Transcript Coastal Landscapes - Charleston Academy

Coastal Landscapes
Higher Geography
Physical Environments: Lithosphere
Topic Outline
1. Name and explain the erosion processes at work.
2. Explain the formation of the following erosional
landforms with the aid of a diagram and named e.g’s:
Cliffs, Wave-cut platforms, Caves, Arches, Stacks,
Stumps, Geos.
3. Explain with the aid of a diagram, the process of
longshore drift.
4. Explain the formation of the following features of
deposition with the aid of a diagram and named e.g’s:
Beaches (note there are various types), Spits,
Tombolos, Sandbars, Sand dunes & Salt Marshes.
5. Identify coastal features on an O.S map.
Aims of the lesson
• To learn about the types of wave affecting
coastal landscapes.
• To learn how to name and describe the
processes of coastal erosion.
• To learn how to describe the formation of
headlands and bays with reference to a
named example.
Swash & Backwash
Constructive Waves
Flat and low in height.
Its has a stronger swash than backwash.
This means that it is responsible for depositing
material on the coastline.
Destructive Waves
Steep and high.
The swash in this wave is weaker than the
backwash.
This means that material is removed from the
beach leading to erosion.
Coastal Erosion Processes
Hydraulic pressure
Abrasion
Corrosion
Attrition
results from large waves hurling
beach /eroded material against a
cliff.
is when waves cause rocks and
pebbles on the beach to bump into
each other and wear down in size.
is the sheer force of the waves
especially when they trap and
compress air in cracks and holes in
a cliff.
is when certain types of rock types
in a cliff are actually slowly
dissolved by the seawater.
Rate of Erosion
Waves - Strength,
frequency, height
Weather frequency of
storm conditions
Geology of the
coastline
Headlands & Bays
Take a copy of the diagram below in your notes.
Arrange the statements in order to describe the
formation of headlands and bays.
The softer rocks therefore erode backwards faster to form
sheltered bays (which may have beaches),
e.g. sandstone and clay and which meet the coast at right angles.
Headlands and bays are formed due to differential erosion,
whereas the harder rock areas jut out into the sea to form
exposed headlands.
An excellent example of this landform is Lulworth Cove on the
Dorset coastline.
Clay is a softer rock than the sandstone so is eroded more quickly.
where rocks along the coastline are formed in alternating bands of
different rock types
Lulworth Cove
Summary
So far we have…
• learnt about the types of wave affecting coastal
landscapes.
• learnt how to name and describe the processes of
coastal erosion.
• learnt how to describe the formation of headlands and
bays with reference to a named example.
On the Wall!
Each table has been given post-its.
Get your answers stuck to the questions posted
around the room
First group wins!
On the Wall
1. Name the type of wave that leads to dominant
erosion.
2. What is swash?
3. How long is the coastline of the UK in
kilometres? Closest guess wins.
4. Name the 4 processes of coastal erosion.
5. Give a factor that will affect the rate of coastal
erosion.
6. Draw a diagram of headlands & bays with a
named example.
Headlands & Bays
Aims of the lesson
• To learn how to describe the formation of a
cliff and wave cut platform.
• To learn named examples of these features.
Cliffs & Wave Cut Platforms
This clip will give you an
introduction to cliffs,
wave cut platforms and
other coastal erosion
features.
BBC Learning Zone - Cliffs
& Wave Cut Platforms
Cliffs & Wave Cut Platforms
Cliffs form where high land reaches
the sea.
Weaknesses (joints and faultlines) in
the rock are progressively undercut
by wave erosion.
This forms what is called a wave-cut
notch.
This notch is enlarged and eventually
the overhanging rock collapses.
As this processes is repeated, the cliff
retreats, exposing a gently sloping
rock surface called a wave cut
platform.
Wave Cut Platform: South Glamorgan, Wales
Hard Rock Cliffs
Hard rocks are more
resistant than soft ones,
and will form steep cliff
faces.
Made up of rocks like
basalt and granite.
Named Example:
Caithness
Soft Rock Cliffs
These cliffs often erode
rapidly.
In these cliffs, sub-aerial
processes can contribute
more to erosion than
marine processes, leading
to mass movements such as
sliding, slumping and falls.
Named Example: Fairlight
Cove, Hastings
Describe the formation of a cliff and a
wave cut platform.
Summary
So far we have…
• Learnt the formation of a cliff and a wave cut
platform with reference to a named example.
Match Up Diagram
Current cliff
location
High tide
point
Cliff is
undercut
and
collapses
Wave-cut
notch
Wave-cut
platform
Original
position of
cliff
Aims of the lesson
• To learn how to describe the formation of
caves, arches and stacks.
• To learn named examples of these features.
