Coastal System ! Flashcards
Coastline can be viewed as a system with inputs processes and outputs what is this called?
The system is open as it interacts strongly with other systems
What is the coastline system
Input -> process -> output
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Feedback
What is feedback in coastal system
Feedback (positive or negative) can increase or decrease the available inputs or outputs as well as enabling equilibrium
What happens if feedback is balanced
If output and inputs are even this produces a dynamic equilibrium
What happens if inputs and outputs change suddenly
If there is a sudden change in inputs and outputs then stores are are forced to change and the equilibrium is upset
What is positive feedback
Occurs when the effects of an action are increased by changes to input/ outputs/ processes
What is negative feedback
Occurs where the effect of an action are decreased by changes to inputs/outputs/processes
Eg/ reduction in smaller sediment if there is less erosion
What is dynamic equilibrium
A system in dynamic equilibrium has inputs and outputs of energy and matter that balance
What is dynamic equilibrium affected by:
-supply of sand
-energy of the waves
-sea level changed
-location of the shoreline
What are landforms
Individual features which are created by coastal processes eg/ stacks, caves
What is a landscape
The entire area of sea, coastline and immediate land behind the sea front. Within the landscape are characteristic landforms
What are the sources of energy in the coastal system
-wind
-waves
-currents
-tides
What generates wind
-the initial energy input for the coastal system is from the sun
-the suns energy causes different air pressure which creates wind.
-the wind then generates waves which is the main form of energy at the coast
What is wind energy and how is it formed
-wind is formated by air moving between areas of different pressure (from high to low) along pressure gradient
-the steeper the gradient the faster the wind moves.
-areas with larger pressure gradients experience strongest winds and areas with low pressure gradients experience weaker winds
What causes wave energy
-wave energy is caused when strong winds blow in the same direction over a long period of time, this creates the highest waves and high wave energy.
-wave energy can be affected by strength of the wind, the fetch, duration of wind
What are constructive waves
They are created in calm weather and are less powerful than destructive waves. They break on the shore and deposit material, building up beaches. They have a swash that is stronger than the backwash. They have a long wavelength, and are low in height.
What are destructive waves
Destructive waves are created in storm conditions. They are created from big, strong waves when the wind is powerful and has been blowing for a long time. They occur when wave energy is high and the wave has travelled over a long fetch. They tend to erode the coast. They have a stronger backwash than swash.
What are tides
-periodic rise and fall in the level of the sea caused by the gravitational pull of the sun and the moon
-low tides = little water
-high tides = lots of water up the beach
What are the causes of tide
Tides are based on the position of the sun and the moon relative to the earth
-neap tides (normal)
-spring tides= with gravitational pull of the sun and moon combine there is high tides and smaller low tides
What do high energy waves create (features)
-contains cliffs and headlands
-rocky coastline
-erosion exceeds deposition
What do low energy waves create (features)
-beaches and spits
-less powerful waves
-sheltered areas
-Sandy and estuaries
What are sources of sediment (what helps sediment to move)
Rivers: sediment is transported in rivers
cliff erosion: rocks and sediment
offshore sediment: waves can carry sediment
wind: wind blown sand can be deposited in coastal regions
What is a sediment cell
-sediment cell is a stretch of coastline which sediment movement is more or less contained
-cells are usually boarded by 2 headlands or deep water
-a sediment cell should be a state of dynamic equilibrium between inputs and outputs
What are marine processes
Marine processes are those associated with the action of waves. This includes erosion, transportation and deposition.
What are sub-aerial processes
Subaerial processes are land-based processes and occur above the waterline. They include weathering and mass movement, which happen on the cliff rocks and run off
What is positive feedback in weathering
If the rate of debris removal is more than the rate of weathering and mass movement than a positive feedback can operate as the rate of mass movement and weathering could increase
What is negative feedback in weathering
If debris removal is slow and ineffective this will lead to a build up of an apron of debris that reduced the exposure of the cliff face. Weathering and mass movement rates will decrease
What is mass movement
The downhill movement of weathered material under the force of gravity
What is soil creep/ solifuction
-the movements of individual soil particles
-nature of movement is flow
-rate of movement is extremely slow
What is mudflow
-saturated soil flows with gravity
-nature of movement is flow
-rate of movement is often rapid
-happens when soil is wet
What is run off
-rain water flows and picks up sediment
-nature of movement is flow
-rate of movement is rapid
-occurs when land is wet
What is a landslide
-the soil/ material slumps down a hill
-nature of movement is slide
-rate of movement is rapid
-happens if soil is wet or dry
What is rock fall
-loose rock falls in chuncks
-nature of movement is falls
-rate do movement is immediate
-happens due to freeze thaw and once land dries it falls
What is terrestrial and what features influence the coastline
-Terrestrial refers to things related to land or the planet Earth.
