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CH. 8 – PLATE TECTONICS
Continental Drift <ul><li>1915:  </li></ul><ul><li>Alfred Wegener </li></ul><ul><li>- hypothesized the supercontinent Pang...
Plate Tectonics <ul><li>WWII  </li></ul><ul><li>New technology = echosounder </li></ul><ul><li>-used to map ocean floor to...
Harry Hess <ul><li>1962: </li></ul><ul><li>Hypothesized sea-floor spreading </li></ul>
Sea-floor spreading <ul><li>a)  Ocean crust splits apart at mid-ocean ridges (MOR) </li></ul><ul><li>- pushes continents a...
Sea-floor spreading <ul><li>b) Ocean crust pulled down into mantle at deep-sea trenches </li></ul><ul><li>New idea :  ocea...
Plate dynamics
Evidence for sea-floor spreading (late 1960’s - 1970’s) <ul><li>1)  Deep-sea Drilling Projects </li></ul><ul><ul><li>Gloma...
Deep-sea drilling projects <ul><li>b) Sediment thickness varies:  </li></ul><ul><li>- thicker further away from MOR </li><...
2) Submersible Expeditions <ul><li>1974 FAMOUS expedition  </li></ul><ul><li>( F rench- A merican  M id- O cean  U ndersea...
Submersible Expeditions <ul><li>Evidence for mafic eruptions:  </li></ul><ul><ul><li>- hydrothermal vents (~350 o  C) </li...
Problem: <ul><li>How does crust move over solid rock of mantle? </li></ul>
3) Clues:  seismic waves <ul><li>Lithosphere  – rigid rx of crust and uppermost mantle </li></ul><ul><li>Asthenosphere  – ...
 
Plate Tectonics Theory <ul><li>Plate  – rigid slab of lithosphere </li></ul><ul><li>7 major plates on Earth  </li></ul><ul...
Plate map
Same plate <ul><li>Locations do not change position relative to one another </li></ul><ul><li>Ex:  NYC & Peoria always sam...
Different plates <ul><li>Locations do change position relative to one another </li></ul><ul><li>Ex:  NYC & London getting ...
Plate Boundaries <ul><li>Identified by geologic activity: </li></ul><ul><li>1) Earthquakes </li></ul><ul><li>2) Volcanism ...
EQ Foci Volcanic Activity
Plate Boundaries <ul><li>3) Mountain Ranges </li></ul><ul><li>- indicates plate collisions </li></ul><ul><li>4) Deep-Sea T...
Subduction <ul><li>Marked by Benioff Zone </li></ul><ul><li>- line of shallow- to deep-focus EQ’s along a deep-sea trench ...
Subduction zone EQ foci
Deep-Sea Trenches <ul><li>NOTE :  Most trenches located in Pacific Ocean </li></ul><ul><li>Atlantic Ocean is predominately...
Types of Plate Boundaries <ul><li>1) Divergent – plates pull away from each other </li></ul><ul><li>Characteristics: </li>...
Divergent Plate Boundaries <ul><ul><li>b) mid-ocean ridges </li></ul></ul><ul><ul><li>Ex:  Iceland </li></ul></ul><ul><ul>...
Close-up of Africa
Types of Plate Boundaries <ul><li>2) Convergent – plates collide </li></ul><ul><li>3 subtypes: </li></ul><ul><li>a) Ocean-...
Ocean-Continent Convergent
Ocean-Continental Convergent <ul><li>Characteristics : </li></ul><ul><li>Deep-sea trenches parallel continent  </li></ul><...
Ocean-Continental Convergent <ul><li>Volcanic arcs  on continental margin  </li></ul><ul><li>- source of magma is melting ...
Types of Convergent Boundaries <ul><li>b) Ocean-ocean </li></ul><ul><li>Denser ocean plate is subducted </li></ul>
Ocean-Ocean Convergent <ul><li>Characteristics : </li></ul><ul><li>Deep-sea trench </li></ul><ul><li>Benioff Zone  </li></...
Ocean-Ocean Convergent <ul><li>Ex:  Japanese Islands </li></ul><ul><li>Aleutian Islands </li></ul><ul><li>Caribbean Island...
Types of Convergent Boundaries <ul><li>c) Continent to Continent </li></ul><ul><li>Characteristics : </li></ul><ul><li>Sha...
 
