1. Fact or Fiction? You decide!!!!!!!!!!!!
CONTINENTAL DRIFT
Fact or Fiction?
You decide!!!!!!!!!!!!

2. Continental Drift
Hypothesis that states that the continents once formed a single landmass about 245 million years ago, broke up, and drifted slowly to their present day locations.
This hypothesis was presented by a German meteorologist named Alfred Wegener in 1912.

3. Pangaea
Mr. Wegener suggested that all of the continents were joined together at some time in the past like a big puzzle.
They were connected as one large landmass or super continent known as Pangaea.
Pangaea means “all land” in Greek.
The giant ocean that formed was called Panthalessa (“all sea”).
Pangaea later broke up in to 2 pieces: Laurasia and Gondwana.

5. Why was his hypothesis so CONTROVERSIAL?
For scientists to believe a new theory or idea, what do they want?
The evidence Wegener presented was not enough to convince the other scientists.
Other scientists could not understand what force could cause the crust to move in this way.
Not until well after his death in 1930 was his idea accepted.

6. What was his evidence? CLUE #1—The Puzzle-like Fit
Wegener noticed that many of the continents fit together like puzzle pieces.
Notice the outlines of South America and Africa.

7. What was the evidence? CLUE #2---MESOSAURUS fossil
The Mesosaurus was a swimming reptile that lived in freshwater.
Fossils of the Mesosaurus have been found in South America and Africa.
How could fossils of Mesosaurus be found on land areas separated by a large ocean of salt water?
What do you think Wegener hypothesized?

9. What is the evidence? CLUE #3—GLOSSOPTERIS fossil
Plant fossil that has been found in Africa, Australia, India, South America, and Antarctica.
The catch….it was a tropical plant.
Why would this be a clue?

10. What is the evidence? CLUE #4---Climate
Evidence of deposits from glaciers were found in South America, Africa, India, and Australia.
They also found rocks whose surfaces were scoured and polished by glaciers.
What does this tell us about those continents?

11. What is the evidence? CLUE #5---Rocks
If the continents were connected at one time, then rocks that make up the continents should be the same in locations where they were joined.
Well…similar rock structures have been found on different continents.
Parts of the Appalachian Mountains of the eastern U.S. are similar to those found in Greenland and western Europe.
Rocks in eastern South America and western Africa are also similar.

12. What do scientists think now?
The majority of scientists now believe in Wegener’s idea.
They have established a concept known as seafloor spreading that explains HOW the continents moved.

13. Seafloor Spreading
Seafloor spreading is the process by which new oceanic crust forms as magma rises toward the surface and solidifies(turns into a solid).
Mid-ocean ridges are places where new sea-floor is being created. They are underwater mountain chains that run through the Earth’s ocean basins.
As tectonic plates move away from each other, the seafloor spreads apart and magma fills in the gaps.
Where is the oldest seafloor? Where is the youngest?