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Creation, Aging and Recycling of the Ocean Floor

Creation, Aging and Recycling of the Ocean Floor. How is the ocean floor made? Why does the ocean floor get deeper with age? How are volcanic arcs made and why are they so dangerous?. Formation of Ocean Lithosphere. Formation of Ocean Lithosphere.

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Creation, Aging and Recycling of the Ocean Floor

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  1. Creation, Aging and Recycling of the Ocean Floor How is the ocean floor made? Why does the ocean floor get deeper with age? How are volcanic arcs made and why are they so dangerous?

  2. Formation of Ocean Lithosphere

  3. Formation of Ocean Lithosphere Mid-ocean ridges-- global circuit of plate divergence-- youngest ocean floor-- shallowest ocean floor Architecture of oceanic plates-- seismic profiling-- ocean drilling-- fossil slivers of ocean floor

  4. Seismic Profiling (sound energy)

  5. Ocean Drilling • International program(20 nations; began 1968) • 2-month cruises • Deepest hole: 2 kmBut, new vessel will drillto >6km!

  6. Fast vs. Slow Spreading Fast Spreading Ridge (10-20 cm/yr) Slow Spreading Ridge (1-5 cm/yr)

  7. Mid-Ocean Ridges Uniform process of mantle melting, lava freezing- magma chambers- effects of spreading rate- segmentation

  8. Ocean Crust Layering

  9. Superfast Spread Crust Mission to Hole 1256D

  10. Superfast Spread Crust Mission to Hole 1256D

  11. o 10 cm Mineralized Volcanic Breccia (1027-1029 mbsf) o

  12. http://www.somethingawful.com/articles.php?a=3743 Signs of the Apocalypse for April, 2006 Apocalypse Rating: (5 out of 7) Drilling Our Way to Satan Meddlesome scientistsclaimed to be pursuing knowledge rather than the chthonian layer of the Unlordwhen they drilled nearly one and a half kilometers beneath the ocean floor. What they found down there was a "fossilized magma chamber" instead of the Beastthey were secretly seeking. I'm not sure how a rock can become fossilized, but what I am sure of is thatdrilling deeper than oil is dangerous. I would have told people not to even drill as deep as oil if at all possible, but I wasn't around when they first started doing that. Whether or not deep oil wells have unleashed Satan on our world is open to debate by the wisest scholars of the Weekly World News, but this deep drilling for no good reason has got to stop. We can't just rove around all willy-nilly and drop a drill miles underground wherever we please. Even if the devil is deeper than our drills could ever reach there's got to be something bad down there like Morloks or CHUDs or something. Having those cats out and about is not going to slow down our careening rollercoaster ride towards the Final Battle…….. Superfast Spread Crust Mission to Hole 1256D

  13. 13th December, 2005, Hole 1256D, Gabbro! Thanks to Captains, Crews, and Happy Science Parties of ODP Leg 206 and IODP Expeditions 309 & 312 Superfast Spread Crust Mission to Hole 1256D

  14. Sea floor deepens with distance from the spreading ridges -- why?

  15. Plate Aging involves heat loss through Conductive Cooling Relation: Depth increases with the square root of age

  16. Conductive Cooling and Sinking Age-depth relation: Mass balanceThe mass in column x1 is equal to the mass in column x2 => “balanced”

  17. And, heat loss through Hydrothermal Circulation

  18. Hydrothermal Circulation

  19. Hydrothermal Circulation Natural consequence of porous, hot rock and seawater Chemical exchange Fluid venting -- black smokers Chemosynthetic ecosystems Crack sealing and sedimentation

  20. Hydrothermal Vent Sites

  21. Hydrothermal Vents Video

  22. The ocean floor ages and accumulates sediments

  23. Plate Aging and Recycling Slab sinking -- denser than asthenosphere

  24. Plate Subduction and Melting

  25. Plate Subduction • Volcanic Arcs • Element recycling • Distillation of the mantle • Growth of continents

  26. Pacific NW

  27. Mt St Helens Water, from slab, promotes mantle melting and leads to explosive danger of arc volcanoes

  28. Krakatoa (1883)Tambora (1815)

  29. Toba (71,000 B.C.) 3000 times as big as Mt St HelensSulfuric acid and dust blocked sunlight, reducing temperatures 5°C for several yearsMay have reduced human population to <5000!

  30. Mt Hood

  31. Broken Top

  32. Three Sisters

  33. Crater Lake (Mt. Mazama)

  34. Volcanic ash (tephra)

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