Continent-Continent Convergent <ul><li>Ex:  Himalayan Mtns. (active) </li></ul><ul><li>Appalachian Mtns. (inactive) </li><...
India into Asia Himalayan Mountains
Types of Plate Boundaries <ul><li>3) Transform- plates slide laterally </li></ul><ul><li>Characteristics : </li></ul><ul><...
 
Transform Boundary <ul><li>Ex:  San Andreas Fault </li></ul><ul><li>North American Plate meets Pacific Plate  </li></ul>
Hot Spot Volcanism (handout) <ul><li>Associated with intraplate volcanism </li></ul><ul><li>Hot spots are stationary w/in ...
Mantle plume
 
Exam 3 <ul><li>EQ & Plate Tectonic Study Guide </li></ul><ul><li>Map on back of PT Study Guide </li></ul><ul><li>Know:  pl...
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Transcript of "Ch7_Plate_Tectonics_students"

  1. 1. CH. 8 – PLATE TECTONICS
  2. 2. Continental Drift <ul><li>1915: </li></ul><ul><li>Alfred Wegener </li></ul><ul><li>- hypothesized the supercontinent Pangaea (“all land”) </li></ul>
  3. 3. Plate Tectonics <ul><li>WWII </li></ul><ul><li>New technology = echosounder </li></ul><ul><li>-used to map ocean floor topography </li></ul>
  4. 4. Harry Hess <ul><li>1962: </li></ul><ul><li>Hypothesized sea-floor spreading </li></ul>
  5. 5. Sea-floor spreading <ul><li>a) Ocean crust splits apart at mid-ocean ridges (MOR) </li></ul><ul><li>- pushes continents away from each other </li></ul>
  6. 6. Sea-floor spreading <ul><li>b) Ocean crust pulled down into mantle at deep-sea trenches </li></ul><ul><li>New idea : ocean crust is moving! </li></ul>
  7. 7. Plate dynamics
  8. 8. Evidence for sea-floor spreading (late 1960’s - 1970’s) <ul><li>1) Deep-sea Drilling Projects </li></ul><ul><ul><li>Glomar Challenger </li></ul></ul><ul><ul><li>Discovered: </li></ul></ul><ul><ul><li>a) Ocean crust is __________ </li></ul></ul>
  9. 9. Deep-sea drilling projects <ul><li>b) Sediment thickness varies: </li></ul><ul><li>- thicker further away from MOR </li></ul><ul><li>c) Sediment age: </li></ul><ul><li>- increases with distance from MOR </li></ul>
  10. 10. 2) Submersible Expeditions <ul><li>1974 FAMOUS expedition </li></ul><ul><li>( F rench- A merican M id- O cean U ndersea S tudy) </li></ul>
  11. 11. Submersible Expeditions <ul><li>Evidence for mafic eruptions: </li></ul><ul><ul><li>- hydrothermal vents (~350 o C) </li></ul></ul><ul><ul><li>- pillow lavas </li></ul></ul>
  12. 12. Problem: <ul><li>How does crust move over solid rock of mantle? </li></ul>
  13. 13. 3) Clues: seismic waves <ul><li>Lithosphere – rigid rx of crust and uppermost mantle </li></ul><ul><li>Asthenosphere – weaker rocks (partially molten) in upper mantle </li></ul>
  14. 15. Plate Tectonics Theory <ul><li>Plate – rigid slab of lithosphere </li></ul><ul><li>7 major plates on Earth </li></ul><ul><li>Each plate moves independently </li></ul>
  15. 16. Plate map
  16. 17. Same plate <ul><li>Locations do not change position relative to one another </li></ul><ul><li>Ex: NYC & Peoria always same distance apart </li></ul>
  17. 18. Different plates <ul><li>Locations do change position relative to one another </li></ul><ul><li>Ex: NYC & London getting further apart </li></ul>
  18. 19. Plate Boundaries <ul><li>Identified by geologic activity: </li></ul><ul><li>1) Earthquakes </li></ul><ul><li>2) Volcanism </li></ul><ul><li>- mid-ocean ridges </li></ul><ul><li>- circum-Pacific belt </li></ul>
  19. 20. EQ Foci Volcanic Activity
