Coasts
VCE Geography
Definition
Coast: Where the land meets the
ocean.
– Usually a 3 or 4 kilometre strip.
Coastal:On, near, or associated with
the coast.
Importance
Lookat the following photos and
note the many uses of the coast by
people.
Why are coasts important?
Coastal regions are about 15% of the
earth’s land surface.
Coastal regions have 50% of the
world’s population.
– 3.1b people live within 200km of the
sea.
75% of the population will live in
these regions by 2025.
For example: Europe
Europe has 89,000 km of coastline.
Almost half of the population now
lives within 50 kilometres of the sea.
The coastal zone resources produce
much of the Union’s economic
wealth.
– The fishing, shipping and tourism
industries all compete for coastal space.
Zones of the coast
Offshore zone
Nearshore zone
Intertidal zone.
Backshore
Hinterland
– The area behind a coast.
Draw and label a cross section.
Four natural systems
The coast is produced by the
interaction of four natural systems.
– Biosphere.
– Lithosphere
– Atmosphere
– Hydrosphere
Biosphere
The living world
– Vegetation which includes
Spiniflex
Marram grass
– These anchor sand and allow sand dunes to form.
– Animals which change the coast.
Fish
Birds
People
Grass
Grass
Vegetation holds the dunes in
place
Animals
Trees
Seaweed
Lithosphere
The earth’s crust.
– Parent rocks erodes to form sand.
– Different rocks erode at a different rate.
– Variations in the rate of erosion cause
bays (where sand is deposited) and
rocky outcrops which form cliffs.
Atmosphere
Winds, air and sun.
– Drives and blows the sand into dunes or
away.
– Cause waves and erosion of the rock
into sand.
Hydrosphere
The water
– Waves wear down rock and produce
sand.
– Waves, currents and tides deposit sand
on the beaches.
– Rivers move sediment to the coast from
inland.
The river brings sediment to the
coast
Four systems in action
Draw a picture of a beach.
– List the four systems and how you think
they produced the coastline shown.
Waves: Hydrosphere and
Atmosphere
Waves: Erosion and Sediment.
– Erosion – wearing away.
– Transportation – moving from one place
to another.
– Deposition – leaving somewhere.
Waves and wind
In Victoria swell is caused by the
wind coming across Bass Strait and
local winds.
Size of the swell is determined by
the speed of the wind and the
distance it has travelled.
The distance the wind moves over
the water is called the fetch.
Waves
Waves and wind
Energytransfers to the water which
moves in a circular motion.
– This becomes simply back and forth in
shallow water.
Waves build and collapse in shallow
water.
– Form a breaker.
Moreturbulence means more
sediment is moved.
Swash and Backwash
The movement of water up the shore
is called the swash.
The movement back is called
backwash.
Constructive Waves
These build beaches.
– Waves of less than 1 metre.
– Less than 10 breaking per minute.
– Swash is stronger than the backwash
and there is a net movement of
sediments onto the beach.
Destructive Waves
These take sediment away.
– Larger than one metre.
– Break more than fifteen per minute.
Thereare coastal treatments to
reduce this damage.
– Groynes
– Some seawalls.
Destructive Waves
Five Types of Coast
Sandy beaches
Cliffs
Wetlands.
– Eg Mangrove Swamps
CoralReefs
Seagrass meadows
– Low wave energy.
Hydrosphere: Tides
Tides are caused by the gravitational
pull of the sun and the moon.
There are two high tides and two low
tides each and every day.
The times vary each day by about
fifty minutes.
Hydrosphere: Tides
The movement of the shoreline from
high to low tide is called the ebb
tide.
The movement of the shoreline from
low to high tide is called the flood
tide.
You get larger tides when the moon
is full. This is the king tide.
Hydrosphere: The Changing Sea
Level
Victoria was below the sea 500 million
years ago but has been land since.
During the last ice age, around 20,000
years ago, sea level was about 100 metres
lower.
The sea has been at its current level for
around 8,000 years.
Changes to the global climate contributes
to a rising sea level.
Questions
1. What is the rising tide properly
called?
2. What are all five types of coasts?
3. How was sea level different in
Victoria during the last Ice Age?
4. When do king tides occur?
Atmosphere: Extreme Weather
Cyclone Althena hit the coast of
Queensland in 1971 and the shore
receded by 14 metres.
A storm in Melbourne caused the loss
of the Middle Park beach in one day
in 2005.
Lithosphere: Geological Processes
There are different types of rock in
different places around Victoria.
– Basaltic lava and tuffs around Phillip
Island.
– Limestone around the south west coasts
such as Port Campbell.
– Sandstone around Brighton and
Mornington.
– Quartz around Wilson’s Promontory and
squeaky beach.
Layers of Rock
Rock
Lithosphere: Landforms created by
erosion
Wave cut platforms
Wave Notch
Cave
Arch
Stack
Bay
Blowhole
Cliff/Bluff
Headland
Wave Cut Platform
Headland
Lithosphere: Landforms created by
deposition
Sandy beach
Sand dune
Lagoon
Sandbar
Spit
Mudflats
Human activity
Significant issues in Victoria are –
– Dredging
– Water quality
– Loss of coastal species and their habitat.
– Coastal development
– Movement of the coastal sediments
– Safety and amenity of beaches.
Issue: Water quality
Generally very good around Australia.
Those located near cities are spatially
associated with marine pollution.
A number of sources
– Runoff (the biggest source)
– Marine transport
– Dumping
– Off shore production waste.
These are issues of hydrosphere
Issue: Loss of species and habitat
Introduced species are a problem.
– Invade the habitat of native species.
– Plants and animals
– Marine life arrives on the hull on foreign
ships.
Rubbish is a threat to sea life.
– Especially six pack plastic rings.
These are issues of biosphere.
Loss of species
Rubbish is a real problem
Coastal development
Homes and other infrastructure.
– Increases human uses of the coast.
– Pedestrian traffic erodes vegetation,
cliffs edges and dunes.
Coastal Homes
Issue: Movement of sediments
70 miles of Victorian coastlines is
modified by groynes, jetties,
breakwaters and piers.
Some buildings have had unexpected
consequences such as the erosion of
beaches or build up of silt.
These are issues of the lithosphere
Sea Wall
Foot traffic
Safety and amenity of beaches
Protect people from the risk of:
– Rock falls
– Cliff and dune collapses
– Drowning
Safety
Erosion and Safety
The End