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Download METAMORPHISM & METAMORPHIC ROCKS
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Transcript
The Sea Floor Origin of the Ocean • Water vapor released during degassing of early earth –volcanism • Salt from chemical weathering Methods of Studying the Sea Floor • • • • • Rock Dredge Corer Sea-Floor Drilling Submersibles Echo Sounder • Seismic Profiler • Surveys - Magnetic, Gravity, Seismic Refraction • Deep Sea Cameras Features of the Sea Floor • Continental Margins – Passive – Active • Oceanic trench • Mid-oceanic ridge • Seamounts Continental Shelves and Continental Slopes • • • • Vertical exaggeration in diagrams Continental shelf Continental slope Continental rise Active Continental Margins • On land- earthquakes, young mountain belt, volcanoes • Continental shelf, continental slope, oceanic trench • Oceanic Trenches – – – – Earthquakes of the Benioff seismic Zones Volcanoes Low Heat Flow Negative Gravity Anomalies Submarine Canyons • • • • • • Abyssal Fans Bottom Currents Down-canyon movement of sand Bottom currents River erosion Turbidity Currents – Graded bedding – Shallow water fossils Passive Continental Margins • Continental shelf, slope, rise • The Continental Rise – Types of Deposition • From turbidity currents • From contour currents • Abyssal plains Fracture Zones • Offset rift valleys • Transform Fault – Portion that has earthquakes Seamounts, Guyots, and Aseismic Ridges • Seamounts • Guyots • Aseismic ridges Reefs • Fringing Reefs • Barrier Reefs • Atolls Sediments of the Sea Floor • Terrigenous Sediment • Pelagic Sediment – thickness increases away from crest of midoceanic ridge Deep-sea sediments, those found at depths greater than about 500 m, cover roughly two-thirds of the Earth. The predominant deep sediment is carbonate ooze, which covers nearly half the ocean floor The Mid-Oceanic Ridge • Rift Valley • Geologic Activity on the Ridge – – – – Shallow-focus Earthquakes High Heat Flow Basalt Eruptions Hot springs • Black Smokers • Biologic Activity on the Ridge – Geomicrobiology Oceanic Crust and Ophiolites • Evidence for composition of the oceanic crust • Ophiolite (from top to bottom) – Marine sedimentary rock – Pillow basalt – Sheeted dike complex – Gabbroic intrusions – Ultramafic rock The Age of the Sea Floor • Younger than 200 million years old • Parts of continents much older
