2. Plate Tectonics

3. The Earth’s Drifting Continents Years ago scientists believed that the continents were drifting apart Scientists have evidence that all of the continents were connected in a giant landmass called Pangaea

4. Evidence of Pangaea Continents look like puzzle pieces Fossils Rock layers Coal, salt, and limestone deposits Most evidence is found in South America and Africa Glossopteris, a tree-like plant from the Permian Period through the Triassic Period. It had tongue-shaped leaves and was about 12 ft (3.7 m) tall. It was the dominant plant of Gondwana

5. Why Do the Continents Move? Ocean-floor spreading –Magma pushes up between 2 plates and pushes the plates apart -Subduction -crust gets pushed below other crust and melts -Trench - a V-shaped valley where one plate is pushed below another

6. Theory of Plate Tectonics Combines the Theory of Continental Drift and Ocean-Floor Spreading. Earth is made up of lithospheric plates that move around Helps to explain volcanoes, earthquakes, and mountain building

7. Plate Tectonics

8. Lithospheric Plates The lithosphere is the topmost part of the Earth There are 9 major lithospheric plates We live on the North American Plate

9. Plate Boundaries

10. 3 Types of Plate Boundaries Divergent - plates pull away from each other Convergent - plates push into one another Strike-Slip- plates slide past one another