Transcript CCC 3

Different
Coastlines
• What do these
photos show?
• What are the
similarities and
differences
between them?
• What produced
these
differences?
Waves
Geology
There Goes Concord Again
The Native Hipsters
Concordant and Discordant Coasts
Investigate concordant and discordant
coasts and the influence of joints and
faults.
Introducing Dorset’s Jurassic Coast
Rock Structure
Rock structure simply means the way different rock types
are arranged.
Rocks are generally found in layers, called strata.
This means there may be several types of rock in one cliff.
The cliff will only be as resistant as its weakest layers.
• Rock strata can be arranged in two ways along coastlines:
– If the layers are parallel to the coastline, the coast is
concordant.
– If the layers are perpendicular (at 90o) to the coast,
the coast is discordant.
• Concordant coasts have the same type of rock all along
the coastline.
• Discordant coasts have lots of different rock types. When
these two types of coast erode, different landforms are
produced, as the diagram shows.
Concordant and Discordant Coasts
• Use three colours to
shade the layers of rock
on your map.
• Complete the key.
• Identify the hard and
soft rock.
• Read the definitions of a
concordant and
discordant coastline.
Label a concordant coast
and a discordant coast on
your map.
Discordant
coastline.
Concordant
coastline
Landforms on a Discordant Coast
Headlands and Bays
The harder rocks (e.g. chalk and
limestone) are more difficult for
the waves to erode, so they stand harder
rock
out as headlands.
The softer rocks, which are clay and
sand in Dorset, are more easily
eroded and so form bays. In the
Swanage area, the alternating
hard and soft rocks are at right
angles to the coast.
Label a bay on your map. Label a
headland.
What other land forms might we
expect to find on a discordant
coast?
Bay
Headland
The Old
Harry Rocks
are here.
Discordant
coastline.
Bay
Concordant
coastline
Landforms on a Concordant Coast
Coves
A cove is an ovalshaped bay with a
narrow opening to the
sea.
Did you know?
Because coves have
narrow entrances from
the sea, but shelered
beaches hidden by
steep cliffs, they were
often used by
smugglers in the past.
Layers
(strata)
parallel
to the
sea
Concordant Coasts: Coves and Cliffs
1. Study the photo of Lulworth Cove
and put these changes into a
correct sequence:
– Erosion by sea
– Less resistant sand and clays
are eroded
– Cuts through resistant
limestone
– Cove forms
– Cliffs of resistant limestone
– Sea can’t erode resistant chalk
so widens cove
– Forms a break in the cliff
– Sea reaches resistant chalk
2. Describe how Stair Hole will change
in the future as it continues to
erode.
3. Draw a sketch of the photo A.
Shade it so show the different rock
strata (layers). Label them.
Photo A
Joints and Faults
• Weaknesses in the rock
forming cliffs influences
erosion. There are two types
of weakness:
– Joints are small, natural
cracks, found in many
rocks.
– Faults are larger cracks
caused in the past by
tectonic movements.
• The more joints and faults
there are in a cliff, the
weaker the cliff will be.
Hydraulic action attacks
faults and joints, causing
erosion.
Joints in
limestone
Faults at
Stair Hole
Different
Coastlines
Find the photos
showing a:
• bay;
• cove.
Bays and Coves
1. a) Find the photos showing a:
• bay;
• cove.
b) Split your page into two columns.
c) Stick a photo at the top of each column.
d) Complete the table to show the differences
between the two landforms. Now add any
similarities you can think of.
2. Annotate the photos to show what you know
about them. E.g. identify the layers of hard
and soft rock.