Geology and Rock Type
The most important feature of a coast is often the
type of rock in the area. Some rocks are resistant
to erosion, whereas other rocks are more easily
eroded.
• Resistant rocks= hard igneous rocks e.g. Granite
and basalt, which are resistant to erosion
• Fairly resistant= sedimentary rocks e.g.
Sandstone, chalk and limestone
• Least resistant= weak sedimentary rocks e.g.
Clay and shale. These will erode at a faster rate
Task:
Complete a hierarchy
from MOST to LEAST
resistant coastal
rocks.
Contrasts in the cliffs in hard rock and in soft rock
areas.
Annotate your photographs to show the contrasts using the table page 70
Boulder clay cliffs,
Holderness coastline
Land’s End, Cornwall
Granite cliffs
Concordant and discordant coasts
This is a DISCORDANT Coastline.
This is where the coastline is made up
of BOTH hard and soft rock. They
are usually at right angles to the
coast.
This picture shows Swanage on the
Dorset coast- it has a mixture of
erosional features including headlands
and bays which are there because of
the alternating hard and soft rock
types.
Dorset coastline
Swanage Bay
An example of headlands and bays on the Dorset coastline.
Discordant coastline
Concordant and discordant coasts
This is a CONCORDANT Coastline.
This is where the coastline is made up
of hard and soft rock that run
parallel to the coastline. This means
the rock erodes at different rates.
This is a picture of Lulworth Cove on
the Dorset Coast. Waves have cut
through the narrow entrance to the
cove and then rapidly eroded the
softer rock behind it.
Use page 75, Geography
GCSE,Edexcel B, to label
the rock types on the
diagram.
Lulworth Cove
Where is the band of
limestone rock?
Where is the band of
clay?
Label the band of
chalk
Explain how the cove
was formed
Plenary
Exam Question
Explain how geological structure and rock
type have a major influence on coastal
development and landforms (6)