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Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
Plate Tectonics Lecture
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Plate Tectonics Lecture

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  • 1. Plate Tectonics Ch 17
  • 2.  
  • 3. Facts <ul><li>South America moving away from Africa at 2-3 cm/year </li></ul><ul><li>Hawaii is moving NW 8-9 cm/yr </li></ul><ul><li>Mount Everest growing 5 cm/year </li></ul>
  • 4. Early Theories <ul><li>Late 1500 Abraham Ortelius (map maker) noticed the fit of the continents in the Atlantic Ocean. </li></ul><ul><ul><li>Proposed N & S America broke off of Europe and Africa by earthquakes and floods </li></ul></ul><ul><li>Late 1800s Eduard Suess (geologist) proposed that the southern continents were joined- “Gondwanaland” </li></ul>
  • 5. Alfred Wegener <ul><li>German Scientist proposed in 1912 “Theory of Continental Drift” </li></ul><ul><li>Scientific community believed ocean basins and continents were a permanent feature of Earth. </li></ul><ul><li>Two flaws with Wegener’s theory caused them reject his hypothesis. </li></ul><ul><ul><li>Cause of movement? </li></ul></ul><ul><ul><li>How continents were moving through a stationary ocean floor? </li></ul></ul>
  • 6. Continental Drift <ul><li>Proposed all continents were joined together in a single land mass </li></ul><ul><ul><li>Pangaea (all – earth) </li></ul></ul><ul><li>Pangaea broke apart 200 million years ago (Mesozoic) </li></ul><ul><li>Began theory with puzzle like fit of continents </li></ul>
  • 7. Evidence <ul><li>Rock formations </li></ul><ul><ul><li>When Pangaea breaks apart large structures (mtn ranges) would be separated </li></ul></ul><ul><ul><li>Using this Wegener hypothesized there would be similar rocks on either side of the Atlantic Ocean </li></ul></ul><ul><ul><ul><li>Matching rocks in Appalachian Mountains, Greenland and Europe (more than 200 million years old) </li></ul></ul></ul>
  • 8. Evidence <ul><li>Fossils </li></ul><ul><ul><li>Similar fossils of plants and animals that lived on land would have been found on separated continents </li></ul></ul><ul><ul><li>Wegener hypothesized that land animals could not have swum great distances across the ocean </li></ul></ul><ul><ul><li>The ages of the fossils confirmed the break-up time period </li></ul></ul>
  • 9. Evidence <ul><li>Climate </li></ul><ul><ul><li>By studying sedimentary rocks he found evidence of climactic changes </li></ul></ul><ul><ul><ul><li>Coal beds in Antarctica meant that it was once warm and rainy </li></ul></ul></ul><ul><ul><ul><li>Glacial evidence in India, Australia, Africa and South America indicate thick ice caps </li></ul></ul></ul>
  • 10. Seafloor Spreading <ul><li>Confirmed Wegener’s theories in the 1960’s </li></ul><ul><li>Technology </li></ul><ul><ul><li>SONAR - sound waves used to map ocean floor </li></ul></ul><ul><ul><li>Magnetometer – detects small changes in magnetic fields of rocks </li></ul></ul>
  • 11. Ocean <ul><li>Vast underwater mountain ranges called mid-ocean ridges </li></ul><ul><li>Deep-sea trenches are narrow long depressions with very steep sides (miles deep) </li></ul>
  • 12. Ages of Rocks
  • 13. Ages of Rocks <ul><li>Ocean crust is much younger than continental crust </li></ul><ul><li>Near ocean ridges crust is new </li></ul><ul><li>In deep sea trenches crust is old </li></ul><ul><li>Figure 17-7 page 450 (your textbook) </li></ul><ul><li>Ocean sediments are much thinner than on continents and increase with distance from ridges </li></ul>
  • 14. Magnetism <ul><li>Paleomagnetism – Study of Earth’s magnetic record </li></ul><ul><li>Basalt – Iron rich rock forms ocean crust </li></ul><ul><ul><li>The iron in the rocks is always aligned with the magnetic poles of the earth (north & south just like a magnet) </li></ul></ul><ul><ul><li>When lava hardens into basalt, iron ions are permanently aligned, recording the magnetic history of the earth </li></ul></ul><ul><li>Magnetic Reversals </li></ul>
  • 15. Magnetism
  • 16. Earth’s Structure <ul><li>Crust- Rocky outer layer (5-35 Km) </li></ul><ul><li>Mantle- 82% of Earth’s Volume, made of silica and molten rock </li></ul><ul><li>Core- iron and nickel </li></ul>
  • 17. Earth’s Layers (Function) <ul><li>Lithosphere (Ball of Rock) Crust and Upper Mantle </li></ul><ul><li>Moho Discontinuity </li></ul><ul><li>Asthenosphere (weak ball) Mantle, rocks near melting point, allows lithosphere to move </li></ul><ul><li>Mesosphere (middle ball) Very hot rock, capable of flow, more rigid because of pressure </li></ul>
  • 18. Earth’s Layers (Function) <ul><li>Outer Core- Liquid Layer, generates magnetic field </li></ul><ul><li>Inner Core- Solid because of high pressure </li></ul>
  • 19.  
  • 20. Plate Boundaries <ul><li>Divergent- (2 movements) places where 2 plates move away </li></ul><ul><ul><li>Oceanic/Oceanic- Mid-Ocean Ridge </li></ul></ul><ul><ul><li>Continental/Continental- Rift Valley </li></ul></ul>
  • 21. Plate Boundaries <ul><li>Convergent (1 Movement)- Places where plates come together </li></ul><ul><li>Classified by types of plates </li></ul>
  • 22. Oceanic-Oceanic <ul><li>Subduction- Oceanic plate goes under another plate, Recycles the rock, May form Island Arc </li></ul>
  • 23. Oceanic-Continental <ul><li>Oceanic plate goes under Continental plate. </li></ul><ul><li>Causes Costal Mountain Range and Arc of Volcanoes </li></ul>
  • 24. Continental-Continental <ul><li>Causes TALL Mountains to form </li></ul>
  • 25. Transform <ul><li>Transform (across)- deforms crust, long faults. </li></ul><ul><li>Usually underwater, except San Andres </li></ul>
  • 26. Causes of Movement <ul><li>Mantle Convection- Movement of warm and cool rock in mantle, similar to conveyor belt </li></ul>
  • 27. Causes of Movement <ul><li>Ridge Push- Weight of uplifting ridge pushes plate toward trenches </li></ul><ul><li>Slab Pull- Weight of Subducting plate pulls the plate into the mantle </li></ul>

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