Week 2 - 3 Oceanography
Week 2 - 3 Oceanography GEOLGY 300
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This 32 page Bundle was uploaded by GreenOwl713 on Thursday August 6, 2015. The Bundle belongs to GEOLGY 300 at University of Wisconsin - Whitewater taught by Rex Hanger in Summer 2015. Since its upload, it has received 58 views. For similar materials see Principles Oceanography in Geology at University of Wisconsin - Whitewater.
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Date Created: 08/06/15
Geology 300 Lecture Notes 1 gt Read Ch 3 gtgt Plate Tectonics 0 Making and Closing Ocean Basins Pangaea ca 250 myBP Southern part Gondwanaland 972014 972014 The frica outh America Fit Plate Tectonics li T gt For many reasons evidence of continental motion was ignored until the 1960 s when it morphs into Plate Tectonics 0 Earth outermost layers are hard brittle and broken into pieces called plates 0 Heat flowing up via convection from lower layers moves the plates over surface so plates drift not continents A cross section through Earth showing the Internal layers Sea Floor Spreading V V V V V Sonar reveals bathymetric variations Vast highlands in ocean centers mid ocean ridges These MOR have extensive volcanic activity and earthquakes 39 Heat rises here at plate boundaries spreading the sea floor apart Pushes continents along Global Distribution of Seismic Events Convection in the Earth39s Interior Atlantic Ocean Mid Atlantic Ridge South America Eurasia Peru Chile quot 39 Trench 39 Philippine Trench Mariana Trench East Paci c Rise Upper mantle Hawaiian Island Chain 972014 Ridge axis Transiorm Slibnuciion Zone Zones oi extension within continenls W Uncertain oiale aoundary Plate Boundary l Divergent gt Making an Ocean Basin gt Caused by tension lt gt stress gt Generates Sea Floor Spreading creates new oceanic crusts and basins gt kextensive basalt volcanism many shallow focus earthquakes gt Creates Mid Ocean Ridge MOR system 972014 972014 Unith quotcan 972014 Plate Boundary 2 Convergent gt 2 Closing an ocean basin gt Continental crustgtgt ltltoceanic crust gt Created by compression stress gt lt gt Extensive andesite volcanism extensive shallow moderate and deepest focus depth earthquakes gt Creates subduction zone with deep ocean trench 972014 972014 000 Ridge 8X18 Trans1orm Subduczlm zone Zones 0 extension wahin contmeols Uncerzam plate aoundary Paleomagnetism proof of SFS 8 PT mm gt Earth has a magnetic field compass points North gt Basalt erupted at MOR contains magnetic minerals that align themselves with this field gt Le lavas have minerals that point in same direction as magnetic field Paleomagnetism field reversals gt The Earth s magnetic field does NOT always point North gt At irregular time intervals the field switches or reverses gt Compass will then New Pew pomt to South pole New PM gt Called Reversed Polarity Reversals and Divergent bounda es gt Fact 1 Basalt lava containing magnetic minerals is constantly erupting at MOR gt Fact 2 The Earth s magnetic field sometimes points North sometimes South gt Fact 3 So the cooled lavas will preserve this pattern of reversals IF plate tectonics is true amp 972014 Rift valley at ridge crest Region of normally magnetized dikes Oceanic crust 39 Magma Upper mantle A Time of normal magnetism Reverser magnetized dikes B Time of reverse magnetism Normally magnetized dikes C Time of normal magnetism 972014 10 Positive magnetic anomal Negative magnetic anomaly 10 Kilometers gr Rift valley at ridge crest Paleomagrretism as Proof of PT gt The pattern of magnetic reversals of seafloor basalt lavas oceanic crust is now found in ALL ocean basins on Earth gt The normalreversed patterns are symmetrical across ALL of these MOR gt So since 1965 geologists have accepted PT as true X Symmetries across MOR J J 4 i i ll39li lr r inquot l GhETIC ANCPMLIE S OCEAN LIDIOSPHERE LITHOSPHENE gt All evidence to support SFS amp PT gt Ages of oceanic crust increase away from MOR gt Ages of sediments increase away from MOR gt Thickness of sediments increase away from MOR gt Magnetic anomaly patterns symm Across MOR 972014 11 Hot Spots gt rising heated magma at a solitary location gt Remains stationary gt Plates above