1. 9.2 & 9.3 Plate Tectonics

2. Earth’s Major Plates
The lithosphere is divided up into segments called plates
These plates continually move and change
Move on average of 5 cm a year (about like your fingernail)
Movements are powered by unequal distributions of heat within the Earth
As they move they interact in various ways

3. Types of Plate Boundaries
Divergent
Convergent
Transform

4. Divergent Boundaries Spreading centers Occurs when 2 plates move apart
Results in upwelling of material form the mantle to create a new ocean floor
Example
Part of the Mid-Atlantic Ridge emerges from the ocean & splits Iceland in half

6. Iceland

7. Divergent Boundaries
Seafloor Spreading: the process where the ocean floor is extended when 2 plates move apart
Oceanic Ridge: underwater mountain range created from a divergent plate boundary
Typically 1000 – 4000 km wide
Example: Mid-Atlantic Ridge (runs the length of the Atlantic Ocean separating N & S American Plates from the Eurasian & African Plates

9. Divergent Boundaries
Rift Valley: deep faulted structure found along the axes of divergent plate boundaries.
These can develop on land or on the ocean floor
Narrow
Runs the whole length of a mid-ocean ridge

10. Convergent Boundaries
Boundary where 2 plates move together
Results in oceanic lithosphere going beneath an overriding plate, and descending into the mantle
The India Plate pushing upward into Eurasian Plate and creating the Himalayan Mountains
Plates carrying continental crust are currently moving toward each other and could one day collide and merge
Boundary that once separated the 2 plates would disappear when the 2 plates join

12. Himalayan Mountains

13. Convergent Boundaries
Subduction zone: a destructive plate where oceanic crust is pushed down into the mantle under the second plate
Ocean-Ocean Boundary: when 2 oceanic pieces converge, 1 goes under the other. Volcanoes form under the ocean.
Ocean – Continental Boundary: when the continental plate converges with an oceanic plate, the less dense continental plate floats. May cause volcanic eruptions.
Continental – Continental Boundary: when an oceanic plate is subducted under the continental. A volcanic arc forms

14. Ocean – Ocean Boundary

15. Ocean – Continental Boundary

16. Continental – Continental Boundary

17. Transform Fault Boundaries
2 plates are sliding past one another without production or destruction of the lithosphere
Example: San Andreas Fault is 800 km long and runs throughout California

18. San Andreas Fault this fence was offset ~8.5 feet

20. Plate Boundaries VideoUs

21. Resources http://www.earthtoleigh.com www.google.com
Prentice Hall Earth Science