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- 1. Theory of Continental Drift
- 2. Review • The earth is composed of layers. • Crust • Outermost layer • Thinnest • Composed of continental crust and ocean crust • Broken into sections, or plates • Mantle • Uppermost section is solid and includes the crust (Lithosphere) • Middle section is pliable, similar to silly putty (Asthenosphere) • Lower section is solid • Outer core • Made of liquid iron and nickel • Inner core • Made of solid iron and nickel
- 3. A Puzzle • How do you put a puzzle together? • What do you look for? • Do you notice anything on this map? • Think “puzzle pieces”
- 4. Alfred Wegener • German scientist who noticed the same thing you did – that South America and Africa look like pieces to a puzzle. • This observation led to his hypothesis that all the continents were once joined together, and have since drifted apart. • Let’s see what he thought!
- 5. Theory Rejected! • The scientists of Alfred Wegener’s day did not accept his theory. • Why? • He had no explanation of how the continents moved! • So he collected evidence to prove them wrong.
- 6. Landform Evidence • When Wegener placed South America and Africa next to each other, he noticed that a mountain range in Argentina matched up with a mountain range on other continents. • He also noticed that coal fields in Brazil were identical to coal fields in South Africa. • What did he infer from this evidence?
- 7. Fossil Evidence • Wegener also used fossil evidence to support his theory. • Glossopteris • Fernlike plant • Grew in tropical climates (warm, wet areas) • Fossils found in Antarctica, as well as Africa, South America, Australia and India. • The seeds were too large to be carried by wind • The seeds were too fragile to survive a trip in the ocean • How did they develop on all those continents? • What did he infer from this evidence?
- 8. Fossil Evidence • Ancient reptiles • Mesosaurus • Lystrosaurus • Cynognathus • These reptiles were land animals, and lived near fresh water. • Wegener found fossils of these reptiles on many continents, too far apart for them to have traveled that distance, UNLESS?
- 9. Climate Evidence • Sptizbergen is an island that is north of Norway in the Artic Ocean. • Coal forms in swampy, tropical areas. • Coal deposits are found on Spitzbergen. • What did Wegener infer from this evidence?
- 10. More Climate Evidence • Continental glaciers are thick layers/rivers of ice that move across the land • Because of their size and weight, they leave grooves, or striations, on the surface of the land. • Wegener found striations left by glaciers in South Africa (glaciation). • What did Wegener infer from this evidence? • Did you know that there are glacial striations in Rhode Island? • What can you infer about Rhode Island?
- 11. Let’s Put It All Together! • http://www.teachersdomain.org/asset/lsps07_int_biogeography/ • Puzzle like fit of continents • Matching mountain ranges • Same fossils found on many continents • Glaciation and other climate clues Now your turn: What do you think Pangaea looked like?
- 12. Questions?