1. What we believe today: Theory of Plate Tectonics Earth’s LithosphereThe Theory of Plate Tectonics states that the Earth’s Lithosphere (crust and uppermost mantle) is broken into pieces called tectonic plates. The plates of the earth slowly move due to convection currents in the Asthenosphere. Developing a Theory of Plate Tectonics (1960)

2. The Lithosphere is broken into approximately 20 pieces called Tectonic Plates

3. Where did this theory come from? The theory of plate tectonics is the sum of two earlier theories: 1.The Theory of Continental Drift 2.The Theory of Seafloor Spreading

4. The Theory of Continental Drift (1912) Pangea, which means “all lands.”Alfred Wegener said that continents were together in one large landmass called Pangea, which means “all lands.” Pangea drifted apart horizontally between 250 - 300 million years ago (mya). Alfred Wegener (1880-1930) German Meteorologist

5. Geologic Time Line

6. Pangea – “All Land ( Early Permian (290 mya to Early Jurassic (200 mya) )” 225 Million Years Ago (mya) During the Triassic Period (248- 209mya) the continents were still together in a large landmass known as Pangea and began to drift apart about 200 (mya). warm and dryThe climate was warm and dry for the entire supercontinent.

7. Tree Fern Ginko- “living fossil” Horsetail Conifer Forest Ferns

8. Evidence Supporting the Continental Drift Theory

9. 1. Jig Saw Puzzle Fit The apparent fit of continental coast lines was the first clue Wegener used to support his theory. Observe a World Map. Which continents look like they could fit together?

10. 2. Fossil Clues

11. Glossopteris Fossil (Tree Fern) Fern fossil found on 5 different land masses: Africa, South America, Antarctica, Australia and India. What is the significance of this discovery? far too large The fern contained seeds that were far too large to be carried by wind across the oceans, so Wegener concluded that the landmasses had to be together when they grew on th planet.

12. Mesosaurus Fossil.Small swimming reptile that lived in freshwater and land about 280 mya. Fossil remains are found in South America and Africa. How could these fossils be found so far apart? They couldn’t swim in salt water and could not swim the distance between the continents, so Wegener hypothesized that they lived on both continents when they were together.

13. 3. Climate Clues

14. Glacial Deposits and Glacial Grooving (scratches in rocks) Glacial deposits of the same age and type & grooved bedrockGlacial deposits of the same age and type & grooved bedrock are found in southern areas of South America, Africa, India, and Australia.

15. Warm Weathered Plants Fossils of warm weathered plants found on island of Spitzbergen in the Arctic. What does this fossil find suggest about the past climate of Spitzbergen What does this fossil find suggest about the past climate of Spitzbergen? Wegener believed that the island drifted from warm weathered areas.

16. Coal Found in Cold Climates Coal forms from compressed plant matter from swamps in Tropical areas!

17. 4. Rock Clues

18. Mountain Ranges Match The North American Appalachian Mountain Range has parts found in Greenland and Western Europe. Mountains are created as a massive mountain range when landmasses collide and their edges fold upward. These landmasses had to be connected to create the Appalachian chain because they line up when pieced together. What is the significance of this discovery?

19. Similar Rock Structures rock structuresSimilar rock structures were found on different continents. How do these clues support the idea that the continents were once together?

20. Weakness of Theory Wegener could not explain How or Why the continents drifted apart, so his theory was rejected at the time.

22. The Initial Break Up About 180 -200 million years ago the Supercontinent Pangea began to break up. Northernmost continentLaurasia was the Northernmost continent and consisted of present day North America, Asia and Europe Southernmost continentGondwanaland was the Southernmost continent and consisted of South America, Africa, Antarctica, Australia and India Panthalassa (“all Ocean”)was the name of the ocean surrounding Pangea.

23. Watch the Break up of Pangea.

24. http://emvc.geol.ucsb.edu/forteachers/flashmovies/Pangea.swf

28. "Pangea Ultima"