1. What Lies Beneath

2. Pre Solar Nebula—4.6 Billion yrs ago

3. Protoplanetary Disk—50 million years later

6. Formation of the moon

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

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

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

11. 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

12. 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

13. Deep-sea Submersibles

14. Features of the Ocean Floor

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

16. Rift valley Transform Faults

17. How Oceans Form

18. Life on the Seafloor? Hydrothermal vents at a mid-ocean ridge. 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 H 2 O –Chemosynthesis Bacteria feed on H 2 S

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

20. 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

21. 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

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

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

24. Carbonate Platforms In warm areas lacking terrigenous sedimentIn warm areas lacking terrigenous sediment –Thriving reef- building organisms –Thick limestone beds accumulate

25. Active Continental Margins Note thickness of shelf –Why is it only this size?