  20. 21. Plate Boundaries <ul><li>3) Mountain Ranges </li></ul><ul><li>- indicates plate collisions </li></ul><ul><li>4) Deep-Sea Trenches </li></ul><ul><li>Subduction = one plate “dives” beneath another </li></ul>
  21. 22. Subduction <ul><li>Marked by Benioff Zone </li></ul><ul><li>- line of shallow- to deep-focus EQ’s along a deep-sea trench </li></ul>
  22. 23. Subduction zone EQ foci
  23. 24. Deep-Sea Trenches <ul><li>NOTE : Most trenches located in Pacific Ocean </li></ul><ul><li>Atlantic Ocean is predominately a spreading center </li></ul><ul><li>Plates converge on Pacific Ocean side </li></ul>
  24. 25. Types of Plate Boundaries <ul><li>1) Divergent – plates pull away from each other </li></ul><ul><li>Characteristics: </li></ul><ul><li>a) shallow-focus EQ’s </li></ul><ul><li>b) mafic magma </li></ul><ul><li>c) rift valleys </li></ul>
  25. 26. Divergent Plate Boundaries <ul><ul><li>b) mid-ocean ridges </li></ul></ul><ul><ul><li>Ex: Iceland </li></ul></ul><ul><ul><li>b) continental rift valleys </li></ul></ul><ul><ul><li>Ex: East African Rift Valley </li></ul></ul><ul><ul><li>Red Sea </li></ul></ul>
  26. 27. Close-up of Africa
  27. 28. Types of Plate Boundaries <ul><li>2) Convergent – plates collide </li></ul><ul><li>3 subtypes: </li></ul><ul><li>a) Ocean-Continental </li></ul><ul><li>- ocean plate subducted beneath continental plate </li></ul>
  28. 29. Ocean-Continent Convergent
  29. 30. Ocean-Continental Convergent <ul><li>Characteristics : </li></ul><ul><li>Deep-sea trenches parallel continent </li></ul><ul><li>Benioff Zone </li></ul>
  30. 31. Ocean-Continental Convergent <ul><li>Volcanic arcs on continental margin </li></ul><ul><li>- source of magma is melting plate </li></ul><ul><li>- composite cones </li></ul><ul><li>Ex: Andes Mtns., S. America </li></ul><ul><li>Peru-Chile Trench </li></ul><ul><li> Cascade Mtns., N. America </li></ul>
  31. 32. Types of Convergent Boundaries <ul><li>b) Ocean-ocean </li></ul><ul><li>Denser ocean plate is subducted </li></ul>
  32. 33. Ocean-Ocean Convergent <ul><li>Characteristics : </li></ul><ul><li>Deep-sea trench </li></ul><ul><li>Benioff Zone </li></ul><ul><li>Volcanic island arcs (composite cones) </li></ul>
  33. 34. Ocean-Ocean Convergent <ul><li>Ex: Japanese Islands </li></ul><ul><li>Aleutian Islands </li></ul><ul><li>Caribbean Islands </li></ul><ul><li>Indonesia </li></ul>
  34. 35. Types of Convergent Boundaries <ul><li>c) Continent to Continent </li></ul><ul><li>Characteristics : </li></ul><ul><li>Shallow-focus EQ’s only </li></ul><ul><li>No volcanism </li></ul><ul><li>Complex folded mountains </li></ul>
  35. 37. Continent-Continent Convergent <ul><li>Ex: Himalayan Mtns. (active) </li></ul><ul><li>Appalachian Mtns. (inactive) </li></ul>
  36. 38. India into Asia Himalayan Mountains
  37. 39. Types of Plate Boundaries <ul><li>3) Transform- plates slide laterally </li></ul><ul><li>Characteristics : </li></ul><ul><li>- shallow-focus EQ’s only </li></ul><ul><li>- crust neither created nor destroyed </li></ul>
  38. 41. Transform Boundary <ul><li>Ex: San Andreas Fault </li></ul><ul><li>North American Plate meets Pacific Plate </li></ul>
  39. 42. Hot Spot Volcanism (handout) <ul><li>Associated with intraplate volcanism </li></ul><ul><li>Hot spots are stationary w/in mantle (“mantle plume”) </li></ul>
  40. 43. Mantle plume
  41. 45. Exam 3 <ul><li>EQ & Plate Tectonic Study Guide </li></ul><ul><li>Map on back of PT Study Guide </li></ul><ul><li>Know: plate boundaries </li></ul><ul><li> characteristics </li></ul><ul><li> locations </li></ul>
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