2. Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics

3. Plate Tectonics

4. Questions... What is the theory of plate tectonics? What is the lithosphere? What is the asthenosphere? What are the two types of plates?

5. What is the Theory of Plate Tectonics? The Earth’s crust and upper mantle are broken into sections called plates Plates move around on top of the mantle like rafts

7. 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” on molten rock.

8. What is the Asthenoshere? The plastic like layer below the lithosphere = asthenosphere The plates of the lithosphere float on the asthenosphere

10. 2 Types of Plates Ocean plates - plates below the oceans (Basalt) Continental plates - plates below the continents (Granite)

11. Plate Boundaries

12. 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?

13. (1) Divergent Boundaries Boundary between two plates that are moving apart   RIFTING causes SEAFLOOR SPREADING - Samples collected by the Glomar Challenger showed that the youngest rocks on the ocean floor are found in the center of mid ocean ridges.

14. Features of Divergent Boundaries Mid-ocean ridges rift valleys fissure (narrow opening) volcanoes

18. (2) Convergent Boundaries Boundaries between two plates that are colliding   There are 3 types…

19. Type 1 Ocean plate collides with a less dense continental plate Subduction Zone: where the more dense plate slides under the less dense plate VOLCANOES occur at subduction zones

21. Andes Mountains, South America

22. Type 2 Ocean plate collides with another ocean plate The more dense plate slides under the more less dense plate creating a subduction zone called a TRENCH

23. Aleutian Islands, Alaska

24. Type 3 A continental plate collides with another continental plate Have Collision Zones: –a place where folded and thrust faulted MOUNTAINS form.

27. (3) Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES along faults –Earthquakes produce seismic waves that travel through Earth.

29. San Andreas Fault, CA

30. Causes of Plate Tectonics

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

32. Convection Currents Hot magma in the Earth moves toward the surface, cools, then sinks again. Creates convection currents beneath the plates that cause the plates to move.

34. Continental Drift The hypothesis of Continental drift was that all the continents once were joined as a single super continent and have since drifted apart. To support his hypothesis, Alfred Wegener provided evidence from fossils to support the theory of continental drift.