1. Warm Up 1. What is the thickest layer of the Earth?
2. What is the thinnest layer of the Earth?
3. What happens to temperature as the depth within the Earth increases?
4. What happens to the density as the depth within the Earth increases?
5. When you put your marshmallow into the candle flame, what type of heat transfer were you modeling?

2. Would someone believe the Asthenosphere is made of Jell-O?

3. It makes sense right?
We know the Asthenosphere is a “plastic solid” or a solid that can move and flow….just like Jell-O!
So why does it sound so crazy?

4. Alfred Wegener (Vegner) got the same response for his theory.

5. Wegener’s Theory of Continental Drift:
All continents had once been joined together in a single land mass (PANGEA) and later began to drift apart.
“Continental Drift”- the idea that the continents slowly move over Earth’s surface.

6. Wegener was not alone in thinking that the continents appeared to fit together like puzzle pieces.
He, however, came up with a theory to suggest that the continents were once joined together and drifted apart.

7. Sit very still! Can you feel the North American plate moving?
It was a pretty radical idea at Wegener’s time to say the continents were moving.
Most scientists were skeptical.
However, Wegener had evidence…..

8. Wegener’s 3 main pieces of evidence:
1. Landforms- Mountain ranges on different continents line up if put together.
This is also true of other
things, like coal deposits.

9. 2. Fossil Evidence
For example, the Mososaurus fossils are found in areas separated by oceans. The reptile could not swim such great distances through salt water. So it is likely that they once lived on a single landmass that split.

11. Also, fossils of the Glossopteris (a fern) have been found in rocks of Africa, South America, Australia, India, and Antarctica!
Finding these fossils on such widely separated landmasses, convinced Wegener that the continents had once been united.

13. 3. Climate Evidence
Wegener used evidence of climate changes to support his theory.
For example, on the island of Spitsbergen, in the Arctic Circle, fossils of tropical plants have been found.
Also, in South
Africa, there
is evidence of
glacial activity!

14. So why didn’t Wegener’s fellow scientists accept his theory?
He was missing one key point to support his theory?
Can you guess what evidence the other scientists wanted to hear?

15. They wanted to know HOW continental drift happened.
Wegener could not provide an explanation for the force that pushes or pulls the continents.
Case closed, not enough evidence!

16. Most scientists believed that the Earth was cooling and shrinking, which created Earth’s mountain ranges. (like the dried up, wrinkled skin of an apple)
Wegener said that if this was true, Mountains should be found all over Earth, but they usually occur in bands along the edges of continents.

17. Unfortunately, Wegener died before his theory was ever accepted.
He went on a Meteorological expedition to Greenland one winter, and got lost in a bad snow storm.

18. continental drift animation link

19. Who can help Wegener now??
Find out by reading pages in your book!
It starts with the discovery of the longest mountain chain in the world.
And with the help of H.H.