Plate boundaries & convection currents

1. Plate boundaries& convection currents

2. Quick Reminders • The Earth’s crust and upper mantle are broken into sections called plates • Plates move around on top of the mantle like rafts

4. What is the Lithosphere? • The crust and part of the upper mantle = lithosphere • 100 km thick • Less dense than the material below it so it “floats”

5. Tuesday Warm-Up: Pick up a sheet from the front cart What are 4 pieces of evidence Alfred Wegner collected to help support his Theory of Continental Drift?

6. 2 Types of Plates • Ocean plates - plates below the oceans (Basalt rock) • Continental plates - plates below the continents (Granite rock)

8. 3 Types of Plate Boundaries • Divergent-Plates Divide or Separate • Convergent-Plates collide or come together • Transform-Plates shear/slide past each other

10. Divergent Plate Boundary ocean plates moving apart exposing Magma= creates NEW Ocean Floor (New Crust) The movement of continents was a result of sea-floor spreading Harry Hess in 1960

11. Sea Floor Spreading: ocean plates moving apart exposing Magma= creates NEW Ocean Floor (New Crust) Old crust Young crust Old crust Young Crust Convection Currents-Warm rises cool sinks Magma Convection Current-cause magma to move Mantle As the magma creates new crust, it pushes the older crust away

13. Convection Currents • Hot magma in the Earth moves toward the surface, cools, then sinks again. • Creates convectioncurrents beneath the plates that cause the plates to move.

14. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualizationhttp://www.youtube.com/watch?v=ryrXAGY1dmEhttp://www.youtube.com/watch?v=CsKTzBZNjtEhttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualizationhttp://www.youtube.com/watch?v=ryrXAGY1dmEhttp://www.youtube.com/watch?v=CsKTzBZNjtE

15. Questions... • What causes plates to move? • How is a convection current formed?

16. Divergent Boundaries • two plates that are moving apart or rifting • Ocean Floor Spreading  

17.   • Creates Landforms: • Mid-Ocean Ridge • Small Volcanos • Rift Valley  

21. Convergent Boundaries • Boundaries between two plates that are colliding   • There are 3 types…

22. Convergent Boundary Type 1 • Subduction: Ocean plate colliding with a less dense continental plate • VOLCANIC MOUNTAINS and TRENCHES Oceanic Continental

24. Andes Mountains, South America

25. Convergent Boundary Type 2 • Subduction Ocean plate colliding with another ocean plate Trench & Island Arc Oceanic Oceanic

27. Aleutian Islands, Alaska

28. Convergent Boundary Type 3 • A continental plate colliding with another continental plate a place where folded mountains form. Continental Continental

31. Transform Fault Boundaries • Boundary between two plates that are sliding/slipping/shearing past each other

32. Forms: 1)Earthquakes Or 2)Faults

33. San Andreas Fault, CA Example

34. Questions... • What are the three types of boundaries? • What direction do plates go for each? • Which boundary has a subduction zone…what occurs at a subduction zone?

35. Causes of Plate Tectonics

36. Iceland

37. Mid Atlantic Ridge

38. Plates collide: Subduction Ocean Continent Andes Mountains

40. Plates collide: Subduction Peru-Chili Trench

41. Convergent-Plates collide: Subduction Ocean Ocean Aleutian Islands

42. Convergent: Plates Collide Continent Continent Himalaya Mountains

43. Transform: Plates Slide San Andres Fault