GCSE Geography: Coastal Environments

How do waves form?

The wind blows over the sea, causing friction with the surface.

Fetch

The distance the wave travels

The longer the fetch…

the more powerful the wave

Tsunami waves

Waves formed from earthquakes and volcanic eruptions

Swash

Water travelling up the beach

Backwash

Water flowing back towards the sea

Constructive waves

• Strong swash

• Weak backwash

• Elliptical movement

• Net sediment gain

Destructive waves

• Weak swash

• Strong backwash

• Circular movement

• Net sediment loss

Name two inputs of sediment:

• Erosion

• Deposition

Erosion

The wearing away of rock by water, wind or ice

Name the four different types of erosion

• Abrasion

• Attrition

• Solution

• Hydraulic action

Abrasion

Rocks wear away cliffs and rocky platforms

Attrition

Rocks smash against each other, becoming smaller and rounder

Solution (erosion)

The dissolving of chemicals in a rock

Hydraulic action

The force of the sea against the rock causes air to be trapped in cracks, causing pressure build up which weakens the rocks

Name the five types of sediment movement

• Solution

• Suspension

• Traction

• Saltation

• Longshore drift

Solution (transportation)

Dissolved chemicals in the water

Suspension

Small sediment held in the sea

Traction

Large particles rolled on the seabed

Saltation

Bouncing of particles too heavy to be suspended

Longshore drift

Movement of sediment along the coastline by the swash hitting he coast at a 45 degree angle and the backwash moving perpendicular to the coast

Weathering

The wearing away of rock in situ

Name the four main types of mass movement

• Slumping

• Rockfalls

• Landslide

• Mudslide

Slumping

Terraces form

Rockfalls

Bits of rock fall off the cliff face , usually due to freeze-thaw weathering

Landslide

Large blocks of rock slide down the hill

Mudslide

Saturated soil falls down a slope

Mechanical weathering

The disintegration of rocks via mechanical means e.g. freeze thaw, salt weathering

Chemical weathering

Caused by chemical changes e.g. carbonation

Biological weathering

Weathering caused by flora and fauna e.g. plant roots grow in the cracks of rocks

Freeze-thaw weathering

Water collects in cracks of rocks, becomes ice, enlarges cracks, rocks breaks off

Salt weathering

Seawater contains salt, water evaporates, salt crystals remain and expand in cracks

Carbonation

Rainwater absorbs CO2 and becomes acidic, contact with alkaline rocks causes chemical reaction

Differential erosion

Uneven erosion of a feature

Concordant coastline

Where there is one type of rock along the coast

Discordant coastline

Where there are many types of rock along the coast. This is where headlands and bays form

How do caves arches stacks and stumps form?

• Waves attack weaknesses in a headland (hydraulic action, abrasion)

• Crack enlarges into a cave

• Erosion on opposite sides of the headland break through forming an arch, widening due to wave action and weathering

• Arch becomes unstable due to erosion and weathering, becoming a stack

• Stack is eroded at its base becoming a stump

Sandy beach

• Constructive waves

• Less steep (2-3 degrees)

• Long stretch inland

• Formations: sand dunes, berms

Shingle beach

• Destructive waves

• Steeper (10 degrees)

• Shorter stretch inland

• Formation: berms

Berms

Small ridges found on beaches, formed by the deposition of sand and shingle

Explain how sand dunes form:

• Embryo dunes form around obstructions

• Foredunes colonised by limegrass and sea couch grass

• Yellow dunes have a greater diversity of plants and a hummus layer due to soil

• Grey dunes have a thicker hummus layer

• Mature dunes are several hundred metres inland and have a soil that supports shrubs and trees

Features of the Swanage coastline

• Ballard point - headland

• Studland beach - features lagoons, saltmarshes, sand dunes etc.

• Poole harbour - features two spits either side

• Swanage bay - Hard rock either side formed popular tourist beach

• Durlston head - Made of limestone, rocky beaches due to mass movement

• Old harry - isolated stack

Morecambe coastal management strategies:

• Beach replenishment (SE) - artificially replenishing sediment to widen the beach

• Groynes (HE) - timber and rock structures preventing longshore drift

• Sea wall (HE) - concrete barrier reflecting water back to sea

Pros of managed retreat at Medmerry:

• Social: more foot and bike paths, 348 protected properties

• Economic: boost in green tourism, caravan park protected

• Environmental: Is now a nature reserve protected by the RSPB, 300 hectares of new habitat

Pros of managed retreat at Medmerry:

• Social: Lost farmland

• Economic: Significant sum of money on sparsely populated area, project cost £28 million

• Environmental: Disturbance of existing habitats