Chapter 4: Marine Provinces

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Chapter 4 Marine Provinces
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Seismic profiling
Fig. 4-4
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Hypsographic curve

• Average depth of ocean 3729 m
• Average height of continents 840 m

Fig. 4-5
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Continental margins

• Shallow ocean close to land
• Underlain by continental crust
• Classified as passive or active

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Passive margins

• Not a plate boundary
• Not tectonically active
• Continental shelf
• Continental slope
• Continental rise

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Active margins

• At plate boundaries
• Tectonically active
• Classified by type of plate boundary

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Continental shelf

• 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

• Extends from shelf break to deep ocean
• Gradient ranges from 1-25o
• Average gradient 4o
• Relief greater at active margin
• Submarine canyons
• Turbidity currents

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Fig. 4-9a
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Continental rise

• Transition between continental margin and deep
  ocean
• Sediments deposited by waning turbidity currents
• Not common convergent active margins
• Rise only exists where sediments can accumulate

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Deep ocean basin

• Underlain by oceanic crust
• Seaward of continental margin
• Abyssal plains very flat
• Fine-grained sediments deposited
• Volcanic seamounts, tablemounts, abyssal hills

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Mid-ocean ridge

• 75,000 km long
• Covers 23 of Earths surface
• Rift valley at crest
• Site of magma (pillow basalts)
• Hydrothermal vents
• Warm water
• White smokers
• Black smokers

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Fig. 4-17a
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• Hot vent communities
• Chemosynthetic autotrophs

Metal sulfide deposits
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• Ocean ridge
• Steeper, rugged, prominent rift valley
• Ocean rise
• Gentler, less rugged, less well-defined rift
  valley
• Fracture zones
• Aseismic scars, extensions of transform faults

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End of Chapter 4 Marine Provinces