Download Paper 1 restless earth

Temperature increases
towards the centre
Plate tectonics
Structure of the Earth
Crust – Two layers of rock that move on top of the mantle
1. Oceanic Lithosphere – heavy rock created at constructive
plate boundaries – thinner than continental crust
2. Continental Lithosphere – less dense (lighter) rock – thick
Mantle – solid – largest part of the inside of the Earth – where
convection occurs – part nearest the crust is partially molten
which allows plates to move across it  Asthenosphere.
Outer core – liquid – rotates giving the Earth it magnetic field
Inner Core – Solid – made of iron and nickel.
Main Tectonic Plates
• The North
American Plate
• The South
American Plate
• The Eurasian
Plate
• The Pacific Plate
• The Nazca Plate
• The Indian Plate
How does plate tectonics occur?
1.
2.
3.
4.
5.
Heat from the core heats the mantle.
The heated rock rises up because it is less
dense than the cooler rock above.
As it rises it begins to cool as it reaches the
crust. This rock is now more dense than
the hotter rock. This causes it to sink.
This rising and sinking rock creates
convection currents.
These convection currents drag the
tectonic plates causing them to move
along the surface. This movement is called
plate tectonics.
Plate margins
Destructive Plate Boundaries
E.g. the boundary between the Nazca and South American
Plates
• Two plates collide – oceanic crust
subducts underneath the continental
crust.
• Many earthquakes and composite
volcanoes.
Constructive Plate Boundaries
E.g. the boundary between the Eurasian and North
American Plates
• Convection currents pull the plates
apart forming a volcanic ridge.
• Lots of volcanoes and some
earthquakes
Conservative Plate Boundaries
E.g. San Andreas Fault, California
• Two plates slide past each other
• Lots of friction created which
Causes earthquakes
Collision Plate Boundaries
E.g. The Himalayas, China
• Two continental plates collide with
each other
• Lots of earthquakes
• No volcanoes
Fold mountains
The formation of fold mountains
Case study of human activity in fold mountains:
The Alps
• Winter sports such as skiing in resorts such
as Chamonix.
• Climbing and hiking in the summer months.
• Summer lakeside holidays, eg Lake Garda.
• Agriculture - takes place mainly on south
facing slopes and includes cereals, sugar
beet, vines and fruits.
• Forestry - coniferous forests for fuel and
building.
• Communications - roads and railways follow
valleys.
• Hydroelectric power (HEP) - steep slopes and
glacial meltwater are ideal for generating
HEP. Hydroelectric accounts for 60 per cent
of Switzerland's electricity production.
The challenges of living in the Alps include: the
relief (high mountains and steep slops give little
flat land for farming), the climate (temperature
drops with height), soils (infertile) and
accessibility (difficult to cross the mountains).
Earthquakes
The magnitude of
earthquakes is measured
on the Richter Scale.
The visual impact of
earthquakes is measured
on the Mercalli Scale.
KEY TERMS:
The focus is the point at which the earthquake happens
beneath the ground.
The epicentre is the point on the surface above the focus. This
is where the effects of the earthquake are worst.
Shockwaves radiate in all directions from the focus.
Location
Port-au-Prince, Haiti
Christchurch, New Zealand
Facts
Magnitude 7
12 January 2010
Magnitude 6.3
22 February 2011
Primary impacts
316 000 dead
250 000 homes destroyed
30 000 offices and factories destroyed
Roads blocked
181 dead
20 000 injured
50% of city buildings damaged
80% of city with no electricity
Secondary
impacts
1 in 5 lost their jobs
Morgues and cemeteries overflowed
Spread of disease eg cholera
Looting of destroyed houses
Businesses out of action
Christchurch could not host the Rugby World Cup
Schools had to share classrooms
Response
$440 million given in aid
810,000 people in aid camps
4.3 million people needing food rations
Chemical toilets provided for 30,000 residents
Temporary housing provided
80% of roads repaired
Volcanoes
Volcanoes
Composite Volcanoes – e.g. Etna, Italy
and Krakatoa, Indonesia
• Destructive plate boundaries
• Thick, highly viscous andesitic lava
that does not flow very far
• Steep sided cone shape
• Alternating layers of ash and lava
• Erupt rarely but are very explosive
Shield Volcanoes – e.g. Surtsey island,
Iceland
• Constructive plate boundaries
• Thin, low viscous, runny basaltic
lava that flows a long way
• Gently sloping sides with a very
wide base
• Erupt frequently but less explosive
and dangerous
Shield Volcano
Montserrat: Fact file
• Montserrat is an island located in the Caribbean, south of the
USA. The composite volcano, in the south east of the island, had
been dormant for hundreds of years. It erupted in 1995 and
1997. Main hazards were ash fall and pyroclastic flows.
• Primary effects: 20 people were killed. 5000 evacuated. Two
thirds of homes destroyed.
• Secondary effects: Cost of rebuilding. Tourist industry
disrupted.
• Immediate responses: Evacuation. Emergency aid for shelter.
• Long-term responses: UK aid to rebuild infrastructure. Volcano
observatory built to monitor. Attempts to re-attract tourists.
Composite Volcano
A
supervolcano
eruption is
1000 times
bigger than a
normal
volcano.
Tsunamis
Tsunamis are a secondary affect of
an earthquake under the ocean…
Case study: The Asian Tsunami (2004)
Sri Lanka: 32,300 dead or missing. 97,000
houses destroyed. Over a million left
homeless.
India: 16,400 dead of missing. 157, 000 houses
destroyed. 4500 fishing boats destroyed.
Thailand: 5400 dead or missing. 5000 homes
destroyed. Loss of income as tourism industry
destroyed.
Managing earthquakes and volcanic hazards
It is hard to predict when earthquakes or
volcanoes will happen because we do not
know…
• When it will happen
• Exactly where it will happen
• How big it will be
• What other impacts (secondary effects)
there might be
• how many people will be effected
Things that can help us predict them are…
• Animals and birds leaving the area
• An increase in ground gas emissions
• An increase in rock/ soil temperature
• The volcano might swell (get bigger)
• Increasing numbers of small earthquakes
• Water stores (lakes and ponds) getting
warmer
Prediction, protection and
preparation
Earthquake
proof
buildings
We can
reduce the
impacts of
earthquakes
by making
buildings
stronger.
Here are
some ways
of doing this.
How to reduce the impacts of earthquakes or volcanoes
• Volunteers and emergency services to clear away debris and look for survivors
• Food and clean water to prevent the spread of disease
• Radio communication in case phones no longer work
• Medical help to aid survivors
• An evacuation plan to relocate people after the event
Test yourself….
Why do
earthquakes
happen?
What causes
tectonic plates to
move?
What are the
different types of
volcanoes?
How could we
predict volcanic
eruptions?
What are the
impacts of
earthquakes?
What causes
tsunamis?