1. What????

2. The DeLorean “Time Machine”

3. Drifting Apart: The Theory of “Continental Drift”

4. What’s the meaning of “Continental Drift”?
Earth’s crust is constantly moving
horizontal
vertical
Crust is drifting on top of the mantle (asthenosphere)
Two types of crust
Continental and Oceanic
Shape and location of the continents and oceans have changed over millions of years (Constructive & Destructive Forces)

5. Alfred Wegener
He hypothesized about 300 MYA the Earth had only one giant continent called Pangaea (meaning “all lands”)
Published The Origin of Continents and Oceans in 1915
Evidence supporting the theory:
Puzzle-Like Fit
Fossil records
Rock sequences
Climates and changing polar regions
Mountain Ranges

6. Alexander Du Toit
Proposed that 200 M.Y.A., Pangaea broke up into two supercontinents:
Gondwanaland
S.A., Africa, Antarctica, Australia, India
Laurasia
N. A., Eurasia (Europe and Asia)
Pangaea was surrounded by a sea called Panthalassa

8. Evidence for Continental Drift
Evidence #1: Puzzle-Like Fit
Matching coastal lines fit together like a jigsaw puzzle
South America & Africa

10. Evidence for Continental Drift cont.
Evidence #2: Fossil Clues
Similar fossils found on several different continents
Separation by oceans suggests that the continents were once connected
Glossopteris: fern (southern continents)
Cynognathus: land reptile (S.A. & Africa)
Lystrosaurus: land reptile (Africa, Antarctica, & India)
Mesosaurus: freshwater reptile (S.A. & Africa)

12. Evidence for Continental Drift cont.
Evidence #3: Rock Types
Similarities in rock types found in S.A., Africa, India, Antarctica, and Australia
Paleomagnetism
Study of the magnetism of ancient rocks and sediments

13. Continental Drift Evidence
Evidence #4: Climate Clues
Continental ice sheets and glacial markings in South Africa
Fossils of tropical plants found in Spitsbergen (small island north of Norway)
Suggests movement from the equator and the poles

14. Continental Drift Evidence
Evidence #5: Mountain Ranges
Similar mountain ranges
Argentina and South Africa

15. Theory Rejected
Wegener could not explain the forces that push or pull the continents
Geologists rejected his theory of continental drift
Lacked information on formation of mountains and continents
Then new evidence was discovered…
As a Jr. Geologist, what kind of forces (give examples) do you “infer” could be used to “push and pull” the continents around???

16. Can you G.R.A.S.P. Continental Drift?