Flashcards in 1C: Coastal Landscapes in the UK Deck (69):
What affects the strength of waves?
1) wind speed
2) length of time the wind has been blowing for
3) how far the wave has travelled
What is the fetch?
The distance the wave has travelled
Describe the formation and breaking of waves
1) wind blowing creates friction with the surface of the sea
2) water begins to move in a circular motion
3) friction with the sea bed slows the base of the wave
4) this causes the water to move in an elliptical motion
5) the top becomes higher and steeper until it breaks
Compare the wave height of constructive and destructive waves
Constructive waves have a smaller wave height (less than 1m)
Compare the wave length of constructive and destructive waves
Constructive waves have a larger wave length and thus a lower frequency
Compare swash the of constructive and destructive waves
The swash of constructive waves is stronger meaning they cause deposition
Compare the back wash of constructive and destructive waves
The backwash of destructive waves is stronger meaning they cause erosion
What is longshore drift?
The zigzag movement of sediment along the shore. The prevailing wind determines the directed of LSD, causing the swash to surge up at an oblique angle and the backwash goes back down at right angles
What are two types of physical weathering
1) freeze-thaw weathering
2) salt weathering
Describe the process of freeze thaw weathering
1) water trickles into cracks in a rock face
2) water freeze and expands by 10%, exerting pressure and widening the crack
3) ice melts and pressure is released
4) constant reputation of this cycle causes angular rock fragments to break away
Describe the process of salt weathering
1) salt crystals are left on rocks after salt water evaporates
2) they enter the pore spaces opening them up and creating holes in the rock
What are three types of chemical weathering?
Describe the process of carbonation
1) carbon dioxide gas dissolved in rain to form weak carbonic acid
2) acid reacts with limestone
3) product carried away in solution
What is mass movement?
The movement of material downslope under the influence of gravity
What is rockfall?
When individual fragments of rock fall off a cliff (usually due to freeze thaw)
What is a landslide?
When rock falls in a linear fashion along fault lines
What is slumping?
The downward rotation of sections of a cliff often after heavy rainfall has made the soil saturated
What is mudflow?
When saturated soil or weak rock flows downslope
What is deposition?
When the sea loses energy and drops the sediment it has been carrying
What is weathering?
The breakdown of rocks in situ
What is erosion?
The wearing away and removing of material by a moving force
What is attrition?
Erosion caused by rocks bashing into each other, becoming smoother and breaking up into smaller pieces
What is abrasion/corrasion?
Erosion of cliffs by sediment flung by breaking waves
What is hydraulic action?
Erosion caused water compressing pockets of air in cliffs causing the crack to widen
What is solution?
Erosion caused by a chemical reaction that dissolves rocks
Give an example of an arch in the Dorset coastline
Give an example of a cove in the Dorset coastline
Give an example of a wave cut platform in the Dorset coastline
Give an example of a cliff in the Dorset coastline
Give an example of a headland in the Devon coastline
Give an example of a stack in the Devon coastline
Old Harry Rocks
Give an example of a spit in the Devon coastline
Give an example of sand dunes in the Devon coastline
describe the formation of headlands and bays
1) Headlands and bays form on coastlines where rocks of varying resistance lie at right angles to the sea
2) Harder rock is more resistant to erosion so forms headlands
3) Softer rock is eroded at a quicker rate to form bays
describe the formation of caves, arches and stacks
1) large crack in the cliff is opened up by hydraulic action
2) the crack is widened by hydraulic action and abrasion, forming a cave
3) the cave breaks through the headland to form an arch
4) weathering from above and erosion from below causes the arch to collapse leaving a stack
5) the stack is further eroded to form a stump
describe the formation of wave cut platforms
1) The erosion of a cliff is greatest at its base where large waves break – hydraulic action and abrasion constantly undercut the foot of the cliff, forming a ‘wave cut notch’
2) The undercutting continues and eventually the overhanging cliff becomes so heavy it collapses downwards – this process continues over time and the cliff gradually retreats inland and become steeper
3) As the cliff retreats, a gently-sloping rocky platform is left at the base, this is known as a wave-cut platform which is exposed at low tide
describe the formation of a spit
1) Swash moves up the beach at the angle of the prevailing wind.
2) Backwash moves down the beach at 90° to coastline, due to gravity.
3) Zigzag movement (Longshore Drift) transports material along beach.
4) Deposition occurs where the coastline changes suddenly causing the beach to extend into the sea, until reaching a river estuary.
5) Change in prevailing wind direction forms a hook.
6) Sheltered area behind spit encourages deposition, salt marsh forms.
what is a berm?
A berm is a terrace on a beach that has formed in the backshore. There may be more than one and they are formed by constructive waves. Storms and spring tides may move an existing berm up the beach whilst destructive waves can erode the sediment and transport it offshore to create and offshore bar.
describe the formation of a bar
a bar is formed when a spit grows across a bay joining up two headlands and forming a lagoon behind it
describe the formation of sand dunes
1) When there are obstacles such as driftwood, the heaviest grains of sand will settle against the obstacle to form a small ridge. Lighter grains may be transported and will settle on the other side of the obstacle
2) Eventually the area facing the wind begins to reach a crest. The pile of sand becomes so steep that it becomes unstable and begins to collapse under its own weight.
3) The lighter grains of sand fall down the other side on the lee (slip) face. Sand stops slipping one a stable angle has been reached at 30-34˚.
4) The repeated cycle of wind blowing up the windward side and slipping down the leeward side causes a sand dune to migrate inland over time.
what is it called when a spit connects the mainland to an island?
how does geology affect coastal landforms?
