Plate tectonics and Earthquakes

• What are natural hazards?


  Naturally occurring events that pose a risk to human life and property
• How do the type, frequency, and magnitude of a hazard affect risk?


  They affect the severity of the risk posed by the hazard
• What are the facts affecting hazard risk?

  • Population Density
  • Wealth
  • Deforestation
  • Climate Change
• What is the process called when two tectonic plates move slowly apart, creating new crust?


  Sea floor spreading
• What happens during subduction?


  The denser oceanic plate is pushed beneath the lighter continental plate
• What is the line between two sliding tectonic plates called?

  Fault line
• Where can earthquakes and volcanoes be found?

  • At plate margins
  • At hotspots
• What is a plate margin?


  The boundary between two tectonic plates
• What is a volcano?


  An opening in the earth's crust from which lava, ash, and gases erupt
• What is an earthquake?


  A sudden or violent movement within the earth's crust followed by a series of shocks
• What does the term 'impact' refer to in the context of natural hazards?


  The effects of a natural hazard on people, the economy, and the environment
• What does 'response' mean in relation to natural hazards?


  What happens after a natural hazard in order to recover
• What is the main cause of earthquakes?

  The sudden movement of tectonic plates
• How does the destructive plate margin cause earthquakes and volcanoes?

  • 2 plates move towards each other due to convection currents/slab pull
  • The oceanic crust is denser and subducts beneath the continental crust
  • Where the plates try to move past each other friction builds & causes an earthquake when released
  • The subducted oceanic crust melts into the mantle, however it is less dense than molten rock so it tries to rise through cracks in the crust above
• How does the constructive plate margin cause earthquakes and volcanoes?

  • 2 plates move away from each other due to convection currents/slab pull, leaving a gap between the two plates
  • Magma rises up from the mantle to fill the new gap, which then cools to create new crust
• How does the conservative plate margin cause earthquakes?

  • 2 plates slide past each other due to convection currents/slab pull
  • This causes friction to build as they become locked together trying to pass each other
  • When the friction & pressure is releases and the rock fractures, it creates vibrations in the crust (earthquake)
  • The line between the two plates is called the fault line
• What are the vibrations sent out by moving tectonic plates called?

  Shock waves
• What is the point of movement in the earth's crust called?

  Focus
• What is the point directly above the focus called?

  Epicentre
• How does distance from the focus and epicentre affect an earthquake?


  The closer you are to the focus and epicentre, the stronger the earthquake will be.
• Do earthquakes affect all people equally?


  No, factors such as distance from the epicentre and level of development affect intensity.
• What is the term for the amount of energy released by an earthquake?

  Magnitude
• On what scale is the magnitude of an earthquake measured?

  Richter Scale
• What does a higher number on the Richter Scale indicate?


  A bigger earthquake
• How is the magnitude of an earthquake typically measured?


  By measuring the size of the seismic waves it produces.
• How can the magnitude of an earthquake be calculated besides measuring seismic waves?


  By measuring the amount of energy released during the earthquake.
• How do collision plate margins cause earthquakes?

  • 2 continental plates push against each other, as the pressure between them increases, the rock to weaken and fracture
  • Fold mountains are created and strong earthquakes are experienced here