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17 Cards in this Set
- Front
- Back
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Oceanography
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The oceans are responsible for our presence.
Blue ocean covers 70.8% of the planet. Oceans… Serve as the basis for life on Earth. Regulate climate. Cycle mass and energy. Atmosphere. Hydrosphere. Lithosphere. Biosphere. 60% of humans live near coasts. |
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undersea landscapes
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Oceans exist because of differences in lithosphere.
Continental lithosphere “floats higher” on the mantle. Oceanic lithosphere “floats deeper” in the mantle. Ocean basins collect water because they are lower. The world’s oceans dominate the globe. Tectonic processes constantly configure oceans. |
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tectonic plates
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On the present configuration of tectonic plates…
Most continental crust is in the northern hemisphere. Most oceanic crust is in the southern hemisphere. |
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seafloor
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The seafloor exhibits highly varied bathymetry.
Continental shelf – Shallow (0 to 500 m), gently sloping (0.3o). Continental slope – Descends from 500 m to 4 km at ~ 2o. Continental rise – Transition zone from 4 to 4.5 km. Abyssal plain – Flat, low-relief bottom below 4.5 km. |
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submarine canyons
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Submarine canyons crosscut continental shelves.
Associated with large rivers. Erosion carved canyons during sea-level lowstands. Submerged canyons funnel sediments to deeper water. Submarine fans grow where canyons empty onto the rise. |
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seafloor tectonics
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The sea floor reflects tectonics.
Continental shelf – Underlain by thinning sialic (felsic) crust. Slope and rise – Transitional between crust types. Abyssal plain – Underlain by mafic oceanic crust. |
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continental margins - passive
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Continental margins are called passive or active.
A passive continental margin… Is located far from a tectonic plate boundary. Develops a broad shelf of sediment overlying sialic crust. |
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continental margins - active
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An active continental margin…
Is immediately adjacent to a tectonic plate boundary. Characterized by a thin, narrow continental shelf. If convergent also characterized by a trench offshore |
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Bathymetry reflects tectonic plate boundaries.
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Mid-ocean ridges (MORs) mark divergent boundaries.
Oceanic transform faults trace strike-slip boundaries. Deep-ocean trenches signify convergent boundaries |
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Abyssal plains develop over broad oceanic areas.
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Oceanic crust cools and sinks away from the MOR.
Pelagic sediment over the basalt thickens with age. Microscopic plankton and fine windblown silt and clay. Bottom features are buried, creating a featureless plain. |
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Oceans preserve mantle plume hot-spot seamounts.
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Volcano forms an island over hot spot.
After volcano goes extinct, it is eroded to sea level. Continued cooling and erosion submerges remnant. Examples of flat-topped seamounts (guyots) include... The Hawaiian Islands and the Emperor seamount chain. The Galapagos Islands. |
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salinity
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Normal marine salinity, reflecting dissolved ions, is…
3.5% (35 grams per liter; 35,000 parts per million) Dissolved ions derive from chemical weathering of rocks. These ions are mostly Cl-, Na+, SO42-, Mg2+, Ca2+, and K+. |
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ocean water composition
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Salt remains behind during freezing or evaporation.
Desiccation yields evaporite mineral salts. Halite (NaCl). Gypsum (CaSO4 . 2H2O). Sylvite (KCl). Surface salinity can vary above and below 3.5%. Higher salinity from evaporation and formation of sea ice. Lower salinity from rainfall, glacial melt, and river input. Salinity becomes more uniform with depth. |
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ocean water temp
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Ocean surface temperature (T) varies inversely with latitude.
Water buffers wide T shifts, thereby moderating climate. Surface water approaches a uniform cold T with depth. Ocean bottom water is near freezing < 4°C (39°F) |
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oceanic currents
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Currents ceaselessly move ocean water in 3-D.
Surface currents (upper 100 m) due to wind shear. Currents spiral by Coriolis deflection into large gyres. |
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the coriolis effect
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Rotation deflects prevailing winds and currents.
Sense of deflection depends upon… Initial direction of motion. Position relative to the equator. Coriolis deflection is illustrated on a merry-go-round. Surface winds and currents are both influenced. Northern hemisphere. South-moving winds and currents are deflected to the West. North-moving winds and currents are deflected to the East. Southern hemisphere. North-moving winds and currents are deflected to the West. South-moving winds and currents are deflected to the East. |
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virtical oceanic currents
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Currents also transport ocean water vertically.
Downwelling – Surface waters are drawn downward. Upwelling – Deep waters are pushed upward. Wind perpendicular to shore drives vertical flow. Onshore – Water piling up along coast drives downwelling. Offshore – Upwelling replaces water moved away. |
