The Birth of a Theory:

1. The Birth of a Theory: Continental Drift

2. Throughout history, most people believed that the continents had always been in the same positions that they are today.

3. Alfred Wegener In 1915, a German scientist, named Alfred Wegener, proposed the idea of “Continental Drift”. Alfred Wegener

5. What is the theory of continental drift? The hypothesis: 1. The earth is always changing, land masses (continents) are constantly moving.

6. What is the theory of continental drift? 2. Originally all of the continents were joined together in one super-continent called Pangaea and slowly moved to their current positions.

7. http://www.auburn.edu/academic/science_math/res_area/geology/camp/Pangaea.jphttp://www.auburn.edu/academic/science_math/res_area/geology/camp/Pangaea.jp g

8. What evidence did Wegener use to support his theory of continental drift?

9. 1 - Earth’s landmasses—especially South America and Africa—fit together like a jigsaw puzzle. http://www.abdn.ac.uk/zoohons/lecture1/img008.GIF

10. Fossil Evidence 2 - The fossils from the exact same land-living animals and plants are found on continents now separated by the Atlantic Ocean.

11. http://wrgis.wr.usgs.gov/docs/parks/animate/A15.gif

12. Matching Rock Layers 3 - The rocks of South America match the rocks of Africa in age and layers.

13. Matching Mountains 4 – The Appalachian Mountains match the mountains in Ireland and Scotland.

15. Fossils 5 – Fossils of tropical swamp plants were found in the eastern United Sates, Europe, and Siberia.

16. Glacier Evidence 6 - Glaciers scars are found on continents such as Asia, India, and Australia which are too warm for glaciers today.

17. Panthalassa

18. Key concepts • Evidence of “continental drift”— • . • Physical fit of continents • Fossil evidence • Rock layer sequences • Glacial evidence • Matching mountain ranges Alfred Wegener

19. Was Wegener’s theory believed? • Scientists did not believe Wegener’s ideas because he couldn’t explain HOW the continents moved!!! NO

20. Harry Hess Harry Hess was a navy sea captain and scientist that proposed the idea of seafloor spreading.

21. A bit of history… Sonar was developed during World War II to locate German submarines.

22. After the war, sonar was used to map the ocean floor.

24. Many new features were discovered… M.A.R. 1 – a huge volcanic mountain range in the middle of the Atlantic Ocean (M.A.R.)

28. 2 – deep trenches in the Pacific Ocean

29. http://www.harcourtschool.com/glossary/science/images/gr6/trench6.jpghttp://www.harcourtschool.com/glossary/science/images/gr6/trench6.jpg

30. Hypothesis: The ocean floor is getting bigger at the ridges and smaller at the trenches. oldest Evidence: youngest • The newest rocks are on the ocean floor along the Atlantic Ridge. oldest • The oldest rocks are on the continents. • The continents are much older than the ocean floor!

31. Volcanoes located along ocean ridges erupt, creating new ocean floor.

35. Iceland’s Volcanoes http://www.navis.gr/photos/images/iceland.jpg

39. http://www.sas.upenn.edu/African_Studies/Map_Satellite/World_Map1_11218.gifhttp://www.sas.upenn.edu/African_Studies/Map_Satellite/World_Map1_11218.gif

40. World Earthquake Data

42. http://www.sas.upenn.edu/African_Studies/Map_Satellite/World_Map1_11218.gifhttp://www.sas.upenn.edu/African_Studies/Map_Satellite/World_Map1_11218.gif

43. The earth’s lithosphere is broken into huge sections called plates that are in constant motion.

44. http://www.iris.edu/seismon/html/plates.html

45. Plate Tectonics Plate Tectonics – The idea that the earth’s surface is broken into huge pieces called plates. These plates are constantly moving and bumping into each other, carrying the continents and ocean floor to new locations.

46. How fast are the plates moving?

47. You may wonder… How are the continents moving?

48. Convection Cells! Magma circulates under the ground, pushing around the plates. (Convection Cells)

50. What are the plates made of? • Ocean plates are made of basalt. • Continental plates are made of granite.