Transcript concordant coastline

Coastal Change and
Conflict
Revision Summary
Coastlines are all different!!!
The type of rock at the coast affects the shape
o f the coastline.
Granite
Basalt
Limestone
Chalk
Sandstone
Hard
Igneous Rock
Shale
Clay
Soft
Sedimentary Rock
Sedimentary
Rock
Describe how this coastline might have change in 50 years
time. Explain the natural processes that contributed to its
change Use diagrams to help.
(6 marks)
Coastlines where the geology alternates between strata (or bands) of hard rock and
soft rock are called discordant coastlines. A concordant coastline has the same type
of rock along the coastline. Concordant coastlines tend to have fewer bays and
headlands.
This is Lulworth Cove on the Dorset coast. It is a concordant coast.
Make sure you can sketch this coastline and describe how Stair Hole will
change in the future as it continues to erode.
Key Terms to know and use:
concordant, hydraulic action, corrosion, abrasion, attrition, sedimentary
rock, headland, bay, limestone, chalk, sand, clay
Lulworth
Cove
Stair Hole
Discordant coast
Task – draw this coast as it would be in 100 years time.
Suggest some rock types for the grey, orange and brown
rocks.
Remember each of these 4
factors affect Coastal Erosion.
The Fetch is
the distance of
water wind
blows over
before it
reaches land.
Dont forget
to have a go
at the wave
Wave
simulator
Summer waves have:
• A strong swash
• Transport sand up the beach
• Sand is deposited as a bank or
beach berm.
Winter Waves
•They have strong backwash
•This erodes sand from the
beach
•The sand is carried offshore
by an underwater rip current
•The sand is deposited out at
sea, forming an offshore bar.
At a river mouth, longshore
drift pushes sediment out
into the river. It is deposited
forming a long neck of sng
and shingle called a spit.
A tombolo is
where a beach
grows out to meet
an island –often
produces when
two longshore drift
currents from
different directions
meet.
Small bays can often be
blocked by a bar of sand
which grows across the
mouth of the bay by
longshore drift. Behind the
bar a shallow lagoon forms.
In the calm water behind a spit or
bar salt marshes can form. As the
salt marsh gradually gets colonised
by plants it will eventually become
new dry land.
Sand dunes are created
parallel to the shoreline when
strong winds blow inland .
Sand dunes are often stablised
by tough plants like Marram
grass
Sea Level rise is due to
A) The melting of Polar icecaps, Glaciers and the ice sheets of Greenland due to higher
global temperatures.
B) Warmer water taking up more space process know as Thermal Expansion.
Diagram A
Diagram B
warmer water
up
more
SPACE!
takes
The Maldives are a group
of low lying islands in the
Indian Ocean.
Most are less that 1
meter above see level.
Sea level rise is predicted
to be around 1 cm a year
so in 100 years the
Maldives will be
underwater.
Problems include gradual
decline of tourism on the
islands creating poverty.
Eventually all the islanders
will become refugees.
Factors leading to a Storm Surge
Natural
Tidal
patterns
Shallow
sloping
beaches and
coastlines
Storm
Surge
Low air
pressure
Large
Waves
Spring
Tides
Sea level rise
Case Study
In 1953, when there was a 5 meter storm serge in the North sea, over 300 people
were killed in the UK and 1800 in the Netherlands in devastating flooding.
http://www.metoffice.gov.uk/corporate/pressoffice/anniversary/floods1953.html
Why Cliffs Collapse
Marine processes
•The base of the cliff is eroded by hydraulic action and abrasion, making the cliff
face steeper.
Sub-aerial processes
•Weathering weakens the rock. This can be mechanical weathering like freezethaw action, or chemical weathering, like solution.
•Heavy rain saturates the permeable rock making the rock heavier.
Human Actions
•Building and walking on top of the cliffs adds weight and pushes down on the
weak cliff.
Groynes – prevent longshore drift
Revetments – break up
incoming waves. Can
be ugly and restrict
beach access.
Rock Armour – absorb wave
energy, cheap and easy to
build.
Sea wall - reflects waves back.
Expensive but can provide
recreational facilities.
Gabions – dissipate wave
enery. They are cheap but
not very strong
Case Study - This is a picture of Barton
of Sea, Dorset.
Causes:
Mass movement is the major cause of cliff
erosion. But increasing bad weather, cliff
foot erosion and water movement in the cliff
all play a part. Human activity such as
building on top of the cliff increases the risk
of collapse.
Impacts:
Homeowners could lose their homes to the
sea. Houses will fall and insurance may be
impossible to get.
Rapid cliff collapses are dangerous for
people on top of the cliff and on the beach.
Roads and other infrastructure
(electricity/phone cables , gas and water
pipes) are destroyed.
Many people would say the erosion makes
the area unattractive.
Solutions:
The people of Barton on sea want se
defences but they are expensive and
there is no agreement of which type of
defence would work best.
Managing the modern way – a Holistic
approach
Soft engineering solutions
• Planting Vegetation to make cliffs more stable .
£20 -£50 per square meter.
• Beach nourishment; sand is pumped onto thje
nbeach to increase its size. £500 - £1000 per
square meter.
• Offshore breakwaters; built using rip-raps they
force waves to break befre reaching the the beach
and cliff. £2000 per meter.