Volcanos

• Volcanoes are found at destructive and constructive plate margins
• Volcanoes at destructive plate margins

  • oceanic plate is subducted and destroyed
  • Forms pool of magma which is forced up
  • Magma rises through cracks in the crust
  • Causes it to erupt and forms a volcano
• at constructive plate margins, magma rises up into the gap and forms a volcano
• When a volcano erupts it emits lava and gases

  • erupt ash —> covers land and blocks sun
  • Pyroclastic flows
• Hotspots are where volcanoes are but away from plate boundaries
• Hotspots:

  • a bit in the earths crust that is hotter than normal
  • Magma can break through the crust and reach the surface —> eruption forms volcano
  • Hawaii is a chain of islands formed by hotspots
• 2 types of volcanoes

  • composite volcanoes
  • Shield volcanoes
• composite volcanoes:

  • destructive plate boundaries
  • Subducted oceanic crust has a lot of water which causes the subducted crust to erupt

  
• shield volcanoes

  • hotspots or constructive plate boundaries
  • not very explosive and made up of only lava
  • lava has a low viscosity (very runny)
  • flows quickly over a wide area
  • low, gentle-sided volcano