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Restless Earth
Contents
1.
1 The Structure of the Earth
2.
2 Distribution of the Earth's Tectonic Plates
3.
3 The Plate Boundaries
4.
4 Volcanic Hazards
1.
4.1 Shield Volcano...
2.
4.2 Composite Volcanoes...
5.
5 Haiti - 7.0 on the Richter Scale
6.
6 What is needed after a natural disaster - Case Study
The Structure of the Earth
The Earth is made up of four concentric layers:
By Surachit [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0 , via
Wikimedia Commons
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Inner Core – This is in the centre of the earth where it is hottest. It is solid and consists of Iron and Nickel with temperatures of
up to 5,500oc.
Outer Core – This is a liquid layer also composed of Iron and Nickel and is extremely hot with temperatures similar to the
inner core.
Mantle – This is the widest section of the Earth at approximately 2,900km. It is made up of semi-molten rock called magma.
Towards the top of the mantle the rock is hard, but lower down nearer to the centre of the earth the rock is soft and beginning
to melt.
Crust – This is the thin outer layer of the earth which is only between 0-60km thick. The crust is the solid rock layer which we
live on. There are two different types of crust:
o Continental Crust – Carries land
o Oceanic Crust – Carries water
Distribution of the Earth's Tectonic Plates
http://pubs.usgs.gov/publications/text/slabs.html
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The Earth's crust is broken up into pieces called plates.
Convection currents in the mantle caused by heat rising and falling generated by radioactive decay in the core, causes the
plates to move.
The plate movements and the activity inside the earth is called plate tectonics.
Plate tectonics cause earthquakes and volcanoes which usually occur on plate boundaries.
The Plate Boundaries
Destructive - Where two plates collide and one plate flows beneath the other – subduction.
- Earthquakes and volcanoes occur here
- E.g.: Nazca Plate and South American Plate
Constructive - Rising convection currents pull crust apart forming volcanic ridge - Mid-Atlantic Ridge
- E.g.: Eurasian and North American Plates
Conservative - Two plates slide past each other
- Earthquakes occur here
- E.g.: San Andreas Fault, California
Collision - Two continental plates collide and the two plates buckle
- Many earthquakes occur here
- E.g.: Indo-Australian and Eurasian plates
Volcanic Hazards
Shield Volcano...
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Are found on constructive plate boundaries
Are formed by eruptions of thin, runny lava which flows a long way before it solidifies
Have gentle sloping sides and a wide base
Contain basaltic magma which is very hot with low silica and gas content
Erupt frequently but not violently
Composite Volcanoes...
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Are found on destructive
plate boundaries
Are formed by eruptions
of viscous, sticky lava
and ash that don’t flow
far
Have steep sloping sides
and a narrow base
Made up of layers of
thick lava and ash
Contain andesitic magma
which is less hot but
contains lots of silica and
gas
Erupt infrequently but
violently, including
pyroclastic flows (mix of
ash, gases and rock)
By Top1963 / TryfonTopalidis (Own work) [CC-BY-SA-3.0 or GFDL],
via Wikimedia Commons
Earthquake Hazard
There are two scales which are used to measure the magnitude
(strength) of an earthquake.
Kashmir, 2005
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The Richter Scale measure the amount of energy which is
released from the earthquake.
o The magnitude increases 10 fold as you move up
the scale
The Mercalli Scale measures the effects or impacts and is
measured in roman numerals I to XII.
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75,000 dead
75,000 injured
2.8 million homeless
Property damage $440
million
Remote mountainous
area
California, 1989
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Up to 12,000 homeless
3757 injured
Built up, accessible area
Property damage $10bn
63 dead
Gas mains burst and fires
broke out
Haiti - 7.0 on the Richter Scale
Secondary Impacts
Primary Impacts
316,000 people were killed and 1
million made homeless
250,000 homes and 30,000 other
buildings destroyed or badly damaged
they had to be demolished
Transport and communication links
were damaged
Hospitals (50+) and schools (1300+)
were badly damaged
The main prison was destroyed
Presidential palace was destroyed
Roads blocked by rubble
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Two years after the earthquake...
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1 in 5 people lost their jobs because
so many buildings were destroyed
Hospitals became full very quickly
Diseases, especially cholera became
a problem
People sleeping in streets for fear of
more earthquakes.H
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80% of the rubble had been cleared
350,000 people still living in tents
Only 111,000 out of the 125,000 shelters planned had been built
Not all the money promised in aid had been sent, making recovery difficult
There is a shortage of safe, clean water
Only 18% of the required homes had been built
Managing Earthquake & Volcanic Hazards
The difficulties of predicting these hazards are that we don’t know…
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When it will happen
Exactly where it will happen
How big it will be
What other impacts it may have
How many people live there
However, there are things we can look out for.
Signs of a volcano nearing eruption
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Animals and birds moving out from an area
An increase in gas emissions – When a volcano is
close to erupting it starts to release gases such as
sulphur. The higher the content of these gases, the
closer it is to erupting.
An increase in soil temperature – The temperature
around a volcano will increase when it is about to
erupt. We can use thermal imaging cameras to detect
these heat changes
The volcano swelling
An increase in small earthquakes – As the magma
moves up through the cracks in the earth’s crust,
many small earthquakes are set off.
Water in ponds getting warmer
Earthquake preparations
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Because it is very hard to predict when an earthquake or
volcano is going to happen, people need to be prepared for
when one may occur. People can…
Create an exclusion zone around the volcano
Make sure they have an evacuation plan
Have an emergency supply of basic provisions such as food
and water
Ensure that money is available to deal with the emergency
Ensure that a good communication system is in place
Do earthquake drills so they know what to do in the event
of a real earthquake
Build earthquake proof buildings. In San Francisco, the
Transamerica Pyramid was designed to absorb the energy
of an earthquake and withstand the movement of the Earth
Build roads and bridges to withstand the power of an
earthquake
What is needed after a natural disaster - Case Study
Izmit Earthquake, 1999
What is needed...
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The Izmit earthquake struck 55 miles east of Istanbul, Turkey near the
industrial city of Izmit
It happened on August 17th at 3:02am local time and lasted 45 seconds.
The rate of urbanisation in Turkey had been rapidly increasing and with the
huge amount of people in the city and lack of housing, people resorted to
building their own houses.
More than half the population in Istanbul is living in illegal accommodation
says Turkey's Chamber of Commerce.
So when the earthquake struck, it was these self-built houses and illegal houses
which didn't meet building regulations that collapsed leaving people trapped in
their houses.
Immediate response and relief efforts
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International Aid
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Trained volunteers to help the injured
people
Clean water to prevent the spread of
disease
Food – shops, towns, roads and
farms are often damaged
Radio communication – phones often
don’t work
Medical help
A plan to evacuate the area if
necessary
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A Swiss team of 98 rescue experts and 18 dogs
The EU said it was sending $2.1 million in aid
Britain donated $800,000 | Germany provided $560,000 | Ireland added $270,000 | Swiss charities promised $2333,000 |
Finnish Red Cross gave $50,000
Many of the survivors were left to help with the rescue effort
Hospitals made triage and were poorly prepared lacking basic medical equipment
Canine search + rescue
Criticisms of the Turkish Authorities
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Inadequate detection system which resulted in relief agencies sending too little aid
Government responded slowly
Failure to provide maps, interpreters and information to foreign aid helpers