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Restless Earth

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The Structure of the Earth
The Earth is made up of four concentric layers:
  • Inner Core – This is in the centre of the 

    By Surachit [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0 , via
    Wikimedia Commons

    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:
    • Continental Crust – Carries land
    • Oceanic Crust – Carries water

Distribution of the Earth's Tectonic Plates

  • 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...

  • 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...

  • 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)

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Earthquake Hazard

    There are two scales which are used to measure the magnitude (strength) of an earthquake.
    • The Richter Scale measure the amount of energy which is released from the earthquake.
      • 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.
      Kashmir, 2005
      • 75,000 dead
      • 75,000 injured
      • 2.8 million homeless
      • Property damage $440 million
      • Remote mountainous area
        California, 1989
        • 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

          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
            Secondary Impacts
            • 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.

              Two years after the earthquake...

              • 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
                • 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
                  • 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
                    • 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.
                      What is needed...
                      • 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
                      Immediate response and relief efforts

                      • International Aid
                      • 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
                      • 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.