housing lost
- Threatens freshwater sources
- Tourist industry declining
193
What are some soft engineering techniques?
- Dune stabilisation
- Cliff re-grading
- Beach nourishment and reprofiling
194
What is dune stabilisation?
The creation or protection of sand dunes
195
How can dunes be stabilised?
Nourishment or planting vegetation
196
Advantages and disadvantages of dune stablisation
Advantages:
- Natural barrier for flooding
- Support wildlife habitats
Disadvantages:
- Only a small area protected
- Ineffective during powerful storms
197
What is cliff re-grading?
Involves restructuring and supporting the cliff to to prevent further collapse from sub-aerial processes
198
Advantages and disadvantages of cliff re-grading?
Advantages:
- Maintains the cliff
- Provides natural habitats for plants and wildlife
Disadvantages:
- There are risks associated as often doesn't go to plan and cliffs end up collapsing in the process
199
What is beach nourishment/reprofiling?
Involves moving material from the upper sections of the beach to elsewhere. It slows down waves by widening beaches.
200
Advantages and disadvantages of beach nourishment?
Advantages:
- Maintains the beach for tourist use
Disadvantages:
- Removing material from the beach threatens creatures (e.g. corals)
- Expensive
- Must be repeated
