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Volcanoes

Volcanoes. Volcanoes. USGS Volcano Hazards Program Google Earth Volcano time lapse. Igneous Activity. Magma intruding into/above crust Magma Placement Extrusive Volcanic Activity Intrusive Most common. Volcanoes.

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Volcanoes

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  1. Volcanoes

  2. Volcanoes • USGS Volcano Hazards Program • Google Earth • Volcano time lapse

  3. Igneous Activity • Magma intruding into/above crust • Magma Placement • Extrusive • Volcanic Activity • Intrusive • Most common

  4. Volcanoes • Magma’s physical properties affect the nature of volcanic events, from gentle to explosive eruptions. • More fluid magma, gentler eruption • More solid magma, explosive eruption

  5. Volcanoes • Magma Properties • 1) Magma Composition Si, O Mg, Fe light dark FelsicMafic solid fluid Rhyolite Basalt Andesite

  6. Volcanoes • 2) Temperature 800 °C - 1200 °C • 3) Pressure • increase melting point temperature ~ solid • 4) Water & Dissolved gases • decrease melting point temperature ~ fluid • 5) Viscosity Resistance to flow • High viscosity = Felsic, low T, high P, low water/gas content • Low viscosity = Mafic, high T, low P, high water/dissolved gases Solid Fluid

  7. 3 Zones of Volcanism

  8. Volcano Locations and Viscosity Felsic Intermediate Mafic Rhyolite Andesite Basalt High V/explosive Low V/ gentle Continental Divergent Oceanic Divergent C-C O-C O-O Continental Hot Spot Oceanic Hot Spot

  9. Volcanic Cone Pyroclastic material ( Tephra ) fire+broken Ash - Blocks Plug/Dome: Solid igneous rock Crater: Bowl-shaped depression Fumarole: gases Parasitic Volcano Fissure: lava + gas Pipe/Vent Caldera: depression left after eruption Volcanic Neck: solid rock Magma Chamber

  10. Calderas • Santorin • Krakatau • Caldera² !!

  11. Types of Volcanoes • Types of volcanoes • Classified based on type of Material & Eruption • Affected by magma viscosity

  12. Shield Cone

  13. Types of Volcanoes • 1) Shield Cone • Magma: Low Viscosity, Basalt • Eruption: gentle, lava flow • Cone: very wide & gentle slope ˂15 ° • Largest cone type • Hawaii

  14. Composite Cone

  15. Types of Volcanoes • 2) Composite Cone • Magma: Medium Viscosity, Andesite • Eruption: Alternate lava flow/Pyroclastic • Stratovolcano = layered cone • Cone: medium size, steep slope ~ 40° • Mt. St. Helens, Vesuvius, Pinatubo, Mt. Fuji

  16. Ring Of Fire

  17. Types of Volcanoes • Composite Cone • The most common cone type • Ring of Fire ~ Pacific Rim • Most dangerous/economically devastating • Nutrient-rich volcanic soil ~ cities/population

  18. Volcanoes • USGS Volcano Hazards Program • Mt. St. Helens • Google Earth ~ Mt. St. Helens • Escape from Mt. St. Helens

  19. Cinder Cone

  20. Types of Volcanoes “Parasitic” volcano • 3) Cinder Cone • Magma: High Viscosity, Rhyolite • Eruption: Pyroclastic explosion • Cone = pyroclastic material = Cinder • Smallest cone type • Steepest slope ˃ 40 ° • Formed on slopes of other volcanoes • Sunset crater

  21. Types of Volcanoes

  22. Phreatic volcanoes • Emerging volcano • Fantastic site in southeast pacific? e-mai • Pillow Lava • Krakatau’s rebirth Google Earth

  23. Volcano Hazards Human Impact

  24. Volcano Hazards • Lava Flow • Viscosity & Slope ~ Flow speed • Down slope movement • Hazards: Economic Loss

  25. Volcano Hazards • Pyroclastic material ~ Tephra • Ash size to large blocks • Ash: • Hazards: heavy abrasive glass mix with moisture = cement Health issues Crop damage planes’ engines

  26. Global Cooling • Ash reaching upper levels of troposphere • Remain for years, block incoming solar radiation

  27. Volcano Hazards • Pyroclastic Clouds • Glowing Avalanche ~ ash + hot gases (1000 °C) • 100 Km/hr • Composite Cones • Pompeii & Vesuvius • Naples today!

  28. Volcano Hazards • Pyroclastic cloud and Mt. Serrate

  29. Volcano Hazards • Lahars ~ volcanic mud flows • Tephra + water (rain, snow melt) • Viscosity & speed

  30. Volcano Hazards CO2, CO, SO2, H2S • Toxic gases ~ • Water vapor main gas in magma • Tsunamis ~ highocean waves • caused by collapse of a cone • Ex. Krakatua • Ex. Hawaii & East Coast of Australia

  31. Volcano Hazards

  32. One Hot Topic • The case of Mt. Pinatubo

  33. Volcanoes • USGS Volcano Hazards Program • Smithsonian Global Volcanism Program • Plate Tectonic Interactive Map

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