1. III. Continental drift

2. 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

3. A. Drifting Continents
1. Alfred Wegener- German Scientist, Wegener’s hypothesized that all continents were once joined together is a single landmass & drifted apart

4. Theory is called: Continental Drift
1st formed Pangaea “super continent”

5. B. Continental Drift Evidence
1. Similar landforms a. Mountain ranges of S. America & Africa line-up b. coal fields of N. America & Europe

6. 2. Fossils- similar fossils found where landforms match

8. 3. Continent’s climate have change when the land drifted.

9. http://science. discovery

10. Wegener’s hypothesis rejected- couldn’t explain why the continents move.
= Convection currents

11. Is there other evidences?
YES!

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

14. What Changed? 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
What Changed?

16. Magnetic Reversals

17. http://science. discovery

19. Final Proof 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?

20. 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 Marianas Trench - 3 min

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

23. Sea-floor spreading activity
Red Textbook: Pg. 148
Answer Analyze & Conclude Questions: 1-6