natural hazards

• Natural hazards


  Environmental events threatening people
• Natural disasters occur where death and destruction result
• As populations grow, so does hazard risk
• Factors that increase risk

  • Urbanisation - densely populated urban areas concentrate those at risk
  • Poverty - expense of housing leads to building on risky ground
  • Farming - attraction of nutrient-rich floodplains puts people at risk
  • Climate change - global warming raises sea levels and generates more extreme weather
• Hazard risk


  The chance of being affected by a natural hazard
• Tectonic plates


  • Driven by convection currents within the Earth's mantle
  • Plates move apart at constructive margins, causing mid-ocean ridges and volcanic eruptions
  • Plates move towards each other at destructive margins, causing subduction, earthquakes, volcanic eruptions and fold mountains
  • Plates slide past each other at conservative margins, causing earthquakes
• Constructive plate margin


  Plates separate, magma rises to the surface, breaking the crust and causing mid-ocean earthquakes and volcanic eruptions
• Destructive plate margin


  Plates move towards each other, one plate is forced under the other, causing subduction, earthquakes, volcanic eruptions and fold mountains
• Conservative (transform) plate margin


  Plates slide past each other, friction builds stress and triggers earthquakes when they slip
• Earthquakes and volcanoes occur at plate margins
• More earthquakes occur than volcanic eruptions
• Earthquakes have primary and secondary effects

  Primary effects include damage to buildings and infrastructure, power and communications cuts, communities cut off. Secondary effects include fires, landslides, flooding, and long-term impacts on the economy and society.
• Plate margins run through densely populated regions such as Japan and southern Europe
• Strategies to reduce risk from tectonic hazards

  • Monitoring - detecting precursors to volcanic eruptions and earthquakes
  • Prediction - using monitoring data to forecast events, though earthquake prediction remains difficult
  • Protection - earthquake-resistant construction, diverting lava flows
  • Planning - risk assessment, hazard mapping, evacuation planning
• Iceland benefits from its location on a plate margin, with geothermal power and a tourism industry based on its dramatic landscapes