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Development of the Theory of PLATE TECTONICS

Development of the Theory of PLATE TECTONICS. Continental Drift. 1912 – Alfred Wegener (German) suggested that the continents were once joined together forming a super-continent called Pangaea. Pangaea – all land Panthalassa – all ocean Laurasia – Northern section of Pangaea

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Development of the Theory of PLATE TECTONICS

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  1. Development of the Theory of PLATE TECTONICS

  2. Continental Drift • 1912 – Alfred Wegener (German) suggested that the continents were once joined together forming a super-continent called Pangaea. • Pangaea – all land • Panthalassa – all ocean • Laurasia – Northern section of Pangaea • Gondwanaland – Southern section of Pangaea

  3. Evidence for Continental Drift • By 1912 the maps of the continents were accurate enough to use scientifically… • 1) THE COASTLINES OF CONTINENTS FIT LIKE A PUZZLE!

  4. Evidence for Continental Drift • Fossil evidence • 2) MESOSAURUS (ancient alligator) – fossils found in South America and Africa • 3) GLOSSOPTERIS (ancient fern tree) – fossils found in Antarctica, India, Australia, Africa, and South America

  5. Evidence for Continental Drift • Rock Types • 4) The Appalachian Mountains have the same composition and age as the mountains found in Iceland and Northern Europe

  6. Evidence for Continental Drift • Climate Change • 5) Glacial erosion (striations and erratics) are found in tropical and sub-tropical locations in Africa, South America, India, and Australia

  7. EVERYONE LAUGHED AT HIM!!! • ALFRED WEGENER COULD NOT EXPLAIN HOW OR WHY THE CONTINENTS MOVED. IT JUST SEEMED TOO IMPOSSIBLE FOR PEOPLE TO BELIEVE.

  8. Sea-Floor Spreading • 1960s – Harry Hess (American), Glomar Challenger • Used modern day SONAR to map the ocean floor. • He discovered the Mid-Ocean Ridges AND suggested that the sea-floor is actually growing

  9. Evidence for Sea-Floor Spreading • 6) Age of Rocks on Sea-Floor • Hess found that the rocks were youngest near the mid-ocean ridge and oldest near coastlines of continents.

  10. Evidence For Sea-Floor Spreading • 7) Paleomagnetism • The magnetic poles of Earth have shifted several times throughout the course of Earth’s History. • When a rock forms it takes on the magnetic orientation of the Earth at that time • The magnetic orientation is mirrored on the ocean floor

  11. PLATE TECTONICS • The theory of Plate Tectonics suggests that the crust and upper mantle (lithosphere) is broken into sections called plates. The plates move and float on the liquidy part of the mantle called the Aesthenosphere.

  12. PLATE TECTONICS • The plates grow, shrink, and move due to CONVECTION CURRENTS IN THE MANTLE

  13. How do the plates interact? • 3 types of plate boundaries: • Convergent Boundary – move toward one another • Divergent Boundary – move away from one another • Transform Fault Boundary – slide past one another

  14. Convergent Boundaries (type 1) • Oceanic Crust/Continental Crust collision • SUBDUCTION ZONE – Example – ANDES MOUNTAINS

  15. Convergent Boundaries(type 2) • Continental Crust/Continental Crust collision • MOUNTAIN BUILDING - HIMALAYAS

  16. Convergent Boundaries(type 3) • Oceanic Crust/Oceanic Crust collision • ISLAND ARC – JAPAN ISLAND ARC

  17. Divergent Boundaries(type 1) • Mid-ocean ridges – MID_ATLANTIC RIDGE

  18. Divergent Boundaries(type 2) • Rift Valleys – AFRICAN RIFT VALLEY

  19. Transform Fault Boundaries • Earthquake-Mania – SAN ANDREAS FAULT

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