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The Ocean Floor
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The Ocean Floor The World Ocean Imaging the Ocean Floor
Continental Margins The Deep-Ocean Floor Oceanic Ridges
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GEOL 131: The Ocean Floor The World Ocean
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The World Ocean Earth’s surface is 71% ocean
GEOL 131: The Ocean Floor The World Ocean Earth’s surface is 71% ocean Majority is in Southern Hemisphere Northern Hemisphere Southern Hemisphere
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GEOL 131: The Ocean Floor: The World Ocean
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Oceans vs. Continents Continents Oceans
GEOL 131: The Ocean Floor: The World Ocean Oceans vs. Continents Continents Average elev.: about 2800 feet above sea level Highest point: about 30,000 feet a.s.l. Oceans Average depth: about 12,200 feet Deepest point: about 36,000 feet
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Imaging the Ocean Floor
GEOL 131: The Ocean Floor Imaging the Ocean Floor
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Ocean Floor Mapping HMS Challenger British 1872-1876
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Ocean Floor Mapping HMS Challenger British All oceans except Arctic Used weighted ropes to find ocean depths
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Ocean Floor Mapping HMS Challenger’s route British 1872-1876
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Ocean Floor Mapping HMS Challenger’s route British All oceans except Arctic Used weighted ropes to find ocean depths
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Ocean Floor Mapping Sonar Single beam Multibeam
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Ocean Floor Mapping Sonar Single beam Multibeam
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Ocean Floor Mapping Sonar Travel time of ping / 2 = depth
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Ocean Floor Mapping Sonar Travel time of ping / 2 = depth
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Seismic Reflection Profiles
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles Seismic waves penetrate mud, bounce off rock
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Seismic Reflection Profiles
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles
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Ocean Floor Provinces Revealed by ocean floor imaging techniques
GEOL 131: The Ocean Floor: Imaging the Ocean Floor Ocean Floor Provinces Revealed by ocean floor imaging techniques Continental margins Passive and active Deep-ocean floor Oceanic ridges
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GEOL 131: The Ocean Floor: Imaging the Ocean Floor
Ocean Floor Provinces
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GEOL 131: The Ocean Floor Continental Margins
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Continental Margin Types
GEOL 131: The Ocean Floor: Continental Margins Continental Margin Types Passive Little geologic activity Gentle slope Flatter coastlines Active Frequent geologic activity Steeper slope More rugged coastlines
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GEOL 131: The Ocean Floor: Continental Margins
Passive Margins
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GEOL 131: The Ocean Floor: Continental Margins
Passive Margins
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Passive Margin Formation
GEOL 131: The Ocean Floor: Continental Margins Passive Margin Formation Crustal stretching & thinning Initial, narrow ocean basin forms Mature basin with passive margins
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Passive Margins: Submarine Canyons
GEOL 131: The Ocean Floor: Continental Margins Passive Margins: Submarine Canyons Undersea “landslides” move down continental slopes and cut into shelves to form submarine canyons.
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Passive Margins: The Hudson submarine canyon
GEOL 131: The Ocean Floor: Continental Margins Passive Margins: The Hudson submarine canyon Modern Hudson River mouth Hudson River mouth during last ice age
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Active Margins (aka subduction zones)
GEOL 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)
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Active Margins (aka subduction zones)
GEOL 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)
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Trenches Deepest places in the oceans Subduction-related
GEOL 131: The Ocean Floor: Continental Margins Trenches Florida Deepest places in the oceans Subduction-related Sediment traps Puerto Rico Trench
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GEOL 131: The Ocean Floor The Deep-Ocean Basin
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Key Deep-Ocean Basin Features
GEOL 131: The Ocean Floor: The Deep-Ocean Basin Key Deep-Ocean Basin Features Abyssal plains Seamounts
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Abyssal Plains Very flat Deep sediment
GEOL 131: The Ocean Floor: The Deep-Ocean Basin Abyssal Plains Very flat Deep sediment
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Abyssal Plains GEOL 131: The Ocean Floor: The Deep-Ocean Basin
Abyssal plains are dark blue
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Form islands if peaks are above sea level
GEOL 131: The Ocean Floor: The Deep-Ocean Basin Seamounts Undersea volcanoes Form islands if peaks are above sea level Most are not
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GEOL 131: The Ocean Floor Oceanic Ridges
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Elevated, linear features
GEOL 131: The Ocean Floor: Oceanic Ridges Oceanic Ridges Elevated, linear features
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Also called “spreading centers” or “divergent plate boundaries”
GEOL 131: The Ocean Floor: Oceanic Ridges Oceanic Ridges Also called “spreading centers” or “divergent plate boundaries” Two crustal plates are spreading apart New crust formed at center of ridge
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Diagram of an oceanic ridge
GEOL 131: The Ocean Floor: Oceanic Ridges Diagram of an oceanic ridge Central rift valley w/ volcanoes Plate motion Plate motion Fault blocks Rising molten rock from mantle
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Oceanic ridge formation
GEOL 131: The Ocean Floor: Oceanic Ridges Oceanic ridge formation
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Earth’s Largest Topographic Feature
GEOL 131: The Ocean Floor: Oceanic Ridges Earth’s Largest Topographic Feature Over 70,000 miles long
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GEOL 131: The Ocean Floor End of Chapter
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