Physical Geography - The Coastal Zone
Key terms for 'The Coastal Zone' topic for AQA Geography A.
- Created by: Zoe
- Created on: 03-12-12 23:11
Wave
A movement of energy created by the frictional drag of wind on the surface of the water. At sea, they have little effect, but closer to coasts they develop into a horizontal movement of water which impacts the coast
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Destructive Wave
A steep, high frequency wave (10-14 per minute) formed by stormy weather conditions that causes a net loss of material from the beach as the backwash is stronger than the swash.
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Constructive Wave
A low height, low frequency wave (6-9 per min) in calmer conditions that build up the beach as the swash is stronger than the backwash.
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Fetch
Distance wind has travelled over open water to create waves. Generally the longer the fetch the larger the wave.
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Backwash
The backward movement of water down the beach after a wave has broken.
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Swash
Forward movement of a wave up a beach.
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Weathering
The breakdown of rocks in situ (in their original position) through the action of weather, plants, animals
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Biological weathering
Weathering resulting from the action of plants/animals. e.g roots growing into cracks, lichens secrete acid to chemically weather rock
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Physical weathering
The breakdown of rocks without changing its chemical composition e.g freeze thaw
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Chemical weathering
Breakdown of rocks by changing its chemical composition e.g carbonation
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Freeze thaw
Involves repeated cycles of freezing and thawing. Water collects in cracks and as expands when freezing can widen crack. This is repeated until stresses within rock cause it to fracture.
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Carbonation
Natural rainwater a weak carbonic acid weathers calcium carbonate rocks
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Mass movement
The large scale downslope movement of material under the influence of gravity e.g Holbeck Hall
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Rockfall
Fragments of rock breakaway from the cliff face, often due to freeze-thaw weathering e.g Beachy Head, Sussex
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Landslide
Masses of rock, earth, or debris move down a slope. Accumulated material puts stress on bedding planes and becomes sufficient enough to lubricate them. Bedding (near) parallel to angle of slope.
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Rotational slip/slump
Slump of saturated soil and weak rock along a curved slip plane
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Mudflow
Saturated soil and weak rock flows down a slope.
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Erosion
The wearing away and removal of rocks by an agent i.e destructive waves
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Hydraulic power
Breakdown of rock through the sheer impact force of waves compressing air in the cracks
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Corrasion
Rock fragments picked up and hurled at a cliff by breaking waves,acting as erosive tools by gradually scraping and scouring away at the cliff face
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Abrasion
'sandpapering' effect of pebble grinding over a rocky platform causing it to become smooth
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Attrition
Eroded particles in the water knock into each other breaking down into smaller pieces. Their edges also become rounded off as they rub together
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Transportation
The movement of sediment by the sea.
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Solution
Soluble chemicals/materials often derived from limestone or chalk dissolve in the water and are carried along
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Suspension
small particles are carried (suspended) within the water.
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Traction
Large particles like boulders/pebbles are rolled along the seabed by the force of the water.
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Saltation
A hopping or bouncing movement of particles to heavy to be suspended
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Longshore drift
The net movement of sediment along a coast caused by waves approaching the beach at an oblique angle (due to prevailing g wind) The sediment is carried up the beach by the swash and back down the beach perpendicular to the swash. A 'zigzag' movement.
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Deposition
The laying down of material when the wave velocities slow or waves enter an area of shallow water. Associated with constructive waves which are low energy.
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Erosion Landforms
Headlands and bays, cliffs, wave cut notches and wave cut platforms, caves, arches and stacks.
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Differential erosion
If there are alternating bands of more resistant and less resistant rock running at right angles to the sea, the sea will erode these bands at different rates
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Headland
A promontory of land jutting out into the sea. More resistant rock erodes at slower rate than less resistant rock therefore is left jutting out as headland.
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Bay
A broad coastal inlet often with a beach. Here less resistant rock is eroded at a faster rate to form a bay.
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Cliff
A vertical, near vertical or sloping wall of rock or sediment that borders the sea.
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Wave-cut notch
A small indentation cut into a cliff roughly at a level of high tide caused by concentrated marine erosion at this level.
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Wave-cut platform
A wide gently sloping rocky surface at the foot of a cliff caused by cliff retreat.
