GEOL/BIOL 309 Oceanography Notes
GEOL/BIOL 309 Oceanography Notes GEOL309
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This 3 page Class Notes was uploaded by Nimra Muhammad on Saturday September 5, 2015. The Class Notes belongs to GEOL309 at George Mason University taught by Dr. Randolph A. McBride in Fall 2015. Since its upload, it has received 112 views. For similar materials see Introduction to Oceanography in Geology at George Mason University.
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Date Created: 09/05/15
Lecture 1 Intro to Oceanography 4 discipline of oceanography o geological oceanography o biological oceanography 0 physical oceanography 0 chemical oceanography early exploration and oceanography o started by vikings phoenicians and others Polynesians were the early explorers vikings homeland was scandinavia discovered iceland in 860 AD Greenland and Baffin island good navigators and great ships Phoenicians explored red sea and some indian ocean Age of Discovery columbus spent time in eastern caribbean magellan 1590 took whole world route 4 years took to circumnavigate the whole world columbus took 3 voyages collected scientific data water depth mapping etc Motives to explore Oceans mostly food fishing and new places to live conquest establishing trade routes Four Oceans pacific largest and deepest Atlantic second largest Indian third largest Arctic shallowest Mariana Trench 11000 m deepest trench in pacific ocean vs sea vs gulf sea and gulfs are smaller and shallower north sea med sea sargasso sea sargasso is a subset in north atlantic ocean area of convergence of water water moves clockwise in the area and its more like a geyer Gulf of Mexico depth close to ocean depth still shallow Sea Vs Gulf both smaller and shallow than ocean Where did all the water came from Outgassing volcanic outgassing earth was initially molten and gas and water which was all out into atmosphere which cooled and dense and that s how the ocean formed until 4 byr the full scale ocean didn t appear stratification led to the outgassing of the planet another way was comet and meteorites brought water to the earth kuiper belt primary source still is volcanic outgassing oceans originated about 4 byr years ago age found through oceanic sediments lecture 2 Plate Tectonics ovenNhelming evidences support plate tectonics first theory was proposed in 1965 wegener proposed his continental drift theory in 1912 didn t explain why continents were moving around propose supercontinent pangaea theory which existed 200 myr ago panthalassa ocean surrounded the supercontinent proto pacific different plate boundaries have different features and plates continue to move isobath same depth of water continental slope is where all continents were joined 2000 m depth thats where the best fit of continents were matched up eg granitic crust with granitic crust Evidence for continental drift matching sequences of rocks and mountain chain similar rocks on different continents some rocks were got covered and some eroded away glacier ages and other climate evidence continental glaciers were covering south africa india and north america evidence of glacier in tropical areas direction of glacier flow and rock scouring underlying bedrock found and shows that glaciers were moving and one major glacier at the supercon nent different climate than today distribution of organism mesosaurus found in south america and africa marsupials were also found in australia and now in america Earth Magnetic Field paleomagnetism study of ancient magnetic field of earth magnetism because of molten outer core earth has polarity and it switches about 250 kyrs normal and reverse polarity recorded in igneous rocks and sed rocks magnetite in basalt line up with poles lava in rocks would line with south and north pole magnetic evidence of seafloor spreading ocean magma orders itself according to polarity making pattern mirror image on each side of the ocean magnetic anomalies create stripes normal towards north and reverse towards the south stripes were symmetrical on either side of MOR Sea Floor Spreading mantle convection cells as driving mechanism MOR is spreading center where new crust form daily denser crust subducts in asthenosphere process driven by mantle convection cells that s driving mechanism for plate tectonic due to sea floor spreading largest MOR making like a baseball around Gulf of California Australia and northern Canada Age of Sea floor deep sea drilling project late 1960s rocks were radiometrically dated youngest rocks were found in MOR active volcanism in the area rocks getting older outwards older rocks in sea floor no older than pangea spreading rates is slower in atlantic than pacific symmetrical pattern in atlantic asymmetrical pattern in pacific oldest ocean floor is 180 myr created and destroyed through subduction rocks on earth so much older because never been subducted
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