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Plate Tectonics

Plate Tectonics. Charity I. Mulig. Tectonics. Refers to the deformation of the Earth’s crust results in the formation of structural features such as mountains. Continental Drift Hypothesis. Proposed by Alfred Wegener

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Plate Tectonics

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  1. Plate Tectonics Charity I. Mulig

  2. Tectonics • Refers to the deformation of the Earth’s crust • results in the formation of structural features such as mountains

  3. Continental Drift Hypothesis • Proposed by Alfred Wegener • stated that the continents had once been joined to form a single supercontinent which started to break up 200MYA ago forming the present land masses

  4. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=08http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=08 • Wegener – continental Drift • Bullard – Continental Drift

  5. Evidences

  6. 1. The Jigsaw Puzzle • Landmasses appear to be connected • If landmasses are joined together at the continental shelves, a better fit is made

  7. 2. Fossils Match Across the Seas • Fossil evidence for continental drift includes several fossil organisms found on different landmasses.

  8. 3. Rock Type and Structure Match

  9. 4. Ancient Cimates

  10. Rejecting the Hypothesis • Wegener couldn’t accunt for a driving mechanism • His proposal was that tides caused the plates to move. • His proposal was immediately countered by the fact that such tides of such magnitude could stop the earth’s rotation in a few days

  11. Plate Tectonics Theory • A more encompassing theory than the continental drift theory • States that • The earth is composed of plates that float above the mantle • These plates interact along their boundaries

  12. Types of Tectonic Plates Continental Plates Oceanic Plates Denser than continental plates Darker and floats deeper in the mantle Composed of basalt and gabro Is younger when found closer to oceanic ridges • Less dense than oceanic plates • Floats higher in the mantle than the oceanic plates • Composed of silica-rich rocks • Found in the continents

  13. Types of Plate Boundaries

  14. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08

  15. Evidences

  16. 1. Paleomagnetism • Molten rocks can provide records of ancient magnetic fields. • There is evidence from these ancient rocks that there seems to be • Polar wandering • Magnetic reversals and seafloor spreading

  17. 2. Earthquake Patterns • Earthquakes frequently occur along plate boundaries • The depth of earthquakes supports can be used as an evidence of the subduction phenomena

  18. 3. Ocean Drilling • Ocean drilling provides evidences that age of rocks increases with distance from midoceanic ridges.

  19. 4. Hot Spots • A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth’s surface; The Pacific plate moves over a hot spot, producing the Hawaiian Islands. • Hot spot evidence supports that the plates move over the Earth’s surface.

  20. Causes of Plate Motion • Convective Flow – major driving mechanism • Slab-pull • Ridge-Push • Mantle Covection • Mantle plumes

  21. Mantle Convection Models http://www.classzone.com/books/earth_science/terc/content/visualizations/es0805/es0805page01.cfm?chapter_no=08

  22. Additional Links • http://serc.carleton.edu/NAGTWorkshops/geophysics/visualizations/PTMovements.html • http://science.nationalgeographic.com/science/photos/plate-tectonics-gallery/#/rift-escarpments-eritrea_1169_600x450.jpg • http://science.nationalgeographic.com/science/earth/the-dynamic-earth/plate-tectonics-article.html

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