Coasts Flashcards
What are inputs?
Things that enter the system from outside sources/systems
What are flows/ transfers?
Processes of movement within a system
What are stores / components?
Parts of a system not necessarily in motion
What are outputs?
Material / energy moving out of a system
What are feedbacks?
Can be positive (flow leads to increase/ growth) or negative (flow leads to decrease / decline)
What does fluvial mean?
River based
What does dynamic equilibrium mean?
A system in dynamic equilibrium has inputs and outputs of energy and matter that balance
Factors that influence dynamic equilibrium in coasts
1) Supply of sand
2) Energy of the waves
3) Sea level changes
4) Location of the shoreline
What are Landforms?
Individual features which are crested by coastal processes.
What are landscapes?
The entire area of sea, coastline, and immediate land behind the sea front. Within the landscape are characteristic land forms.
What are the four sources of coastal energy?
- Wind
- Waves
- Currents
- Tides
How does the sun create wind?
The sun heats different parts of the globe at different rates. Warmer areas have higher pressures, causing air to rise, creating low surface pressure. Gas will move from high pressure to low pressure areas, creating wind.
Tides definition
The periodic ride and fall in the level of the sea, caused by the gravitational pull of the sun and the moon
Spring tides
More extreme low / high tide
The sun and the moon’s gravity is pulling the oceans on the same plane
Neap tide
Less extreme low/ high tides
The sun and moon are pulling on opposite plains
What does a low tidal range cause?
Increased, concentrated erosion
What does a large tidal range cause?
Increased transportation and deposition of sediment, due to increased energy
Constructive waves
Strong swash, weak backswash. More deposition
What are the sources of sediment?
- Rivers
- Cliff erosion
- Offshore sediment
- Wind
What is a sediment cell?
A stretch of coastline within which sediment is more or less contained. An (almost) closed system.
How many sediment cells are there on the UK coastline?
11.
Sub Aerial geomorphological processes
-Weathering
- Mass movement
Marine geomorphological processes
- Erosion
- Transportation / deposition
Mass movement
The downhill movement of weathered material under the force of gravity
The 5 types of mass movement
- Soil creep/ solifluction
- Mudflow
- Run off
- Landslide
- Rock fall
What is rock fall?
When rocks collapse from a VERTICAL cliff and fall to the ground
What is mud flow
Earth any mud flowing downhill over weak bedrock such as clay
What is the run off mass movement?
When overland flows occur down a slope or cliff face, small particles are moved with it
What is a landslide
Rocks moving very rapidly down a planar surface
What is soil creep?
An extremely slow movement of individual particles down hill. Involves particles rising and then returning down due to gravity
What are the marine processes?
- Erosion
- Transportation
- Deposition
5 types of erosion
- Hydraulic action
- Wave quarrying
- Abrasion
- Attrition
- Solution
What is hydraulic action?
The impact on rocks of the sheer force of the water itself.
What is wave quarrying?
A braking wave traps air as it hits the cliff face. The air is compressed into tiny gaps causing huge pressure. As the water retreats there is an explosive effects which weakens the cliff face
What is abrasion?
Eroded material being thrown at the rocks by waves.
What is attrition
Rock which are carrying our abrasion are slowly worn down into smaller and rounded particles.
What is solution?
Not common with sea water as it tends to be alkaline. However, where sea water interacts with fresh water supplies carbon based rocks may be dissolved.
What are the four types of transportation of sediment?
- Traction
- Saltation
- Suspension
- Solution
What is traction?
Large particles like boulders are pushed along the sea bed by the force of the water
What is saltation?
Pebble sized particles are bounced along the sea bed by the force of water
What is suspension?
Small particles like silt and clay are carried along in the water
What is solution?
Soluble materials dissolve in the water and are carried along
What are the two factors that influence what type of transportation takes place?
- Particle size
- Energy
What is littoral drift?
The movement of material along a beach, usually at the angle of the prevailing wind
Concordant coast lines
Rocks on these coastlines run parallel to the sea
Discordant coastlines
Rocks on these coastline run perpendicular to the sea.
Why might the creation of wave cut platforms lead to negative feed back on the rate of erosion?
The waves will have to travel over shallow water ( the platform) before getting to the cliff. Therefore the waves are more likely to break before hitting the cliff, losing energy. Hence, erosion decreases.
Describe the formation of caves, arches, stacks and stumps.
