Alfred Wegener: Pangaea

1. Has the continents always looked as they do now on the map, or have they changed shape or location throughout Earth's history? • Write your ideas on a sheet of paper.

2. Alfred Wegener: Pangaea • In early 1915, the German scientist Alfred Wegener developed a theory that the continents once formed a giant supercontinent that he called Pangaea. • Pangaea means all lands. • Wegener proposed the theory of “Continental Drift:” that all the continents had once been joined together in a single landmass and have drifted apart over time.

3. Evidence for Continental Drift • Wegener based the idea on 4 different types of evidence: • The continents fit together like a puzzle • Fossil evidence • Rock type and Structural Similarities • Paleoclimaitc Evidence

4. Plate Tectonics • Even with the pervious stated evidence, Wegener’s idea of continental drift was not accepted, because no one could come up with a reasonable mechanism for the movement of the continents, until about the 1960’s when the development of the theory of plate tectonics.

5. Plate Tectonics • Plate tectonics – is a theory that explains how Earth’s exterior is broken into large slabs of lithosphere (plates) that are in continual motion with each other. This movement is due to convection currents. • A convection current is a cycle created as hot matter rises, cools, and sinks. (Is a cycle created as hot matter rises & cold matter sinks.) • Where else are there convection currents, or where else do we used convection currents?

6. Plate Tectonics • Plate tectonics – is a theory that explains how Earth’s exterior is broken into large slabs of lithosphere (plates) that are in continual motion with each other. This movement is due to convection currents. • A convection current is a cycle created as hot matter rises, cools, and sinks. (Is a cycle created as hot matter rises & cold matter sinks.) • Where else are there convection currents, or where else do we used convection currents? • Cloud formation, the water cycle, cooking, chemistry. • A plate is a large piece of lithosphere that is able to move about the surface of the earth. Plates move about an inch a year on average. As plates move, they interact with each other. • What are some of the causes of these interactions?

7. Plate Tectonics • Plate tectonics – is a theory that explains how Earth’s exterior is broken into large slabs of lithosphere (plates) that are in continual motion with each other. This movement is due to convection currents. • A convection current is a cycle created as hot matter rises, cools, and sinks. (Is a cycle created as hot matter rises & cold matter sinks.) • Where else are there convection currents, or where else do we used convection currents? • Cloud formation, the water cycle, cooking, chemistry. • A plate is a large piece of lithosphere that is able to move about the surface of the earth. Plates move about an inch a year on average. As plates move, they interact with each other. • What are some of the causes of these interactions? • Mountain building, earthquakes, rift valleys, volcanos, trenches.

8. Like a Puzzle • The continents’ fitting so well together is the first suggestion of continental drift. • Take a look at the maps, and can you see where some of the other continents can fit together?

10. Fossil Evidence • Fossil - The remains of an animal or plant preserved from an earlier era inside a rock or geological deposit, often as an impression or in a petrified state. • Identical fossils were found on widely separated continents: such as Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris. Lystrosaurus

11. Break into Groups • Share your information with your groups. • Draw or label this information on the map. • Where are Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris found?

13. Rock Type and Structural Similarities • There are similar rock types on continents on opposite sides of the Atlantic Ocean. • Also, mountain ranges like the Appalachian Mtns. and mountains in Scotland and Scandinavia (Caledonia Mtns.) are similar in age, structure, and rock types. • Don’t forget to label these mountains on your map.

14. Rock Type and Structural Similarities • When the continents are reassembled, the mountain chains form a continuous belt.

15. Paleoclimatic Evidence • Glacial till of the same age is found in southern Africa, South America, India, and Australia– areas that would be very difficult to explain the occurrence of glaciation. • Also large coal deposits were formed from tropical swamps in N. America and Europe. • Pangaea with S. Africa centered over the South Pole could account for the conditions necessary to generate glacial ice in the southern continents. • Where would N. America and Europe be if the coal deposits were formed from tropical swamps?

16. Paleoclimatic Evidence • Glacial till of the same age is found in southern Africa, South America, India, and Australia– areas that would be very difficult to explain the occurrence of glaciation. • Also large coal deposits were formed from tropical swamps in N. America and Europe. • Pangaea with S. Africa centered over the South Pole could account for the conditions necessary to generate glacial ice in the southern continents. • Where would N. America and Europe be if the coal deposits were formed from tropical swamps? • The areas with extensive coal deposits from the same time period occur in regions that would have been equatorial.

17. One last look at how the continents' drifted.

18. Questions • What theory did Alfred Wegener propose? • Continental drift.

19. Questions • What is the theory of Continental Drift? • that all the continents had once been joined together in a single landmass and have drifted apart over time.

20. Questions • What are 2 types of evidence for continental drift? • The continents fit together like a puzzle. • Fossil evidence. • Rock type and Structural Similarities • Paleoclimaitc Evidence.

21. Questions • Why wasn’t Wegener’s idea of continental drift accepted? • because no one could come up with a reasonable mechanism for the movement of the continents, until about the 1960’s when the development of the theory of plate tectonics.

22. Questions • What are some of the causes of plate interactions? • Mountain building, earthquakes, rift valleys, volcanos, trenches.

23. Questions • Are mountains still building/growing?

24. Questions • Describe a convection current.

25. Question/Homework • Predict what you think the continents of the earth will look like in the future?

26. Question/Homework • How has continental drift effected how species evolve over time?