A. Wegener believed that the continents had drifted (moved) because of:
1. the shape of the continents.
2. matching rocks and fossils found on different continents.
B. About 200 million years ago, all the continents were joined in one large land mass called Pangaea.
1. He believed that the supercontinent existed because the same rocks and fossils can be found in South America and Africa.
2. The supercontinent theory also explained coal deposits in the Antarctic.

I have a message taped to the board. If you can read the message and you think you understand the message because you know how the pieces fit together, and because the message makes sense.

In 1912, Wegener advanced what he called the theory of continental drift. Besides the fact that the shape of the continents suggested that they had once been together, he cited other reasons. Among them were reports that similar fossils were found in rock from Africa and South America. These fossils could not occur on two continents separated by vast ocean unless the continents were once part of a single land mass. In Wegener's mind, continental drift was the only way to explain the evidence.

Wegener's theory was initially rejected by other scientists. (Ask students to give reasons why they think other scientists might have rejected Wegener's theory.) (Students' reasons should include the fact that Wegener did not know how or why the continents drifted. Other scientists wanted to know what caused South America to separate from Africa and move across the Atlantic Ocean.

The mechanism for continental drift was not discovered until the early 1950's when scientist began to map the ocean floor. In the middle of the ocean they found a long chain of mountains that seemed to circle the earth. This mountain system, the longest in the world, is called the mid-ocean ridge. It is also the sight where new crust is created. As new crust is created, the Atlantic gets larger, and Africa and South America gets farther apart.

Today, Wegener's idea is included in plate tectonics, the theory that the earth's surface is made up of large moving plates.

An excellent laboratory activity can be found in Challenges to Science, Earth Science, Second Edition, pp. 352 & 353.

1. State the theory of continental drift in your words.
2. What was the name of the supercontinent?
3. What evidence supports the theory of continental drift?
4. The theory that the earth's crust is made up of large moving plates is called what?

1. Who was the first to advance the theory of continental drift?
2. What was Pangaea?
3. Why was the theory of continental drift initially rejected?
4. Besides matching rocks and fossils, what other evidence suggested that the continents had drifted?

Holt General Science, Elements of Ecology, Investigating the Earth, and Challenges to Science Earth Science.
American Geological Institute. Investigating the Earth. Third Ed. U.S.A.: Hopughton Mifflin Company, 1978.
Head, J.J. Biogeography. North Carolina: Carolina Biological Supply Company, 1986.
Heller, Robert. Challenges to Science Earth Science. Second Ed. New York: Webster Division, McGraw-Hill Book Company, 1979.
Kormondy, Edward J., Bernice E. Essenfeld. Addison-Wesley Biology. California: Addison-Wesley Publishing Company, 1984.
Ramsely, William L., et al. Holt General Science. New York: Holt, Rinehart, and Winston, 1983.

Continental Drift Film. Earthquake Center, Memphis State University, 38152, Phone 901-454-2007