volcanic hazards

• Volcanoes


  Occur on plate boundaries where plates melt and magma erupts through a plate, or on hotspots
• Volcanic hazards


  • Lava flows
  • Lahars (mudflows)
  • Glacial floods (jökulhlaups)
  • Tephra
  • Toxic gases
  • Acid rain
  • Nuées ardentes/pyroclastic flows
• Lava flows


  • Can flow quickly or slowly depending on viscosity, silica makes lava viscous and slow which is common in explosive eruptions
• Lahars


  Mudflows caused by a number of reasons, usually by melting ice at high latitudes
• Glacial floods (jökulhlaups)


  When temperatures are high from magma, glaciers or ice sheets quickly melt and a large amount of water is discharged
• Tephra


  Any type of rock that is ejected by a volcano
• Toxic gases


  Released during some eruptions, even CO₂ can be toxic as it is heavier than oxygen
• Acid rain


  Caused when gases such as sulfur dioxide are released into the atmosphere
• Nuées ardentes/pyroclastic flows


  Clouds of burning hot ash and gas that collapses down a volcano at high speeds, average speeds of around 60 mph but can reach 430 mph
• Volcanic Explosivity Index (VEI)


  Measures vulcanicity, the more powerful and explosive the eruption the higher the VEI. The scale is logarithmic from VEI 2 and onwards. Multiple features are considered when calculating the VEI, including how much tephra is erupted, how long it lasts, how high the tephra is ejected etc.
• Frequency of eruptions


  Varies per volcano, volcanoes are classed as either active, dormant or extinct. An estimated 50-60 volcanoes erupt each month, meaning volcanic eruptions are always frequent (and some volcanoes erupt constantly). Usually, a higher frequency eruption means the eruptions are effusive whereas low frequency means the eruptions are explosive.
• Regularity of volcanic eruptions

  Volcanic eruptions are regular in that the eruptions on each type of boundary are similar (e.g. eruptions on destructive boundaries will regularly be explosive). Sometimes eruptions may be irregular and not fit patterns.
• Predictability of volcanic eruptions


  Regularity of eruptions can help estimate when eruptions will take place (i.e. every 10 years). Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption.
• Primary effects of volcanic hazards


  • Ecosystems damaged
  • Wildlife killed
  • Businesses and industries destroyed or disrupted
  • People killed
  • Homes destroyed from lava/pyroclastic flows
  • Government buildings and other important areas destroyed or disrupted
• Secondary effects of volcanic hazards


  • Water acidified by acid rain
  • Volcanic gases contribute to greenhouse effect (global warming)
  • Jobs lost
  • Profit from tourism industry
  • Fires can start which puts lives at risk
  • Mudflows or floods
  • Trauma
  • Homelessness
  • Conflicts concerning government response, food shortages, insurance etc.
• Ways to respond to volcanic hazards


  • Preventing them directly
  • Being prepared for the next hazard
  • Mitigating the effects
  • Completely adapting your lifestyle to limit the hazard's effects
• andesitic lava


  viscous, with intermediate silica content (55 to 65 per cent). Lavas have temperatures between 800 and 1000°C. Eruptions can be very destructive, especially when the volcano has been dormant and hasn’t erupted recently.
• basaltic lava

  low-silica content (45 to 55 per cent) and is relatively fluid because of its low viscosity (low gas content). Eruptions are effusive (non-explosive) and regular. Lavas have temperatures between 1000 and 1200°C and can flow quickly over long distances.