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Coastal Processes
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- 1The coast is constantly changing, due to what?Due to the effects of land, air and marine processes.
- 2What id the most dominant process that changes the coast line?The action of waves.
- 3Describe how waves are formed.Circular orbit in open water is created due to the transfer of energy from the wind blowing over surface of sea. As the waves reach the beach friction slows down base of waves, causing orbit to become more elliptical in movement. As there is more friction further up beach the elliptical orbit increases, top of wave moves faster. Eventually the wave begins to break.
- 4Why are some waves larger than others?They contain more energy. Largest waves are formed when winds are very strong, blow for lengthy periods and cross large expanses of water.
- 5What is the maximum distance of water over which winds can blow called?The fetch.
- 6What do water particles in a wave do?Water particles within a wave move in a circular orbit. Each particle, or a floating object, tends to move vertically up and down.
- 7What happens to waves when they reach shallow water?The velocity at its base will be slowed down due to friction with the sea-bed, and the circular orbit is changed to one that is more elliptical.
- 8What is the swash and backwash?Swash transfers energy up the beach; water going up beach.
Backwash returns energy down the beach; water going back down beach. - 9What causes the wave to break?Water hits shore, friction slows base of wave down, yet the top of wave keeps going at same speed, this causes the wave to break as the top overtakes the bottom part of the wave.
- 10What are the two types of waves?Destructive and constructive waves.
- 11What are constructive waves?Usually low and gentle waves (smaller in height; less energy).
Strong swash which carries sediment up the beach.
Weak backwash which brings little sediment back with it; little erosion. - 12What is the point where the sediment is taken the furthest up the beach known as?A berm.
- 13What are destructive waves?Usually high and strong (larger in height; more energy).
Weak swash, so little sediment carried up beach; little beach-building.
Strong backwash: scours the beach, pulling sand and shingle down the beach; this wears down the beach. - 14What is the crest and trough of a wave?Crest = peak of wave.
Trough = bottom of wave. - 15How does corrasion/abrasion erode the coast?Large waves hurling beach material against cliffs.
- 16How does corrosion (solution) erode the coast?When slats and other acids in seawater slowly dissolve a cliff.
- 17How does Hydraulic action erode the coast?Force of waves compressing air in cracks in a cliff.
- 18How does scouring erode the coast?Backwash, dragging of the sand back into sea.
- 19How does attrition erode the coast?When waves cause rocks and boulders on beach to bump into each other and to break up into small particles.
- 20What is differential erosion?When soft rock gets warn away not the hard rock.
- 21How are headlands and bays formed?The bays are made of soft rock and the headlands are made of hard rock.
The soft rock is eroded and hard rock is not (differential erosion). This creates bays as the soft rock recedes and headlands because the hard rock does not recede back. - 22How is a concordant coastline formed?The coast has a layer of hard rock, then soft rock then hard rock again.
Weaknesses in hard rock which allow it to be breached and it begins to be eroded. An oval bay is formed as sea erodes soft rock parallel with the coast; stopped by hard rock at the back, so it doesn't keep eroding backwards. - 23How is a wave cur notch formed?Wave erosion (hydraulic action) is greatest when large waves break against foot of cliff. With wave energy at its maximum, the waves undercut the foot of the cliff to form a wave cut notch.
- 24How is a wave cut platform formed and higher cliffs in the process?Over a period of time the wave cut notch enlarges until the cliff above it, left unsupported, collapses. As this process is repeated, cliff retreats and, often, increases in height. The gentle sloping expanse of rack marking foot of retreating cliff is called a wave cut platform (they are exposed at low tide but covered at high tide).
- 25How are caves formed in cliffs?Cliffs more likely to form where the coastline consists of resistant rock. However, within resistant rocks there are usually places of weakness, such as a joint or a fault. Corrosion, corrasion and hydraulic action by the waves will widen any weakness to form, initially a cave.
- 26How are arches formed in a headland?If a cave forms at a headland the cave might be widened and deepened until the sea cuts through to form a natural arch.
- 27How is a stack formed at a headland?An arch is formed first. Then the waves will continue to erode (abrasion, pounding & hydraulic action) the foot of the arch until its roof becomes too heavy to be supported. When the roof collapses it will leave part of the former cliff isolated as a stack.
