Ch7_Plate_Tectonics_students
- 1. CH. 8 – PLATE TECTONICS
- 2. Continental Drift 1915: Alfred Wegener - hypothesized the supercontinent Pangaea (“all land”)
- 3. Plate Tectonics WWII New technology = echosounder -used to map ocean floor topography
- 4. Harry Hess 1962: Hypothesized sea-floor spreading
- 5. Sea-floor spreading a) Ocean crust splits apart at mid-ocean ridges (MOR) - pushes continents away from each other
- 6. Sea-floor spreading b) Ocean crust pulled down into mantle at deep-sea trenches New idea : ocean crust is moving!
- 8. Evidence for sea-floor spreading (late 1960’s - 1970’s) 1) Deep-sea Drilling Projects Glomar Challenger Discovered: a) Ocean crust is __________
- 9. Deep-sea drilling projects b) Sediment thickness varies: - thicker further away from MOR c) Sediment age: - increases with distance from MOR
- 10. 2) Submersible Expeditions 1974 FAMOUS expedition ( F rench- A merican M id- O cean U ndersea S tudy)
- 11. Submersible Expeditions Evidence for mafic eruptions: - hydrothermal vents (~350 o C) - pillow lavas
- 12. Problem: How does crust move over solid rock of mantle?
- 13. 3) Clues: seismic waves Lithosphere – rigid rx of crust and uppermost mantle Asthenosphere – weaker rocks (partially molten) in upper mantle
- 15. Plate Tectonics Theory Plate – rigid slab of lithosphere 7 major plates on Earth Each plate moves independently
- 16. Plate map
- 17. Same plate Locations do not change position relative to one another Ex: NYC & Peoria always same distance apart
- 18. Different plates Locations do change position relative to one another Ex: NYC & London getting further apart
- 19. Plate Boundaries Identified by geologic activity: 1) Earthquakes 2) Volcanism - mid-ocean ridges - circum-Pacific belt
- 20. EQ Foci Volcanic Activity
- 21. Plate Boundaries 3) Mountain Ranges - indicates plate collisions 4) Deep-Sea Trenches Subduction = one plate “dives” beneath another
- 22. Subduction Marked by Benioff Zone - line of shallow- to deep-focus EQ’s along a deep-sea trench
- 23. Subduction zone EQ foci
- 24. Deep-Sea Trenches NOTE : Most trenches located in Pacific Ocean Atlantic Ocean is predominately a spreading center Plates converge on Pacific Ocean side
- 25. Types of Plate Boundaries 1) Divergent – plates pull away from each other Characteristics: a) shallow-focus EQ’s b) mafic magma c) rift valleys
- 26. Divergent Plate Boundaries b) mid-ocean ridges Ex: Iceland b) continental rift valleys Ex: East African Rift Valley Red Sea
- 28. Types of Plate Boundaries 2) Convergent – plates collide 3 subtypes: a) Ocean-Continental - ocean plate subducted beneath continental plate
- 30. Ocean-Continental Convergent Characteristics : Deep-sea trenches parallel continent Benioff Zone
- 31. Ocean-Continental Convergent Volcanic arcs on continental margin - source of magma is melting plate - composite cones Ex: Andes Mtns., S. America Peru-Chile Trench Cascade Mtns., N. America
- 32. Types of Convergent Boundaries b) Ocean-ocean Denser ocean plate is subducted
- 33. Ocean-Ocean Convergent Characteristics : Deep-sea trench Benioff Zone Volcanic island arcs (composite cones)
- 34. Ocean-Ocean Convergent Ex: Japanese Islands Aleutian Islands Caribbean Islands Indonesia
- 35. Types of Convergent Boundaries c) Continent to Continent Characteristics : Shallow-focus EQ’s only No volcanism Complex folded mountains
- 37. Continent-Continent Convergent Ex: Himalayan Mtns. (active) Appalachian Mtns. (inactive)
- 38. India into Asia Himalayan Mountains
- 39. Types of Plate Boundaries 3) Transform- plates slide laterally Characteristics : - shallow-focus EQ’s only - crust neither created nor destroyed
- 41. Transform Boundary Ex: San Andreas Fault North American Plate meets Pacific Plate
- 42. Hot Spot Volcanism (handout) Associated with intraplate volcanism Hot spots are stationary w/in mantle (“mantle plume”)
- 43. Mantle plume
- 45. Exam 3 EQ & Plate Tectonic Study Guide Map on back of PT Study Guide Know: plate boundaries characteristics locations