keep moving over it gt Volcanoes form on moving overhead plate gt Produces line of progressively older volcanoes 01W quotAn when HA3904 0 M 139 aluminum may Magma Quinlan Oceanic Crust L i rlmsplrerr llmlcrplaling 972014 12 972014 Paclllc Plate Ridge Trench Fault A Antarctic Plate Copynml 1999 Jam Wiley and Sun In All Ighls reserved llquot Oceanic lplateaus v thickened masses of basalt oceanic crust may be large enough to be emergent islands Originate at MOR pushed toward subduction zones TOO thick to be subducted instead they get scraped off onto continent obduction or now Accretion v v v 13 972014 Tb lt Eoc gensluchom 15M imyk Pr Ce 3 Jr y QLConS new GE JAM i gtT r39arv mums I m 140 1E Dquot 180quot 150 Te rranes gt bodies of land found today as part of the edges of continents BUT gt May have originated as oceanic plateaus far far away so sometimes called gt Exotic terranes or suspect terranes gt most of western North America originated near Asia 0 All of California Alaska Oregon Washington etc are MORE Asian than North American 14 More on T erranes gt Usually added to continents by accretion so called accreted terranes gt Can contain exotic fossils too gt Also called micro plates or micro continents gt Known only since 1980 s Franny3 an G39nnl u39nlcy rccmls Bel Susanna In mm Kim Iwmnm K it P raulm Pingion an MMtr quotteem Mama Slain m Sr Senna Nnmmn Swvn um um 54mm wrsuta 51km Tm rm y A western Tans and Eileen 3 KW Juman 972014 15 972014 Geology 300 Seafloor Features gt Read Chapter 4 gt Margins of ocean basins HVP SOQlFathiC l Mountainsi Trenches island arcs seamounts abyssal hills Land Land platforms 0 lt Land area gt 100 50 l l l l l r I I I I l I l l I I l l l I 50 0 lt Ocean area gt 11 ContinentalOcean Margin gt the transition from continental crust to oceanic crust Or granite dominance to basalt dominance Usually quotrMicrite submerged neath seawater V V Active vs Passwe Wins coincide with plate tectonic boundaries especially we nt UsuaHy mountainous Immature sediments delivered to sea 1 39 I l V rgtrquotl I r l V V V V 972014 Active vs Passive gt Passive margins gt Do NOT coincide with plate tectonic bounda es gt Usually low relief broad coastal plains gt Very mature sediments delivered to sea 972014 972014 972014 972014 972014 Mid Atlantic Ridge Tonga Kermadec Trench 9ampon 972014 Continental Shelf QXWEQ N 0 P WlMS gt Shallow submerged extensions of continents gt Underlain by granite continental crust gt 74 of Earth s reface Continental Shelf 2 gt Variable widths 0 Few km to 350km gt Usually low slopes E o 20mkm E gt Mostall usually end at l 40m water depth gt Active margins with steeper and 39nner shelves 2 600 700 300 900 10301100120013 100 200 300 400 500 Dlstanoafrunsrmmm 972014 10 Active vs Passive shelves 130w 120w 50w 110 W100 W 90 W 80quotW 70 W 60 W 50 W 40 W 30 W 20 W 10quotW 0 E Continental shelf 3 gt Continental shelves extremely resource rich 0 Especially oil gas life Shelf break seaward edge of shelf 0 1540m depth 0 May have coral reefs or ancient non coral reefs V Continental Slope gt transition to the deep oceans gt Still granitic crust usually gt Increased slope o 70mkm o steepest road grade allowed on Interstate highways gt Average 20km width gt Most end at 3700m water depth 099mmquot 6 010020030040050060070080 Dismfromsrue 972014 11 Sulbmalrine Canyons V deep canyons cutting across shelfslope Conduit for terrigenous seds from land to sea oor UsuaHy perpendicular to shoreline extensions of nd rivers V V V Sulbmalrine Canyons 2 Upper parts cut by rivers during sea level lowstands But extend to depths of gtgt1000m so other processes gt Turbidity Currents o Landslides quakes catalyst for massive downslope movement V V 972014 12 972014 m m 9 materials 13 Continental Rise gt Usually only at passive margins gt Tremendous sediment accumulations at base of continental slopes gt Width 100 to 1000 km 100 200 300 400 500 600 700 800 90010001100l2001300 Distanoelromsrmotm slopes Io 9mkm Deep Ocean Basins 972014 14 Deep Ocean Basins gt MOR hydrothermal vents from divergence gt Island arcs trenches from convergence gt Seamounts gt Abyssal plains 972014 15 972014 16 972014 17
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