Coasts Flashcards
What’s a coastline
A place at which land meets the sea
What’s weathering
The break down of rocks at earths surface by rain water, temperature, biological, chemical and physical activity
What’s biological weathering
Roots from plants find a way into gaps in rock and weaken as gaps expand and widen so pieces fall off
Animal burrowing and walking over surface can wear away and weaken surface so prices fall away
What’s physical weathering
Wind can blow small grains of sand against rock and wear it away
Rain and waves hit rock - wear it away
Tell me about freeze thaw weathering which is physical btw
What expands when it freezes, so water enters cracks and freezes, the crack expands and when ice melts it can get further in crack and freeze and melt and so on until crack is so big the rock is to weak so it falls off
What’s chemical weathering
Reactions break down bonds holding rock together so they fall apart
More common in location with a lot of water as it is needed for for chemicals to reach the rock
What’s oxidation (chemical weathering)
When oxygen combines with other elements to make another type of rock, it’s broken down Becuase it’s become softer
What’s hydrolysis (type of chemical)
When water combines with substances in rock to form new substances which are softer than original rock
What’s carbonation (chemical)
Carbon Dioxide reacts with rock to become a solution and is carried away
What are mud slides, rock falls and slumping?
Types of mass movements
Tell me about mud slides
They occur on steep cliffs that have been weakened by weathering
The saturated mass falls down along a distinct SLIP PLANE which is likely a fault
Occur after heavy rain
Tell me about rock slide
Where a large amount of rock slides down the cliff, it happens along a fairly straight slip plane- something along natural plane in rock
Tell me about rock falls
Rocks prone to freeze thaw weathering result in falling rocks losing contact with cliff face
Need a vertical cliff and seasonal climates
At bottom of cliff they land and fan out to form a SCREE SLOPD
Tell me about slumping
Soft rock saturates permeable surface but stops at impermeable surface beneath, the saturated rock slips along curved plane towards beach
Happens again as waves undercut cliff base do its unstable and slumps
Define a mass movement
Downslope movement of rock or mud and soil under influence of gravity
Heavy rain usually triggers it
Scale of movement is determined by extent of weathering
What’s a wave
A body of water moving towards the coastline at a higher than average level
Tell me about waves approaching the coast
First there is a circular orbit in open water
Friction with seabed sorrows the circular orbital motion
There’s an increasing elliptical orbit at the top of wave moves faster
Wave begins to break
Then hits beach
What’s the backwash
ALWAYS AT RIGHT ANGLE TO SEA its water from a wave that returns
What’s swash
Water that rushes up the beach and goes up at angle of the wind
What’s a destructive wave like
High wave in proportion to length
A tall wave breaks downwards with great force near Beach
Long fetch
Short wavelength
Strong backwash
Weak swash
Created in storm conditions
Tend to erode coast
What’s a constructive wave like
Low wave in proportion to length
Strong swash
weak backwash
Long wavelength
Created in calm weather
Break at shore and deposit material to build up beaches
What’s the fetch
Distance wing travels to create a wave
Define erosion
Break down and removal of rock
What can affect rates of erosion
Rates of weathering
Power of backwash
Location
Fetch length
Rock type/resistance
Direction of wing
Shape of coastline
Human intervention
What’s attrition
Material carried by waves bump info eachother and are smoothed and broken down into smaller pieces
What’s hydraulic action
Waves enter cracks (faults ) in coastline and compress air within crack
When wave retreats the wake expands causing a minor explosion
What’s corrosion/ solution
Chemical action of sea water, acids in salt water dissolve rocks on the coast
Limestone and chalk prone to it
What’s abrasion and corrasion
This is a process where coast worn down by matieral carried by waves hit the rock sometimes at high velocity
What’s a headland
Area of resistant rock which protude (stick out) from coastline
What’s a bay
Area of soft rock between 2 headlands that erodes quickly
How does a bay form
When there’s is variation in rock type the softer rock erodes faster and over hundreds of years a bay is formed
What’s the difference between coves and bays
Coves due to rock type changing parallel to sea
Bays due to variation so bands of rock meet at a right angle to sea
Describe formation of a wave cut platform
Waves break on cliff face and erode
Erosion continues between high and low water mark and undercut(called a wave cut notch) rest of cliff face over hundreds of years
The notch becomes deeper and wider and overhand formed
The overhand collapsed and cliff retreats leaving a wave cut platform (bur of rock at bottom of cliff face)
Explain the formation of a stack
Lines of weakness in headland form form erosion
Continues to form a small sea cave
Over hundreds of year it deepens and widens to make a cave
Cave erodes back and breaks through other side forming an arch
Weathering breaks down roof of arch and collapsed leaving stack
Erosion weakens it to form a stump as it collapsed
What is the cause of waves
Waves are caused by wind the direction the waves travels depends on sing direction
The direction most win travels in is prevailing wind - it’s south westerly in uk
What’s traction
Pebbles and larger sediment rolled along sea bed
What’s saltation
Load bouncing/hopping along the sea bed eg small pieces of shingle
What’s suspension
Small particles eg silts are carried in water which make it appear cloudy
What’s solution (transportation)
Dissolved chemicals in sea water carried in solution - not visible
Define longshore drift
The transport of sediment along a stretch of coastline caused by waves approaching the beach at an angle that’s not 90 degrees
When does deposition occur?
