Volcanoes + Tsunamis

• Volcano


  where magma from the earths mantle is repeatedly extruded at the earth surface
• Where do you find volcanoes?


  -convergent plate margins

  Continent to ocean

  Ocean to ocean

  -divergent plate margins

  Hot spots or magma plumes
• How is a shield volcano formed?

  They form when later upon layer of basaltic accumulated only when oceanic crust is present- ocean to ocean, divergent
• How do composite volcanoes form?


  Composed of interbedded (generally andesitic) lava flows and layers of pyroclastic debris

  -greater outgassing

  -vicious thick magma

  -high silica (polluted)
• Volcanic hazards


  pyroclastic flows, lahar, flank collapse, ash fall/clouds, gas, tsunami, climate change, acid rain
• Tsunamis (secondary hazard)


  -ocean floor drops (a few 100ft)

  -water fills the space
• Ways to monitor tsunamis


  -water pressure sensors

  -seismic activity

  -water retreat visible from shoreline