Dorset Coastline Case Study

Question 1

Name a high energy coastline

Answer 1

Dorset coastline

Question 2

Prevailing wind direction

Answer 2

South west

Question 3

Secondary wind direction

Answer 3

S/south-east

Question 4

Domination /longest fetch length

Answer 4

7000km

Question 5

Tidal range

Answer 5

2-3m

Question 6

Average wave height

Answer 6

0.5-1m

Question 7

Imputs of fluvial sediment

Answer 7

Osmington river

Question 8

Sediment input from cliff/shoreline erosion

Answer 8

200 000 m3

Question 9

Nature of longshore drift

Answer 9

From west to east but limited volumes of sediment moved

Question 10

Geology of coastline and length of geology

Answer 10

50m wide Portland limestone
70m wide Wealden Clay
Narrow section of greensand and sandstone

Question 11

Formation of Lulworth cove

Answer 11

1) A stream breaches the bastion (sea level) of the resistant limestone
2) Erosion continues to evolve the cove behind the narrow portland limestone entrance - the sea begins to erode the less reisistant wealden clay
3) The bay widens as the sea erodes the wealden rocks on either side
4) The seaward side the clays and sands are eroded away
5) The clay and sands are continually eroded and become wider and deeper, whilst the entrace is still a narrow gap in the portland limestone - wave action and weathering
6) The back of a cove is a 250m wide band of chalk - more resistant than clay and sandstone - shape
7) Chalk is slowly eroded and the wide section of clay and sands are have eroded - result of wave diffraction - narrow entrance ensures the waves enter into an arch shape

Question 12

What type of coastline type does lulworth cove form on?

Answer 12

Concordant coastline

Question 13

Describe the formation of Swanage Bay and Old Harry’s Rocks

Answer 13

Secondary wind direction more influcential than prevailing wind
Tidal range over a large fetch
Swanage Bay is a clay and portland limestone geology - less resistant clay eroded hence a bay formation and limestone more resistant hence headlands
Old Harry’s rocks chalk geology - more resistant - landforms
Discordant coastline

Question 14

Describe the formation of Man O’ War Cove

Answer 14

Portland limestone more resistant - reinforced by the purbeck beds behind
This blocks the formation and erosion of the chalk and wealden clay behind
The cove behind is easily eroded - less resistant rock
High energy coastline with a strong preveailing wind
Concordant coastline