-tectonics, supply of sediment, fluvial process
What is human intervention and what are the features that affect the coastline
-features that have been built by humans that affects the coastline
-sea defences, industrial and residential development, tourism, global warming
What is atmospheric factors in coastlines
-pollution, winds, precipitation, temperature, solar energy
What is hydraulic action
Impact on rocks of the sheer force of the water itself on the rock and banks etc. Causing erosion
What is wave quarrying
A braking wave traps air as it hits a cliff face. The air is compressed into any gaps causing huge pressures. As the water retreats there is an explosive effect of the air pressure being released. This weakens the cliff face and allows storms to remove large chunks of it.
What is abrasion
When rocks hit the bed of a river or ocean and erodes
What is attrition
Rocks continue to collide with eachother and break down
What is solution/corrosion
Acidic water breaks down rocks like chalk
What is transportation
Movement of sediment
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 the water
What is suspension
Small particles like silt and clay are carried along the water
What is solution
Soluble materials dissolve in the water and are carried along
What is Longshore drift
Transfer of material along a beach due to prevailing wind
What do high energy coasts look like
They have small particles (clay and sand) easily transported whilst larger and heavier material is deposited forming single beaches
What do low energy coasts look like
Even the smallest material is deposited forming mudflats and slat marshes
Formation of spit
-LSD and prevailing wind
-material is deposited offshore
-material builds upwards and outwards which develops a permanent feature
-material is forced to stop moving outwards by estuaries or change in wave direction
Formation of tombolos
-the same as spit but the material continues moving outward until it hits an island and joins mainland to island
Formation of bar
-same as spit but the material keeps moving until it hits the other side of mainland
What is barrier beach
The beach created from a bar
What is barrier island
Formation of land parallel to coast but not touching coastland
What is barrier beach
Parrellel to the coastland and seperated form land by a lagoon
What are sand dunes
Accumulation of sand blown into mounds by the wind and found at the back of beaches
Formation of sand dunes
1.sand accumulates on the beach from LSD
2.at low tide the sand dries out allowing the prevailing winds to move the loose sand up the beach
3. Larger inter tidal zone for sand to be dry
4. Sand is transported by process of saltation
5. Debris on beach traps sand
6. Grass grows which stabilises the dunes
What are the 6 different types of dunes
-embryo dunes: very little dunes 1st stage
-fore dunes: plants begin to grow but very little amount and 20% exported. 2nd stage
-yellow dunes: more plant diversity, 5-10m high. 3rd stage
-grey dunes: 100% vegetation, 50-100m from sea and very sheltered form beach. 10m+ high. 4th stage
-dune slack: 5th stage
-nature dunes: 100m form sure, mostly to all vegetation. 6th stage
What are mudflats
Created by the deposition of fine silts
And clay in low energy areas (usually bays), the sea water mixes with the mud at high tide and causes muddy quicksand
What are salt marshes
An area of coastal grassland that is regularly flooded by water
What is eustatic and Isostatic change
Eustatic:A global change in sea level resulting from a fall or rise in the sea itself
Isostatic:local changes in sea level resulting form the land rising and falling relative to the sea
Why do sea levels rise
-thermal expansion(where the volume of water increases as it gets warmer)
-land ice melt(melting of glaciers and ice sheets)
What is substance of coastal areas and how is water volume changed
Substance:Coastal areas sinking
Water volume:changes due to either thermal expansion or addition of extra water from land stores
Why does coast need managing
-coastal erosion
-coastal flooding
-failure of former defences
What are the Mangement strategies for coastline erosion (natural)
-hold the line: maintain current defences or build new ones to ensure coastline stays where it is
-advance the line: build new defences seaward of existing line
-retreat the line: allow the coastline to retreat due to flooding and erosion by closely manage the rate and location of this retreat
-do nothing: low value areas left to natural coastal processes as not deemed viable to spend on defences
What is resilience, mitigation and adaption
R: the capacity to recover quickly form difficulties
M: the action of reducing the severity seriousness or painful less of something
A: the process of change by which something becomes better suited to its environment
Formation of fjord
-When glaciers extend across the earth, they make a big impact. As they move, they pick up debris and rocks that they slowly take with them. This process effectively carves deep U-shaped valleys in the land - the beginning of the fjords.
-water enters the valley when the glaciers melt
-emergent feature
Formation of raised beach
-A raised beach is formed by wave action when it is close to the waterline. During a later period, a change in sea level or an uplift of the land can put it beyond the water’s reach.
-emergent feature
Formation of ria’s
funnel-shaped estuary that occurs at a river mouth and is formed by the submergence of the lower portion of the river valley. Generally occurring along a rugged coast perpendicular to a mountain chain, many rias were formed by the rise in sea level after the melting of the vast continental glaciers.
-submergant feature
Formation of marine platform
As sea level rises, waves move underwater sediment, sand and gravel, back and forth against bedrock, acting like sandpaper to hone bedrock into flat, broad platforms. When sea level falls, wave-cut surfaces are exposed above water.
-emergent feature
Formation of Dalmatian coast
A dalmation coastline is formed where the geology creates valleys parallel to the coast so that when sea level rises, a series of elongated islands remain offshore.
-submergant feature
Formation of fossil cliff
Fossil cliff. a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level. they may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion.
-emergent feature
