Lecture12 volcanoes
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Lecture12 volcanoes

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Lecture12 volcanoes Lecture12 volcanoes Presentation Transcript

  • Volcanoes
  • Seismogram 3 types of waves
  • P- waves (Primary, Compression)
  • S- waves (Secondary, Shear)
    • http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm?chapter_no=visualization
  • Surface waves
  • How do we know about the Core?
  • S-waves S-wave Shadow
  • S-waves
  • How do we know about the Core?
    • studies of earthquake wave reflection and velocity
    • differentiates layers
    • shows increase in density, pressure, & temperature w/ depth
  • Volcanism
    • = when molten magma extrudes onto Earth’s surface
  • Types of Volcanoes Shield Volcano Stratovolcano/Composite Volcano Cinder Cone 9 km 3 km 0.3 km
  • Shield volcano 150 km
  • Hawaii
    • Rivers of lava - very fluid
    Hawaii
  • Shield Volcanoes on Mars: Olympus Mons
  • Stratovolcano
  • Stratovolcano Alternating Layers of Lava flows & Pyroclastic deposits AKA Composite Volcano
  • Flows don’t go as far from vent Lava is more viscous Higher Silica (~55-65%) More volatile gases in lava Stratovolcanoes / Composite Volcanoes
  • Pyroclastic flows
    • Avalanche of rock material, hot ash & gas
      • Highly destructive
      • Typically faster than 80km/hr and up to 700°C
      • Can incinerate, burn, and asphyxiate people
  • Caldera = basin-shaped depression e.g., Crater Lake (Mount Mazama) Oregon
  • Yellowstone Caldera
  • Cinder Cone Diamond Valley, UT Small in size Pyroclastic Material- Fall Steep Slopes
  • SP Crater, Arizona
  • Volcanic hazards
    • volcanic gases (H 2 O, CO 2 , sulfur oxides)
    • pyroclastic flows = avalanche of hot gas, ash, & rock fragments
    • lahars (mudflows)
    • lava flows
  • Pyroclastic flows
  • 1902- Mt. Pelée, Martinique, Caribbean St. Pierre
  • Before the eruption
  • After the eruption 20,000 inhabitants were killed
  • Mt St Helens lahars
  • Mt St Helens lahars
  • 2 Types of eruptions
    • Effusive
      • gentle, low viscosity lava
      • shield volcanoes
      • e.g., Hawaiian volcanoes
    • Explosive
      • violent, high viscosity lava
      • composite volcanoes
      • e.g., Mount St. Helens, Nevada del Ruiz, Yellowstone