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 earth’s 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 Earth’s magnetic field (dipole, or like a “bar magnet”) • Inclination varies with latitude • Magnetic South Pole to North Pole Magnetic reversals: • Magnetic reversal time scale • Earth’s 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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