Everything you need to know for The Coastal Zone

Freez-thaw weathering (mechanical) 1)

Water gets into cracks in the rock and expands the crack when it freezes. When the water thaws it contracts and more water can enter the crack

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Freez-thaw weathering (mechanical) 2)

The continuing expansion and contraction of water puts stress on the rock as the crack widens, Eventually the rock breaks away

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Carbonation (chemical weathering)

Rainwater mixes with carbon dioxide to form a weak carbonic acid which dissolves rock containing calcium carbonate (chalk and limestone)

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Slides (mass movement)

Material shifts in a straight line down the cliff

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Slump (mass movement)

Material shifts with a rotation down the cliff

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Hydraulic power

The force of waves smashing water against rock and compressing air in cracks which puts pressure on the rock and causes erosion

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Abrasion

Eroded particles in the sea is scraped against the rock removing small pieces

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Attrition

Sediment is bumped against each other causing it to wear down and break apart

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Solution

Rocks like chalk and limestone become soluble with acid

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Destructive waves

Occur at times of storms. Erode the beach due to strong backwash and weak swash (steep beach gradient). Have a high frequency

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Constructive waves

Occur at times of calm weather. Build the beach due to weak backwash and strong swash..DEPOSITION (shallow beach gradient). Have a low frequency

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Wave cut platform 1)

Waves erode a WAVE CUT NOTCH at the foot of the cliff by hydraulic action and abrasion. The notch increases in size and the cliff above it becomes unstable and collapses

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Wave cut platform 2)

This process repeats until the cliff has retreated and a wave cut platform is left behind

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Headlands and bays

More resistant rock (e.g chalk) is not eroded and forms a headland. Less resistant rock (e.g clay) is eroded and forms a bay

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Cave to arch

Hydraulic action weakens a fault in a cliff and enlarge it, forming a cave. Eventually the cave becomes an arch due to erosion

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Arch to stack

The top of the arch becomes weak and collapses into the sea, leaving a stack

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Stack to stump

Further erosion may cause the stack to topple over, leaving a stump

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Longshore drift 1)

The transport of material along a coastline: prevailing wind directs the waves towards the coast at an angle

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Longshore drift 2)

The swash carries sediment up the beach and the backwash carries it back down at a right angle. The sediment zigzags across the coast

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Traction

Boulders pushed/rolled along seabed by force of water

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Saltation

Pebbles bounced along the seabed

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Suspension

Tiny particles carried with the sea

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Solution

Dissolved materials transported by sea

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Beaches

Formed by constructive waves depositing material

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Shingle/ pebble beach

Steep and narrow. Too heavy to be moved back down the beach

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Sand beach

Wide and flat. Creating a long gentle slope/ gradient

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Spits

Beaches extending past sharp bends in the coastline due to longshore drift

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Bar

When a spit crosses a bay/joins two headlands together. A lagoon forms behind it

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Rising sea level

Rising at 2mm per year because of global warming heating oceans and melting ice

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Heating of oceans

When water heats up it expands (thermal expansion) - the volume increases

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Melting ice

The melting of ice caps and sheets in polar regions, due to the increase of global temperature, adds a greater volume of water to the oceans

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Economic effects of sea level rise

Loss of tourism. Damage repair. Loss of agricultural land

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Environmental effects of sea level rise

Vegetation and animals killed by salt water. Increased erosion

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Social effects of sea level rise

People lose houses. Unemployment. Damage of water supplies. Deaths

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Political effects of sea level rise

Government have introduce policies to reduce the impacts by building defences or managing areas to be used for flooding

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Economic effects of sea level rise in East Anglia

Industry lost (especially in London). Norfolk broods flooded - no tourism. Defences to reduce impacts

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Social effects of sea level rise in East Anglia

Communities destroyed e.g Kings Lynn. Farmland destroyed. Fear of storm surge that hit the east coast (killing 300) happening again

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Political effects of sea level rise in East Anglia

Government deciding whether to protect some areas and let others flood. Do they protect Kings Lynn?

