Ocean Ocean BasinsBasins

Structure of the OceansStructure of the OceansFrom Continental Shelf toFrom Continental Shelf to

Abyssal DepthsAbyssal Depths

22

Measuring DepthMeasuring Depth

85 BC Posidonius ~2km85 BC Posidonius ~2km Hemp line and greased lead weightHemp line and greased lead weight

tensiontension Fathoms (6 feet)Fathoms (6 feet)

Piano wire and cannonball w/ winchPiano wire and cannonball w/ winch By 1895 only 7000 measurements to 2000m and 550 By 1895 only 7000 measurements to 2000m and 550

to >9000mto >9000m Echo sounder (depth recorder) 1920sEcho sounder (depth recorder) 1920s

MeteorMeteor- mid-Atlantic ridge- mid-Atlantic ridge 1950s detailed mapping of ridges and trenches1950s detailed mapping of ridges and trenches

Heezen and TharpHeezen and Tharp

Echo Sounder

44

BathymetryBathymetry

LADS (shallow water)LADS (shallow water) Laser airborne depth sounderLaser airborne depth sounder Fixed winged aircraft/ GPSFixed winged aircraft/ GPS Operating depth of 0.5-70mOperating depth of 0.5-70m

Gravity measurementsGravity measurements Changes in sea surface elevationChanges in sea surface elevation

Seamounts +5m and ridges +10mSeamounts +5m and ridges +10m Trenches -25-30mTrenches -25-30m

Satellite altimetrySatellite altimetry Side-scan sonarSide-scan sonar

Marine Gravity Anomalies by Satellite Altimetry

88

Bathymetry of the Sea FloorBathymetry of the Sea Floor

Continental Margin- Passive and ActiveContinental Margin- Passive and Active Continental shelf (Flat- 10-1500km, 65km; 20-Continental shelf (Flat- 10-1500km, 65km; 20-

500m deep)500m deep) Continental shelf breakContinental shelf break

Continental slope (Steep)Continental slope (Steep) Submarine canyonsSubmarine canyons

Turbidity currents and turbiditesTurbidity currents and turbidites

Continental riseContinental rise

Ocean FloorOcean Floor Ridges, Rises and TrenchesRidges, Rises and Trenches

Shelf BreakSlope

Rise

Computer Drawn Topographic Profiles

Mid-Atlantic ridge

Continental Shelves

Formation of Shelves by trapping of land derived sediments

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

Submarine Canyon

Ancient Turbidite SequenceBouma SequenceTop- (E)Pelagic Seds

(D)Parallel Laminated Sands

(C)Rippled, wavy or convoluted laminae

(B)Plane Parallel LaminaeBottom-(A)Massive Graded

D

C

A

1717

Bathymetry of the Sea FloorBathymetry of the Sea Floor Ocean FloorOcean Floor

Deep seafloor (4000-6000m cover 30% of Deep seafloor (4000-6000m cover 30% of Earth’s surface)Earth’s surface)

Abyssal Plain (Flat)Abyssal Plain (Flat) Pelagic sediments and turbiditesPelagic sediments and turbidites

Abyssal hills and seamounts & GuyotsAbyssal hills and seamounts & Guyots <1000m high; steep sided volcanoes<1000m high; steep sided volcanoes Found on 50% Atlantic and 80% Pacific seafloorFound on 50% Atlantic and 80% Pacific seafloor Some become atollsSome become atolls

Ridges, Rises and TrenchesRidges, Rises and Trenches 65,000km mountain range65,000km mountain range Challenger Deep (Mariana Trench 11,020m)Challenger Deep (Mariana Trench 11,020m)

Major Ocean Basins

2424

SedimentsSediments

Continental margins and ocean basins receive Continental margins and ocean basins receive continuous supplycontinuous supply

OrganicOrganic planktonplankton

Terrigenous (Land)Terrigenous (Land) Rivers, beachesRivers, beaches

AtmosphericAtmospheric windwind

SpaceSpace tektites (meteorites)tektites (meteorites)

2626

Continental MarginContinental Margin

Thick Sequence of sediments (1000’s m)Thick Sequence of sediments (1000’s m) Passive marginPassive margin

Gravels, sands, mudsGravels, sands, muds Rates of deposition vary 8m/yr in estuariesRates of deposition vary 8m/yr in estuaries 5m/1000yr quiet bays5m/1000yr quiet bays Shelf and slope 10-40cm/1000yrsShelf and slope 10-40cm/1000yrs

CarbonatesCarbonates SaltsSalts Potential for resourcesPotential for resources

OilOil GasGas Methane HydratesMethane Hydrates

2727

Sand and GravelSand and Gravel

1.2 billion tons/yr1.2 billion tons/yr Reserves of 800 billion tonsReserves of 800 billion tons

