Volcanoes

• Volcano


  • Formed when magma erupts onto the Earth's surface as lava through a vent in the Earth's crust
• Volcanic Explosivity Index (VEI)

  Measure of the magnitude of a volcanic eruption
• The highest VEI in recorded history was 8 (Tambora 1815)
• Composite (strato-volcanoes)


  • Steep-sided
  • Sticky (viscous) lava
  • More explosive eruptions
  • Formed from alternating layers of ash and lava
  • Tend to form on convergent (destructive) plate boundaries
• Shield volcanoes


  • Gently sloping sides
  • Runny/thin lava
  • Less explosive-gentle eruptions
  • Tend to form on divergent (constructive) plate boundaries or hot spots
  • Frequent eruptions
• Volcanic eruption features


  • Lava
  • Ash
  • Pyroclastic flow
  • Lahars
  • Earthquakes
  • Volcanic bombs
• Lava


  Magma that erupts to the surface
• Ash


  Pulverised solid lava which measures less than 2mm in diameter
• Pyroclastic flow


  Fast moving, very hot clouds of poisonous gases mixed with ash
• Lahars


  When volcanoes erupt, snow and ice on the peak melts and combines with the ash to create fast moving mudflows
• Volcanic bombs


  Fragments of molten rock which are ejected from the volcano, between 60mm and 5m in diameter
• Most volcanoes occur at divergent (constructive) and convergent (destructive) plate boundaries
• Approximately 75% of active volcanoes are located around the 'Ring of Fire' around the Pacific Ocean
• Hotspots


  Plumes/columns of magma which escape through the Earth's crust, away from plate boundaries
• Divergent (constructive) plate boundary

  1. Plates are moving apart

  2. Lava erupts through the gap

  3. New crust is formed
• Convergent (destructive) plate boundary

  1. Denser oceanic plate subducts under lighter continental plate

  2. Friction causes heat which melts rock

  3. Magma rises to the surface
• Volcanoes do not occur at collision or transform plate boundaries
• Volcanoes at hot spots

  1. Magma plume rises through cracks in the crust

  2. As plate moves over plume, a line of islands forms
• Impacts of earthquakes and volcanic eruptions

  • Loss of life and injury
  • Collapse or destruction of buildings
  • Damage to transport networks
  • Loss of jobs and businesses
  • Loss of crops
  • Damage to power and water supply
  • Damage to the environment
  • Closure of airports
• It is easy to confuse the primary and secondary effects/impacts for earthquakes and volcanic eruptions
• Opportunities associated with living near volcanoes

  • Fertile soils
  • Tourism
  • Mining of minerals and precious stones
  • Geothermal energy
  • Creation of new land area
• Remote sensing and GIS

  • Used for land use planning in areas vulnerable to earthquakes and volcanic eruptions
• La Palma is part of the Canary Islands, an autonomous region of Spain
• There are 33 volcanoes across the Canary Islands, 10 of which are in La Palma
• The Cumbre Vieja volcano on La Palma erupted from 19th September to December 2021, with a VEI of 2-3
• Effects of the La Palma eruption

  • Over 7,000 people evacuated
  • Almost 1,500 houses destroyed
  • Over 1,500 other buildings destroyed
  • Coastal highway cut off
  • Water supply cut off for 3,000 people
  • 400 hectares of banana farms destroyed
  • 1,300 hectares of land affected
  • 1 death
• Immediate response to La Palma eruption

  1. Warnings issued

  2. Evacuations carried out

  3. Alert level raised

  4. Air traffic suspended

  5. Monitoring of lava flow and gas emissions

  6. Food and shelter provided

  7. €5.4 million EU donation
• Long-term response to La Palma eruption

  1. €400 million promised for rebuilding

  2. Prefabricated housing built

  3. Constant monitoring of volcanoes

  4. Improved crisis management processes
• Divergent (constructive) plate boundary


  Plates are moving apart
• Divergent plate boundary


  1. Volcanic eruptions can occur

  2. Earthquakes can occur
• Magma rises to the surface through fractures, fissure vents or central vent systems.
• What can be used to predict when a volcanic eruption is likely to occur

  • Seismometers
  • Heat Increase
  • Gas emissions
  • Animal Behaviour
• How can impacts of volcanoes be reduced

  Land use planning

  Volcano Monitoring

  Lava bomb sheltering