A headland is eroded, causing faults in the rock to become a cave. After more erosion, the cave erodes through the other side to make an arch. Eventually, the arch collapses leaving a stack. This is further eroded until it eventually collapses to leave a stump.
What does the cliff profile refer to?
How steep the cliff face is at its meetings point with the sea
What are sedimentary rocks?
Rocks formed as layers of depositional sediment, either on the bends of oceans or rivers.
What is the bedding plane of a cliff face?
The point where layers of sedimentary rock are joined. Provides weakness for weathering
What happens if the bedding planes are horizontal in a cliff?
The cliff profile with be steep and stable
What happens if the beddings planes are titled downwards away from the coast to due tectonic activity?
A sloped, stable cliff is created
What happens when bedding plans are tilted upward?
The cliff profile is similar to the angle of tilt
What happens when bedding planes are tilted towards the sea?
A gravitational pull is created on the cliff, making cracks vertically which causes it to be very vulnerable.
What are sand dunes?
Accumulations of sand blown into mounds by the wind
What is a dune slack?
When the dune dips underneath the water line, creating a pool of fresh water
What is the sequence of different dune types?
- Embryo dune
- Fore dune
- Yellow dune
- Grey dune
- Mature dune
Describe Embryo dunes
- Sand continuously moving
- High pH (over 8)
- High wind speeds
- Lots of salt spray
- No more than 1m high
- 80% of sand exposed
- Plant type: sea twitch and lyme grass
Describe fore dunes
- Drought resistant plants colonise e.g lyme and marram grass
- As they grow, more sand is trapped and dunes increase in height
- 20% of sand exposed
Describe yellow dunes
- Greater diversity of plants
- Humus layer builds up
- pH slightly alkaline
- More shelter, less salt spray
- Marram grass dominates, other vegetation: moss, heather, sea holly
- Dunes 5-10m high
- 80% of sand vegetated
Describe grey dunes
- Stable
- 100% vegetation - more sea spurge and small shrubs
-50-100m from sea - Sheltered from winds
- Humus darkens allowing soil to form
- pH more acidic
- Water content low
- 10m Higher and wider
Describe dune slacks
- Found between mature dunes and where the water table reaches the surface
- Plants adapted to damp and shelter
- Can get peaty soil
Describe mature dunes
- Found 100m from shore
- If undisturbed can support shrubs, trees
- Humus may plant fast growing conifers
What are the different coastal depositional landforms?
- Beaches
- Simple spits
- Compound spits
- Tombolos
- Sand dunes
- Offshore bars
- Barrier beaches / islands
What is a spit?
A long narrow piece of land joined to the mainland which projects out to sea or across a river estuary.
What is a tombolo?
A spit that has connected to an island
What are barrier islands?
Spits that have disconnected from the coastline, to form a stand alone island of deposited material.
What are barrier beaches?
A spit that has gone all the way across a bay and joined at the other side.
What are mudflats?
Created by deposition of fine silts and clays in sheltered low energy coastal environments.
What is a salt marsh?
An area of coastal grassland that is regulatory flooded by sea water
What kind of tidal range do sand dunes require to form?
A large tidal range, in order to give sand enough time to dry out to allow it to be transported up the beach.
What does Aeolian mean?
In relation to the wind
What does positive feedback mean?
Something which occurs and accelerates an already existing process
What are swash aligned beaches?
Beaches at which the waves meet the beach straight on
What are drift aligned beaches?
Beaches where waves meet the beach at angles, causing littoral movement of sediment
What are pioneer species
The first species of plants to colonise something
What are halophytes?
Plants that are tolerant of salt and periodic soaking
What is a positive feed back loop in salt marshes?
More plants = more deposition
What are Eustatic changes?
A global change is sea level resulting from a fall or rise in the level of sea itself
What is an isostatic change?
Local changes in relative sea level resulting from the land rising and falling relative to the sea
What are the two main factors influencing eustatic changes?
- Thermal expansion
- Land ice melt
What causes isostatic changes?
- Glaciation / melting of land causing it to fall / rise (rebound)
What causes an emergent coastline?
A eustatic rise or an isostatic fall
What causes submergent coastlines?
An isostatic fall or a eustatic rise
List of emergent land forms
- Raised beaches
- Relict / fossil cliffs
- Marine platforms / terraces
List of submergent
- Fjords
- Rias
- Dalmation coasts
What are raised beaches?
