1. + Unit 4: Lesson 2: Theory of Plate Tectonics

2. + REVIEW What layer of the Earth is broken into tectonic plates? What layer of the Earth has convection that moves the plates?

3. + Minute Physics - Plate Tectonics Explained Introductory Video Describe something new that you learned about plate tectonics. https://www.youtube.com/watch?v=kwfNGatxUJI

4. + World Map Do the continents look like they fit together?

5. + What evidence suggests that continents move? Late 1800’s Alfred Wegener – Continental Drift Continents once formed a single landmass that broke up and drifted apart. Evidence Same species on both sides of the Atlantic Ocean Location of mountain ranges and rock formations Same climate on sever different continents

6. + What is Pangaea? 245 million years ago Pangaea - all the continents were one landmass Mountains formed as the continents formed Pangaea Panthalassa – ocean that surrounded Pangaea

7. + What is Pangaea? 200 million years ago two continents Laurasia and Gondwana Laurasia – North America Eurasia Gondwana – South America and Africa Antarctica, Australia, India

8. + What is Pangaea? 150 million years ago South America and Africa began to split form the South Atlantic Ocean India, Australia, and Antarctica began to split India moved northward toward Eurasia 65 million years ago - after the move

9. + What is Pangaea? 50 million years ago Continents moved into their present position Oceans formed and others disappeared India collided with Eurasia to form the Himalaya Mountains 3 million years ago - after the move

10. + Comparing Pangaea to the modern location of the continents

11. + The Theory of Continental Drift

12. + Support For the Theory Mid-Ocean ridges –huge mountain ranges on the ocean floor Led to the theory of plate tectonics, that is based on some of Wegener’s ideas.

13. + Support For the Theory Age Of the Sea Floor Youngest rock is closest to the ridge Oldest rock is furthest away from the ridge Magnetic Properties of the Sea Floor Sea-floor rock has magnetic patterns that are the same on both sides of the ridge.

14. + Support For the Theory Sea-Floor Spreading – molten rock from inside Earth rises through the cracks in the ridges, cools, and forms new oceanic crust. The old crust splits in the middle, and the two pieces moves away from each other

15. + Support For the Theory Ocean Trenches – huge trenches in the sea floor Dense oceanic crust is sinking into the asthenosphere Old crust is destroyed at the same rate as new crust is forming

16. + The Theory of Plate Tectonics

17. + What is plate tectonics? Plate Tectonics - Large-scale movements of Earth’s lithosphere, which is made up of the crust and the rigid, upper part of the mantle. Tectonic Plate – pieces of the lithosphere that move on top of the asthenosphere

18. + Major Tectonic Plates Pacific North American Nazca South American African Australian Eurasian Indian Antarctic

19. + Plate Boundaries Three types of plate boundaries Divergent – two plates move away from each other Transform – two plates move past each other horizontally Convergent – two plates collide

20. + Types of Convergent Boundaries Continent-Continent Collisions: Two plates of continental lithosphere collide, Buckle and thicken Forms mountains

21. + Types of Convergent Boundaries Continent-Ocean Collisions: Oceanic lithosphere collides with continental lithosphere Oceanic lithosphere subducts because it is denser Subduction – the sinking of Earth’s crust under another plate

22. + Types of Convergent Boundaries Ocean-Ocean Collisions: Two oceanic plates collide The cooler, denser plate subducts under the other plate

23. + Divergent Plate Boundaries Two plates that move away from each other Forms a mid-ocean ridge or rift valley

24. + Divergent Plate Boundaries 1. Asthenosphere rises between the plates 2. Magma is created when the lithosphere melts 3. Lava erupts from between the plates 4. Lava cools and hardens to form new rock on the ocean floor 5. The new rock is thin, warm, and lightweight so it sits higher than the surrounding sea floor making a ridge. Steps to form a mid-ocean ridge

25. + Transform Plate Boundaries Two plates move past each other horizontally Edges do not slide smoothly Earthquakes caused when the plates slip past each other

26. + The Driving Forces of Plate Tectonics

27. + What drives plate tectonics? Mantle convection – movement of material in the mantle as the hotter parts rise and the cooler sections sink BUT scientists believe that it doesn’t create the force needed to move plates

28. + What drives plate tectonics? Main Driving Forces Ridge push – as new crust is formed at mid-ocean ridges it pushes the crust away from the ridge Slab pull – when a cold, dense plate subducts under another plate it sinks and pulls the rest of the plate down with it