AQA Geography A - The Restless Earth

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The Restless Earth
Nature of the earth's crust
Distribution of plates
The earth's crust is split up into plates.
They vary in size
Types of plates
Oceanic Continental
Newer ­ most are less than 200 Older ­ most are over 1500 million
million years old. years old
Can be renewed and destroyed Cannot be renewed or destroyed
Denser Less dense
Can sink Cannot sink
Plate margins
Destructive
· Subduction
A continental and oceanic plate moving together.
The oceanic is forced to sink under the continental as it is
denser.
As a result of the friction between the plates pressure builds
up; it is then released in Earthquakes.
Volcanoes are also present at these boundaries because as
the oceanic plate is forced down it melts to form magma.
The collects to form magma chamber which then rises up
through cracks in the continental crust. Pressure increases
until an eruption is triggered.
As the plates push together, the continental crust is
squashed and forced upwards. This causes Fold Mountains.
· Collision
Two continental plates moving together.
Neither can be destroyed so the land is pushed upwards to
form Fold Mountains.
Earthquakes are common as fiction of the plates rubbing
together builds up and is released in the form of an
earthquake.
Constructive
· Two plates moving away from each other.
· Mostly found under the sea.
· As the plates move apart, magma rises to fill the cracks in the crust.
New land is formed.

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Earth quakes occur as the magma erupts to the surface.
· Eventually volcanoes are found here due to the build up of new
rock
· After many eruptions, the volcanoes often erupt out of the sea to
form volcanic islands.
Conservative
· Plates moving side by side.
· Because they move at different speeds and angles they often get
stuck.
· Pressure builds until released in the form of a violent earthquake.…read more

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Farming
· Subsidence farming
Terraces have been built into the mountainsides.
The flat areas retain water and nutrients that would
otherwise drain away, making the land more fertile and
suitable for farming.
· Lamas
Provide transport for goods and people
Provide meat, wool and milk.
Surefooted and strong so suitable for the mountainous
environment.
Hydro Electric Power
· Have exploited the steep slopes, high drops and narrow valleys.
· Melting snow adds to the water supply.
· Generates cheap electricity for the area.…read more

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Acid lava: Viscous which means it Basic lava: Runny which means it
doesn't travel far before cooling. flows long distances before cooling.…read more

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Local economy boosted as a result of tourism; everyone
wants to see the `famous' volcano.
· Negative
Lives lost
Ecosystems damaged
Housing, farmland and woodland destroyed.
The economy has suffered.
Responses
· Immediate
Shelter offered
Search and rescue for survivors
Ash cleared to allow traffic to flow
Distribution of masks
· Long term
Buildings and bridges rebuilt
Replanting forests
Roads repaired
Efforts to ensure tourism again.
Monitoring and predicting volcanic eruptions.…read more

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Super volcanoes
Characteristics
Mega colossal volcano
Erupts at least 1000km3 of material.
Have calderas
· Depression marking the extent of the collapsed magma chamber.
Formation
Magma rises at a weak point in the earth's crust: hotspot
Magma creates a large bulge in the earth's surface
A large mass of rock stops the escape of the magma
Cracks appear and gas and ash erupt from the chamber
Magma chamber collapses leaving a caldera.
Likely effects of an eruption.…read more

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Constructive Friction and pressure from plates
moving apart produces less severe
earthquakes.
Conservative As plates slide past each other they
often get stuck. The pressure builds
until released in the form of an
earthquake.…read more

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Cause
· Indian and Eurasian plate colliding
Effects
· Primary
88,000 people killed
374, 000 people seriously injured
80% of buildings collapsed
Telecommunication links were broken
· Secondary
11 million people were homeless
Roads blocked by landslides
$75 million worth of damage
Landslides blocked rivers
Responses
· Immediate
Foreign aid requested
20 helicopters rescued people
· Long term
Rebuilding of houses, buildings etc.…read more

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Further 6 months to fix all of the roads
New rules for buildings to ensure less damage next time
Built further apart to stop domino effects
Flexible steel frames for high rise buildings
Rubber blocks under bridges to act as shock
absorbers
Differences
Effects
· More people killed and injured in LEDC than in MEDC
Lack of preparation in LEDC in comparison mainly due to lack
of funds
No training for public resulting in panic
No emergency services
Had to rely on foreign aid ­…read more

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Computer controlled weights on the roofs of buildings that
counteract the shaking of an earthquake.
Fire resistant building materials
Automatic window shutters to prevent falling glass
Steel frame that can sway with the earth movement
· How it will help
There will be less damage
Less to repair
Saves money in the long term
Preparation
· Example
Earthquake drills
Primary schools every week
On one day a year in Japan everyone does a mock
earthquake.…read more

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