Theory of Plate Tectonics

1. Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics

2. Plate Tectonics

3. 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.

5. 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”

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

8. 2 Types of Plates • Oceanic plates - plates below the oceans. • Contain mostly basalt. • Continental plates - plates below the continents. • Contain mostly rhyolite.

9. Plate Boundaries

10. Divergent Boundaries • Boundary between two plates that are moving apart or rifting.   • RIFTING causesSEAFLOOR SPREADING.

11. Features of Divergent Boundaries • Mid-ocean ridges • Rift valleys • Fissure volcanoes

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

15. Type 1 • Oceanic plate colliding with a less dense continental plate. • Subduction Zone: where the more dense plate slides under the less dense plate. • VOLCANOES occur at subduction zones. Ring of FireAnimations

17. Andes Mountains, South America

18. Type 2 • Oceanic plate colliding with another oceanic plate. • The more dense plate slides under the less dense plate creating a subduction zone called a TRENCH.

20. Aleutian Islands, Alaska

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

24. Transform Fault Boundaries • Boundary between two plates that are sliding past each other. • EARTHQUAKES occur along these faults.

26. San Andreas Fault, CA

27. Causes of Plate Tectonics

28. 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.