The Ocean Floor The Ocean Floor The World

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The Ocean Floor

The Ocean Floor

The Ocean Floor • • • The World Ocean Imaging the Ocean Floor Continental

The Ocean Floor • • • The World Ocean Imaging the Ocean Floor Continental Margins The Deep-Ocean Floor Oceanic Ridges Seafloor Sediments

PSCI 131: The Ocean Floor The World Ocean

PSCI 131: The Ocean Floor The World Ocean

PSCI 131: The Ocean Floor The World Ocean Earth’s surface is 71% ocean Majority

PSCI 131: The Ocean Floor The World Ocean Earth’s surface is 71% ocean Majority is in Southern Hemisphere Northern Hemisphere Southern Hemisphere

PSCI 131: The Ocean Floor: The World Ocean

PSCI 131: The Ocean Floor: The World Ocean

PSCI 131: The Ocean Floor: The World Oceans vs. Continents • Continents – Average

PSCI 131: The Ocean Floor: The World 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

PSCI 131: The Ocean Floor Imaging the Ocean Floor

PSCI 131: The Ocean Floor Imaging the Ocean Floor

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Mapping • HMS Challenger –

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Mapping • HMS Challenger – British – 1872 -1876 – All oceans except Arctic – Used weighted ropes to find ocean depths

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Mapping • HMS Challenger’s route

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Mapping • HMS Challenger’s route – British – 1872 -1876 – All oceans except Arctic – Used weighted ropes to find ocean depths

PSCI 131: The Ocean Floor: Imaging the Ocean Floor • Sonar Ocean Floor Mapping

PSCI 131: The Ocean Floor: Imaging the Ocean Floor • Sonar Ocean Floor Mapping – Single beam – Multibeam

PSCI 131: The Ocean Floor: Imaging the Ocean Floor • Sonar Ocean Floor Mapping

PSCI 131: The Ocean Floor: Imaging the Ocean Floor • Sonar Ocean Floor Mapping – Travel time of ping / 2 = depth

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles • Seismic

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles • Seismic waves penetrate mud, bounce off rock

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Seismic Reflection Profiles

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Provinces • Revealed by ocean

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Provinces • Revealed by ocean floor imaging techniques • Continental margins – Passive and active • Deep-ocean floor • Oceanic ridges

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Provinces

PSCI 131: The Ocean Floor: Imaging the Ocean Floor Provinces

PSCI 131: The Ocean Floor Continental Margins

PSCI 131: The Ocean Floor Continental Margins

PSCI 131: The Ocean Floor: Continental Margins Continental Margin Types • Passive – Little

PSCI 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

PSCI 131: The Ocean Floor: Continental Margins Passive Margins

PSCI 131: The Ocean Floor: Continental Margins Passive Margins

PSCI 131: The Ocean Floor: Continental Margins Passive Margins

PSCI 131: The Ocean Floor: Continental Margins Passive Margins

PSCI 131: The Ocean Floor: Continental Margins Passive Margin Formation Crustal stretching & thinning

PSCI 131: The Ocean Floor: Continental Margins Passive Margin Formation Crustal stretching & thinning Initial, narrow ocean basin forms Mature basin with passive margins

PSCI 131: The Ocean Floor: Continental Margins Passive Margins: Submarine Canyons Undersea “landslides” move

PSCI 131: The Ocean Floor: Continental Margins Passive Margins: Submarine Canyons Undersea “landslides” move down continental slopes and cut into shelves to form submarine canyons.

