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What Lies Beneath

What Lies Beneath. Pre Solar Nebula—4.6 Billion yrs ago. Protoplanetary Disk—50 million years later. Formation of the moon. Return of the Volatiles. Comets and Asteroids -lingering remnants of planetary formation. Oceans and Basalt. Oceans cover 71% of Earth’s surface

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What Lies Beneath

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  1. What Lies Beneath

  2. Pre Solar Nebula—4.6 Billion yrs ago

  3. Protoplanetary Disk—50 million years later

  4. Formation of the moon

  5. Return of the Volatiles Comets and Asteroids -lingering remnants of planetary formation

  6. Oceans and Basalt • Oceans cover 71% of Earth’s surface • 5 km deep on average, up to 11 km in trench

  7. If the ocean floor is so deep, how do we study it?

  8. Sampling Methods • Collecting sediment/rock directly • Dredge • Large net dragged along ocean floor • Sediment Core • Weighty hollow pipe dropped to ocean floor—sediment sample • Drilling • Cylindrical cores of sediment/rock

  9. Remote Sensing • Remote “sampling” • Magnetometers • Instrument that measures a magnetic field • Magnetic stripes • Echo sounders • Sound signal from a ship—deeper stuff=longer time to return to ship

  10. Deep-sea Submersibles

  11. Features of the Ocean Floor

  12. Mid-Ocean Ridge System Continuous, submarine mtn chain 80,000 km long rising an average of 2- 3 km above the surrounding sea floor

  13. Rift valley Transform Faults

  14. How Oceans Form

  15. Life on the Seafloor? • Black smokers • Hot water dissolves materials as it passes through rock • Black color: fine- grained metals that precipitate in “cool” ocean water • 400°C sulfurous H2O • Chemosynthesis • Bacteria feed on H2S Hydrothermal vents at a mid-ocean ridge.

  16. Ocean Trenches, Island Arcs • Accreted Terranes • Do the continents grow?

  17. Seamounts and Guyots • Basaltic seafloor features • Seamount: Submarine mountain, ≥1 km above sea floor created by a hot spot • Guyot: a flat-topped seamount cut by waves

  18. Wh Atoll Is It Made Of? • Atoll: Circular coral reef forming a ring of islands around a lagoon • Lagoon: shallow, enclosed water basin • Living coral keep up with rate of sinking

  19. “Young” Oceans, Thin Sediments • Why aren’t the seafloors as old as the continents? • Structure of the ocean floor

  20. Passive Continental Margins • Contin. Shelf • Sedimentation and Isostasy • Contin. Slope • Thinner cont. crust • Contin. Rise • Apron of debris

  21. Carbonate Platforms • In warm areas lacking terrigenous sediment • Thriving reef- building organisms • Thick limestone beds accumulate

  22. Active Continental Margins • Note thickness of shelf • Why is it only this size?

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