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Plate Tectonics Earth layers History of plate tectonics Plate movement and margins Passive margins, spreading margins, and the Ring of Fire Ocean floor.

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Presentation on theme: "Plate Tectonics Earth layers History of plate tectonics Plate movement and margins Passive margins, spreading margins, and the Ring of Fire Ocean floor."— Presentation transcript:

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 LifeCirculation

2 Crust4-60kmMantle2885km Outer core 2270km Inner core 1216km Lithosphere100kmAsthenosphere250km Lower mantle 2550 Outer Core Inner core Layers of the Earth

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 Margin Divergent 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 Gondwana Rifting

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

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

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

15 Neitherconstructive nor destructive Strike-slip, shear: shear: 2 plates slide San Andreas Earthquakes no volcanoes Active Margins: Transform Boundaries

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

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

22 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 deep sea fans

23 Provinces: Deep Abyssal plain >4km Ocean ridges, topography on plain Seamounts, guyots: other volcanic activity Trenches >6.7km DLW Japan Trench Mariana Trench Philippine Trench Aleutian Trench Peru-Chile Trench Puerto Rico Trench Java Trench

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


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