The Theory of Plate Tectonics

1. The Theory of Plate Tectonics

2. Plates • Lithosphere is broken into separate sections called plates. • Fit closely together along cracks in lithosphere. • Carry the continents or parts of the ocean floor, or both.

3. Scientific Theory Well-tested concept that explains a wide range of observations

4. Theory of Plate Tectonics Combined what scientists knew about sea-floor spreading, Earth’s plates, and continental drift into a single theory

5. Plate Tectonics • Pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle • Explains the formation, movement, and subduction of Earth’s plates

6. How do plates move? • Plates of lithosphere float on top of asthenosphere • Convection currents rise in asthenosphere and spread out under the lithosphere • Cause movement of plates

7. As Plates Move… • Affect others around it • Collide • Pull apart • Grind past each other • Produce changes in Earth’s surface • Volcanoes • Mountain ranges • Deep-sea trenches

8. Plate Boundaries Lines where edges of different pieces of lithosphere meet

9. Faults Breaks in Earth’s crust where rocks move past each other

10. Plate Movements Foldable Instructions

11. Making the Foldable • Align 2 pages of paper with one on top of the other with a 1 inch gap (like the foldable for Layers of Earth) • Fold over so that you have 3 flaps. • Staple together.

12. Label as Follows

13. Divergent Boundary • Plates move apart • Occur at mid-ocean ridge and on land • On land, deep valley forms called a rift valley • As rift valley widens, the floor drops. • Great Rift Valley, Africa

14. Convergent Boundary • Plates come together or collide • Density of plate determines which plate comes out on top • 2 continental plates collide -> build up mountains • Oceanic and continental collide -> oceanic subducts into the mantle

15. Transform Boundary • Plates slip past each other, moving in opposite directions • Crust is not created or destroyed • Earthquakes occur frequently • San Andreas Fault, California

16. Pangaea

18. Snickers Science

19. Use a fingernail to make a few breaks in the top of the candy bar. What layer of the earth does the chocolate represent? Crust

20. What layer of the earth do you now see? What type of boundary would this represent? What type of land feature would you find at this type of boundary? Mantle Divergent boundary Rift valley or mid-ocean ridge To illustrate tension, gently pull on the edges of the candy bar.

21. What type of boundary would this represent? Describe what happens to the earth as you do this. Transform boundary Earthquakes occur Now push the plates back together and then slide one half of the candy bar forward and the other backwards.

22. What type of boundary would this represent? What type of land feature develops as you push the two halves together? Convergent boundary Mountains To illustrate the force of compression push on both ends of the candy bar to squeeze it together.