Reading MaterialOcean BasinsSlide 3Earth’s SurfacePlate Tectonics – mechanism that moves crustSlide 6BathymetrySlide 8Slide 9Sub-Environments on Continental MarginsSlide 11Central California area of Monterey CanyonMonterey CanyonSlide 14Continental MarginsSlide 16Materials filling ocean basinsSlide 18Slide 19Classification of marine sedimentsSlide 21Reading MaterialOn reserve in:Ocean-Fisheries library (Oceanography Teaching Building)Undergrad Library(web access)“Ocean Basins”, from “Oceanography”M.G. Gross, Prentice-HallOcean BasinsWhat creates the Earth’s surface?What is the shape of the surface below sea level (the seafloor)?What types of sediment are burying the seafloor?Earth’s SurfaceHypsographic Diagram30% land10% continental margins (boundary)60% deep seaTwo distinct levels for Earth surface0-1000 m above sea level4000-5000 m below sea levelThese represent two distinct types of crust (Earth’s rigid upper layer)continental crust – thick, granite, not so denseoceanic crust – thin, basalt, denserPlate Tectonics – mechanism that moves crustPlatesseparate pieces of crustmove due to convection of heat in underlying layer (Mantle)plates can move in different directions, and collideCollisionsa) two continental plates collide, form high mountain rangese.g., Himalayasb) two ocean plates collide, form island arc and submarine trenche.g., Aleutian islands and trenchc) ocean and continental plates collide, form mountains and trenche.g., Andes and South American TrenchSubductionoccurs when ocean crust carried down into Mantle (e.g., b and c above)basalt and sediment heated to form volcanic magmaBathymetryMid-Ocean Ridges (underwater mountain ranges)water depth – 2000-4000 mcan be less – where islands occur (e.g., Iceland)volcanic eruptions create new ocean crusthot basalt, thermal expansion creates elevationmoves away from ridge axis in both directionsAbyssal basinswater depth – 4000-6000 m (only trenches are deeper)abyssal hills, include rough relief from volcanic formationabyssal plains, smooth surface due to burial by sedimentContinental marginscreated by sediment from land that builds into ocean basinsOpening of new ocean and formation of mid-ocean ridgeSub-Environments on Continental MarginsContinental shelfsmooth, gently dipping (less than 0.1 degrees)land surface during lowstand of sea levelglacial ice melted and flooded portion of continentContinental slopesteep (more than 4 degrees), rough topographyedge of continental crustsubmarine canyons, larger than canyons on landnot eroded by rivers directly (too deep), but by slurry of sedimentContinental risemore gentle gradient and reliefsediment from land piled on ocean crustTrenches (collision of plates, deeper places in ocean)Abyssal plains (sediment from land buries abyssal hills)Trailing-Edge MarginCentral California area of Monterey CanyonMonterey CanyonContinental MarginsTwo types:Trailing-edge marginscontinental and oceanic plates move in same direction at same speedexamples – margins around Atlantic Oceancontain: coastal plain (was continental shelf during higher sea level)broad continental shelfcontinental slope and riseCollision marginscontinental and oceanic plates move toward each otherexamples – margins around Pacific Oceancontain: coastal mountain range, volcanoes, earthquakesnarrow, steep continental shelfcontinental slope and submarine trenchCollision MarginMaterials filling ocean basinsDissolved chemicalsespecially from rivers and mid-ocean ridges (volcanic eruptions)some remain dissolved (e.g., producing salt water)some precipitate inorganically (e.g., producing Manganese nodules)some precipitate organically (e.g., producing biogenic oozes)Solid particles, from:wind (aeolian) – dust blown from land, only important in deepest ocean forms “red clay”rivers (fluvial) – most important source90% mud (silt, clay), 10% sandglaciers (glacial) – greatest impact at high latitudes supplies wide range of sizes (boulders to rock flour)Authigenic Sediments(manganese nodules)and red clayBiogenic Sediments, microscopic in size(single-celled plants and animals)Classification of marine sedimentsLithogenic – from disintegration of rock on landaeolian, FLUVIAL, and glacial sourcesBiogenic – organic precipitation of dissolved components dominated by single-celled plants and animals (create oozes) calcium carbonate (limestone) = calcareous silicon dioxide (opal) = siliceousAuthigenic – inorganic precipitation of dissolved components seawater becomes supersaturated with regard to some chemicalsCosmogenic – from outside Earth meteorites, usually very small (tektites)Cosmogenic Sedimentstektites
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