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Plate Tectonics

Plate Tectonics. Earth layers History of plate tectonics Plate movement and margins Passive margins, spreading margins, and the Ring of Fire Ocean floor topography and plate tectonics Ocean floor effects: horizontal and vertical zonations Life Circulation. Layers of the Earth.

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Plate Tectonics

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  1. Plate Tectonics Earth layers History of plate tectonics Plate movement and margins Passive margins, spreading margins, and the Ring of Fire Ocean floor topography and plate tectonics Ocean floor effects: horizontal and vertical zonations Life Circulation

  2. Layers of the Earth Crust 4-60km Mantle 2885km Outer core 2270km Inner core 1216km Lithosphere 100km Asthenosphere 250km Lower mantle 2550 Outer Core Inner core

  3. Earth topography

  4. Movement of Continents Old views: Geosyncline cycle no continent movement Instead, continent growth through sediment accretion

  5. Movement of Continents Alfred Wegener: Plate Tectonics: 1912 Continents like “puzzle pieces” Fossils on different continents Carey and the Southern Hemisphere geologists

  6. Movement of Continents Morey: Canada Hess: mantle convection and sea floor spreading Continental Drift: theory

  7. Movement of Continents Vine and Matthews: tested Continental Drift Magnetic “stripes” Magnetic reversals Symmetrial Theory of Plate tectonics accepted.

  8. Istostacy Density differences Density: closeness of molecules Mass/volume Istostacy: Crustal floatation on the mantle Like ice cube: part above the mantle surface part beneath “Root” balances “top”: floats in equilibrium Ocean crust more dense, floats lower

  9. Plate Movement: Cross Section

  10. Active MarginDivergent Plate Boundaries Crustal formation, spreading Mid-ocean ridges mantle convection upward volcanism new crust made Begin in continent Africa/South America African rift valley Volcanoes, earthquakes

  11. African Rift Valley Rifting Gondwana

  12. Active MarginConvergent Plate Boundaries Subduction: destructive Ocean - ocean Island arc Japan Ocean-continent Continent-continent Volcanoes, earthquakes, trenches

  13. Active MarginConvergent Plate Boundaries Subduction: destructive Ocean - ocean Continent - ocean Volcanic arc Andes, Cascades Continent - continent Volcanoes, earthquakes, trenches

  14. Active MarginConvergent Plate Boundaries Subduction: destructive Ocean - ocean Continent - ocean Continent - continent: tall mountains Tibetan plateau Volcanoes, earthquakes, trenches

  15. Active Margins: Transform Boundaries Neither constructive nor destructive Strike-slip, shear: 2 plates slide San Andreas Earthquakes no volcanoes

  16. Passive Margins Stable margins Development of wide continental shelf or ramp East coast North America Mountains from previous continent-continent collisions Small earthquakes from ancient faults But no effects from margin

  17. Hot Spots Mantle plumes: “stationary” as plates move over them Record of plate movement Land or ocean Land: Yellowstone Ocean: island formation Hawaii

  18. Hot Spots Superplumes in Cretaceous: High rates of sea floor spreading: Ocean crust warm --> sea level much higher Sundance Sea CO2 into atmosphere: greenhouse effect

  19. Ocean Depths

  20. Ocean Depths Supralittoral zone: “spray zone”: terrestrial Littoral zone: tidal range Sublittoral zone Inner sublittoral zone: 0- 50m Outer sublittoral zone:50- 200m Bathyal zone: 50m - 4km Abyssal zone: 4km - 6km Hadal zone: 6km + (deepest: Mariana Trench: 11km)

  21. Provinces: shallow Continental shelf Wide: passive margins; narrow: active margins Shelf break ~135m, but wide range Continental slope: Submarine canyons Turbidity currents Continental Rise: deep sea fans

  22. Provinces: Deep Abyssal plain >4km Ocean ridges, topography on plain Seamounts, guyots: other volcanic activity Trenches >6.7km D L W Japan Trench 10.5 2200 120 Mariana Trench 11.0 2550 70 Philippine Trench 10.8 1400 55 Aleutian Trench 7.7 3700 50 Peru-Chile Trench 8.1 5900 100 Puerto Rico Trench 8.4 1550 120 Java Trench 7.5 4500 80

  23. Life in the ocean Horizontal zonation: Geographic range Proximity to resources Latitude (Temperature) Circulation patterns Salinity Vertical zonation (water column) Resources Pressure Temperature Light Water Chemistry Geographic range + vertical zonation Resources, life history, habitat constraints determine

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