Coasts Flashcards
What are sediment cells ?
Length of a coastline which is self contained as far as movement of sediment is concerned. Interruptions to movements will not affect each independent sediment cell.
Define wave period
Time it takes for a wave to travel 1 wave length
What are characteristics of constrictive waves?
Long wavelength Low frequency Low height Build up beach Strong swash Weak backwash
What are characteristics of destructive waves?
Short wavelength High frequency High height Pulls material away from the beach Weak swash Strong backwash
Define hydraulic action
Waves move towards a cliff and the water enters the cracks, trapping air in the cliff face creating pressure. This continues and weakens the cliff making it unstable so the cliff falls.
What are sub-cells ?
A sediment cell spilt into smaller more manageable units with boundaries at which there’s only a limited exchange of sediment.
Define abrasion
The tides picking up rocks and then throwing them at a cliff due to the waves power. This damages the base of cliffs making them weak.
Define solution ?
Where the waves dissolve the base of cliffs making them slowly weaker.
Define backwash
The return of water back down the beach as a result of gravitational pull. This moves sediment back down the beach.
Define wave trough
Lowest point of a wave
Define attrition
Where rocks scrape along the base of a cliff causing the cliff to erode due to the force of friction.
Types of transportation
Backwash/swash
Longshore drift
Traction, saltation, suspension in waves
Traction and saltation of beach sand
Types of sub-aerial weathering
Salt crystal growth
Freeze thaw
Acidic rainfall
Biological weathering
What does mass movement include ?
Rock fall
landslides
mudflows
slumps
Describe estuarine coastlines
Found in mouths of rivers
Gradual transition from land to sea
What is runoff
Effects of surface wash over cliff faces as well as the effects of rivers entering the sea
Define wave frequency
Number of waves per minute
Define Wave crest
Highest point of a wave
Define waves
Created by the transfer of energy from the wind blowing on the surface of the sea. Therefore waves are movement of energy in water.
Define Wave steepness
Ratio of wave height to the wave length
Define fetch
Distance over which the wind blows over water. Greater distance means to increased wave energy.
Define swash
Movement of water up the beach from a breaking wave. It goes up the same angle as it breaks and carries sediment up the beach with it.
Define Wave length
Distance between 2 successive crests
What are the sources of sediment?
Anywhere outside the cell, for example rivers and eroded cliffs.
What are cliff profiles ?
The height and angle of a cliff face as well as all of its features.
What is the littoral zone?
Area where the land meets the sea, most erosion occurs here and shoreline areas are permanently submerged.
What factors affect coasts ?
Resistance erosion of rock Faults Joints Fissures Dip of rock strata in relation to the coastline
How can you classify coasts?
Cliffed coastlines
Sandy coastlines
Estuarine coastlines
Describe a cliffed coast
Transition from land to sea is abrupt
Low tides
Foreshore zone exposed
Describe sandy coastlines
Dune vegetation stabilises the coast and erosion
Define mass movement
Process where soil, sand and rocks fall under the force of gravity
Define wave refraction
When waves leave deep water they’re affected by drag from the sea bed. Waves will therefore realign themselves parallel with the coastline. However on irregular coastlines the waves concentrate on the headland meaning more erosion there and deposition at bays due to the low energy waves.
Define tides
Rise and fall of sea level due to the gravitational pull of the sun and moon
Define spring tides
Highest monthly tidal range when the moon sun and earth are in a straight line and tide raising force is strongest.
Define neap tides
Lowest monthly point due to the moon and sun are 90 degrees apart from each other in relation to earth.
What influences the size/energy of waves?
Wing speed
Duration of wind
Fetch
Define sub-aerial processes
Non-marine processes that affect the coastline.
Define freeze thaw
Process where water repeatedly freezes and and melts within cracks of rock. This means that the rock will expand as water expands by around 9% when frozen. Therefore the rock gets weaker and can easily break off.
Define diurnal range
Temperature change over night
Define biological weathering
Can be due to tree roots growing into joints in rocks or animal burrowing.
Define chemical weathering
Carbonation occurs as co2 dissolves into rain water and as it falls onto rocks made of limestone, the carbonic acid attacks the calcium in the rock forcing it to break away.
Run-off
Move small materials downslope like soil in areas where there’s little vegetation.
What are output systems ?
Where a loss of energy occurs from a natural process.
