1. Plate Tectonics

2. Theory of Plate Tectonics States that Earth’s crust & rigid upper mantle are broken into slabs called plates The plates move in different directions and at different rates The edges of the plates are called Plate Boundaries

3. Earth Layers

7. Plate Boundaries There are three types of plate boundaries: –Divergent –Convergent –Transform Let’s look at each type and notice what happens to the plates at these boundaries and what features are formed as a result of what happens.

8. Divergent Boundaries Plates move apart from each other ← → Results: –Rifts – gap in crust –Ridges - Chain of high land on both sides of the rift Magma freezes and builds up Magma pushing up causes edges of plates to rise

9. Diverging Boundary

10. Convergent Boundary Plates move towards each other Results depend on crust type involved –continent vs. continent –continent vs. ocean –ocean vs. ocean

11. Convergent: continent vs. continent crusts push up mountain building (orogeny) e.g. Indian Plate vs. Eurasian Plate = Himalayan mountains

12. Continent vs. Continent

14. Continent vs. Ocean one plate (ocean) sliding under other (continent) in process called subduction. results in trenches, earthquakes, volcanoes on land e.g. Nazca Plate + S. Am. Plate = Peru- Chile trench

15. Continent vs. Ocean

17. Ocean vs. Ocean subduction (one of the two subducts) results in trenches, earthquakes, island arcs. e.g. Pacific Plate + Philippine Plate = Marianna Trench, Philippine Islands

18. Ocean vs. Ocean

20. Transform Boundary one plate slides past another ↑ ↓ results in earthquakes when built up tension is suddenly released e.g. Pacific Plate + N. Am. Plate = San Andreas Fault

21. Transform Boundary

23. Plate Motion Convection –plates are believed to move by convection currents (warmer material increases in volume, becomes less dense and therefore, rises; cooler material condenses, becomes denser and sinks. –diverging boundaries are associated with rising convection currents. –converging boundaries are associated with sinking convection currents

24. Convection

25. Plate Motion Ridge Push –process where weight of uplifted ridge pushes plate toward trench. Slab Pull –process where weight of subducting plate helps pull the trailing lithosphere into subduction zone.

26. Plate Motion

27. Hot Spots Why are some volcanoes located in the middle of plates? –They are on hot spots –Hawaii is an example Hot Spot –Place in Earth’s crust where magma plume exists and reaches surface –Plume remains stationary –Plate moves over hot spot plume –Chain of volcanoes form

28. Hot Spots

29. Hawaii