jurassic coast case study

state the length of the jurassic coast

95 miles

state the age of the jurassic coast

185 million years

state what old harry is

a stack

state the geology of old harry

• cretaceous chalk

• found on a headland

• and discordant coastline

explain how geology affects old harry

• chalk is harder than surrounding clays and sands in studland bay and swanage bay

• differential erosion causes it to stick out as a headland

• as the headland stick out of the coastline

• wave refraction is caused

• which attacks the headland

• cretaceous chalk has lots of fault lines

• meaning there are spaces for freeze-thaw weathering and erosion to weaken

explain how climate affects old harry

• cliffs were originally created in much warmer climates 65 million years ago

• the colder, stormier climate present in swanage will increase erosion of old harry

state what type of coastline the jurassic coast is

discordant

state the geology of swanage bay

• clay

• sands

• found on discordant coastline

explain how geology affects swanage bay

• the bay is made of a softer rock than the surrounding areas

• it therefore erodes faster

• the bay is therefore cut further inland

• as waves are refracted off the headland into the bay, they lose energy

• as the bay is sheltered

• this causes them to become constructive waves

• this causes a deposition of material

• forming a beach in the bay

state what type of landform durdle door is

arch

state the geology of durdle door

• portland limestone

• found on a concordant coastline

explain how geology affects durdle door

• portland limestone is a harder rock than the surrounding clay and sand

• causing it to be more resistant to erosion in comparison

• the headland formed is susceptible to high rates of abrasion, hydraulic action and freeze-thaw weathering

• as portland limestone has many fault lines

• increasing rates of erosion in the headland

explain how climate affects durdle door

• a warming climate will mean less freeze-thaw weathering

• the constant spray from the ocean will result in a wetting and drying cycle

• causing the limestone to suffer from carbonation

state the geology of swanage beach

• clay and sands

• from eroded soft rock

• limestone

• from durlston head erosion

explain how geology affects swanage beach

• wave refraction from the 2 surrounding headlands creates an area of reduced wave energy

• causing the deposition of sediment

• sediment is eroded from the 2 adjacent headlands

• and deposited in the beach

explain how climate affects swanage beach

• transportation and longshore drift move sediment from the southern end of the beach north

• due to a south-westerly prevailing wind

state the direction of longshore drift along the jurassic coast

north

state the direction of the prevailing wind along the jurassic coast

south-west

state the name of the tombolo on the jurassic coast

chesil beach

state the length of chesil beach

18 miles

state the geology of chesil beach

• sands and shingle beach

• from erosion further up the coastline

• shape of the coastline allows a lagoon to form behind the tombolo

state the influence of climate on chesil beach

• the south-westerly prevailing wind determines the direction of longshore drift

• the calmer waters at the beach allow deposition across the bend in the coastline

• this allows the tombolo to form

explain how building hotels has affected geomorphic processes along the jurassic coast

• the major slip of the pines hotel in 2012 meant they implemented drainage pipes in the ground

• to prevent slip plane forming on the impermeable wealden clay

• and a mass movement occurring

• this decreases surface runoff

• which decreases erosion of the clay

• and leading to a decrease in the eroded material ending up in the sea

state the geology of the cliff the pines hotel is built on

wealden clay

state what the swanage sea defences consist of

• 18 wooden groynes

• 90,000m³ of beach replenishment

• concrete sea wall

state when the wooden groynes were built in swanage

2005

state when the beach replenishment in swanage was last done

2005

state how often the beach has to be replenished in swanage

every 20 years

state when the concrete sea wall was built in swanage

1920

explain how the wooden groynes affect geomorphic processes along the jurassic coast

• they limit longshore drift

• encouraging deposition on the beaches in front of the cliffs in swanage bay

explain how the concrete sea wall affects geomorphic processes along the jurassic coast

• limits wave erosion through hydraulic action and abrasion

• decreasing the sediment that is deposited further along the coastline

explain how beach replenishment affects geomorphic processes along the coastline

• increases deposition of sediment on swanage beach

• by increasing the amount of sediment available to be eroded and transported

state the advantage of using wooden groynes to protect the jurassic coast

• the groynes are so successful they are overtopping

• meaning they have stopped the transportation of deposited material

• through longshore drift

state the advantage of the management strategies on the jurassic coast

the aggressive defending of the coastline has allowed for the build up of sediment and protected the landscape behind

state the disadvantage of the management strategies on the jurassic coast

• all the defences have been costly

• they are all multi-million pound projects

state the disadvantages of using wooden groynes to protect the jurassic coast

• wooden groynes are starting to rot and fall apart, meaning they are less effective

• ‘terminal groyne syndrome’ - groynes starve sediment from places beyond the final groyne, meaning the beach in front of north bay cliff is less protected

state the advantage of using beach replenishment to protect the jurassic coast

beach replenishment need redoing every 20 years