Beaches that are above the current sea level due to an isostatic rise
What are relict / fossil cliffs?
A cliff that has risen above sea level after an isostatic rise
What are marine platforms / terraces?
A wave cut platform that now exists as an extensive flat area in front of a relict cliff face above the current shore. Caused by an isostatic rise
What are fjords?
River valleys are eroded by ice during periods of glaciations, creating a steeper and deeper and narrow valley. The ice melted and filled the valley
What are rias?
A river valley that has been flooded after a eustatic rise in sea level. Similar to a typical river valley but with more water. The floodplain is also flooded
What are dalmation coastlines?
Similar to fjords and rias; river valleys that were flowing parallel to the coastline are flooded after a eustatic rise, creating islands running parallel to the coastline.
Example of a raised beach
Jura, Scotland
Example of a relict / fossil cliff
The second high cliff, Barbados
Example of marine platforms / terraces
Saint Clemente Island, USA
Example of fjord
Sognefjord, Norway
Example of Rias
Kingsbridge Estuary, Devon
Example of Dalmation coast
Croatia’s Dalmation coast
What are the two factors that cause climate change sea level changes
- Subsistence
- Water volume
What is subsistence?
Coastal areas sinking. Often this is due to excess groundwater extraction, Makes sea level relatively higher. Isostatic
What is water volume (in terms of sea level changes)
Changes due to either thermal expansion or addition of extra water from land store. Eustatic
By how much would sea level rise if all the major ice sheets melted?
72m
What percentage of UK manufacturing is done near the coast?
40%
What percentage of the UK is within 10km of the coast?
23%
How many people live near the coast in the UK?
16.9 million
What are the 3 main reason for coastal management?
- Coastal erosion
- Coastal flooding
- Failure of former defences
What are the four management strategies for coastal management?
- Hold the line
- Advance the line
- Retreat the line
- Do nothing
What is ‘holding the line’ coastal management?
Maintain current defences or build new ones to ensure coastline stays where it is
What is advancing the line coastal management?
Build new defences seaward of existing line
What is retreating the line coastal management?
Allowing the coastline to retreat due to flooding and erosion but closely manage the rate and location of this retreat
What is doing nothing coastal management?
Low value areas left to nature coastal processes as not deemed viable
What is cost benefit analysis?
The weighing up of the cost and the benefits of a coastal management strategy.
What are tangible costs / benefits
Where costs and benefits are known and can be given a monetary value
What are intangible costs?
Where costs may be difficult to asses but are important
What is soft engineering?
Coastal defences that work with nature and natural systems to protect the coast
What is hard engineering?
Making a physical change to the coastline using man made materials and/or structures
What are 6 hard engineering coastal defence strategies?
- Sea walls
- Groynes
- Gabions
- Offshore reef
- Revetments
- Barrages
What are sea walls?
Concrete structures that absorb and reflect wave energy by utilising a curved surface
What are groynes?
Timber or rock protrusions that trap sediment and stop littoral drift from moving it
What are Gabions?
Metal cages that are fitted with loose rock placed at a coastline.
They absorb energy and reduce rates of erosion
What are revetments?
Wooden or concrete ramps that are built on the coast to help absorb wave energy
What are barrages?
Partly submerged structures containing sluice gates that control tidal flow of seawater from land.
What are offshore reefs?
Barrier of rock that are built offshore which forces waves to break before reaches the shore.
What are 5 soft engineering coastal strategies
- Beach nourishment
- Dune regeneration
- Managed retreat
- Land use management
- Do nothing
What is beach nourishment?
Sediment taken from offshore sources is deposited to build up the existing beach.
What is dune regeneration?
Where sand dunes are helped and protected from erosion?
For example, maram grass may be planted
What is a managed retreat?
The planned movement ans realignment of an existing coastline to a new location in land
What is land use management?
When the use of land is managed and restricted so as to not allow areas at risk to be built on
What is the doing nothing coastal strategy?
Doing nothing
How long is the UK’s coastline?
12429km
How many shoreline management plans have the government split England’s shoreline into?
22
What is SMP?
Shoreline management plan.
Britains coastal management scheme that aims to consider the long term impact beyond the financial costs before doing coastal management.
What is integrated coastal zone management? (ICZM)
A global coastal management strategy that aims to create a sustainable approach that balances environmental, social and political needs of many stakeholders
