1.3B Volcanic Hazards

• Primary hazards:

  • lava flow
  • Pyroclastic flow
  • ash fall
  • gas eruption
• lava flow = Extensive areas of solidified lava, which can extend several kilometres from volcanic vents if the lava is basaltic and low viscosity

  -> occurs at the subduction zone or hot-spot
• pyroclastic flow = Very large, dense clouds of hot ash and gas at temperatures of up to 600'C. They can flow down the flanks of volcanoes and devastate large areas. 

  -> occur at subduction zone
• ash fall = Ash particles, and larger tephra particles, can blanket large areas in ash, killing vegetation, collapsing buildings and poisoning water sources
• gas eruption = The eruption of carbon dioxide and sulphur dioxide, which can poison people and animals in extreme cases
• secondary hazards:

  • Lahars
  • J​ökulhlaups
• Lahar = Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction.
• J​ökulhlaups = floods caused when volcanoes erupt beneath glaciers and ice caps, creating huge volumes of meltwater