Introdcution to Coastal Environments Flashcards
What are the 3 inputs of a coastal system?
River sediment
Sediment from cliffs that have been eroded
Sediment that have been transported craves from offshore
What are the 6 coastal processes?
Wave action Tidal movement Erosion Weathering Transportation Deposition
What are the 2 coastal outputs?
Sediment washed out to sea
Sediment deposited further along the coast
Define a coastal sediment cell.
Lengths of a coastline that are self-contained for the movement of sediment
What are waves responsible for?
Erosion and deposition of beach sediment
How are waves created?
By the wind blowing over the surface of the sea.
Friction between the wind and the surface of the sea gives the water a circular motion
What determines the affect a wave has on a coastline?
The height of the wave
Hat affects the height of the wave?
Wind speed
Fetch of the wave
Define fetch.
Maximum distance of sea the wind has blown over in creating the waves
What are the characteristics of a high waves
High wind speed
Long fetch
What is the process of a wave?
Waves approach shore and they break
Friction with sea bed slows the bottom of the waves (makes motion more elliptical)
Crest of the wave rises up and then collapses
What are the two types of waves?
Constructive
Destructive
What are the characteristics of a constructive wave?
Low frequency (6-8 waves a minute)
Low and long - elliptical cross profile
Strong swash, weak backwash
Deposits material on the beach
What are the characteristics of a destructive wave?
High and steep - circular cross profile
Higher frequency (10-14 waves a minute)
Strong backwash, weak back swash
Takes material away
What are tides?
The periodic rise and fall of the ocean surface
What causes tides?
The gravitational pull of the moon and the sun
What do tides affect?
The position at which waves break on the beach
A high tide = break higher up the shore
Where are landforms created in relation to tides?
Between maximum high tide and minimum low tide
What are sub-aerial processes?
They describe coastal processes that are not linked to the action of the sea
Includes free-thaw and salt weathering
What can make cliffs more unstable
Through flow and runoff caused by heavy rain
Increases likelihood of mass movement
Define mass movement.
The movement of material downhill due to gravity
Includes landslides, slumping and rockfalls
What are the 5 ways that waves erode the coastline?
Abrasion/corrosion Hydraulic action Quarrying Corrosion/solution Attrition
Describe abrasion/corrasion
Bits of rock and sediment transported by the waves smash and bring against rocks and cliffs, breaking bits off and smoothing surfaces
Describe hydraulic action
Air in cracks in cliffs is compressed when waves crash in, pressure exerted by the compressed air break off rock pieces
Describe quarrying
Energy of a wave as it breaks against a cliff is enough to detach bits of rock
Describe corrosion/solution
Soluble rocks (limestone) get gradually dissolved by the seawater
Describe attrition
Bits of rock in water smash against each other and break into smaller bits
What are the 5 factors affecting the rate that the coastline is eroded
Width of beach Breaking point of the wave The aspect Rock type Fetch of the waves
Describe how the width of the beach affects erosion rates
Beaches slow down waves, reducing heir erosive power
Wide flat beach will protect cliffs more than a narrow steep beach
Describe how the breaking point of the wave can affect the rate the coastline is eroded
Waves breaking at foot of cliff transfers most energy to the cliff, causes most erosion
Waves breaking earlier on sill cause less damage
Describe how the aspect of a beach can affect the rate the coastline is eroded
If coastline faces dominant wind and wave direction, erosion will be faster
Describe how rock type of a beach can affect the rate the coastline is eroded
Hard rocks (granite) are more resistant to erosion than softer rocks (clay).
Describe how fetch of the waves can affect the rate at which the coastline is eroded
Waves with larger fetch are much higher and steeper, more energy, causes most erosion
Define currents
General flow of water in one direction
What do currents do?
Move material along the coast through longshore drift
Explain process of longshore drift
Swash carries sediment (shingle) yo the beach, parallel to the prevailing wind.
Backwash carries sediment back down the breach, at right angles to the shoreline.
When there’s an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along the shoreline
What does a coastal system have?
Inputs
Processes
Outputs
