ESS15_LEC5F10_PTect1_2perpage - Lecture 5 Plate Tectonics...

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1 Introduction to Oceanography Lecture 5: Plate Tectonics part 1 Adapted from USGS image by various wikimedia commons contributors, Public Domain Introduction to Oceanography •Check lab exercise key outside 3820 Geology. •1st lab quizzes this week! “mid-ocean ridge” at Thingvellir, Iceland, Julius Agrippa, Wikimedia Commons, C C A S-A 2.5
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2 Morphology of the Oceans Continental Margins Abyssal Plains Mid-Ocean Ridges Deep-sea Trenches Continent Ocean Basin Plumbago, wikimedia commons, C C A S-A 3.0 LA OC Catalina Santa Barbara SD Southern California Margin Southern CA has an unusual margin Map Courtesy C. Goldfinger and J. Chaytor, OSU, from USCD Earthguide online classroom ~30 km
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3 Southern Californian Borderland Pervasive active faulting and tectonics – No broad flat shelf region – Instead, fault bounded ridges and basins – Ridges can form islands (i.e., Catalina) – Basins can be 1 - 2 km deep – Continental slope ~80-100 km west Los Angeles sits on a silted up basin! LA OC Catalina Santa Barbara SD Deep Ocean Basins What about in the very center of the ocean basins? Mid-ocean ridge Plumbago, wikimedia commons, C C A S-A 3.0
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4 Mid-Ocean Ridges Earth’s longest continuous mountain chain ~ 60,000 km long, ~1/3 of ocean floor area Relief: ~ 2-3 km above abyssal plains NOAA global relief map, Public Domain The Mid-Ocean Ridge System GEBCO world map, , education use ok.
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5 The Mid-Ocean Ridge System Abyssal Plain MARGIN Mid-ocean ridge GEBCO world map, , education use ok. Mid-Ocean Ridge Features Ridge Axis Rift Valley – Depth ~ 1 km, Width ~ 10 -20 km – Widespread volcanism – Shallow earthquakes – Right-angle fracture zones GEBCO world map, , education use ok. East Pacific Rise Mid-Atlantic Ridge
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6 Mid-Ocean Ridges & Isostasy Keeping isostasy in mind, why do mid-ocean ridges stand up so high above the ocean bottom? ~2 km NASA art, , Public Domain Questions? Why do we have oceanic and continental crusts? Why are there deep-sea trenches, mid-ocean ridges and long seamount chains? Shelf Break Slope Rise Cont’l Crust Oceanic Crust Sediment Cidnye, wikimedia commons, Public Domain (Not to scale)
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7 Introduction to Plate Tectonics NOAA global relief map, Public Domain History of Plate Tectonic Theory Plate tectonics is a fundamental, unifying theory in all of the Earth Sciences. Explains locations of most earthquake zones, volcanoes, the age of the sea floor, and the shape of the Earth’s surface.
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