earthquakes and volcanoes

• Plate margins

  • Destructive
  • Constructive
  • Conservative
• Destructive margins

  1. Convection currents move two plates towards each other

  2. The oceanic plate is denser and so subducts under the less dense continental plate

  3. Due to friction, and heat in the mantle, the oceanic plate melts

  4. Pressure builds up. Magma is eventually released

  5. An explosive eruption forms a composite volcano
• Constructive margins

  1. Convection currents move two plates away from each other

  2. Magma from the mantle rises through the gap

  3. The lava is very runny so travels a long distance before cooling

  4. Over many eruptions, a shield volcano is formed
• Conservative margins

  1. Convection currents move the plates side by side

  2. Friction builds up causing tension

  3. Eventually the tension will be released as waves of energy which is an earthquake
• There are no volcanoes at conservative margins
• Management can reduce the risks from tectonic hazards

  • Planning
  • Prediction
  • Protection
  • Monitoring
• Earthquake risk reduction examples

  • Future development avoids high risk areas
  • Educate people to know what to do (drills)
  • Plan evacuations
  • Stockpile emergency supplies i.e. water
  • EQ proof buildings i.e. reinforced concrete
  • Bridges strengthened with steel frames
• Volcano risk reduction examples

  • Educate people to know what to do (drills)
  • Plan evacuations
  • Stockpile emergency supplies i.e. water
  • Roofs strengthened (heavy ash)
  • Trenches or barriers to divert lava (not successfully)
• Reasons why people continue to live in areas at risk from tectonic hazards

  • Low frequency
  • Always lived there
  • Monitoring
  • Poverty
  • Benefits
  • Protection
• Low frequency

  People think they won't happen in their lifetime
• Always lived there

  Don't want to leave family/friends
• Monitoring

  People feel safe as they'll be warned if a hazard is imminent
• Poverty

  People can't afford to leave
• Benefits

  Volcanoes have fertile soil and geothermal energy (Economic)
• Protection

  EQ proof buildings make people feel safe