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Today – 4/13

Today – 4/13. More volcanoes!. First Mars shot - hill. Matian basalt. Martian dune field. Frozen Martian Sea. Last Time. Hotspots – mantle plumes reach the surface; decompression melting to form basaltic magma; Hawaii, Mars, Venus; independent of plate boundaries

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Today – 4/13

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  1. Today – 4/13 • More volcanoes!

  2. First Mars shot - hill

  3. Matian basalt

  4. Martian dune field

  5. Frozen Martian Sea

  6. Last Time • Hotspots – mantle plumes reach the surface; decompression melting to form basaltic magma; Hawaii, Mars, Venus; independent of plate boundaries • Intrusive v. extrusive: coarse v. fine texture depends on cooling rate • Three kinds of volcano: shield, stratovolcano, caldera – depends on magma type

  7. Last Time – Shield Volcano • Built up from repeated basalt flows • Basalt has high Fe / Mg, high temperature, low Si, low gas content, low viscosity (stickiness) • MOR’s, hotspots, areas of continental extension

  8. Stratovolcano • Built from alternating layers of pyroclastic & andesite lava flows • Magma – intermediate temperature, gas content, composition, viscosity • St. Helens, Monserrat, Pinatubo, Tambora • Form above subduction zones • Wet melting of the mantle

  9. Wet Melting of the Mantle

  10. Mount Ngauruhoe, New Zealand Classic Stratovolcano --- 1000s of feet high.

  11. PyroclasticFlows- - - - - MayonPhilippines1968- - - - -Hot: 600oCFast: 60 to 100 mph

  12. Mt. Vesuvius & Pompeii, Italy AD 79

  13. Cascade Volcanic Arc-----Lassen PeakCrater Lake Mt.St.Helens Mt. Rainier- - - -Part of Pacific Ring of Fire.

  14. Mt. Saint Helens, May, 1980 Eruption After Before

  15. Mount St. Helens Volcanocam • http://www.fs.fed.us/gpnf/volcanocams/msh/

  16. Space Needle view Seattle, WA and Mount Rainier:Most dangerous volcano in North America?

  17. Mount Rainier, Most dangerous volcano in North America?

  18. Mount Pinatubo Tectonic Setting

  19. Volcanoes – Agents of Climate Change Mount Pinatubo, Philippines 1991

  20. Mt. Pinatubo Ash Circles the Earth Earth’s surface cooled 1 °F for two years.

  21. Climatic Effects of Volcanism • Volcanic particles in stratosphere interact with man-made CFC’s to destroy ozone. Particles settle out in 2-3 years, ozone layer recovers. • Volcanoes add CO2 to the atmosphere (10% of anthropogenic emissions), contributing to long-term global warming • SO2 in the stratosphere reacts with water to form sulfuric acid, which absorbs solar energy and re-radiates it into space, creating short term cooling. Sulfuric acid droplets settle out after several years

  22. Edvard Munch’s “The Scream”

  23. Indonesia Tectonic Setting

  24. Indonesia Volcanoes – 130 Active!

  25. Tambora, April 1815 • Largest stratovolcano eruption in recorded history • 1816 – year without a summer. June snow in New England, frost in July and August. Crop failure – oats from 12 cents to 92 cents. Settlers move to midwest, Mary Shelley writes Frankenstein. Famine in Europe.

  26. Stratovolcano v. Caldera Explosions

  27. St. Helens v. Caldera Explosions

  28. Caldera Explosions • Caldera – LARGE volcanic crater caused by the collapse of a magma chamber after a big eruption • Convergent margins, hotspots under continents • Wet melting of the continental crust • Inconceivably cataclysmic • Often called “supervolcanoes” • Magma – low temperature, high gas content, high viscosity, high silica content = HIGHLY explosive

  29. “Nice” Caldera – Kilauea

  30. Wet Melting of the Continental Crust

  31. CalderasOften formed by explosive eruption. Crater Lake fills caldera formed by collapse during massive eruption of Mt. Mazama 6600 years ago.

  32. Caldera Formation Eruption  Collapse Figure 7.12: Sequence of events in the formation of Crater Lake.

  33. Last Big One – 74 Ka, Toba, Sumatra • 2,800 cubic kilometers of material ejected • Cause of the human genetic bottleneck?

  34. Long Valley Caldera, California - A very dangerous volcanohttp://quake.wr.usgs.gov/recenteqs/Maps/Long_Valley.html Left: Cross section of Long Valley Caldera. Right: Lasers monitor ground swelling at Long Valley Caldera

  35. Hot Spot Volcanism

  36. YellowstoneHot Spot

  37. Yellowstone Hotspot Volcanoes Go to the Movie

  38. Internal Heat Generation Earth • Remnant heat from formation, much of which is stored in the liquid core • Decay of radioactive elements Satellites of large planets • Gravitational energy turned into heat – “tidal friction”

  39. Io – Most Volcanically Active Spot in the Solar System

  40. Io v. Titan • Io – moon of Jupiter • Sulfur / silicate magma • Titan – moon of Saturn • Ammonia-water solution magma

  41. Igneous Rock Bodies Small ones • Sill – horizontal tabular body • Dike – vertical tabular body • Volcanic neck – pipelike remains of a vent Big ones • Pluton – large igneous intrusion • Batholith – really large igneous intrusion

  42. Igneous Rock Bodies Figure 7.15 on page 148 of The Blue Planet

  43. Igneous intrusive landforms Plutons and Batholiths: Large igneous intrusive rock bodies. Crystallized deep within crust. Exposed by uplift and erosion.

  44. Igneous intrusive rocks formed close to surface: Dikes, Sills, Volcanic Necks Sills Volcanic Necks Dikes

  45. Beneficial Aspects of Volcanoes • Outgassing formed oceans, atmosphere • Ash produces rich, fertile soil • Mineral deposits • Geothermal energy • Beautiful sunsets!

  46. Geyser, New Zealand Water circulates through cooling magma bodies.

  47. Hot brines deposit minerals with copper, lead, zinc, gold, silver.

  48. Gold & Quartz Veins gold Deposited in fractures by hot water (50 to 200 oC). quartz

  49. Volcanic Hazards • Ash falls – choke people, animals, kill animals that eat it, collapse roofs – worsened by rain • Pyroclastic flows – suffocation and burning, knock over anything in their way • Mudflows (lahars) – ice and snow melt, rain on ash flow • Volcanic landslide • Lava flow • Poisonous gas emission – Lake Nyos in Cameroon, 1700 CO2 suffocation deaths http://perso.wanadoo.fr/mhalb/nyos/webcam.htm

  50. Igneous Rocks Tell Their Story • Just as sedimentary strata record the environments of their deposition, igneous rock bodies and layers record the history of magmatism and volcanism in and on the Earth. Rock types and rock distribution tell what kind of activity occurred and radioisotopic dating tells when

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