Volcanoes: Why are some more hazardous than others?
- Created by: brittany_pe
- Created on: 28-09-16 16:31
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- WHAT ARE VOLCANIC HAZARDS INFLUENCED BY?
- 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
- Temperature
- Basic magma is rich in Al, Mg and Fe
- Acid magma is rich in silica. Low temp
- 3 main factors that determine the viscosity of magma
- 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
- Constructive plate margin
- 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
- Ash clouds
- 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
- O VEI- Non-explosive eruption
- Explosiveness of an eruption can be measured by the Volcanic Explosivity Index (VEI)
- 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
- There are several reasons why people live close to volcanoes
- 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
- Scientists don't always get it right and imminent eruption might never occur
- Viscosity of magma
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