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