When a wave enters shallow water
Waves enter a sheltered area eg a cover or bay
There’s little wind
There is a good supply of material
Wide expanse of beach so swash expands out and weakens waves - weaker backwash
What is a beach/ tell me some stuff
Formed by deposition
A beach is a gently sloping area of land between the high and low water marks
Beaches are no permanent they are altered by waves
Where does sea material come from
Material at mouth of rivers
Cliff erosion
What are orthogonals
Lines to show concentrations of wave energy in wave refraction
What’s wave refraction
As waves approach the coast they are refracted so that their energy is concentrated around headlands(shallow water) but reduced around bays. Waves tend to approach the coastline parallel to it, their energy decreases as water depth increases
What are the 2 types of beach
Sandy and pebble
Tell me about sandy beaches
Sometime is has sand dunes behind it
Very gently sloping - almost flat
Formed by generally constructive waves
At low tide water filled depressions called tunnels form
Tell me about pebble beaches
Storm beach with large pebbles at the back of it
Pebbles get generally larger towards the back of the beach
Generally quite steep
Don’t stretch far inland
Formed largely by powerful destructive waves
Tell me the orders of shores starting from furthest away from cliff face
Offshore, nearshore, foreshore, backshore, coastal terrain
Tell me about the offshore
Destructive waves drag beach depositors offshore from berms or sand dunes: forming an offshore bar- lowers height of beach
Waves are not breaking
Tell me about the nearshore
This is where waves breaks
Tell me about the foreshore
Inter tidal zone that is covered then uncovered by changing tides - where sea hits sand
Tell me about the Backshore
Not usually affected by waves so usually dry
Berms form
Tell me about coastal terrain
Dunes or storm beach
cliffs or plain too
Rarely affected by waves
What’s a berm
Terrace in backshore, above the water level at high tide, formed in calm weather when constructive waves transport material
What’s a spit
A spit is a finger of land made of sand and shingle thag extends into the sea from a coastline
How does a spit form
Longshore drift carries sediment along the coast, the swash is how the material is carried up the beach and the backwash takes it back down, in this way material is moved along the coast in the direction of the prevailing wind. If the coast changes direction then sediment is continued to be dropped in original direction. In this way a long ridge of material is deposited - this is a spit. Further out to sea the end of the spit it often curved due to waves approaching from a different direction
How does a bar form
Longshore drift caused by prevailing wind deposits material in that direction
When there is a bay - LSD direction does not change and so form a spit to enclose the bay from headland to headland leaving a lagoon
Where are sanddunes found
On the backshore of the beach
What are some essential conditions for sand dunes to form
Large flat beach - wind can blow sand across beach
Large supply of sand - needed to build up sand dune
Onshore Wind - needed so material can be pushed into beach
Large tidal range - allows sand to dry out to be blown by wind
Obstacle such as drift wood
Sand hits obstacle and so sand can build up around it
Tell me what creep is
Aeolian transportation
Large material rolled along beach surface
What’s saltation
Aeolian transportation
Small material bounced along surface by wind
What’s suspension
Aeolian transportation
Smaller/ fine sand and material carried in wind
Tell me how a sand dune forms
At back of beach there’s an obstacle eg drift wood
The heaviest grains settle against obstacle and lighter ones on other side
Side facing wind begins to form a crest
Because the pile of sand is too steep to build up the crest collapses under own weight
Sand stops slipping at a gradient of 30-34 degrees
