Coastal system and landscape Flashcards
What are the 4 shores on the beach in order?
Cliff edge - Backshore - Foreshore - Nearshore - Offshore Sea
What is backshore?
Area between high water mark and cliff or barrier
What is foreshore?
Area between high water mark and low water mark
What is nearshore?
Area between low water mark and point where waves cease to have influence
What is offshore?
Area beyond where waves cease to have impact upon seabed
What is nearshore?
Area extending from higher water mark to area where waves begin to break
What are the 3 parts of nearshore (zones)?
- Swash zone
- Surf zone
- Breaker zone
What is the swash zone?
Area where a turbulent layer of water washes up the beach after break of wave
What is the surf zone?
Area between point where waves break (foamy, bubbly surface) and where waves wash up the beach (swash zone)
What is the breaker zone?
Area where waves approaching coastline begin to break (depth of 5-10m)
What are inputs of a coastal system?
- Energy from waves, winds, tides and sea currents
- Sediment
- Geology of coastline
- Sea level change
What are components of a coastal system?
- Erosional landforms and landscapes
- Depositional landforms and landscapes
What are outputs into a coastal system?
- Dissipation of wave energy
- Sediment removal
- Accumulation of sediment above tidal limit
What 4 factors provide energy in a coastal system?
- Waves
- Wind
- Tides
- Currents
What 3 factors affect the energy of a wave?
- Strength of wind
- Fetch
- Duration of wind
What is the fetch?
Distance of open water over which a wind blows uninterrupted by major land obstacles
What are compoents of a wave?
- Crest (top)
- Trough (bottom)
- Wavelength (distance between to crest)
- Wave height (distance between crest and trough)
What is the wave period?
Time for one wave to travel one wavelength
What is swash?
Rush of water up the beach
What is backwash?
Water running back down the beach
Explain the wave movement as it travels towards the beach
1) Friction with seabed slows down base of wave
2) Crest rises, velocity and wavelength decrease
3) This increases the elliptical orbit
4) Wave steepens until wavelength: wave height of 7:1
%) Water swashes up the beach then backwashes down
What are the 2 types of wave?
- Constructive
- Destructive
What are constructive waves?
- Low wave height
- Long wavelength
- 6/8 per min
- Stronger swash than backwash (material moves up beach)
What are destructive waves?
- High wave height
- 10/14 per min
- Stronger backwash than swash (more sediment removed)
What can constructive waves lead to formation of?
Ridges (berms)
What can destructive waves lead to formation of?
Storm beach
How do destructive waves create negative feedback?
They move material back down the sea - reducing the angle of the slope which encourages constructive waves
What occurs when waves meet a headland?
Wave refraction
What is wave refraction?
- More drag in shallow water near headland and speeds up in front of bay due to deeper water
- Causes wave to bend as energy if waves becomes focused on headland
- Low energy waves spill into bay creating deposition
What is current?
Permanent or seasonal movement of surface water in seas and oceans
What are the 3 types of current?
- Longshore currents
- Rip currents
- Upwelling
What are longshore currents?
Waves approach beach at angle, this generates a flow of water running parallel to the coastline
What are rip currents?
- Strong currents moving away from shoreline
- Develop when sea water is piled up along coastline by incoming waves
What is upwelling?
- Movement of cold water from deep in ocean towards the surface
- Replaces warm surface water and it is rich in nutrients
What are tides?
Periodic rise and fall in the level of the sea due to gravitational pull of sun and moon
What are the 2 types of tide?
- Spring tide
- Neap tide
How is a spring tide created?
When earth, moon and sun are in straight line this produce the largest bulge and highest tide
How are tides created?
- Moon pulls water towards it creating high tide and a bulge is formed on the opposite side is formed as well
- As moon orbits earth the tides change
How is a neap tide created?
- When moon and sun are positioned at 90 degrees 4 bulges
- Lowest monthly tide (10-30% lower than average)
What factors affect tide in individual locations?
- Morphology of seabed
- Proximity of land masses
- Coriolis effect
- Tidal range
What is tidal range?
