Systems And Processes 3.1.3.2 Flashcards
Where does energy come from at the coast?
Wind
Wave formation
-wind causes air to move over water
-ripples form due to frictional drag
-water moves in an orbital motion under the water
-at the shore the bottom of the waves slow down due to friction with the seabed
-this means the shape changes from orbital to elliptical, wavelength and velocity decrease while wave height increases and the wave breaks
Destructive waves
-weaker swash stronger backwash
-higher energy
-taller waves
-erode sediment
-builds a steep beach
Features of constructive waves
-strong swash weak backwash
-lower energy
-shorter waves
-deposits sediment
-builds a gently sloping beach
Rip currents
-waves pass over obstacles on the sea floor eg. Sand bars
-when waves wash back out to sea they struggle to pass over the sand bar and are forced through the gap creating a rip current
-they are fast and dangerous
Longshore currents
-waves approach the coastline at an angle
-results in flow of water running parallel to the coastline
-means water moves and transports sediments parallel to the shoreline
Upwelling currents
-movements of cold water from deep in the ocean towards the surface
-dense cold water rises and replaces the warmer surface water
-creates a nutrient rich cold ocean current and transports sediment well
-these currents form part of the global ocean circulation currents
High energy coastlines
-strong destructive waves
-rate of erosion is greater than the rate of deposition
-forms landforms eg. Headlands, bays and wave cut platforms
-stretches of Atlantic facing coast eg. Cornwall, North-West Scotland
Low energy coastline
-less powerful constructive waves
-rate of deposition is greater than the rate of erosion of sediment
-landforms include sheltered estuaries, beaches and spits
-examples eg. Lincolnshire
Wave refraction
-waves approach headlands as wave energy is concentrated on the headland as it is a high energy zone
-the waves reaching the bay therefore have less energy so are constructed and will build up the beach
-as the waves approach the coastline they ‘bend’ to mirror the coastline
-wave energy is concentrated on the headland and is dispersed
-headland is eroded and deposition occurs in the bay
Features of sediment cells
-rivers
-cliff erosion
-Longshore drift
-wind
-offshore sources
Sediment budget- Addition of sediment
-return of sand to the beach system following erosion of dunes during severe storms
-transport of sand along the dry beach due to wind energy
-movement of sand onto the beach due to shoreward waves/currents
-Longshore drift
Sediment budget- removal of sediment
-removal of sand from beach systems due to Longshore drift
-sand blown inland
-loss of sand due to tidal currents
-movement of sand offshore due to waves and currents during a storm
What is weathering
Breakdown and weakening of rock in situ
Mechanical weathering types
-freeze thaw action
-salt crystallisation
-wetting and drying
Freeze thaw action
-water enters cracks in the rocks when it rains
-in cold weather it freezes resulting in volume increasing by 10%
-resulting in cracks widening which repeats overtime causing fragments of rock to break
-this collects at the bottom of the cliff called ‘scree’
-scree used in marine erosion
Salt crystallisation
-water on the surface of rocks is slightly saline (salty)
-as the water evaporates salt crystals remain on the surface
-crystals of salt then accumulate and grow this causes stress on the rock and causes it to break overtime
Biological weathering types
Roots
Birds/animals
Roots biological weathering
-plants grow on cliffs and roots grow into small cracks on cliff face
-when roots grow the cracks are forced to widen causing rocks to break apart
Birds/animals biological weathering
-birds and animals burrow into cliffs breaking them apart
-marine animals called piddocks burrow into rocks
Chemical weathering types
Carbonation
Oxidation
Solution
Carbonation
-rainwater absorbs co2 from the atmosphere making it slightly acidic forming carbonic acid
-carbonic acid reacts with calcium carbonate in rocks (chalk/limestone) to form calcium bicarbonate
Oxidation
-oxygen reacts with iron in rocks forming iron oxide (rust)
-iron oxide is weak making rocks vulnerable
