Volcanoes: Why are some more hazardous than others?

HideShow resource information
View mindmap
    • Viscosity of magma
      • 3 main factors that determine the viscosity of magma
        • Temperature
          • High temperature= low density of magma
        • Dissolved gases
          • Greater the amount of dissolved gases=more fluid magma
        • Chemistry
          • High silica content= more viscous magma
      • Basic magma is rich in Al, Mg and Fe
      • Acid magma is rich in silica. Low temp
    • Plate margins
      • Constructive plate margin
        • Plates are moving away from each other
        • Magma has a low viscosity enabling easy flow
        • Frequent eruptions, non-violent and lava flow and ash
      • Destructive  plate margin
        • Plates are moving towards one another
        • Magma has high viscosity with resistant flow
        • Very violent and dangerous eruption involving ash and pyroclastics
    • The materials ejected
      • Ash clouds
        • Explosive eruptions blast solid and molten rock fragments into the air at tremendous force
      • Pyroclastic flows
        • Clouds of incandescent gas, ash and rock. Reaching temperatures up to 800 degrees celsusn
      • Lahars
        • Mudflows consisting of volcanic ash and water. Reach speeds of 100kph
      • Tsunamis
        • When volcanoes erupt out of the sea and create huge waves
    • Explosiveness of eruption
      • Explosiveness of an eruption can be measured by the Volcanic Explosivity Index (VEI)
        • O VEI- Non-explosive eruption
          • 8 VEI- Mega-colossal eruption
    • Proximity to population centres
      • There are several reasons why people live close to volcanoes
        • If space is limited on an island
        • Fertile soil
        • Benefits for human habitation such as building materials and hot water
      • Volcanoes close to population centres are much more hazardous than those located in remote regions
    • Frequency of eruptions and perception of risk
      • Many people live close to the really dangerous destructive margin volcanoes
      • Memories are short lived if eruptions aren't frequent
        • People are less inclined to worry about an eruption from a volacno
        • The frequency of eruptions has a profound impact on people's perception of the volcanic hazard
    • Prediction, forecasts and reactions
      • Monitored by Satellites using IR which indicates rising magma
      • Geologists use past eruptions to create hazard maps and eruptive scenarios
      • Governments don't always respond to predictions and disasters can result
        • Scientists don't always get it right and imminent eruption might never occur
          • Reducing scientist credibility both with the locals and governments


No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Natural hazards resources »