Plate Tectonics

1. Plate Tectonics Preview: What does the sea floor have to do with plate tectonics?

2. Evidence we already know • Pangaea= continents all together • Begin to split and rifts occur to form new continents • Oceans begin to form around new continents • India crashes into Eurasia= Himalaya Mountains • Fossils found on 2 sets of continents • Mountain ranges match up

3. Sea floor • Under water mountain ranges- mid-ocean ridges • Mid-ocean ridges • Form on cracks by crust • Youngest rock near ridge • Oldest rock furthest away from ridge • Contains magnetic patterns that creates mirror image on other side of ridge • Sea- floor spreading • Molten rock rises through cracks, cools, forms new oceanic crust • Old crust breaks at ridge and pieces move in other directions, causing continents to move • Ocean trenches • Heavier oceanic crust sinks into asthenosphere • Old crust sinks as new crust rises

4. What is Plate Tectonics • Movement of earth’s lithosphere • Tectonic plates • Made up of lithosphere on top of asthenosphere • Major plates • Pacific • North American • Nazca • South American • African • Australia • Eurasian • Indian • Antarctic

5. Plate Boundaries • Can be on ocean floor, edge of continents, within continents • Convergent • 2 plates collide • Continent-Continent • Lithosphere • Mountains form • Continent-Ocean • Oceanic lithosphere and continental lithosphere • Volcanoes • Ocean-Ocean • Older plate subducts under other plate

6. Plate Boundaries • Divergent • 2 plates move away from each other • Asthenosphere rises and lava erupts • Lava cools and forms new rock • Form mid-ocean ridges • Transform • 2 plates move (slide) past each other • Earthquakes

7. Why plates move • Mantle convections • Hot parts of rocks move up and cooler rock sinks • Ridge push • New rock is higher than older rock • New rock cools and continues to push further away from ridge • Slab pull • Subduction- 1 plate sinks under another • Leaning edge of plate pulls rest of plate with it