Transcript Chapter 4: Marine Provinces - Washington University in St

Chapter 4: Marine Provinces
Seismic profiling
Fig. 4-4
Hypsographic curve
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Average
depth of
ocean 3729 m
Average
height of
continents
840 m
Fig. 4-5
Continental margins
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Shallow ocean close to land
Underlain by continental crust
Classified as passive or active
Passive margins
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Not a plate boundary
Not tectonically active
Continental shelf
Continental slope
Continental rise
Active margins
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At plate boundaries
Tectonically active
Classified by type of plate boundary
Continental shelf
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Coast to shelf break (average depth
135m)
Generally flat
May be narrow or wide
Average width 70 km
Active margin narrower
 Passive margin wider
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Continental slope
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Extends from shelf break to deep
ocean
Gradient ranges from 1-25o
Average gradient 4o
Relief greater at active margin
Submarine canyons
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Turbidity currents
Fig. 4-9a
Continental rise
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Transition between continental
margin and deep ocean
Sediments deposited by waning
turbidity currents
Not common convergent active
margins
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Rise only exists where sediments can
accumulate
Deep ocean basin
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Underlain by oceanic crust
Seaward of continental margin
Abyssal plains very flat
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Fine-grained sediments deposited
Volcanic seamounts, tablemounts,
abyssal hills
Mid-ocean ridge
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75,000 km long
Covers 23% of Earth’s surface
Rift valley at crest
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Site of magma (pillow basalts)
Hydrothermal vents
Warm water
 White smokers
 Black smokers
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Fig. 4-17a
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Metal sulfide deposits
Hot vent
communities
 Chemosynthetic
autotrophs
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Ocean ridge
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Ocean rise
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Steeper, rugged, prominent rift valley
Gentler, less rugged, less well-defined
rift valley
Fracture zones
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Aseismic scars, extensions of
transform faults
End of Chapter 4: Marine
Provinces