Difference in height of water at high and low tide
What are tidal or storm surges?
When meteorological conditions give rise to strong winds which produce water levels higher than high tide
What area in Britain experiences storm surges?
East coast
What are low energy coastal?
Coastline where wave energy is low and rate of deposition exceeds rate of erosion
What are high energy coasts?
Coastline where strong, steady prevailing winds create high energy wave and rate of erosion is higher than deposition
What are typical landforms of low energy coasts?
Beaches and spits
What are typical landforms of high energy coasts?
Headlands, cliffs and wave-cut platforms
What are different sources of coastal sediment?
- Estuaries
- Cliff erosion
- Streams and river flowing into sea
- Offshore sand banks
What is a sediment cell?
Where sediment moves in distinct areas where inputs and outputs are balanced (between headland and headland)
11 in uk
What is the coastal sediment budget?
Balance between sediment being added and removed from a coastal system (within each sediment cell)
What are marine processes?
Those that operate on a coastline and are connected to the sea
What are examples of marine processes?
- Waves
- Tides
- LSD
What are sub-aerial processes?
Operate on land but affects the shape of the coastline
What are examples of sub-aerial processes?
- Weathering
- Mass movement
- Run-off
What are the process of marine erosion?
- Hydraulic action
- Abrasion
- Attrition
- Solution
- Wave quarrying
What is hydraulic action?
Force of water hitting rocks
What is abrasion?
Where material is picked up and hit the coastline
What is solution?
Where acidic water breaks down rocks (limestone)
What is wave quarrying (cavitation)?
Where air bubbles trapped in the water get compressed into small spaces which implode creating a small shockwave that weakens the rocks.
What factors affect the rate of coastal erosion?
- Wave steepness and breaking point
- Fetch
- Sea depth
- Coastal configuration
- Beach presence
- Human activity
How does wave steepness and breaking point affect coastal erosion?
- Steeper waves are high energy waves
- Waves that break at foot of cliff have more energy
How does fetch affect coastal erosion?
How far wave has traveled affects how much energy has been generated
How does sea depth affect coastal erosion?
Steeply shelving seabed will create higher and steeper waves
How does coastal configuration affect coastal erosion?
Headlands attract wave energy though refraction
How does beach presence affect coastal erosion?
Beaches absorb wave energy and protect the coast
How does human activity affect coastal erosion?
- Sea defences (however may increase erosion elsewhere)
- People may remove protective sand/shingle
What 3 geology factors affect rate of erosion?
- Lithology
- Structure
- Morphology
What is lithology?
Refers to characteristic of rocks
What is structure of rocks?
how rocks lie along coastline
What is differential erosion?
Variation in the rates at which rocks wear away
What are the 2 types of coastline?
- Concordant (same rock type)
- Discordant (different rock types)
Do rocks that lie horizontal or vertical cause faster erosion?
Horizontal
Do rocks that slope inland or towards the sea cause faster erosion?
Slopes inland
What are the 4 transportation methods of sediment?
- Traction
- Saltation
- Suspension
- Solution
What is traction?
Large stones and boulders rolled along sea bed
What is saltation?
Small stones bouncing along sea bed
What is suspension?
Very small particles carried along by water
What is solution (sediment transport)?
Dissolved materials are transported within the mass of moving water
What is longshore drift?
1) Swash move up the beach same direction as waves (at an angle carrying material))
2) Backwash drags material back down beach perpendicular to coastline
3) Swash then carries this material back up the beach at an angle and the process repeats
What are aeolian processes?
Refer to transport and deposition of sediment by wind
en train is when sediment is picked up
What are the 2 ways sand is transported by wind?
- Surface creep (wind rolls grains along surface)
- Saltation (wind lifts grains intp airflow)
What are the 3 sub-aerial processes?
- Weathering
- Mass movement
- Run-off
What are the 3 types of weathering?
- Mechanical
- Biological
- Chemical
Name examples of mechanical weathering
- Freeze thaw
- Exfoliation
- Salt crystallisation
- Wetting and drying
What is mechanical weathering?
