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Volcanoes

Volcanoes. Volcanoes. Evidence that we live in an active planet The gods of the underworld Millions of people live near active volcanoes The greatest geological hazard. Mount Saint Helens- after. Hazard. Future hazard. Population near big, recently active volcanoes Seattle Mexico City

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Volcanoes

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  1. Volcanoes

  2. Volcanoes • Evidence that we live in an active planet • The gods of the underworld • Millions of people live near active volcanoes • The greatest geological hazard

  3. Mount Saint Helens- after

  4. Hazard

  5. Future hazard • Population near big, recently active volcanoes • Seattle • Mexico City • Quito • Indonesia • Japan

  6. Lava • Molten rock that flows on the surface • Basaltic Lava • low silica, • fluid, • low gas, • not explosive • Andesitic Lava • high silica • viscous • gas-rich • explosive

  7. Types of volcanoes • 1. Shield Volcanoes • Hawaii, Iceland • Basaltic • 2. Stratovolcanoes (or composite) • Mt. Saint Helens, Pinatubo, etc • Andesitic • Explosive

  8. Shield Volcanoes • Huge broad cones • Gentle slopes • Made from lava flows • Basaltic • Form at hotspots • Not very dangerous • Predictable

  9. Stratovolcanoes(composite) • Andesitic lava • Rich in dissolved gases • Violent eruptions alternate with lava flows • Steep-sided cones • Very dangerous • Unpredictable

  10. Pyroclastic Flows • Product of explosive eruptions • Hot ash shot up into the atmosphere • Ash column collapses • Pyroclastic flow can travel 60 mi/hr • Ash can fall 100’s of miles away • Ash may affect global climate

  11. Mt. Saint Helens before

  12. Phreatic (vapor) eruption

  13. Bulge

  14. Mt. St. HelensPyroclasticEruption

  15. After the eruption

  16. Lahars (mudflows)

  17. Lahars (mudflows) • Very destructive • Kill as many people as the eruption itself • Loose ash forms mud avalanches • Glaciers on top of volcano melt • Rain

  18. Inside a volcanoe

  19. Pyroclastic eruption

  20. Volcanic landscape: A Caldera (Crater Lake)

  21. Crater lake formation(caldera) • 1. Early eruptions from composite cone • 2. Great eruption empties the magma chamber • 3. Summit collapses • 4. Caldera fills with water

  22. Plate Tectonic Settings of Volcanism

  23. Plate tectonic settings of volcanoes

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