volcanoes

• what is a volcano

  openings in the earths crust through which lava, ash and gases erupt from. associated with plate margins.
• how do volcanos erupt

  1. plates move so pressure builds
  2. hot magma and gasses push up from the mantle to the crust
  3. lava cools and forms a rock so as a volcano erupts overtime it grows bigger
• primary hazards

  1. lava flows
  2. pyroclastic flows
  3. tephra and ash falls
  4. gas eruptions
• lava flows

  streams of lava which have erupted from a volcano onto the earths surface. very slow but destroy everythin.
• pyrocalstic flows

  mixture of dense hot rock,lava,ash and gasses ejected from a volcano which move quickly.
• tephra and ash falls

  • tephra: pieces of rock and ash the blast into the air during an eruption
  • ash falls: cover everything causing slippy roads, poor vision etc
• gas eruptions

  magma contains dissolved gases that are released into the atmosphere during an eruption
• secondary hazards

  1. lahars
  2. jökulhlaup
• lahars

  masses of rock, mud and water that travel quickly down volcanos. causes when an eruption melts snow + ice, heavy rainfall, loss of soil ans rock
• jökulhlaup

  heat from the eruption melts snow causing floods. releases large amounts of water, ice etc causing damage
• measuring volcanoes

  uses the volcanic explosivity index which is a logarithmic scale from 0-8.

  uses several factors: duration, amount of material ejected etc
• predicting eruptions

  predict volcanos from equipment placed on the volcano (GPS and satellite based radars)

  • signs of eruption: small earthquake, changes to volcano surface, changes to tilt
• spatial predictability

  knowing where / when hazards will occur
• 3 characteristics of lava

  1. basalt
  2. andesite
  3. rhyolite
• basalt

  fine grained, igneous rock underlying most the earths surface. associated with constructive plate boundary’s.
• andesite

  found in lava flows produced by stratovolcanos. formed after an oceanic plate melts whilst descending into the subduction zone