US 450 billion tonsUS 450 billion tons

UK & Japan take 20% from seafloorUK & Japan take 20% from seafloor Other materials found within such as Fe, Other materials found within such as Fe,

U, Pt, Au & DiamondU, Pt, Au & Diamond The Tin Belt of SE AsiaThe Tin Belt of SE Asia Carbonate sandsCarbonate sands

Oil and Gas account for 95% of material exploited from the sea24.8% of oil and 20.7% gas in US came from offshore production (1997)

Gas Hydrates and other Gases

• Geopressurized zones• Methane Hydrates, crystalline

solids of gas and water abundant in arctic regions and marine sediments

• 1 ft3 releases 160 ft3 gas• Offshore east coast area of

potentially 1300 trillion ft3 gas• Reserves 4x1020 ft3

3232

Atmosphere-WindAtmosphere-Wind

Winds from deserts transfer terrigenous Winds from deserts transfer terrigenous sediment 1000’s kms into ocean basinsediment 1000’s kms into ocean basin

Annual supply to oceans 100x10Annual supply to oceans 100x1066 metric metric tonstons

Sahara-Caribbean connectionSahara-Caribbean connection ReefsReefs SoilsSoils

Sorting

Poorly Well

4444

Biogenous SedimentBiogenous Sediment Planktonic- Siliceous and Carbonate OozesPlanktonic- Siliceous and Carbonate Oozes

PhytoplanktonPhytoplankton Diatoms (silica)Diatoms (silica) Coccolithosphorids (carbonate)Coccolithosphorids (carbonate)

ZooplanktonZooplankton Radiolarians (silica)Radiolarians (silica) Foraminefera (carbonate)Foraminefera (carbonate)

Lysocline (dissolution)Lysocline (dissolution) CCD (carbonate compensation depth) <20% CCD (carbonate compensation depth) <20%

preservation CO3 ~4500mpreservation CO3 ~4500m Atlantic (5000m)Atlantic (5000m) Pacific (4200-4500m); Equatorial Pacific (5000m)Pacific (4200-4500m); Equatorial Pacific (5000m)

Diatoms Coccolithosphorids

Radiolarians

Foraminifera

4848

Hydrogenous SedimentHydrogenous Sediment Slow formation in water columnSlow formation in water column Chemically precipitatedChemically precipitated

Carbonates (ooids, calcareous muds)Carbonates (ooids, calcareous muds) Phosphorites (fertilizers)Phosphorites (fertilizers)

Continental shelf and slopeContinental shelf and slope Reserve ~ 50 billion tonsReserve ~ 50 billion tons Nodules or crustsNodules or crusts Due to high nutrients-upwellingDue to high nutrients-upwelling

Salts (Mediterranean)Salts (Mediterranean) Manganese nodulesManganese nodules

Concentric layeringConcentric layering High in Fe, Cu alsoHigh in Fe, Cu also 1-10cm diameter1-10cm diameter

Hydrothermal vents (smokers)-ores (sulfides)Hydrothermal vents (smokers)-ores (sulfides)

4949

UpwellingUpwelling When wind blow offshore, they When wind blow offshore, they push the warm surface waters push the warm surface waters away from the coastlineaway from the coastline

This creates a region of low This creates a region of low pressure and may result in pressure and may result in upwelling of deep water to upwelling of deep water to replace surface water.replace surface water.

The deep waters contain The deep waters contain dissolved nutrients which can dissolved nutrients which can support abundant life at the support abundant life at the surfacesurface

Many fishing grounds exist in Many fishing grounds exist in these areas, notably the west these areas, notably the west coast of N. & S.coast of N. & S. America and w America and w coast of Africacoast of Africa

5555

Laws and TreatiesLaws and Treaties

200-mile EEZ200-mile EEZ Law of the Sea (1982)Law of the Sea (1982)

All wealth is shared by humanityAll wealth is shared by humanity Regulated by UNRegulated by UN Profits sharedProfits shared US did not sign treatyUS did not sign treaty

Provisional Understanding Regarding Deep Provisional Understanding Regarding Deep Seabed Matters (1984)- Western countries (US, Seabed Matters (1984)- Western countries (US, UK, Germany, Japan…)UK, Germany, Japan…) 4 consortia awarded exploration licenses4 consortia awarded exploration licenses

5656

Sediments as RecordsSediments as Records

PaleoceanographyPaleoceanography Isotopic studiesIsotopic studies

Oxygen isotope ratios in skeletal material to Oxygen isotope ratios in skeletal material to infer past climate (infer past climate (1818O:O:1616O)O)

Dependant on ratio in seawaterDependant on ratio in seawater During glaciations is During glaciations is 1616O removed, so O removed, so 1818O:O:1616O O

ratio increases in seawaterratio increases in seawater

Marine plankton distributionMarine plankton distribution Circulation modelsCirculation models