1. Ocean Basins Structure of the Oceans From Continental Shelf to Abyssal Depths

2. 2 Measuring Depth  85 BC Posidonius ~2km  Hemp line and greased lead weight  tension  Fathoms (6 feet)  Piano wire and cannonball w/ winch  By 1895 only 7000 measurements to 2000m and 550 to >9000m  Echo sounder (depth recorder) 1920s  Meteor- mid-Atlantic ridge  1950s detailed mapping of ridges and trenches  Heezen and Tharp

3. Echo Sounder

4. 4 Bathymetry  LADS (shallow water)  Laser airborne depth sounder  Fixed winged aircraft/ GPS  Operating depth of 0.5-70m  Gravity measurements  Changes in sea surface elevation  Seamounts +5m and ridges +10m  Trenches -25-30m  Satellite altimetry  Side-scan sonar

5. Marine Gravity Anomalies by Satellite Altimetry

8. 8 Bathymetry of the Sea Floor  Continental Margin- Passive and Active  Continental shelf (Flat- 10-1500km, 65km; 20- 500m deep)  Continental shelf break  Continental slope (Steep)  Submarine canyons  Turbidity currents and turbidites  Continental rise  Ocean Floor  Ridges, Rises and Trenches

9. Shelf Break Slope Rise Computer Drawn Topographic Profiles Mid- Atlantic ridge

10. Continental Shelves

12. Formation of Shelves by trapping of land derived sediments

14. Turbidity Currents- 90km/hr, 300kg of sed in suspension

15. Submarine Canyon

16. Ancient Turbidite Sequence Bouma Sequence Top- (E)Pelagic Seds (D)Parallel Laminated Sands (C)Rippled, wavy or convoluted laminae (B)Plane Parallel Laminae Bottom-(A)Massive Graded D C A

17. 17 Bathymetry of the Sea Floor  Ocean Floor  Deep seafloor (4000-6000m cover 30% of Earth’s surface)  Abyssal Plain (Flat)  Pelagic sediments and turbidites  Abyssal hills and seamounts & Guyots  <1000m high; steep sided volcanoes  Found on 50% Atlantic and 80% Pacific seafloor  Some become atolls  Ridges, Rises and Trenches  65,000km mountain range  Challenger Deep (Mariana Trench 11,020m)

18. Major Ocean Basins

24. 24 Sediments  Continental margins and ocean basins receive continuous supply  Organic  plankton  Terrigenous (Land)  Rivers, beaches  Atmospheric  wind  Space  tektites (meteorites)

26. 26 Continental Margin  Thick Sequence of sediments (1000’s m)  Passive margin  Gravels, sands, muds  Rates of deposition vary 8m/yr in estuaries  5m/1000yr quiet bays  Shelf and slope 10-40cm/1000yrs  Carbonates  Salts  Potential for resources  Oil  Gas  Methane Hydrates

27. 27 Sand and Gravel  1.2 billion tons/yr  Reserves of 800 billion tons  US 450 billion tons  UK & Japan take 20% from seafloor  Other materials found within such as Fe, U, Pt, Au & Diamond  The Tin Belt of SE Asia  Carbonate sands

29. Oil and Gas account for 95% of material exploited from the sea 24.8% of oil and 20.7% gas in US came from offshore production (1997)

30. Gas Hydrates and other Gases Geopressurized zones Methane Hydrates, crystalline solids of gas and water abundant in arctic regions and marine sediments 1 ft 3 releases 160 ft 3 gas Offshore east coast area of potentially 1300 trillion ft 3 gas Reserves 4x10 20 ft 3

32. 32 Atmosphere-Wind  Winds from deserts transfer terrigenous sediment 1000’s kms into ocean basin  Annual supply to oceans 100x10 6 metric tons  Sahara-Caribbean connection  Reefs  Soils

36. Sorting Poorly Well

44. 44 Biogenous Sediment  Planktonic- Siliceous and Carbonate Oozes  Phytoplankton  Diatoms (silica)  Coccolithosphorids (carbonate)  Zooplankton  Radiolarians (silica)  Foraminefera (carbonate)  Lysocline (dissolution)  CCD (carbonate compensation depth) <20% preservation CO3 ~4500m  Atlantic (5000m)  Pacific (4200-4500m); Equatorial Pacific (5000m)

45. DiatomsCoccolithosphorids

46. Radiolarians

47. Foraminifera

48. 48 Hydrogenous Sediment  Slow formation in water column  Chemically precipitated  Carbonates (ooids, calcareous muds)  Phosphorites (fertilizers)  Continental shelf and slope  Reserve ~ 50 billion tons  Nodules or crusts  Due to high nutrients-upwelling  Salts (Mediterranean)  Manganese nodules  Concentric layering  High in Fe, Cu also  1-10cm diameter  Hydrothermal vents (smokers)-ores (sulfides)

49. 49 Upwelling  When wind blow offshore, they push the warm surface waters away from the coastline  This creates a region of low pressure and may result in upwelling of deep water to replace surface water.  The deep waters contain dissolved nutrients which can support abundant life at the surface  Many fishing grounds exist in these areas, notably the west coast of N. & S. America and w coast of Africa

55. 55 Laws and Treaties  200-mile EEZ  Law of the Sea (1982)  All wealth is shared by humanity  Regulated by UN  Profits shared  US did not sign treaty  Provisional Understanding Regarding Deep Seabed Matters (1984)- Western countries (US, UK, Germany, Japan…)  4 consortia awarded exploration licenses

56. 56 Sediments as Records  Paleoceanography  Isotopic studies  Oxygen isotope ratios in skeletal material to infer past climate ( 18 O: 16 O)  Dependant on ratio in seawater  During glaciations is 16 O removed, so 18 O: 16 O ratio increases in seawater  Marine plankton distribution  Circulation models