Ocean Resources Midterm Outline

Ocean Resources Midterm Outline - Ocean Resources Midterm...

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Unformatted text preview: Ocean Resources Midterm 19:38 Marine Provinces Oceans vs. Continents Bathymetry - Depth measurement, submarine Topography Continental Margins - shallow ocean close to land, underlain by continental crust, classified as passive or active Passive (Atlantic) : Not a plate boundary Not a tectonically active Continental shelf Continental slope Continental rise Active (Pacific) : Plate boundaries Tectonically active Narrow Shelf Steep Slope Deep trench Continental Shelf : Flat Narrow (active) or wide (passive) Continental Slop : Extends from shelf break to deep ocean Average gradient 4 degrees Submarine canyons o Turbidity currents Continental Rise : Transition between continental margin and deep ocean Sediments deposited by waning turbidity currents Abyssal Plains (Deep Ocean Basin) : Underlain by oceanic crust Seaward of continental margin Abyssal plains very flat o Fine-grained sediments deposited Volcanic seamounts, etc. Mid-ocean Ridges : 75,000km long Covers 23% of earths surface Rift valley at crest o Site of magma (pillow basalts) Hydrothermal vents Resources: o Metal sulfide deposits o Hot vent communities Chemosynthetic autotrophs Deep Ocean Trenches : As oceanic lithosphere ages, it subsides because it cools and its density increases Plate Tectonics Four Lines of Evidence for Continental Drift The Fit of the Continents-Pangea Similarity of Rock Sequences and Mountain Ranges Glacial Evidence Fossil Evidence Earths magnetic field (dipole, or like a bar magnet) Inclination varies with latitude Magnetic South Pole to North Pole Magnetic reversals: Magnetic reversal time scale Earths magnetic field periodically reverses +/- Magnetic reversals recorded in lava sequences Anomalies o Anomalies match magnetic time scale o Crust is progressively younger toward mid-ocean ridges o New ocean crust formed at mid ocean ridges Proof of Seafloor Spreading: Cause continental drift Proof of continental drift led to concept of plate tectonics Further evidence from the deep ocean drilling o Basal sediments are younger at mid-ocean ridges, age increases as distance from mid-ocean ridge increases o Ocean crust formed at mid-ocean ridges and is progressively buried by sediment New ocean crust formed at mid-ocean ridges=mechanism for seafloor spreading Young crust=hot-ridges buoyant and stick up Subduction Zones: Deep ocean trenches Recycling of Oceanic Plates Plate destruction (vs. plate formation at mid-ocean ridges) Plates = 100 km thick...
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Ocean Resources Midterm Outline - Ocean Resources Midterm...

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