9.2 & 9.3 Plate Tectonics

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

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

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 subductedunder 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

20. Plate Boundaries Video • https://www.youtube.com/watch?v=NtqumXEHKUs

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