Lecture12 volcanoes

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Lecture12 volcanoes

  1. 1. Volcanoes
  2. 2. Seismogram 3 types of waves
  3. 3. P- waves (Primary, Compression)
  4. 4. S- waves (Secondary, Shear)
  5. 5. <ul><li>http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm?chapter_no=visualization </li></ul>
  6. 6. Surface waves
  7. 7. How do we know about the Core?
  8. 8. S-waves S-wave Shadow
  9. 9. S-waves
  10. 10. How do we know about the Core? <ul><li>studies of earthquake wave reflection and velocity </li></ul><ul><li>differentiates layers </li></ul><ul><li>shows increase in density, pressure, & temperature w/ depth </li></ul>
  11. 11. Volcanism <ul><li>= when molten magma extrudes onto Earth’s surface </li></ul>
  12. 12. Types of Volcanoes Shield Volcano Stratovolcano/Composite Volcano Cinder Cone 9 km 3 km 0.3 km
  13. 13. Shield volcano 150 km
  14. 14. Hawaii <ul><li>Rivers of lava - very fluid </li></ul>Hawaii
  15. 15. Shield Volcanoes on Mars: Olympus Mons
  16. 16. Stratovolcano
  17. 17. Stratovolcano Alternating Layers of Lava flows & Pyroclastic deposits AKA Composite Volcano
  18. 18. Flows don’t go as far from vent Lava is more viscous Higher Silica (~55-65%) More volatile gases in lava Stratovolcanoes / Composite Volcanoes
  19. 19. Pyroclastic flows <ul><li>Avalanche of rock material, hot ash & gas </li></ul><ul><ul><li>Highly destructive </li></ul></ul><ul><ul><li>Typically faster than 80km/hr and up to 700°C </li></ul></ul><ul><ul><li>Can incinerate, burn, and asphyxiate people </li></ul></ul>
  20. 20. Caldera = basin-shaped depression e.g., Crater Lake (Mount Mazama) Oregon
  21. 21. Yellowstone Caldera
  22. 22. Cinder Cone Diamond Valley, UT Small in size Pyroclastic Material- Fall Steep Slopes
  23. 23. SP Crater, Arizona
  24. 24. Volcanic hazards <ul><li>volcanic gases (H 2 O, CO 2 , sulfur oxides) </li></ul><ul><li>pyroclastic flows = avalanche of hot gas, ash, & rock fragments </li></ul><ul><li>lahars (mudflows) </li></ul><ul><li>lava flows </li></ul>
  25. 25. Pyroclastic flows
  26. 26. 1902- Mt. Pelée, Martinique, Caribbean St. Pierre
  27. 27. Before the eruption
  28. 28. After the eruption 20,000 inhabitants were killed
  29. 29. Mt St Helens lahars
  30. 30. Mt St Helens lahars
  31. 31. 2 Types of eruptions <ul><li>Effusive </li></ul><ul><ul><li>gentle, low viscosity lava </li></ul></ul><ul><ul><li>shield volcanoes </li></ul></ul><ul><ul><li>e.g., Hawaiian volcanoes </li></ul></ul><ul><li>Explosive </li></ul><ul><ul><li>violent, high viscosity lava </li></ul></ul><ul><ul><li>composite volcanoes </li></ul></ul><ul><ul><li>e.g., Mount St. Helens, Nevada del Ruiz, Yellowstone </li></ul></ul>

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