Green Arch of Wales
Durdle Door, Dorset
Caves, Arches, Stacks & Stumps
Caves, Arches, Stacks & Stumps
Read p123 & 124 of the
Higher Textbook.
Using the information
contained on those pages,
you are going to create a
model that shows the
formation of these
landforms.
Use the labels on the cards
to annotate your model.
Your model must include:
• A crack
• A cave
• An arch
• A stack
• A stump
• A blowhole
Large crack opened
up by hydraulic
action.
The crack grows into
a cave by hydraulic
action and abrasion.
Wave action creates
wave cut notches at This leaves a tall rock
the base of the arch,
stack.
widening it over
time until it
collapses.
The cave becomes
larger.
The cave eventually
breaks through the
headland to form an
arch.
The stack is eroded
by marine and sub
aerial processes to
form a stump.
Continued erosion of
a vertical joint in the
headland may
eventually form a
blow-hole.
Large crack opened
up by hydraulic
action.
The crack grows into
a cave by hydraulic
action and abrasion.
Wave action creates
wave cut notches at This leaves a tall rock
the base of the arch,
stack.
widening it over
time until it
collapses.
The cave becomes
larger.
The cave eventually
breaks through the
headland to form an
arch.
The stack is eroded
by marine and sub
aerial processes to
form a stump.
Continued erosion of
a vertical joint in the
headland may
eventually form a
blow-hole.
Fieldsketch
On plain A4 paper, create a simple fieldsketch of
your model with all of the appropriate
annotations.
Use a ruler and pencil.
Homework
With the aid of annotated diagrams, explain the
formation of a stack.
Tips:
• Ensure you include fully annotated diagrams
• You will need to refer to caves and arches also.
• You must include the processes that form the
features e.g. for stack, hydraulic action, attrition,
corrasion.
Homework
With the aid of annotated diagrams, explain the
formation of a stack.
Tips:
• Ensure you include fully annotated diagrams
• You will need to refer to caves and arches also.
• You must include the processes that form the
features e.g. for stack, hydraulic action, attrition,
corrasion.
Summary
So far we have…
• learnt how to describe the formation of caves,
arches and stacks.
• learnt named examples of these features.
True or False
1. A constructive wave has a stronger swash than backwash.
2. Hydraulic action is the impact of rocks and other material
on the cliff face.
3. Our named example of a wave cut platform is Durdle
Door.
4. Hard rock cliffs are more vulnerable to weathering and
often slump rather than collapsing into the sea in blocks.
5. The formation of headlands and bays is a result of a
process called differential erosion.
6. A blowhole is a made up landform.
7. Our named example of an arch is in South Glamorgan,
Wales.
Aims of the lesson
• To be able to describe the process of
longshore drift in coastal environments with
reference to a diagram.
Longshore Drift
Waves often approach a beach at an angle.
The swash carries material up the beach at an
angle and then the returning backwash drags
much of the material back down.
Over time, the material is moved along the
shore in the direction of the prevailing wind.
This processes of transportation is called
longshore drift.
Direction of movement
Backwash is
always at
right angles to
the beach
Swash
Backwash
This movement of sediment along the
coastline is called longshore drift.
Longshore Drift Poster
Activity
Each of you is going to create a
poster to demonstrate the
process of coastal
transportation.
You must use all of the
equipment provided.
Use p128 of the Higher
Textbook to help you.
Equipment
• Set of cards & arrows
• Scissors
• Glue
• A4 coloured paper
• Pen/pencils
Swash Arrows
Backwash Arrows
Transported Material
BEACH
DIRECTION OF TRANSPORTED MATERIAL
4
6
BACKWASH
BACKWASH
BACKWASH
1
2
3
5
7
SEA
Review Question
With the help of a labelled diagram, show the
main features of longshore drift.
Summary
So far we have…
• described the process of longshore drift in
coastal environments with reference to a
diagram.
Starter
Draw an annotated diagram to demonstrate a
named process of coastal transportation.
Use the whiteboards.
BEACH
DIRECTION OF TRANSPORTED MATERIAL
4
6
BACKWASH
BACKWASH
BACKWASH
1
2
3
5
7
SEA
Aims of the lesson
• To learn how to describe the formation of the
following depositional landforms with reference
to a diagram.
–
–
–
–
Beach
Spits
Tombolos
Sandbars & Lagoons
• To learn named examples for these landforms.
Coastal Deposition
Transportation of material stops once the
environment becomes more sheltered.
Currents weaken and they no longer have the
energy to transport material.
The water will also be much more shallow.
Deposition Landforms
There are 4 main landforms that it is important we learn
about:
1.
2.
3.
4.
