5.6

    Cards (8)

    • Volcanic debris avalanches

      Landslides that occur in volcanic slopes
    • Volcanic debris avalanches
      • Abnormally large volumes of volcanic material traveling at great speeds
      • Bury areas far and wide
      • Considered the worst-case scenario for volcanic hazards
    • Volcanic landslides range in size from less than 1 km3 to more than 100 km3
    • A nonvolcanic landslide may reach a horizontal distance of 166 m for every 100 m it descends vertically, but volcanic debris avalanches can reach as far as 1000m horizontally for the same amount of vertical drop
    • Debris avalanche danger zones and mitigation
      1. Anticipate the coming of a debris avalanche as much as possible
      2. Identify areas prone to debris avalanches through hazard maps
    • Debris avalanche events are difficult to anticipate due to too many unknowns associated with magmatic systems and seismicity
    • The 1980 debris avalanche at Mt. St. Helens was preceded repeatedly by earthquakes within two months before the failure of its northern sector
    • What to do before, during, and after an eruption
      1. Before: Monitor volcanic activity, prepare evacuation plan, fireproof house, participate in community efforts
      2. During: Evacuate to designated shelters, use gas mask, stay alert for advisories
      3. After: Proceed with caution, participate in community efforts to restore necessities, maintain peace and order