Chapter 4: Marine Provinces. Seismic profiling Fig. 4-4

Chapter 4: Marine Provinces Seismic profiling Fig. 4-4 Hypsographic curve Average depth of ocean 3729 m Average height of continents 840 m Fig. 4-5 Continental margins Shallow ocean close to land Underlain by continental crust Classified as passive or active Passive margins Not a plate boundary Not tectonically active Continental shelf Continental slope Continental rise Active margins At plate boundaries Tectonically active Classified by type of plate boundary 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 Continental slope Extends from shelf break to deep ocean Gradient ranges from 1-25 o Average gradient 4 o Relief greater at active margin Submarine canyons Turbidity currents Fig. 4-9a 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 Deep ocean basin Underlain by oceanic crust Seaward of continental margin Abyssal plains very flat Fine-grained sediments deposited Volcanic seamounts, tablemounts, abyssal hills 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 Fig. 4-17a Hot vent communities Chemosynthetic autotrophs Metal sulfide deposits 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 End of Chapter 4: Marine Provinces