1. __________________ THEORY
Continental Drift
__________________ THEORY

2. Today’s Objectives be able to describe the Continental Drift Theory
be able to describe the evidence for the Continental Drift Theory including:
Jigsaw puzzle fit of continents
Geological structures
Fossils
Climatic evidence

3. What might you notice about the continents on this map?

4. Continental Drift…
This theory was proposed by Alfred Wegener, a German scientist about 100 years ago.
He hypothesized that the continents were not always in the same location that they are today, but that they have “drifted” there over millions of years.

5. He proposed that millions of years ago – the continents were all attached in one “super-continent” called PANGAEA.
In Greek:
Pan – means “all”
Gaea means “Earth”

6. His theory of what happened…
250 million years ago, was Pangaea
220 million years ago… it started to drift apart.

7. Continental Drift Theory
the continents are still moving today

8. How did he come up with this theory… Evidence.
#1: He looked at maps of the world and noticed all the continents looked like puzzle pieces that “fit together”.
North America
Africa
South America

9. #2- Matching Geologic Structures
Mountain Ranges: He noticed that mountain ranges that began on one continent, then ended at the coast-line, seemed to continue on another continent across the Ocean!

10. Matching Geologic Structures
Rock structures: such as Folds in the Earth’s crust, and the types of rocks were similar on different continents
Eg. Rocks found in Newfoundland (North American continent) are the same type and age as rocks found in Greenland and Ireland/Scotland (European Continent)
Giant’s Causeway
(Ireland and Scotland)

11. #3- Matching Fossils
Wegener found that similar fossils are found on different continents despite the continents being separated by vast oceans
How did the creatures get between the continents?
Creatures could not swim or fly that great of distance
Most likely explanation = continents were closer together at some point in time

13. #3- Matching Fossils
One fossil that intrigued him was Mesosaurus (a sharp-toothed freshwater reptile). These fossils have only been found in 2 places – Southeastern “South America” and Southwest “Africa”

15. There were many other fossils where he found the same thing.
Gossopteris (a fern). It’s fossils were found on every continent including Antarctica…It can’t grow in cold temperatures, so Antarctica must have been warmer millions of years ago because it must have been closer to the equator.

16. Cynognathus and Lystrosaurus (land dwelling creatures) Fossils found on different continents. They could not have swam that far to get onto different continents …so the continents must have been joined.

17. #4- Climatic Evidence Paleoglaciation
Rock markings left behind from ancient glaciers
suggest tropical regions may have once been more polar
(allowing for the formation of glaciers)
This suggests that the continents were once closer together

18. More Climatic Evidence
Coal deposits
coal is formed from decay of tropical plants
coal deposits are found in Antarctica
suggests Antarctica was once a tropical climate that was closer to the equator 18

19. Summary of Evidence for Continental Drift…
1) Map show that continents fit together like ________ ________
puzzle pieces
2) __________ _________ that seem to be split between 2 distant continents
Mountain ranges
3) _________ found on different continents
Fossils
4) ______________ pattern that makes sense if continents were once connected
Paleoglaciation

20. LOOK at the evidence:

21. Summary of Continental Drift