PSCI 131: The Ocean Floor: Continental Margins Passive Margins: The Hudson submarine canyon Modern

PSCI 131: The Ocean Floor: Continental Margins Passive Margins: The Hudson submarine canyon Modern Hudson River mouth during last ice age

PSCI 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)

PSCI 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)

PSCI 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)

PSCI 131: The Ocean Floor: Continental Margins Active Margins (aka subduction zones)

PSCI 131: The Ocean Floor: Continental Margins Trenches Florida • Deepest places in the

PSCI 131: The Ocean Floor: Continental Margins Trenches Florida • Deepest places in the oceans • Subduction-related • Sediment traps Puerto Rico Trench

PSCI 131: The Ocean Floor The Deep-Ocean Basin

PSCI 131: The Ocean Floor The Deep-Ocean Basin

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Key Deep-Ocean Basin Features • Abyssal

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Key Deep-Ocean Basin Features • Abyssal plains • Seamounts

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Abyssal Plains • Very flat •

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Abyssal Plains • Very flat • Deep sediment

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Abyssal Plains Abyssal plains are dark

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Abyssal Plains Abyssal plains are dark blue

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Seamounts • Undersea volcanoes • Form

PSCI 131: The Ocean Floor: The Deep-Ocean Basin Seamounts • Undersea volcanoes • Form islands if peaks are above sea level – Most are not

PSCI 131: The Ocean Floor Oceanic Ridges

PSCI 131: The Ocean Floor Oceanic Ridges

PSCI 131: The Ocean Floor: Oceanic Ridges • Elevated, linear features

PSCI 131: The Ocean Floor: Oceanic Ridges • Elevated, linear features

PSCI 131: The Ocean Floor: Oceanic Ridges Earth’s Largest Topographic Feature • Over 70,

PSCI 131: The Ocean Floor: Oceanic Ridges Earth’s Largest Topographic Feature • Over 70, 000 miles long

PSCI 131: The Ocean Floor: Oceanic Ridges • Also called “spreading centers” or “divergent

PSCI 131: The Ocean Floor: Oceanic Ridges • Also called “spreading centers” or “divergent plate boundaries” • Two crustal plates are spreading apart • New crust formed at center of ridge

PSCI 131: The Ocean Floor: Oceanic Ridges Diagram of an oceanic ridge Central rift

PSCI 131: The Ocean Floor: Oceanic Ridges Diagram of an oceanic ridge Central rift valley w/ volcanoes Plate motion Fault blocks Plate motion Rising molten rock from mantle

PSCI 131: The Ocean Floor: Oceanic Ridges Oceanic ridge formation

PSCI 131: The Ocean Floor: Oceanic Ridges Oceanic ridge formation

PSCI 131: The Ocean Floor Seafloor Sediments

PSCI 131: The Ocean Floor Seafloor Sediments

PSCI 131: The Ocean Floor: Seafloor Sediments Ocean Sediment Types • Terrigenous (~45% of

PSCI 131: The Ocean Floor: Seafloor Sediments Ocean Sediment Types • Terrigenous (~45% of ocean floor) – “Terra” = earth – Derived from continents • Biogenous (~55%) – Created by organisms • Hydrogenous (<1 %) – Crystallize out of seawater

PSCI 131: The Ocean Floor: Seafloor Sediments Terrigenous Sediments • Concentrated along continental margins

PSCI 131: The Ocean Floor: Seafloor Sediments Terrigenous Sediments • Concentrated along continental margins • Mineral and rock material • From rivers, wind, glaciers

PSCI 131: The Ocean Floor: Seafloor Sediments Biogenous Sediments • Concentrated away from continents

PSCI 131: The Ocean Floor: Seafloor Sediments Biogenous Sediments • Concentrated away from continents • Mainly dead plankton shells Plankton shells at high magnification White Cliffs of Dover, England – ancient biogenous seafloor sediment

PSCI 131: The Ocean Floor: Seafloor Sediments Hydrogenous Sediments • Dispersed throughout ocean and

PSCI 131: The Ocean Floor: Seafloor Sediments Hydrogenous Sediments • Dispersed throughout ocean and along shorelines • Chemical precipitation of minerals from seawater Manganese nodules in south Pacific, depth 15, 000 feet • Common examples – Manganese nodules – Calcium carbonate

PSCI 131: The Ocean Floor End of Chapter

PSCI 131: The Ocean Floor End of Chapter