Earth hazards

• Crust


  • Soil, rocks
  • goes down 25 miles
• Mantle 


  • thickest layer of the earth
  • range from 1300℃ to 5000℃
• Outer core


  • made of iron and nickel
  • liquid
• Inner core


  • made of iron and nickel
  • solid
  • tempurature can reach 5500℃
• Earth Hazards

  Events such as earthquakes and volcano eruptions that cause harm
• Continental Drift


  The idea proposed by Alfred Wegner that continents were together in mega continent Pangea, then drifted away that forms our planet now and will drift back together.
• Evidence of Continental Drift


  • Study of fossils - similar fossils are found in different continents
  • Shape of continents - they fit together like a jigsaw
  • Pattern of rocks - similar patterns of rock layers on different continents
• Continental crust

  The older continental crust is mainly made from granite. It is the thicker of the two plates. This is a less dense than the oceanic crust, so therefore it does not sink.
• Oceanic crust

  The younger oceanic crust is mainly made from basalt. It is the thinner of the two plates. This is more dense than the continental crust and is frequently being destroyed.
• Constructive plate boundaries


  Two plates move apart, magma rises and fills the gap

  Non violent shield volcanoes are formed

  Causes earthquakes
• Destructive plate boundaries (2 different types of crust)


  Oceanic and Continental plates colide, oceanic plate sinks as it's more dense

  Creates volcanoes and earthquakes
• Destructive plate boundaries (same type of crust)


  no plates sink, land is pushed up creating mountain ranges

  creates earthquakes

  no volcanoes
• Conservative plate boundaries


  the plates slide past one another

  different direction or same direction but one faster

  friction between the two creates earthquakes
• Earthquakes


  A suddent movement in the Earth's crust. The sudden release of energy that causes a sesmic wave. They usually occours at margins.

  
• Richter scale

  • each step up the scale has 30 times more energy released than the previous one
  • special equipment needed to measure the strength of vibrations
  • measure the amount of energy released (magnitude)
  • humans can't feel magnitude 1 - 2 on the scale
  • over 5 is a major earthquake
  • no upper limit
• Mercalli scale

  • measured by eye witness and photographic evidence
  • measure the effects and damage caused by an earthquake
  • uses a scale of 1 - 12
  • not effective in areaas which have no buildings or infrastructure
• Dangers of areas of tectonic hazards:

  • eruption: plyroclastic flow, ash clouds
  • damage to environment
  • damage of homes
  • impacts to livelihoods
  • deaths & injuries
  • air pollution
• Reasons why people live near tectonic hazards

  • soil are extremely fertile
  • living there for generations
  • good climate
  • good views/landscape
  • cheap land
  • unaware of dangers
  • tourism - positive economic impacts
  • religous reasons
  • used to the risks
• Monitoring and prediction: Volcanoes

  • signs of volcanic activities - eg. gas, smoke
  • remote sensing - detect heat
  • tilt meter - shows deforms in volcano
• Protection: Volcanoes

  • embankments & explosives to redirect lava to minimise damage
• Planning: Volcanoes

  • exclusion zones - moving people away from volcanoes
  • sending warnings and information to the public
• Monitoring and prediction: Earthquakes

  • most likely after long periods without any plate movements
  • seismograph can measure small foreshocks before the main quake
  • animals often act strangely before one
• Protection: Earthquakes

  • all new buildings must comply with strict earthquake planning regulations
  • frequent safety checks
  • existing buildings, roads and bridges should be strengthened
• Planning: Earthquakes

  • prepare disaster plans and carry out regular practices - earthquake drills
  • train emergancy services such as police, fire and ambulance crews
  • organise and prepare hospitals and evacuation centres in safe areas
  • educate people about what to expect and what will happen
• Tsunami


  A large sea wave triggered by a sudden displacement of ocean water caused by volcanic eruptions, earthquakes, meteorites etc.