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Plate Tectonics Ch 17
 
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><...
Early Theories <ul><li>Late 1500 Abraham Ortelius (map maker) noticed the fit of the continents in the Atlantic Ocean. </l...
Alfred Wegener <ul><li>German Scientist proposed in 1912 “Theory of Continental Drift” </li></ul><ul><li>Scientific commun...
Continental Drift <ul><li>Proposed all continents were joined together in a single land mass </li></ul><ul><ul><li>Pangaea...
Evidence <ul><li>Rock formations </li></ul><ul><ul><li>When Pangaea breaks apart large structures (mtn ranges) would be se...
Evidence <ul><li>Fossils </li></ul><ul><ul><li>Similar fossils of plants and animals that lived on land would have been fo...
Evidence <ul><li>Climate </li></ul><ul><ul><li>By studying sedimentary rocks he found evidence of climactic changes </li><...
Seafloor Spreading <ul><li>Confirmed Wegener’s theories in the 1960’s </li></ul><ul><li>Technology </li></ul><ul><ul><li>S...
Ocean <ul><li>Vast underwater mountain ranges called mid-ocean ridges </li></ul><ul><li>Deep-sea trenches are narrow long ...
Ages of Rocks
Ages of Rocks <ul><li>Ocean crust is much younger than continental crust </li></ul><ul><li>Near ocean ridges crust is new ...
Magnetism <ul><li>Paleomagnetism – Study of Earth’s magnetic record </li></ul><ul><li>Basalt – Iron rich rock forms ocean ...
Magnetism
Earth’s Structure <ul><li>Crust- Rocky outer layer (5-35 Km)  </li></ul><ul><li>Mantle- 82% of Earth’s Volume, made of sil...
Earth’s Layers (Function) <ul><li>Lithosphere (Ball of Rock)  Crust and Upper Mantle </li></ul><ul><li>Moho Discontinuity ...
Earth’s Layers (Function) <ul><li>Outer Core- Liquid Layer, generates magnetic field </li></ul><ul><li>Inner Core- Solid b...
 
Plate Boundaries <ul><li>Divergent- (2 movements) places where 2 plates move away </li></ul><ul><ul><li>Oceanic/Oceanic- M...
Plate Boundaries <ul><li>Convergent (1 Movement)- Places where plates come together </li></ul><ul><li>Classified by types ...
Oceanic-Oceanic <ul><li>Subduction- Oceanic plate goes under another plate, Recycles the rock, May form Island Arc </li></ul>
Oceanic-Continental <ul><li>Oceanic plate goes under Continental plate. </li></ul><ul><li>Causes Costal Mountain Range and...
Continental-Continental <ul><li>Causes TALL Mountains to form </li></ul>
Transform <ul><li>Transform (across)- deforms crust, long faults. </li></ul><ul><li>Usually underwater, except San Andres ...
Causes of Movement <ul><li>Mantle Convection- Movement of warm and cool rock in mantle, similar to conveyor belt </li></ul>
Causes of Movement <ul><li>Ridge Push- Weight of uplifting ridge pushes plate toward trenches </li></ul><ul><li>Slab Pull-...
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Plate Tectonics Lecture

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Plate Tectonics Lecture

  1. 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>
  3. 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>
  4. 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>
  5. 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>
  6. 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>
  7. 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>
  8. 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>
  9. 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>
  10. 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>
  11. 12. Ages of Rocks
  12. 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>
  13. 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>
  14. 15. Magnetism
  15. 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>
  16. 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>
  17. 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>
  18. 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>
  19. 21. Plate Boundaries <ul><li>Convergent (1 Movement)- Places where plates come together </li></ul><ul><li>Classified by types of plates </li></ul>
  20. 22. Oceanic-Oceanic <ul><li>Subduction- Oceanic plate goes under another plate, Recycles the rock, May form Island Arc </li></ul>
  21. 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>
  22. 24. Continental-Continental <ul><li>Causes TALL Mountains to form </li></ul>
  23. 25. Transform <ul><li>Transform (across)- deforms crust, long faults. </li></ul><ul><li>Usually underwater, except San Andres </li></ul>
  24. 26. Causes of Movement <ul><li>Mantle Convection- Movement of warm and cool rock in mantle, similar to conveyor belt </li></ul>
  25. 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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