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Environmental effects of sea level rise in East Anglia

Weaken sea defences so more erosion. 20% of saltmarshes lost by 2050. Habitats and biodiversity destroyed

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Holderness erosion case study

Coastline is 61km long. 1.8m lost every year.. 10m in Great Cowden.

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Holderness erosion causes

Weak rock type (clay). Narrow beaches. Groynes in place updrift causing deprivation of sediment. Directly facing the prevailing wind with long fetch, so powerful waves

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Social impacts 1)

Homes near cliffs at risk of collapsing. Property prices fallen. Roads to some settlements closed. Businesses at risk e.g Seaside Caravan park so threat of unemployment.

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Social impacts 2)

Gas terminal accounting for 25% of Britain's supply is 25m from edge. 80,000m2 of farmland lost per year

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Environmental impacts

some SSSI's (Sites of Scientific Special Interest) such as the Lagoons near Easington are in danger

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Groynes (hard engineering)

£10,000 each. Wooden structures built at right angles to the beach which stop longshore drift by trapping the material - to prevent erosion of coastline

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Advantages of groynes

They are relatively cheap. Wider beaches means less erosion and more tourism

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Disadvantages of groynes

They are unattractive. They starve areas of beach downdrift of them which leads to erosion elsewhere

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Sea walls (hard engineering)

£6mil per km. Reflect the power of the wave back into the sea to try to stop erosion

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Advantages of sea walls

Effective at preventing erosion and flooding. Can be used as a promenade

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Disadvantages of sea walls

Are unnatural and obtrusive. Are very expensive to build and maintain. Create a strong backwash which erodes under it

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Rock armour

£1,000-£4,000 per m. Boulders piled up along the coast which absorb the force of the wave

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Advantages of rock armour

Relatively cheap. Tourist interest. Easy to maintain and put together

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Disadvantages of rock armour

Obtrusive and unnatural. Transport from other countries is expensive

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Beach nourishment (soft engineering)

£3000 per m. Collecting sediment from the seabed and adding it to the beach to give more protection against erosion

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Advantages of beach nourishment

Natural and unobtrusive. Creates bigger beaches so more tourism. Cheap and easy to maintain

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Disadvantages of beach nourishment

Has to be maintained often.

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Dune regeneration (soft engineering)

£2000 per 100m. Adding plants and extra sediment to sand dunes

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Advantages of dune regeneration

Cheap. Natural for people and wildlife

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Disadvantages of dune regeneration

Takes time to work as plants need to grow. Damaged by storms

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Managed retreat

Allowing some areas of the coast to be eroded to reduce the intensity of erosion elsewhere

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Advantages of managed retreat

Cost effective - compared to other maintenance schemes. Creates habitat for wildlife

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Disadvantages of managed retreat

Agricultural areas/ farmland destroyed and owners need to be compensated

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Bridlington, Holderness

4.7km sea wall and groynes

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Hornsea, Holderness

Sea wall, groynes, rock armour

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Withersea, Holderness

Groynes and sea wall. Rock armour placed in front of wall after storm in 1992

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Mappleton, Holderness

£2mil rock groynes

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Less erosion at Holderness

The Humber estuary is more likely to flood as it is carrying less material. More erosion along the Lincolnshire coast. Bays forming between protected areas so they become headlands. Spurn head spit at risk.

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Keyhaven salt marsh

Formed behind Hurst Castle spit. Retreating by 6m a year

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Keyhaven salt marsh wildlife

Cordgrass. Sea lavender. Oystercatcher bird. Butterflies. Wold spider

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Threats to Keyhaven salt marsh

In 1989 a storm exposed 80m to the sea which was eroded in 3 months. Increasing demands for leisure and tourism (trampling, parking, pollution). Rising sea levels

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Responses to threats to keyhaven salt marsh

1996, £5mil spent on rock armour and beach nourishment to protect the spit. Is a SSSI and a nature reserve so is carefully monitored

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Everything you need to know for The Coastal Zone

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