- 28How is a stump formed at a headland?When a stack is formed, further wave action will result in the stack collapsing to leave a stump.
- 29What can happen if there is a vertical joint in the headland?Occasionally water rises up a vertical joint and is ejected through a blowhole.
- 30What is the major movement of material along the coast called?Material moved along the coast by a process called Longshore Drift.
- 31How does longshore drift carry material along the beach?Waves approach beach at an angle - similar direction to that of the prevailing wind. When wave breaks, swash carries material obliquely up beach (at same angle wave approached shore). Backwash carries material directly down beach under influence of gravity. Material is slowly moved along coast in a zig-zag course.
- 32Why do wooden groynes best show the effects of longshore drift?Wooden groynes slow down movement of longshore drift and widen beach.
The direction which sediment is moving, when it hits groynes there is an accumulation of sand on one side, then on the other side of the groyne there is a depletion of sand. - 33How is a spit formed?Prevailing wind blows at right-angle to coastline, causing longshore drift. The change in shape of headland, initiates the deposition of material carried by longshore drift. This creates an extended bit of coastline that is attached to the mainland at one end and goes into the sea at the other end. Spits have recurved laterals, created by short term change in wind direction.
- 34What is formed behind a spit and why?Salt marshes or mud flats are created behind spits in the low energy zone (waves cannot get past spit which creates a sheltered area of low energy).
- 35What can prevent a spit from growing any further?If the spit has formed near to a river outlet, it can be stopped growing any further due to this river outlet removing material.
- 36What is a bar?A spit that has formed across a bay. The water behind this bar, which cannot get to the ocean, is called a lagoon.
- 37What erosion takes place for large waves to undermine a cliff?Abrasion.
Hydraulic action.
Freeze thaw.
Weathering.
Solution etc. - 38What could the primary effects of erosion be?Erosion of coastline.
Rock fall and cliff collapse.
Mud floes. - 39What could the secondary effects of erosion be?Land slips/slides/slumps.
Lack of insurance for buildings.
Loss of communication.
Loss of farmland, caravan parks & other businesses.
Loss of habitats.
Loss of housing. - 40What could short term responses be to coastal erosion?Council purchase of cliff top land.
Demolition of cliff top properties.
Migration. - 41What could the long term responses be to coastal erosion?Coastal defences, e.g. groynes, seawalls, riprap/rock armour, revetments and gabions.
Hold the line/retreat the line.
Integrated coastal zone management.
Migration. - 42What are the hard engineering types of coastal management?Flood gates.
Sea walls.
Groynes.
Revetments.
Offshore reefs.
Riprap or rock armour.
Cliff stabilisation. - 43What are the soft engineering types of coastal management?Beach nourishment or replenishment.
Beach drainage.
Sand dune stabilisation.
Managed retreat. - 44What do wooden groynes do?Trap sediment from longshore drift.
Protects beaches and land.
Normally wooden.
An ecological approach.
Does not last long and expensive to build. - 45What do rock groynes do?Trap sediment from longshore drift.
Last longer than wooden groynes.
Keeps sand on beach and protects land.
Less visually polluting than wooden groynes. - 46What are gabions, what do they do?Rocks placed in wire cages to keep them in one place.
These absorb the energy of waves.
Not too visually polluting as vegetation does sometimes grow on the rocks.
More effective than riprap as the rocks can't move easily. - 47What does a curved sea wall and riprap do?Absorb the impact of waves.
The curved design reflects energy back out to sea.
May pose a slight danger to people as they could fall of the top.
Quite visually polluting as it is a big concrete wall, not that natural.
Very expensive - costs £5000 per metre. - 48What are accropodes, what do they do?Concrete accropodes mesh together more than irregular riprap and absorb the energy of waves.
More visually polluting as they are man-made from concrete.
Lasts longer than riprap, more effective as well. - 49What do floodgates do?The gates can be closed at high tide to keep the water out. It works, but it doesn't protect the sea wall, which may eventually erode.
Very visually polluting. - 50What are revetments, what do they do?Expensive slopes.
To slow the impact of waves down protecting the beaches and land.
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- GCSE Geography (Coastal Processes) Karteikarten am Coastal Processes, erstellt von Rebecca Smith am 23/04/2017.
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- Rebecca Smith
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