Tectonic Hazards

• Two types of crust

  • Continental - thicker (30-50km) and less dense
  • Oceanic - thinner (5-10km) and more dense
• Why do plates move

  Convection currents in the mantel
• What is the place called where plates meet

  Plate margins or plate boundaries
• Destructive plate margins

  Two plates moving towards each other

  When oceanic plate meets a continental plate the denser oceanic plate is subducted and destroyed creating gas-rich magma.

  Volcanoes and ocean trenches occur here

  When two continental plates meet the ground is folded upwards creating fold mountains
• Constructive Margins

  • Two plates moving away from each other
  • Magma rises from the mantel to fill the gap and cools, creating new crust

  
• Conservative Margins

  • Two plates moving sideways past each other - or moving in same direction but at different speeds
  • Crust isn't created or destroyed
  • Example pacific plate is moving in the same direction as the North American plate but faster

  
• Destructive Margin

  Two plates moving towards each other

  When oceanic plate meets a continental plate the denser oceanic plate is subducted and destroyed creating gas-rich magma.

  Volcanoes and ocean trenches occur here

  When two continental plates meet the ground is folded upwards creating fold mountains

  
• Volcanoes at destructive plate Margins

  denser oceanic plate moves down into the mantle where it melts. A pool of magma forms which then rises through cracks in the crust called vents. Magma erupts forming volcano
• Volcanoes at constructive margins

  the magma rises up into gaps created by plates moving apart forming a volcanoe
• Hotspots

  • Some volcanoes form over parts of the mantle that are really hot (hotspots) e,g, Hawaii
• What does a volcano emit when it erupts

  Lava and gas and some volcanoes emit ash which can block out the sun (volcanic winter) and form pyroclastic flow
• Earthquakes - destructive plate Margins

  Tention builds when one plate gets stuck as it melts past the other
• Conservative Plate Margins

  Tension builds up when plates are grinding past each other and get stuck
• Earthquakes at Conservative Plate Margins

  Tension builds along crack in the plates they move away from each other
• Stage 2 for an earthquake to occur

  1. The plates eventually jerk past each other sending shock waves
  2. These shock waves spread out from the focus (where the earthquake starts in the earth) - waves are stronger nearer to focus and cause more damage the closer they are
• Chile Earthquake 2010

  Magnitude 8.8
• Chile is a middle-income country. This had an impact on the effect and responses to the earthquake.
• Foreign aid wasn't needed to enable Chile to recover.
• Cause of the Chile earthquake

  • Subduction of the Nazca plate under the South American Plate
• The epicentre of the Chile earthquake was just off the coast of Chile
• Primary effects of the Chile earthquake

  • 500 people were killed
  • US$30 billion of damage
• Secondary effects of the Chile earthquake

  • Coastal areas were flooded by a tsunami
  • Landslides blocked some roads
• Immediate responses to the Chile earthquake

  • Rapid response by emergency services
  • Main roads were repaired within a day
  • 30,000 emergency shelters were built
• Long-term responses to the Chile earthquake

  A reconstruction plan to help 200,000 households
• Nepal Earthquake 2015


  Magnitude 7.8
• Nepal is a low-income country. The lack of resources had an impact on both the effects and the response to the earthquake.
• Foreign aid was needed to support recovery.
• The effects were more severe because many people lived in poor quality housing.
• Cause of the Nepal earthquake

  • Collision of the Indo-Australian and Eurasian plates
• Primary effects of the Nepal earthquake

  • 9,000 people were killed
  • US$5 billion of damage
• Secondary effects of the Nepal earthquake

  • Flooding and damage to roads from landslides
  • An avalanche on Mount Everest which killed 19 people
• Immediate responses to the Nepal earthquake

  • Overseas aid from NGOs (non-governmental organisations) such as Oxfam
  • 300,000 people left the capital city (Kathmandu)
• An international conference was held to appeal for funding for long-term responses to the Nepal earthquake