3. Let’s Review! a. transfer of heat through liquids and gases = convection b. transfer of heat by physical contact = conduction c. transfer of heat through waves = radiation

4. A. Continental drift theory. Alfred Wegener- German Scientist, Wegener purposed that all continents were once joined together in a single landmass & then have slowly drifted apart. He called his super continent …Pangea

5. a. Theory is called: Continental Drift b. 1 st formed Pangaea “super continent”

6. The Evidence…. 1. He first noticed that the continents seem to fit together. 2. Look at the fit of South America’s east coast and South Africa's west coast.

7. More Evidence. 1. Similar landforms a. Mountain ranges of S. America & Africa line-up b. coal fields of N. America & Europe line up

8. More Evidence. Fossils- similar fossils found where landforms match. I.E Mesosaurus

10. . Another piece of evidence Continent’s climates have change when the land drifted. What are some clues one might find of past climate?

11. Lots of evidence that supports CD but did people believe him?  http://science.discovery.com/videos/100- greatest-discoveries-shorts-continental- drift.html http://science.discovery.com/videos/100- greatest-discoveries-shorts-continental- drift.html

12. Wegener’s hypothesis was rejected- couldn’t explain why the continents move. The answer we now know = Convection currents caused by our core. Convection box demo

13. Science Exercise: Answer the following questions….

14. Is there other evidences? YES! http://www.youtube.com/ watch?v=6CsTTmvX6mc

15. Modern day Evidences.

16. C. Sea-floor Spreading 1. Mid-ocean ridges (MOR)- sea floor spreads & new ocean floor creates underwater mountain chains

17. East Pacific Rise & Others

18. Magnetic polarity

19. Polar Reversals  Late 1950’s began mapping the ocean bottoms  Sonar, gravity and magnetics  Magnetic data showed odd phenomenon  Appeared to be striped  Polarity reversal were identical on each side of oceanic ridge  1960, Harry Hess proposes sea- floor spreading  Confirmed by mini-Submarine Alvin in 1960’s

21. Reversed magnetism seen in Rocks.

24. Final Proof… The age of the ocean bottom.  1968 United State Geologic Survey (USGS)  Deep sea drilling w/ Glomar Challenger  Drilling showed the age correlation in ocean floor rocks.  Where do you think the oldest rocks are located on the sea floor? Youngest?

25. What's happening at the other end of the sea floor spreading centers???? 3. Subduction- process of the ocean floor sinking back into mantle a. Deep-ocean trenches- deep water canyons in ocean

27. Sea-floor Spreading MOR-New ocean crust Asthenosphere Melting Subduction