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Hotspots, Plumes and Mass Extinctions

Hotspots, Plumes and Mass Extinctions. Is Hawaii more than a great vacation spot? How does life respond to geologic catastrophes?. Plate Tectonics - Distribution of Volcanic and Earthquake Activity. The Earth’s surface is broken into plates. 1. Wilson Cycle (ocean basin fm). 2. Examples:

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Hotspots, Plumes and Mass Extinctions

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  1. Hotspots, Plumes and Mass Extinctions Is Hawaii more than a great vacation spot? How does life respond to geologic catastrophes?

  2. Plate Tectonics - Distribution of Volcanic and Earthquake Activity

  3. The Earth’s surface is broken into plates

  4. 1 Wilson Cycle (ocean basin fm) 2 Examples: 1. East African Rifts 2. Red Sea 3. Atlantic Ocean 4. Pacific Ocean 5. Mediterranean Sea 6. Himalayas, Tibet 3 4 5 6

  5. Hawaii

  6. Easter

  7. Galapagos

  8. Samoa

  9. The Hawaiian Hotspot

  10. Volcanoes to atolls (Darwin)

  11. Tahiti -- shield volcano

  12. Moorea -- fringing reef

  13. Raiatea - barrier reef

  14. Bora Bora -- lagoon

  15. Maupiti -- the oldest volcanonext stage is the coral atoll

  16. French Polynesia from space atoll fringing reef barrier reef

  17. Pacific Hotspot Volcanic Chains

  18. Questions: • Where do Hotspots come from? • How do Hotspots start? • How long do they last?

  19. Indian Ocean • Hotspot tracks and 3 spreading ridges • A complete record of hotspot activity

  20. JOIDES Resolution drillship

  21. Reunion hotspot track, central Indian Ocean

  22. “flood” basalts in western India>300 lava flows, each 1000 km3

  23. Western India • An accumulation of lava flows 5 km thick! • Occurred at the same time as the extinction of the dinosaurs

  24. Mass Extinction(K-T Boundary) • What killed the Dinosaurs? • 65 million yr ago • A meteorite, or volcanic activity, or BOTH?

  25. Impact Site: Yucatan Peninsula

  26. Volcanic catastrophes and Mass Extinctions

  27. Greenland • Birth of the Iceland hotspot • Next came the opening of the North Atlantic Ocean basin

  28. Global Distribution of large, rapidly-erupted volcanic events

  29. red = hotspot-related volcanism since 250 Ma Columbia River Basin Flood Basalts with source at Yellowstone Flood basalts, India

  30. Large Igneous Provinces are: • BIG!! • NOT explained by Plate Tectonics • Initial Plume and Hotspot Activity

  31. Mantle Plumes • Part of the circulation in the Mantle • Driven by temperature differences • Hot and cold => density differences • Gravity Rules!http://www.youtube.com/watch?v=f37Gf6IVj6o&feature=related

  32. Mantle convection - the driving force for plate tectonics What causes the warmer material to rise?

  33. Mantle Plumes

  34. Cross-sections of the Earth Mantle convection and hotspot formation Red = hot upwelling from core-mantle boundary Blue = cold downwelling Cold lithosphere sinks, hot plumes rise. Computer Model Cartoon Schematic

  35. Which is not a hotspot? Yellowstone Iceland Hawaii Mt. St. Helens

  36. Degassing Magma • Gases include CO2, SO2, Cl, F that make “acid rain” • Shuts down photosynthesis

  37. Laki, Iceland (1783) -- the year without a summer

  38. Laki, Iceland (1783) -- the year without a summer

  39. Submarine: Hydrothermal Exchange – Release of Metals

  40. Ocean Anoxic Eventsproductivity or preservation? Marine sedimentary layers exposed in Italy

  41. Hydrothermal Plumes from LIPs

  42. Effects of Submarine Plateaus • Release of “reduced” metals uses up oxygen in the oceans • Trace metals are “nutrients”, so promote rapid growth of plankton • Sinking organic matter also uses up oxygen in the oceans • Extinctions of “benthic” marine organisms

  43. Two Styles of Mantle Convection

  44. Evolution of Life • “Punctuated” by rapid change events • Where there is chaos there is opportunity • Extinctions lead to new ecosystems

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