ES 106 2006 April 24 Oceanography Water planet A 71 covered by sea B All oceans are interconnected C Less land exposed in southern hemisphere II Ocean basins four main basins A Pacific 1 of all ocean surface 2 greater than area extent of all continents 3 average depth 3940 m 4 has deepest ocean trench in western portion Mariana Trench B Atlantic 1 size of Pacific 2 Narrow bounded by continents with similar shoreline shape 3 less average depth than Pacific C Indian 1 depth nearly same as Atlantic 2 slightly smaller than Atlantic 3 bounded by land on north mostly in southern hemisphere D Arctic 1 small 7 of Pacific 2 shallow average depth of other oceans E Average elevation Continents vs Oceans 1 continents 840 m above sea level 2 oceans 3730 m below sea level 4 times elevation above sea level III Ocean Floor A Mapping 1 Challenger 127 500 km voyage in 1870s a Depth by weighted line b Salinity temperature clarity 2 Modern depth measurements by SONAR a SOund Navigation And Ranging b Ping emitted is received c Distance calculated by travel time of ping d Sidescan instruments show details not depth 3 Seismic Reflection Profiles a Explosions produce sediment penetrating sound waves b Shows information about character of sea floor 4 Satellilte Radar Altimiters a Measure height of sea surface b Gravity causes irregularities 1 Higher surface over undersea mountains 2 Lower surface over deep sea floor c Ability to detect small scale differences B Provinces of the sea floor I 1 continental margin a continental shelf 1 part of continental crust flooded by ocean 2 narrow gently sloping zones to about 130 m depth b drops off at continental slope 1 very narrow 2 markedly steeper than shelf c submarine canyons 1 cut outer shelf and slope 2 deliver sediment to ocean basin floor 2 ocean basin floor a most is abyssal plains flat featureless surface b deep ocean trenches small portion at lithosphere plate convergence c seamounts volcanic peaks d plateaus volcanic plains 3 oceanic ridge a tectonic feature of divergent lithospheric plates b 1000 to 4000 km wide 2000 to 3000 m high not topographic marvel in appearance IV Sea Floor Sediments A Most of ocean floor covered by sediment B Most of this sediment is fine mud C Three broad groups of sea floor sediment types 1 terrigenous from land sources 2 biogenous from organisms 3 hydrogenous precipitated straight from water D Terrigenous 1 sand and gravel a usually near shore b can be carried to deep ocean via submarine canyons in a turbidity current 1 density flow of sediment and water 2 expansive once it reaches deep sea floor 3 unique bedding pattern coarse to fine in a single bed 2 abyssal clay layer a washed in by streams takes decades to settle b carried from continents by wind settles on sea surface c red or brown due to extensive time for oxidation of iron in it d slow accumulation rates 1 cm 50 000 years exists extreme E Biogenous 1 shells and skeletons of marine organisms plankton etc 2 mostly microscopic organisms near surface 3 calcareous ooze of algae and foram tests a coat bottom in areas shallower than 4500 m b below 4500 m completely dissolve due to elevated CO2 in deep sea water 4 siliceous ooze a diatoms algae b radiolarians animals 5 phosphate rich material from bones teeth scales of larger animals F hydrogenous 1 crystallize directly from sea water 2 can be diagnostic of environment because they are not common 3 types a manganese nodules to 20 cm across deep sea b calcium carbonate precipitation shallow warm seas c metal sulfides from undersea hot springs with high mineral content in water d evaporites if sea is restricted and subject to high evaporation 1 halite NaCl 2 anhydrite CaSO4 gypsum CaSO4 2H2O G Distribution of Sea floor sediments 1 coarse grained near continents 2 abyssal clay over wide expanses 3 biogenous sediments where there is high biologic productivity a will predominate over other types of sediment b calcareous where 4500 m siliceous in deeper areas 4 very little present in youngest area of ocean floor ridge crest H Climate change can be traced in sea floor sediment 1 biogenic productivity changes character in different climates 2 isotopes of various elements differ with differing temperatures V Resources from the sea floor A Energy resources 1 Gas and oil deposits on continental shelf a Ancient marine organisms buried before decay b Persian Gulf Gulf of Mexico California North Sea East Indies c Deeper deposits not yet discovered 2 Methane Hydrate a Mixture of water and methane forms crystalline structure b Low temperature or high pressure to create it 1 Permafrost 2 Deep continental shelf areas B Other resources 1 sand and gravel a building material adjacent to urban areas b rare areas contain metals or gems diamond garnet tin gold platinum titanium 2 salt evaporated from shoreline ponds 30 of world total salt use 3 manganese nodules also contain iron cobalt copper nickel
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