Evidence for
Plate Tectonics (6-8)
 
Introductory activity

Testing the fit

This short activity serves as a good introduction to Alfred Wegener’s ideas about continental drift and how he tested his hypothesis.

Grades: 6-8

Materials:

Advance preparation:

Time: 15-20 minutes

Grouping: groups of 3-4 and whole class

Vocabulary: hypothesis, Pangaea

Teacher background: Alfred Wegener (1880-1930)


Procedure:

1. Pass out a bag of magazine pieces to each team of students. Tell the students to open the bag and take no more than five minutes to create something with the contents. No further directions are necessary at this point. Students will begin to move the pieces about and most groups will “automatically” try to re-create the magazine page. Depending upon the intricacy of the page(s) you select, this may well take less than five minutes.

2. When most of the groups have finished moving pieces about, ask them to describe what they created and to explain why they did what they did. If some groups did not re-create the magazine page, simply focus on those groups that did. [E.g., “Several groups seemed to have created roughly the same thing. What made you decide to do what you did?”

3. Guide the discussion so that students recognize that there were some “clues” on the pieces of paper that led them to the assumption that the pieces would fit together to re-create a single page from a magazine.

4. Further guide the discussion to connect this activity to developing and testing a hypothesis. Students looked at the pieces of paper (made observations) and made a hypothesis that originally the pieces fit together. They used the “clues” (shape, text, colors, patterns) to test this hypothesis. Make sure that the students understand that shape alone would not have supported the hypothesis.

5. Many of the students will have heard of continental drift, Alfred Wegener, and/or plate tectonics. This is a good time to introduce the initial hypothesis of Wegener that the continents were no longer in the same positions that they were in the past.

6. Read the following information to your students and place a large version of the map on the overhead projector:

In the autumn of 1911, Wegener came across a scientific paper that listed fossils of identical plants and animals found on opposite sides of the Atlantic. Intrigued by this information, Wegener began to look for, and find, more cases of similar organisms separated by great oceans. He proposed, therefore, that land bridges once connected these far-flung continents and that they have subsequently sunk. But Wegener noticed the close fit between the coastlines of Africa and South America. Might the similarities among organisms be due, not to land bridges, but to the continents having been joined together at one time? As he later wrote: "A conviction of the fundamental soundness of the idea took root in my mind."

Wegener proposed that about 300 million years ago, the continents had formed a single mass, called Pangaea (from the Greek for "all the Earth"). Pangaea had rifted, or split, and its pieces had been moving away from each other ever since.

Wegener was not the first to suggest that the continents had once been connected, but he was the first to present extensive evidence from several fields. However, Wegener recognized that he would need a large amount of evidence to support such a theory.

7. Say to your students:
With the luxury of time, additional research and technology, we may be able to help Wegener out. We are going to examine four lines of evidence: fossil distribution, earthquakes, volcanoes, and sea-floor spreading.

Information adapted from UC Museum of Paleontology website: Alfred Wegener (1880-1930)