Beaches
Sanspits
Sandbars & Lagoons
Tombolos
Using the information on each of the stations you will:
• Summarise formation into 4 bullet points
• Draw a diagram
• Give a named example
5 minutes at each station
Beaches
Beaches are the main features of coastal
deposition.
Beaches form in sheltered environments,
such as bays.
They are mainly produced by constructive
waves with a strong swash and weak
backwash.
Named Example: Weymouth Beach
Types of Beach
Shingle
Sand
Steep and narrow
Wide and flat
Large coarse
material
Smaller, finer
material
Produced by strong
swash
Produced by strong
backwash
Sandspits
Long, narrow accumulations of sand or shingle
in the sea/ocean with one end attached to the
land. The other end may be hooked due to
currents
Longshore drift moves
material along the
coastline.
There is a sudden change
in the direction of the
coastline that allows
material to be deposited,
building up and out.
Over time, the spit grows and
develops a hook if wind direction
changes further out. This can
also form if the spit crosses a
river estuary.
Waves cannot get past a spit,
which creates a sheltered
area where silt is deposited
and mud flats or salt marshes
form.
Sandbars & Lagoons
Sandbars: Ridges of sediment formed parallel to
the coast, these can join two points of headland.
Lagoon: An area of still water cut of from the sea
by coastal deposition.
Example: Fleet Lagoon, Dorset.
What are bars and how are they
created?
A bar is formed where a spit continues to grow
across a bay, creating a lagoon behind it. The
lagoon, becomes an area of still water and a salt
marsh forms in this low energy zone.
Over time the lagoon will become infilled by
deposition as either rivers flows in to it
depositing material, or as waves break over the
top of the Bar depositing coastal material
Tombolos
Essentially this is a sand bar that joins the
mainland to an island.
An example of this is Chesil Beach, Dorset.
What are tombolo's and how are they created?
Tombolo's are ridges of sand and shingle (SPITS) which join the
mainland to an island.
They are created through the process of longshore drift.
Past Paper Question
With the aid of annotated diagrams, explain the
formation of a sandspit. (10 marks)
Tips:
• What does a sandspit look like?
• What conditions are needed for coastal deposition to
occur?
• What process is taking place?
• What may form behind the sandspit?
• What other landforms can be created by its expansion?
• Named example?
Sample Answer: Sandspit
A sandspit is a long, narrow accumulation of sand or shingle extending out to sea or
across a river estuary. It is a depositional coastal landform.
Longshore drift is the process responsible for the transportation of material along
coastlines. The prevailing winds drive the swash onshore at an angle which carries
material up the beach. Once it has run out of energy the backwash retreats at a right
angle to the beach carrying material with it. This process repeats itself and material is
slowly transported along the coastline.
Transportation of material stops once the environment becomes more sheltered.
Currents weaken and they no longer have the energy to transport material.
A sandspit will form if there is a sudden change in the direction of the coastline that
allows material to be deposited, building up and out.
Over time, the spit grows and develops a hook if wind direction changes further out to
sea. This can also form if the spit crosses a river estuary as river currents will affect the
build up of material.
Waves cannot get past a sandspit, which creates a sheltered area where silt is
deposited and mud flats or salt marshes form.
Other landforms can be created by the expansion of a sandspit such as a sandbar or a
tombolo. A sandbar is created if the spit grows across a bay or cove, cutting off some
of the sea to form a lagoon. A tombolo forms if the sandspit connects an island with
the mainland.
An excellent example of this landform is Sandbanks in Dorset.
Erosional or Depositional Feature?
Divide the landforms below into two columns,
one for features created by erosion and one for
features created by deposition.
Arch
Stack
Sandbar
Wave cut
platform
Tombolo
Cliff
Cave
Sandspit
Beach
Lagoon
Aims of the lesson
• To be able to identify erosional and
depositional coastal landforms on an O.S.
map.
Coastal Landforms on O.S. Maps
As with the all of the other landscapes we have studied,
you are expected to be able to identify coastal landforms
on an O.S. map.
This type of question can be worth as many as 12 marks!
You will then be asked to explain the formation of one or
more of the landforms you have identified.
Digimap for schools - Aberdeen
O.S. Map Sections
You have each been given a pair of O.S. Maps.
One shows a coastline of erosion, the other shows a
coastline of deposition.
In groups, try to identify as many features as you
can.
In pencil annotate the O.S. maps to show coastal
landforms.
Coastline of Erosion
Coastline of
Deposition
2008 Past Paper Question
Study O.S. Map of Swanage and Reference
diagram Q1.
Describe the map evidence that shows:
• Area A and B are areas of coastal erosion.
• Area C is an area of coastal deposition.
12 marks
Summary
So far we have…
• identified erosional and depositional coastal
landforms on an O.S. map.