Thermal Energy Transfer Drives Plate Tectonics

1. Thermal Energy Transfer Drives Plate Tectonics Chapter 12 – Science 10

2. 12.1 Evidence for Continental Drift • Continental drift theory • Earthquakes • Hot spot • Magnetic revearsal • Paleoglaciation • Plate tectonic theory • Spreading ridge • Tectonic plate • Volcanoes

3. Continental Drift Theory • 20th Century German Scientist – Alfred Wagner • Jigsaw Puzzle Fit • “Supercontinent” called Pangaea • Greek words pan, meaning all & gaea, meaning Earth • Continental shelves match across oceans

4. Continental Drift Theory

5. Matching Geological Structures and Rocks • Wagener analyzed and reasoned: • Mountain ranges begin on one continent, end at the coastline, and then appear to continue on another continent across the ocean so continents must have once been attached.

6. Matching Fossils Across the Planet • Wegener studied the fossils of Mesosaurus • Mesosaurus was a fresh water reptile • Fossils found only in 2 places: • Southeastern South America • Southwestern Asia • Could the small reptile swim 6000 km of open ocean?

7. Matching Fossils Across the Planet • Land dwelling animal fossils even more convincing • Cynognathus and lystrosaurus • Fern Fossil • Glossopteris • Found all over the planet even Antarctica! • Antarctica must have once been near the equator.

8. Climactic Evidence for Continental Drift • When glaciers retreat they leave a mark • Valleys, deeply scratched rocks etc.. • Evidence of glaciers in what is now the equator area • Coal deposits • Only occur where life once thrived • Found in Antarctica!

9. How Can Continents Move • Earth is divided into movable slabs of rock called tectonic plates • Related to Volcano locations • Related to where Earthquakes occur • The depth of oceans and the Mid Atlantic Ridge • A massive underwater mountain range

11. Bill Nye – Earth’s Crust • The worksheet is your passport.

12. Mid Atlantic Ridge

13. Rock sample ages • Oceanographers studied the age of the ocean floor • Discovered the youngest rocks were found closest to the ridge in the ocean. • More sediment (becoming thicker) the farther the rock was away from the ridge.

14. Paleomagnetism: • Earth has magnetic poles like a bar magnet • Poles can reverse: magnetic reversal • Not really known why! • Probably because the liquid core changes direction • Happens 4-5 times every million years • Rocks as they are formed keep their “magnetic needles” inside them frozen in place as they cool • A pattern of stripes of the iron direction of rocks was discovered on both sides of the ridge!

15. Paleomagnetism: magnetic striping

16. Sea Floor Spreading • Harry Hess, 1960 tied it all together! • Magma from inside Earth rises • Rises because it is hot and less dense then the material surrounding it • Magma cools and hardens when it breaks through the surface • This happens at the spreading ridge • This is the new sea floor! • As hot magma rises it pushes away the magma that cooled earlier! • Like a conveyor belt • See Table 12.1!

17. J. Tuzo Wilson: Canadian Geologist • Combined the concepts of sea floor spreading and paleomagnetism into the theory of continental drift • Introduced the idea of hot spots • Chains of volcanic islands were formed when a tectonic plate passed over a stationary molten area of hot rock in the Earth

18. Hot Spots: Volcanic Island Formation

19. It’s all coming together…

20. Wilson’s Conclusions • Continents must break up at certain areas , move across the Earth’s surface, and then rejoin! • This would explain where mountains form, earthquakes happen and where we find volcanoes • Also explains the how rocks get recycled inside the Earth. • Rocks can transform from one type into another • Wilson’s theory became known as the Plate Tectonic Theory. • VIDEO