Sand dunes migrate inland as repeated movement of material up windward side and down leeward side
Sand dune itself becomes and obstacle so others form In front of it
Tell me the order of the way sand dunes are named starting from the sea moving back inland
Embryo dune
Fore dune
Yellow dune
Grey dune
Mature dunes
What’s a concordant coastline
Where bands of different rock types run parralel to coastline
What’s a discordant coastline
Layers of rock run at right angles to coast
Tell examples of bays on Dorset coastlines
Swanage bay
Christchurch bay
Pool bay
Stud land bay
Tell me examples of a cove at Dorset coastline
Lulworth cove
tell me examples of headlands on Dorset coastline
Durlston head
Ballard point
Tell me some beaches on Dorset coastline
Broad bench beach
Tell me an example of an arch on Dorset coastline
Durdle door
Tell me some cliff names on Dorset coastline
Seacombe cliff
Canford cliff
Tell me some examples of spits on Dorset coastline
Sandbanks
Hurst spit
Tell me an example of a salt marsh on Dorset coastline
Keyhaven salt marsh
How is a cove formed
A line of weakness in a hard rock eg Portland stone allowed water through
Behind this hard concordant layer, soft rock allows erosion
Over time cove widens due to lateral erosion but neck stays quite narrow
When is reached a hard rock at back of cove, erosion is slowed and lateral erosion of soft rock continues
Tell me the options of coastal management
Do nothing - let sea undertake natural processes
Hold the line- build protection st the current cliff face to prevent further damage
Advance the line - build defences aimed at reclaiming small areas of land to assist with protection
Managed retreats - allow some managed loss
Tell about groynes
Designed to build up material on one side to prevent it being moved by LSD
Starved material downwind of material
Life span 20-30 years
Relatively cheap £5000 each
Cause barrier for pedestrians
Tell me about rock armour
Large boulders piled along shoreline to form a sea wall
Allows some water through to disperse energy but reduces erosion of cliffs
Must be large strong rocks eg granite or basalt with are expensive
Quick to build
Natural looking
Tell me about beach nourishment
Sand added to replace sand washed away
Absorb wave energy so it can’t reach cliffs to erode it
Must be replaced regularly
Natural appearance
Little environmental impact
Tell me about gabions
Large steel mesh cages filled with Rocks at right angles to coastline
Absorb wave energy
Cheap £110 a metre
Only work on sandy beaches (pebbles would break them down)
Can be hazardous if not replaced when needed
Tell me about sea walls
Concrete walls built to protect coast from erosion
Stops waves hitting coastline
Seen as ugly
Gives tourists place to walk
If poorly maintained could collspse leading to damage
Tell me about dune regeneration
Artificial creation of dunes
Can take several heart for dunes to be established
Must provide walkways to avoid trampling
Cheap £2000 per 100m stretch
Improved coastal Eco systems
Natural and appealing
Tell me about managed retreat
Creating a man made position for coastline - generally moving coast inland
Less chance of area flooding somewhere else
Long term sustainable
Less money spent on other problems
Can disrupt other area
Compensation for land and housing being destroyed a lot
Very expensive eg medmerry land £28 million
Tell me about beach profiling
Material moved back by a storm is brought forward to protect areas behind
Expensive £200,000 a year due to time and equipment
Can seem artificial looking as high crest
No new material needed to be bought just added
Tell me some reasons Bournemouth is worth protecting
Tourism £472.8 a year
Toursism employs 11,600
3000 homes at erosion risk
100 businessss at erosion risk
Tell me some stakeholder groups
Tourist board
Bournemouth council
People further down coast
Environmental groups
Bournemouth locals
Developers eg builders
