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Plate Tectonics I Theory and early evidence

Delve into the history and evidence of plate tectonics, from early continental drift theories to modern geological discoveries. Explore the fit between continents and the mechanisms driving their movement, from glaciers to fossil distribution. Understand the Earth's structure, density layers, and the dynamics of the lithosphere. Learn about the impact of pressure on melting points, the distinction between continental and oceanic crust, and the principle of buoyancy. Witness isostatic adjustments and rebound phenomena in action as we unravel the secrets of our dynamic planet.

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Plate Tectonics I Theory and early evidence

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  1. Plate Tectonics I Theory and early evidence

  2. Continents 'drift' Abraham Ortelius in 1596 “…torn away from Europe and Africa ... by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents]…” FromThesaurus Geographicus

  3. Antonio Snider-Pellegrini (1802-1885) Ben Franklin (1706-1790) a Création et ses mystères dévoilés "The Creation and its Mysteries Unveiled" Francis Bacon (1561-1626)

  4. Alfred Wegener~ 1912“could these land masses have been joined together at some distant time and subsequently drifted apart?”

  5. Fit

  6. The Fit between the Edges of Continents Suggested That They Might Have Drifted The fit of all the continents around the Atlantic at a water depth of about 137 meters (450 feet), as calculated by Sir Edward Bullard at the University of Cambridge in the early 1960s. Best Fit – using a depth of ~ 2000 m

  7. Mountains: For example – The Appalachian Mountains extend to mountains in Greenland, the United Kingdom and Norway, indicating that these land masses were once joined….

  8. Glaciers ~ 300 million ya deposits Worldwide ice age Or… Continents moved

  9. The Giant Puzzle: How does it all fit together?1885~ Edward Seuss: Glossopteris fernIndia, Australia, South Africa, South America

  10. Fossils

  11. Continental Drift Hypothesis Lines of Evidence Fit of Continents Matching Mountain Sequences Evidence of Glacier Distribution - global ice age? -continents moved Fossil Distribution of Organisms

  12. Mechanisms and Doubt Continents “plow” through the ocean basins.  Calculations showed this to be incorrect. Continents moved because of gravitational attraction of equator and sun/moon.  Gravitational forces are too small.

  13. Structure of the Earth  all about density….. Density Stratification: Earth has distinct layers Each deeper layer is heavier than the next. Density: expression of heaviness amount of mass contained in a volume (Density = mass/volume; D=g/mL; D=g/cm3)

  14. Hydrosphere - 4 km Mantle – 68.1% ~ 2900 km Dense, hot rocks Magnesium, iron, silicon, and oxygen Continental crust – 0.4% 35-40 km Low density rocks made of Aluminum, Silicon, and Oxygen. Core – 31.5% ~ 3500 km Outer core – liquid Inner Core – Solid Iron, Nickel ?

  15. Pressure Affects Melting Points!Increase in pressure = higher melting point! pressure 9900 F 9900 F will not melt! melts! pressure pressure 12000 F 22,000 F temp still not hot enough~ will not melt! melts b/c of increase in temp.

  16. Pressure Effects Melting Point Outer core 9900F Inner core 12000F solid! liquid! melts

  17. Land Ocean Continental Crust: Thick, light (relatively)  2.7 g/cm3 Oceanic Crust: Thin, dense  3.0 g/cm3 Thickness: ~30 - 40 km Granite Texture: Course Color: Light Thickness: ~ 4-10 km Basalt Texture: Fine/Course Color: Dark

  18. Land Ocean Continental Crust: Thick, light (relatively)  2. Oceanic Crust: Upper Mantle – even denser rock ( ~3.3 g/cm3) Boundary named after the discoverer: Andrija Mohorovicic – called the Moho ? – where is the Moho closest to the surface of the earth? Ocean or Continents? A – Ocean – bc oceanic crust is ~ 4-10 km thick vs. continental crust (~30 – 40 km)

  19. BUOYANCY & ISOSTATIC PRESSURE!If weight added or removed from object floating, equilibrium disturbed!

  20. Isostatic Adjustment – the vertical mvmt. of the crust. The result of the buoyancy of the earth’s Lithosphere as it floats on the denser, plastic-like asthenosphere below. Oceanic Crust is denser, floats lower in the mantle. Continental Crust is thicker, less dense; floats higher. Where the Continental Crust is thickest –it floats even higher… bc there is a thick mass of crustal material Beneath them, buoying them up… **higher an iceberg rises, the deeper the its base projects in the water…

  21. Isostatic Rebound Canada depressed from 1640-2300 feet below its present level under cover of ice 1.2-1.9 miles thick!

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