Hard rocks (chalk, granite) erode slowly. Clay and sandstone are softer and erode faster. Hard rocks will form headlands and erode slowly.
Soft rocks will form bays and erode quickly.
what are the characteristics of an arch?
1) unsupported top of arch
2) wave cut notches at base of the arch
3) water is going right through the gap
4) arch is an extension of the headland
what are the characteristics of a stack?
1) detached blocks or pillars of rock locates near a headland
2) may be pinnacle shaped
3) often several meters high
4) wave cut notches at base
5) made of hard rock
what are the characteristics of a cliff?
1) near vertical face
2) fallen rocks at the bottom
3) horizontal layers of rock
4) wave cut notch at base
what are the characteristics of a wave-cut platform?
1) slopes gently down at an angle of 3-4 degrees
2) overall pitted appearance of bare rock interspersed with rock pools
3) bare rock smoothed in places by abrasion
4) covered at high tide
what are the characteristics of a bay?
1) more sand accumulating at one end
2) soft rock
3) crescent shaped beach
4) headland on either side of the bay
what are the characteristics of a sandy beach?
1) shallow (almost flat)
2) stretched a long way inland
3) sometimes sand dunes at the back of the beach
4) small water filled depressions called runnels exposed at low tide
what are the characteristics of a pebble beach?
1) generally steep
2) doesn't stretch far inland
3) sometimes large pebbles at the back
4) increasing pebble size towards the back of the beach
What is required for a sand dune to form?
1) large flat beach
2) large supply of sand
3) large tidal range
4) onshore wind
5) obstacle for the dine to form against
what are the characteristics of a sand dune?
1) Unstable steep slip slope (30-34˚) on the sheltered leeward side
2) Crests (heights vary up to approximately 15 meters)
3) Gentle slope on windward side
what happens as sand dunes move inland?
1) pH becomes more acidic
2) soil changes from yellow to grey/black
3) vegetation cover increases
4) variety and height of plant species increases
5) dunes grow taller
what are the pros and cons of sea walls?
1) long life span
2) protects from flooding
3) can develop the top into a promenade
1) curved shape encourages erosion of beach deposits
2) expensive (5,000-10,000 per meter)
how do sea walls protect coasts from erosion?
have a curves face ('wave return lip') that reflects the waves back to the sea which in turn impedes the next wave and reduces its energy
what are the pros and cons of rock armour?
1) relatively cheap
2) effective at reducing the waves
3) long life span
2) dangerous for public
3) require regular maintenance
how does rock armour protect coasts from erosion?
dissipate/absorb wave energy which reduces the power of waves
what are the pros and cons of gabions?
2) blend in better than other hard engineering strategies once vegetation grows over them
1) doesn't last very long (25 years)
2) cages can break making it dangerous for the public
3) ugly at first
how do gabions protect the coast from erosion?
absorb/dissipate the wave energy reducing the power of the waves
what are the pros and cons of groynes?
1) relatively cheap
2) creates wider beaches
3) beach still accessible
1) restrict the supply of sediment down drift so erosion down coast]
2) make beaches look messy
how do groynes protect coasts from erosion?
trap sediment transported by longshore drift which creates a lager beach which acts as a buffer
what are the pros and cons of beach nourishment/reprofiling?
2) bends seamlessly with environment
3) attract tourists
1) sand collection (dredging) damages sea bed and can kill organisms like sponges and corals
2) high overhead costs of hiring a dredger
3) needs replacing every 5 years
how does beach nourishment/reprofililng protect the coast from erosion?
creates a larger beach which acts as a more effective buffer against the waves (absorbing some of their energy)
what are the pros and cons of dune regeneration?
1) maintains natural environment protecting habitats
3) blends seamlessly with natural environment
1) areas off limits (signage may deter tourists)
2) time consuming
how does dune regeneration help protect coasts from erosion?
act as a physical barrier between the sea and the land absorbing the wave energy
what are the pros and cons of a managed retreat?
1) reduces flood risk further along the coast
2) creates new inter tidal wildlife habitats
3) low maintenance, long term solution
1) local people may have to be relocated
2) some ecosystems may be lost
3) short term costs are very
what were the reasons for the Medmerry Project?
1) The Environmental Agency (EA) considered the area west of Selsey to be the area of south east England the most at risk of flooding
2) From the 1990s beach reprofiling had taken place every winter at an annual cost of ₤200,000
3) Defences were breached in 2008 at the cost of ₤5 million
4) Flooding threatened 300 homes, the main road and water treatment works
what were the negative effects of the Medmerry Project?
- Local residents feel that EA should have done more to protect their land
- Some people outside the area resented such expenditure in a sparsely populated area
- Scheme cost ₤28 million but it was only costing ₤0.2 million a year to maintain the shingle wall
- Three farms growing rapeseed oil and winter wheat had to be abandoned
- Despite planning some existing species (e.g. badgers) were still disrupted
what were the positive effects of the Medmerry Project?
- Selsey now has a 1 in 1,000 chance of coastal flooding
- Now there are 10km of footpaths (formerly only had 2 small footpaths)
- Tourism expected to increase with more people visiting nature reserves (2 new car parks and 4 viewing points)
- Newly flooded area expected to become an important fishing nursery
- Salt marsh vegetation will be used for extensive cattle farming, producing expensive salt-marsh beef
- Measures were taken to protect existing species (e.g. water voles)
- 300 hectares of new intertidal habitat are forming seaward of the embankment attracting large numbers of ducks and lapwings (are is turning into huge nature reserve managed by the RSPB)