Hazards - Volcano

• Distribution of active volcanoes


  • Most active volcanoes occur at or near to plate boundaries
  • 75% around the Ring of Fire, surrounding the Pacific Ocean
  • Vulcanicity (volcanic activity) is focused at constructive and destructive plate margins
• Constructive plate margins


  • Small
  • Effusive (lava flows)
  • Basaltic lava - low gas content, low viscosity (runnier lava so flows faster), higher temperature
• Destructive plate margins


  • Explosive as the magma is forcing its way to the surface
  • Andesitic rhyolitic lava - high gas content, high viscosity, lower temperature
• Volcanoes can also be found at hot spots in the middle of plates, eg. Hawaii
• Volcanic Explosivity Index (VEI)


  Scale from 0-8 used to measure the magnitude of volcanic eruptions, calculated based on a series of measurements and observations
• Primary volcanic hazards


  • Tephra (solid material of varying sizes that's ejected by a volcano)
  • Ash fallout (large quantities of ash carried by the wind and deposited on the ground)
  • Pyroclastic flow (hot mixture of gas and tephra that flows at speeds of up to 700km/h)
  • Lava flow (travel at different speeds depending on slope, topography and viscosity)
  • Volcanic gases (eruptions can release large quantities of gases, eg. sulphur dioxide and CO2)
• Secondary volcanic hazards


  • Lahars (mudflows that occur when tephra mixed with water)
  • Acid rain (forms when sulphur dioxide emitted during the eruption reacts with water vapour in the atmosphere to form sulphuric acid)
  • Floods (caused by a sudden release of water and rocks when glacial ice is melted by the eruption)
• Shield volcanoes


  • Constructive plate margins
  • High frequency
  • Low magnitude
  • Gentle sloping sides due to runny lava, with layers of cooled lava
• Stratovolcanoes


  • Destructive plate margins
  • Low frequency
  • High magnitude
  • Steep slopes due to thick sticky lava, with layers of ash and lava
• Some volcanoes erupt more frequently and regularly than others
• Volcanoes with varying eruption frequency


  • Mt Stromboli, Italy, erupts every 20-40 minutes
  • Mt Pinatubo, Philippines, hadn't erupted for around 500 years before its eruption in 1991
• Predicting volcanic events


  1. Volcanologists monitor changes using GPS, tilt meters, satellites, seismometers and gas detection

  2. Signs of an eruption include magma rising, ground deformation, increased emissions of sulphur dioxide and other gases, and increased seismic activity caused by magma movement
• Primary impacts of volcanic eruptions


  • Deaths and injuries
  • Displacement of people
  • Damage to properties and infrastructure causing disruption to people's lives
• Secondary impacts of volcanic eruptions


  • Mental health issues, eg. stress, anxiety, depression
  • Homelessness
  • Disruption to services, eg. healthcare and education
  • Loss of cultural heritage sites
• Economic impacts of volcanic eruptions


  • Destruction of property and infrastructure leading to significant costs for repair and reconstruction
  • Disruption of trade and economic activity
  • Loss of income and employment
  • Costs of immediate responses, eg. food, aid, temporary shelter, medical treatment
• Environmental impacts of volcanic eruptions


  • Poor air and water quality
  • Loss of biodiversity
  • Destruction of habitats and ecosystems
  • Acid rain can damage ecosystems
  • Release of greenhouse gases can lead to a rise in global temperatures
  • Ash clouds can lead to a fall in global temperatures due to solar energy being reflected back into space
• Political impacts of volcanic eruptions


  • Pressure on governments to coordinate emergency response
  • Social unrest and political instability
  • Changes in government policy and regulations to reduce future risk
• Short-term responses to volcanic hazards


  • Evacuation - moving people out of the danger zone
  • Search and rescue - using sniffer dogs and heat sensors to locate survivors
  • Emergency aid - providing food, water, medical aid to affected communities
• Long-term responses to volcanic hazards


  • Hazard mapping and land use zoning - identifying areas at most risk and limiting the activities that can take place there
  • Building codes - creating a set of building codes to increase the resilience of buildings to volcanic hazards
  • Education and training - preparing communities to improve education and response
• Prevention


  It's impossible to prevent a volcanic eruption, governments can restrict access and prevent building in high risk areas through land use zoning
• Preparedness


  Measures that ensure people are ready to respond to volcanic hazards when they occur, helping to minimise risk, including monitoring systems to improve prediction and warning
• Mitigation


  Measures that aim to stop the volcanic eruption posing a threat to populations through direct intervention to the volcano, such as building walls or embankments to divert lava flows
• Adaptation


  Measures that involve people changing their behaviour to reduce risk or to cope with the impacts of eruptions, such as promoting tourism as an alternative industry