COASTS: The Coastal System Flashcards
Why are coasts considered natural systems?
They have inputs, outputs, flows and stores of sediment and energy.
There are 4
What are the inputs of sediment into the coastal system?
- Eroded sediment from rivers and cliffs.
- Crushed shells of marine organisms.
- Offshore deposits transported by waves, tides and currents.
- Sediment from the formation of estuaries from sea levels rising.
What are the inputs into the coastal system?
Sediment.
Energy - wind, waves, tides and currents.
What are the outputs of coastal systems?
Sediment washing out to sea or being deposited further along the coast.
What are the flows/transfers within the coastal system?
Erosion
Weathering
Transportation
Deposition
What are the stores/components of the coastal system?
Landforms, eg beaches, dunes and spits.
Give an example of negative feedback in the coastal system:
- Beach is eroded.
- Cliffs are exposed to wave attack.
- Sediment eroded is deposited on beach.
- Beach grows in size.
Give an example of positive feedback in the coastal system:
- Beach forms.
- Waves slow down.
- More sediment is deposited.
- Beach size increases.
What do negative feedbacks do to the system?
Restore the balance of the system.
What do positive feedbacks do to the system?
Change the balance of the system.
Create a new equilibrium.
What are the sources of energy in the coastal system?
Wind
Waves
Tides
Currents
What are winds created by?
Air moving from areas of high pressure to areas of low pressure.
What can strong winds generate?
Powerful waves.
Prevailing winds
When the wind blows from the same direction.
What type of waves do prevailing winds cause?
Higher-energy waves than winds that change direction frequently.
What are waves created by?
Wind blowing over the surface of the sea, causing friction and giving the sea a circular motion.
The effect of a wave on the shore depends on what?
The height of the wave.
What is wave height affected by?
Wind speed
Fetch of the wave
Fetch
The maximum distance of sea the wind has blown over in creating the waves.
High wind speed and long fetch create what sort of waves?
Higher and more powerful waves.
What causes a wave to break as it nears the shore?
- Friction with sea bed slows the bottom of the waves.
- Wave motion becomes more elliptical.
- Crest rises up and collapses.
What is the frequency of constructive waves?
6-8 waves per minute
What is the frequency of destructive waves?
10-14 waves a minute
Describe constructive waves:
- Low frequency
- Low & long
- Elliptical cross profile
- Powerful swash deposits material
Describe destructive waves:
- High and steep
- Circular cross profile
- Higher frequency
- Strong backwash removes material from the beach
Tides
Periodic rise and fall of the ocean surface caused by the gravitational pull of the Moon and the Sun.
What do the tides affect?
The position at which waves break on the beach.
Current
The general flow of water in one direction which moves material along the coast.
Can be caused by wind or by variations in water temperature and salinity.
Give the characteristics of high-energy coasts:
- Inputs of energy from large, powerful waves.
- Sandy coves
- Rocky landforms
- Rate of erosion is higher than rate of deposition.
Give the characteristics of low-energy coasts:
- Low inputs of energy from small, gentle waes.
- Saltmarshes
- Tidal mudflats
- Rate of deposition is higher than the rate of erosion.
Sediment budget
The difference between the amount of sediment that enters the system and the amount that leaves.
Positive sediment budget
More sediment enters the system than leaves it and the coastline builds outwards.
Negative sediment budget
Sediment cells / littoral cells
Lengths of coastline (often between two headlands) that are largely self-contained for the movement of sediment.
Are sediment cells open or closed systems?
How many sediment cells are there in the UK coastline?
11
When the wind blows from the same direction.
Prevailing winds
The maximum distance of sea the wind has blown over in creating the waves.
Fetch
Periodic rise and fall of the ocean surface caused by the gravitational pull of the Moon and the Sun.
Tides
The general flow of water in one direction which moves material along the coast.
Can be caused by wind or by variations in water temperature and salinity.
Current
The difference between the amount of sediment that enters the system and the amount that leaves.
Sediment budget
More sediment enters the system than leaves it and the coastline builds outwards.
Positive sediment budget
Negative sediment budget
Lengths of coastline (often between two headlands) that are largely self-contained for the movement of sediment.
Sediment cells / littoral cells