Processes that occur at coasts that depend on the climate
What is freeze-thaw action?
Water enters the cracks and freezes at low temperatures, as it freezes water expands by 10% which exerts pressure on the surrounding rock
What is pressure release?
When overlying mass is unloaded mechanisms within the rock cause it to develop weakness (cracks and joints form as it expands)
What is biological weathering?
Processes that lead to the breakdown of rocks by the action of vegetation and coastal organism
How does vegetation cause weathering?
- Some organisms can go into solid rocks which breaks it up
- Some organisms release chemicals capable of promoting solution
What is chemical weathering?
Where rocks and exposed to air and moisture so chemical processes can breakdown the rocks
What are the different types of chemical weathering?
- Oxidation
- Carbonation
What is oxidation?
Causes rocks to disintegrate when the oxygen dissolved in water reacts with some rock (staining of rock surface, rusting)
What is carbonation?
Occurs where dissolved in rainwater makes a weak carbonic acid, this reacts with calcium carbonate in rocks which dissolves
What affects mass movements?
- Level of cohesion within sediment
- Height of slope and slope angle
- Grain size within sediment
- Temperature and level of saturation
What are the types of mass movements?
- Landslides
- Rock falls
- Mudflows
- Slumping
- Soil creep
What are landslides?
Cliffs made of soft rocks - which slip usually following heavy rainfall
What are rock falls?
Occur from cliffs undercut by the sea or on slopes affected by mechanical weathering
What are mudflows?
Heavy rain can cause large quantities of fine material to flow downhill, soil becomes saturated and surface layers become fluid and flow downhill
What is rotational slumping?
Where softer material overlies more resistant material moves downwards with a slide plane that is concave
What is soil creep?
Occurs where there is very slow movement of individual soil particles downslope
What is run-off?
The movement of water over the surface reaching the coastline
What is the difference between concordant and discordant coastlines?
Concordant coastlines have the same rocks type along it, discordant have different types
How are headlands and bays formed?
On a discordant coastline erosion takes place on softer rock creating bays and the hard rock as headlands (wave refraction then takes place)
How are coves formed?
On concordant coastline water finds a weakness and penetrates through hard rock layer where it then reaches soft rock and arounds outwater creating a cove
How is a wave cut-notch formed?
Erosion is concentrated at base of cliff and begins to undercut it
How is a wave-cut platform formed?
As cliff retreat after wave-cut notch collapses a gently sloping (5 degrees) wave-cut platform is made at the base of the cliff
What happens to waves as the wave-cut platform grows?
The waves break further out and have to travel across more platform so there is less cliff erosion
What formations are made due to erosion on a headland?
- Geo
- Cave
- Arch
- Stack
- Stump
What is the process of a stump being formed
1) On cliff weakest parts (cracks, joints bedding planes) are attacked by sea
2) The joint can wider forming a geo or the cliff is undercut to form a cave (marine processes)
3) Erosion can occur upwards forming a blowhole but usually meet on other side forming an arch
4) Arch will eventually collapse under weight (by sub aerial processes) leaving an isolated part called a stack
5) In time sea will create a wave-cut notch on the stack leading for it to collapse and a wave-cut platform may be left (in the same position) forming a stump
How do landform of coastal deposition form?
Where sand and shingle accumulate faster than they are removed
How does sand affect the backwash?
- Sand particle size is small so become compact when wet so percolation cant take place,
- Most swash therefore returns as backwash and little energy is lost to friction
- Leads to development of ridges and runnels (run parallel to shoreline)
What is exfoliation?
In heat is expands and when cools contracts
What gradient do sand beaches usually create?
Gentle (usually below 5 degrees)
What do sand beaches usually lead to development of?
Ridges and runnels
What are ridges and runnels?
- Develop at low water mark
- Run parallel to shoreline
Where does shingle usually form?
Upper part of beach
What is the gradient of shingle beaches?
Steeper gradient (10-20 degrees)
