Oceanography Week 2 notes
Oceanography Week 2 notes GEOL309
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This 9 page Class Notes was uploaded by Nimra Muhammad on Sunday September 13, 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 58 views. For similar materials see Introduction to Oceanography in Geology at George Mason University.
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Date Created: 09/13/15
Lecture 1 Intro to Oceanography 4 discipline of oceanography geological oceanography biological oceanography physical oceanography chemical oceanography early exploration and oceanography started by vikings phoenicians and other explorers 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 took to circumnavigate the whole world columbus took 3 voyages collected scientific data water depth mapping etc FIGUFIE 17 Voyages of Columbus and l V I I of Turdesillqs 1494 739 39 Madeira K Azores r I il Magellan l vlamslnm39inglhe dalcsnnd 39 39 4 539 r 39 E u an a quot I39Uulus ul39 ulmnhus s l irsl vul39zmgu r quot Q31 1 9 39CI39E39Ii39l39y I and life l39il39xl circumnavigleinn of didKi 5ng 3 t quotF39 ig 39 the glnhc I13quot h lugullnn s purly if I d quot a TLANTIC c a 39y A 7 NORTH 132 005quot 3935 f L uJIuInhms 39j r quota 39 I I Hiquot 7 All 5 ll92 quot 39 139 AMERICA 12 4 i has 39 Msdlm S i 5 J 7 39 1 firmMI OH I Sc11l20 1519m quotI Mama Eg x l mu M112 Sept61522 g 39 runquot quot 7 mugging killed 39 quot 1 39 quot 3 Pan Mm 1 PACIFIC 2 17 4h g fa OCEAN VT 39 1 x I 7 AFHIcA J m V K 39 quoti 39 I y f 301m Milts ll ljdlll L r l ill of Magellan quotl 1530 5 39 I I 151quot EHIDH Kilometers E 1 r mrsi39 17 i tars 1 ANTARCTICA 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 etc 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 overwhelming 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 that39s where the best fit of continents were matched up eg granitic crust with granitic crust Evidence for continental drift 0 matching sequences of rocks and mountain chains on different continents 0 similar rocks on different continents some rocks were got covered and some eroded away with time o glacier ages and other climate evidence o glaciers found in india and similar in Australia 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 super continent 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 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 mid ocean ridge F 1 139 r quot Purlmag quot nmrnai magm m 1 Sea Floor Spreading mantle convection cells as driving mechanism MOR is spreading from the center where new crust form daily denser crust subducts in asthenosphere 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 Ocean Floor deep sea drilling project late 1960s rocks were radiometrically dated 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 conveyor belt and tectonic plates keep earth s size same It doesn39t get big or small Heat Flow releases from earth39s interior to surface very high at MOR lowest at the subduction zone Global Distribution of earthquakes japan started seismic activity in 1950s Global plate boundaries largest plates pacific and eurasian medium size plates nazca plate south american plate smaller plates Juan de Fuca plate Earth39s composition Crust granitic and basaltic rocks silicate composition hard shell granitic crust continental basaltic crustbasalt is igneous molten and crystallizes oceanic inner core iron and nickel rigid outer core liquid lithosphere plates move on asthenosphere asthenosphere molten ex potato chipslithosphere on honeyasthenosphere mesosphere solid and brittle Plate Tectonic Theory lithosphere 12 to 14 tectonic plate that float on ductile asthenosphere a lot of features occur at the plate boundaries major tectonic feature slab pull slab suction more heat at mor and cooler at trenches Acceptance of plate tectonic evolved from hypothesis to this still test and not disproven average plate movement giving enough time plate move across entire earth s surface it provides basins for oceans 3 types of plate boundaries Divergent create the crust ex Mid Atlantic Ridge shallow focus earthquake dominates MOR and rift valleys plates move apart new floor being created East african rift valley on continent that39s how ocean forms like atlantic wasn39t there 200 myr ago Convergent destroy the crust Transform san andreas fault look at table in the book 21 Types and Rates of Spreading Centers Oceanic Rise fast spreading gentle slopes east pacific rise oceanic ridge slow spreading 25 cmyr steep slope MAR Ultra slow deep valley rift widely scattered volcanoes Arctic and southwest indian ridge Spreading center MAR and east pacific rise less dense continental crust floats on denser mantle continental crust is less dense so it rides high 28 gcm3 vs 30gcm3 ocean convergent boundaries 3 sub types oceanic to continental ocean to ocean continental to continental subtype A oceaniccontinental convergence subduct under granitic crust ex fuca plate subducted under north american plate continental volcanic arcs generated cascade mountains explosive andesitic volcanic eruption nazca subducted under south american plate Subtype B Oceanic to Oceanic convergence denser plate subducts deep trenches subduction taking place volcanic island due to magma whichever slightly denser plate is subducts oceanic crust same basaltic continental crust same as granitic Subtype C Continental to continental collision india collided with eurasia both have densities of 27 gccm3 so don39t want to subduct ex Himalayas fomred study table 21 for exam Transform boundary features side swapping each other like one car going fast and other slow oceanic transform fault ocean floor only continental transform fault san andreas fault transform fault orient perpendicular to MOR shallow earthquake no subduction and no volcano transform fault vs fracture zone Global hot spot zones ex hotspots gt galapagos hawaii iceland and yellowstone EEPLANJ Ti i l imrgent plate boundaries Wham nlefw must is use naerater as the states will email from Kara ch EFH39IE II39 trimquotwargamt plats noundiarie Willem sumst is nsnunaiumEEl in the Eavrth s iraterim its one plate Eli39ar Ers under another Tlilll39l Eliarm platen lha rulmLllr ism Where crust is neither produced rum desirered as platas sii e hmilmlnltalllllr p331 rl h rth E r Plate haululnslzllmy armies irqu belts in which deformation is diffJea ElmEll lbunumzlarriax are mat WitIll rilelined i Selected prominent ho tspm r 77 r r r w big island Hawaii has active volcanism Mauna loa is there too Plate tectonics intraplate feature seamounts vs guyots seafloor spread volcano occur and the become extinct and move further finally get subducted guyots water erosion flattens seamount coral reef development fringing reefs developed along landmasses barrier reefs atolls paleogeography study of ancient continents continental accretion added stuff to edges of continents that39s how they get bigger they are getting bigger through time atlantic going to get bigger and pacific would get smaller in 100 myr North american would collide to japanese islands and pacific would vanish JT Wilson talks about life cycle of ocean basins 0 formation 0 growth 0 destruction red sea going under divergence area of low topograph terminal stage because north america is moving towards japanese island and japanese island moving towards north america and pacific vanishing Past Supercontinents supercontinent 1 30 to 25 bya columbia 19 to 17 bya Rodinia 12 to 07 bya Pangea 200 mya next supercontinent americas run into japan around pacific northern pacific ocean where major subduction zone is most ocean features are generated through plate tectonics bathymetry water depth measure vertical distance from ocean surface to mid ocean ridges trenches abyssal plain and other seafloor features isobath same line connecting passive and active continental margins at cost of va facing MOR atlantic ridge passive continental margin west coast US active continental margin fuca plate subducting passive faces MOR active faces continental margin
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