Primary damage. - What has been caused by the volcano;
  • Lava Flows
    • Thus, in general, lava flows are most damaging to property, as they can destroy anything in their path.

      Violent Eruptions and Pyroclastic Activity
      • Hot pyroclastic flows cause death by suffocation and burning. They can travel so rapidly that few humans can escape.
      • Lateral blasts knock down anything in their path, can drive flying debris through trees.
      • Tephra falls can cause the collapse of roofs and can affect areas far from the eruption. Although tephra falls blanket an area like snow, they are far more destructive because tephra deposits have a density more than twice that of snow and tephra deposits do not melt like snow.
      • Tephra falls destroy vegetation, including crops, and can kill livestock that eat the ash covered vegetation.


      Poisonous Gas Emissions
      • Volcanoes emit gases that are often poisonous to living organisms.

Secondary damage - what has been caused by things other than the actualvolcano;

  • Mudflows (Lahars)
    • Heat off the volcano melts snow or ice during the eruption, emptying of crater lakes during an eruption, or rainfall that takes place any time with no eruption.
    • Mudflows are a mixture of water and sediment that varies between thick water and wet concrete, and can remove anything in their paths like bridges, highways, houses, etc.

  • Debris Avalanches and Debris Flows
    • Volcanic mountains tend to become oversteepened as a result of the addition of new material over time as well due to inflation of the mountain as magma intrudes.
    • Oversteepened slopes results in landslides, debris slides or debris avalanches.


  • Flooding
    • Drainage systems can become blocked by deposition of pyroclastic flows and lava flows. Such blockage may create a temporary dam that could eventually fill with water and fail resulting in floods downstream from the natural dam.
    • Volcanoes in cold climates can melt snow and glacial ice, rapidly releasing water into the drainage system and possibly causing floods.


  • Tsunami
    • Debris avalanche events, landslides, caldera collapse events, and pyroclastic flows entering a body of water may generate tsunami.


  • Volcanic Earthquakes and Tremors
    • Earthquakes usually precede and accompany volcanic eruptions, as magma intrudes and moves within the volcano.
    • Although most volcanic earthquakes are small, some are large enough to cause damage in the area immediately surrounding the volcano, and some are large enough to trigger landslides and debris avalanches.

  • Atmospheric Effects
    • Since large quantities of tephra and volcanic gases can be injected into the atmosphere, volcanism can have a short-term effect on climate.
    • Ash in the atmosphere will ground aircraft as the particles can get into the engines and cause them to stall.

  • Famine and Disease
    • Ash falls can cause extensive crop damage and kill livestock. This can lead to famine.
    • People have to be evacuated, breakdown of sewerage and water systems, cut off of other normal services can lead to disease for years after an eruption, especially if the infrastructure is not in place to provide for rapid relief and recover.