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Cave
A hollowed out feature at the base of an eroding cliff due to marine erosion processes attacking fault in resistant rock
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Arch
A headland that has been partly broken through by the sea to form a thin roofed arch. Formed when cave is broken through by continued marine erosion to form an arch which is continually widened at its base
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Stack
An isolated pinnacle of rock sticking out to sea, formed when roof of arch becomes to heavy and collapses.
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Stump
Isolated rock that is covered up at high tide, formed when stack is undercut and collapses.
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Depositional landforms
Beaches, spits, bars, barrier beach, salt marshes
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Wave refraction
The tendency for waves to become more parallel to the coastline as they approach it. Caused by the slowing of waves at their base as they enter shallower water. Wave energy converges at headlands (erosion) and diverges at bays (deposition)
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Beach
An accumulation of sand and shingle found where deposition occurs at the coast. Deposition occurs in sheltered bays due to wave refraction as the water gets shallower which causes the waves to diverge and lose energy.
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Ridges/Berms
a low ridge towards the rear of a beach marking the uppermost level that waves reached during the previous high tide.
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Spit
A finger of new land made of sand or shingle, jutting out into the sea from the coast.Deposition occurs when longshore drift is disrupted at a point where the coastline changes direction e.g a river estuary.Extends out to sea with more deposition.
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Bar
A spit that has grown across a bay. Area of water behind is a lagoon.
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Salt march
Area of semi-vegetated tidal mudflat often formed in low energy sheltered side of spit.
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Barrier beach
A bar parallell to the shore which has been built up so that it rises above sea level.
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Sea level rise
Rise in mean global sea level (by 3mm per year) due to global warming - melting ice caps, thermal expansion and glacial rebound.
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Global warming
Increase over time in average temperature due to increased green house gas emissions.
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Thermal expansion of sea water
As it absorbs more heat from atmosphere sea water expands therefore sea levels rise
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Eustatic changes
Global changes in sea level due to changes in the volume of water held in the ocean
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Glacial rebound - During the last Ice Age, northern of Great Britain were covered with glacial ice so they were pushed down by the weight.
As this melted the weigh was lifted from northern britain causing land to REBOUND upwards and sea levels to fall relative to the rising land. Consequently sea levels are falling in northern scotland and rising in Southern Britain.
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Isostatic changes
The rise and fall of the land relative to the sea
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Shoreline management plan (SMP)
An integrated coastal plan for a stretch of coastline in England and Wales.
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Hard engineering
Building artificial structures such as sea walls aimed at controlling natural processes
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Sea wall
3-5m high concrete or rock barrier to sea placed at foot of cliffs or top of beach, curved face to reflect waves. £6million per km.
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Groynes
Timber or rock structures that trap sediment being moved by longshore drift thereby enlarging the beach which acts as buffer to dissipate wave energy. £10,000 each.
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Rock armour
Piles of large boulders dumped ay cliff foot that force waves to break, absorbing energy and protecting cliffs. £1,000-£4,000 per m.
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Soft engineering
A sustainable approach to managing coast without using artificial structures
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Beach nourishment
Addition of sand of shingle to existing beach to make a larger beach to dissipate more wave energy before it reaches cliff face. £3000 per m.
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Dune regeneration
Plant mamram grass to stabilise sand dunes which act as
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Marsh creation (managed retreat)
Allowing low lying coastal areas to be flooded to become salt marches which act as effective barriers to sea. An example of managed retreat. £5,000 - £10,000 per Ha.
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Managed retreat
Allowing controlled flooding of low-lying coastal area or cliff collapse in areas where the value of the land is low.
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Pioneer plants
The first plant species to colonise an area that is well adapted to living in a harsh environment. e.g Cordgrass in salt marsh
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Vegetation succession
A sequence of vegetation species colonising an environment. (In salt marsh soil fertility improves, reduced salinity, reduced flooding.)
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Other cards in this set
Card 2
Front
A steep, high frequency wave (10-14 per minute) formed by stormy weather conditions that causes a net loss of material from the beach as the backwash is stronger than the swash.
Back
Destructive Wave
Card 3
Front
A low height, low frequency wave (6-9 per min) in calmer conditions that build up the beach as the swash is stronger than the backwash.
Back
Card 4
Front
Distance wind has travelled over open water to create waves. Generally the longer the fetch the larger the wave.
Back
Card 5
Front
The backward movement of water down the beach after a wave has broken.
Back
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