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

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

Earth topography

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

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

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

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

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

Plate Movement: Cross Section

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

African Rift Valley Gondwana Rifting

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

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

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

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

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

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

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

Ocean Depths

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)

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

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

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