LOTUK- Jurassic Coast Case Study

Question 1

What is the length of the coastline discussed?

Answer 1

95 miles

Question 2

How old is the coastline?

Answer 2

185 million years old

Question 3

What is the name of the stack landform?

Answer 3

Old Harry

Question 4

How does geology influence Old Harry?

Answer 4

Chalk is harder than surrounding clays and sands in Studland Bay and Swanage Bay and therefore sticks out as a headland
As headland sticks out, this causes wave refraction which attacks the headland
As a rock with lots of joints and bedding planes, there are spaces for weathering and erosive processes to exploit, weakening the cliffs

Question 5

What is the influence of climate on old harry

Answer 5

Cliffs were originally created during a much warmer climate 65 million years ago
Stormier climates will increase erosion - e.g. 1896 storm destroyed Old Harry’s Wife (another stack which used to be there)

Question 6

What event in 1896 affected Old Harry?

Answer 6

A storm destroyed Old Harry’s Wife, another stack that used to be there

Question 7

What is the name of the bay landform?

Answer 7

Swanage Bay

Question 8

What type of geology is found in Swanage Bay?

Answer 8

Clays and sands, found on a discordant coastline

Question 9

How does geology influence swanage bay?

Answer 9

It is softer rock than surrounding geology and therefore erodes at a faster rate
Bay is therefore cut further inland and also at a lower elevation than surrounding headlands
As waves are refracted in the bay, this shelters the location and therefore the waves approach with less force
- Waves are often constructive rather than destructive
This is an environment of deposition (hence the build up of beach

Question 10

What is the name of the arch landform?

Answer 10

Durdle Door

Question 11

What type of geology is Durdle Door and where is it located?

Answer 11

Portland limestone, On a concordant coastline

Question 12

How does geology influence durdle door?

Answer 12

As a harder rock than surrounding area it has withstood much of the erosion the rest of the coastline has suffered
Coastline is susceptible to lots of abrasion and hydraulic action but DD is standing strong
Limestone has joints and bedding planes and therefore susceptible to more weathering

Question 13

What is the name of the beach landform?

Answer 13

Swanage Beach

Question 14

How does climate affect swanage beach?

Answer 14

Wave refraction from the two headlands creates an area of reduced energy leading to deposition of sediment. Sediment is eroded from the two adjacent headlands and deposited in the beach. Transportation and longshore drift move sediment from the southern end of the beach northwards due to a south-westerly prevailing wind

Question 15

What is the name of the tombolo landform?

Answer 15

Chesil Beach

Question 16

How long is Chesil Beach?

Answer 16

18 miles long

Question 17

What type of geology is Chesil Beach?

Answer 17

Sand and shingle beach from erosion further up the coastline

Question 18

How does climate impact Chesil Beach?

Answer 18

Prevailing wind determines direction of LSD. Calmer waters allow deposition across the bend in the coastline allowing the tombolo to form

Question 19

What impact does building hotels have on geomorphic processes?

Answer 19

Major slip in 2012 meant they implemented drainage pipes to stop a slip plane being created on the impermeable clay. Considered a success as now hotels and 45 beach huts are supported.

Question 20

What was the change made to the pines hotel to reduce its impact of geomorphic processes?

Answer 20

Pines hotel 10m away from cliff edge. Built on Wealden clay cliff top 30m high.

Question 21

What type of sea defences were built in Swanage?

Answer 21

18 wooden groynes built in 2005.
Beach replenishment of 90,000m3 last done in 2005, recharge needed every 20 years.
Concrete sea wall - built in 1920.

Question 22

What is the impact of these defences on geomorphic processes

Answer 22

Groynes - limits longshore drift, encourages deposition on the beach in front of cliffs in Swanage Bay.
Concrete sea wall - limits wave erosion through abrasion and hydraulic action.
Beach replenishment - increases amount of deposition in Swanage Bay on the beach. More sediment available for transport along the beach.

Question 23

What are the pros and cons of these management strategies?

Answer 23

+ Aggressively defending the coast has built up sediment and protected the landscape behind.
+ Groynes so successful they are overtopping - so much sediment has been deposited and trapped (stopped from moving through longshore drift) - they’ve been a real success (a noticeable difference in rates of erosion where the groynes are and aren’t built).
- Defences have been costly - all sea defence projects are multi million pound projects
- Beach replenishment needs redoing every 20 years.
- Wooden groynes are starting to fall apart already so are less effective.
- Groynes ‘starve’ sediment from places beyond the final groyne - ‘terminal groyne syndrome’ and mean there is less protective beach in front of the cliff in the north of the bay.