Systems and Processes Flashcards
What are the 4 sources of energy in the coastal system?
Wind
Waves
Currents
Tides
Wind: When is wave energy likely to be higher?
When wind speeds are greater
Wind: How are waves created?
Wind transfers energy when it blows over the sea surface due to friction
Fetch
Distance of open water over which wind blows uninterrupted by major obstacles
Determines the magnitude and energy of waves
Waves: What happens as they reach the coast?
Approach shallower water
Sea bed friction increases so base of the wave slows down
Increases wave height and steepness
Until upper part of the wave plunges forward
Waves: Constructive wave characteristics
Low frequency (6-8 a min) Low wave height and long length (up to 100m) Swash > backwash, as there's insufficient energy to pull sediment off the beach Material slowly but constantly moved up the beach (ridges)
Waves: Destructive wave characteristics
High frequency (10-14 a min)
High wave height and short length
Backwash > swash, material pulled down beach, wave’s force can project shingle to back of beach (storm beach)
Little material moved up the beach
Strong backwash inhibits swash of next wave
Waves: Link between constructive and destructive waves
Constructive waves build up beaches Steeper profiles Encourages destructive waves to erode Shallower profiles Encourages constructive waves etc
Waves: Wave Refraction
Occurs when waves approach an irregularly shaped coastline
Near shore, slow down due to friction
Parts of the wave that haven’t reached shore bend- travel faster
Energy focused on headland- increasing erosion
Waves reaching the bay have less energy, so deposit material
Currents: Current
The permanent or seasonal movement of surface water in the seas and oceans
Currents: 3 types of current
Longshore Current
Rip Currents
Upwelling
Currents: Longshore Current
Occurs when waves have an angled approach to the coastline
Transports sediment
Currents: Rip Currents
Strong currents moving away from the shoreline
Develop when sea water is piled up along the coastline by incoming waves
Currents: Upwelling
Movement of cold water from deep in oceans to the surface
More dense, cooler water replaces warmer surface water, creating nutrient rich cold ocean currents
Tides: Tides
The periodic rise and fall in the level of the sea, caused by the pull of the sun and moon
Tides: Why does the moon have a greater influence on tides than the sun?
Because it’s closer to the Earth
Tides: Spring Tide
Highest monthly tidal range, as sun and moon are aligned so greater force
Tides: Neap Tide
Lowest monthly tidal range where sun is perpendicular to moon, with tides between 10-30% lower than average
Tides: What 2 factors do they determine?
Upper and lower limits of erosion and deposition
Amount of time each day the shoreline is exposed to sub aerial weathering
Tides: What causes tidal (storm) surges? What makes them worse?
They occur when meteorological conditions give rise to strong winds, producing much higher water levels than high tide, increasing erosion in the short term
They are worsened by spring tides
Low Energy Coast
A coastline where wave energy is low and the rate of deposition exceeds the rate of erosion
Contains depositional features
i.e. Baltic Sea
High Energy Coast
A coastline where strong, steady prevailing winds create high energy waves, so the rate of erosion exceeds the rate of deposition
Contains erosional features
i.e. North Cornish Coast
Sources of sediment
Offshore sand banks
Cliff erosion
Shells and coral fragments
Fluvial sources
Sediment Cell
A distinct area of coastline separated from another by a well-defined boundary like a headland or stretch of deep water
