The theory of plate tectonics explains that Earth's outer layer is made up of plates that have moved throughout geological history. These plates float on top of the mantle and move at boundaries where they diverge, converge, or slide past one another. Convection currents in the upper mantle provide the driving force that causes plates to move over time.

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

3. The plate tectonic theory Plate tectonics is the theory that Earth's outer layer is made up of plates, which have moved throughout Earth's history. The theory explains the how and why behind mountains, volcanoes, and earthquakes, as well as how, long ago, similar animals could have lived at the same time on what are now widely separated continents.

4. Pangaea In 1912 a German meteorologist named Alfred Wegener (1880-1931) hypothesized a single proto-supercontinent that divided up into the continents we now know because of continental drift and plate tectonics. This hypothesis is called Pangaea because the Greek word "pan" means "all" and Gaea or Gaia (or Ge) was the Greek name of the divine personification of the Earth. Pangaea, therefore, means "all the Earth."

5. Plate Tectonics

6. What is 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

8. 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”

10. What is the Asthenosphere ? The plastic layer below the lithosphere = asthenosphere The plates of the lithosphere float on the asthenosphere

12. 2 Types of Plates Ocean plates - plates below the oceans Continental plates - plates below the continents

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

14. Plate Boundaries

15. Divergent Boundaries Boundary between two plates that are moving apart or rifting   RIFTING causes SEAFLOOR SPREADING

16. Features of Divergent Boundaries Mid-ocean ridges rift valleys fissure volcanoes

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

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

23. Andes Mountains, South America

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

26. Aleutian Islands, Alaska

27. Type 3 A continental plate colliding with another continental plate Have Collision Zones: a place where folded and thrust faulted mountains form.

30. Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES along faults

32. San Andreas Fault, CA

33. 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?

34. Causes of Plate Tectonics

35. 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 .

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