Text Work… Read pages 110 – 111, 114-116 Complete questions on page 118 #1, 2abc, 3, 4

1. What was probably the first evidence that led people to think that the continents were once connected? The first evidence that led people to think that the continents were once connected was the shape of South America and Africa. They look like they could fit together. (p. 114)

2.a) What did Alfred Wegener mean by “continental drift”? “Continental drift” is a theory that proposes that 300 million years ago, all of Earth’s land masses, which are in constant motion, collided to form one supercontinent called Pangaea. About 200 million years ago Pangaea broke apart and the continents have drifted apart to their present locations. (glossary)

2.b) What proof did he have to support this theory? He saw the jigsaw fit between South America and Africa. He found fossils of the same plants and animals on both continents. There are mountains of similar age and structure on both sides of the Atlantic. Ice sheets covered parts of southern Africa, India, Australia, and South America. How could ice have developed in places that are so warm today? (p. 115)

2.c) Why did most scientists of his day disagree with his theory? Most scientists at the time did not accept Wegener’s theory because he could not explain what force was powerful enough to move continents.

3. Explain the theory of plate tectonics. The theory of plate tectonics states that Earth’s outer shell is made up of about 20 plates, made up of continental and oceanic crust. These plates float on a layer of hot rock which moves like slow moving plastic (or frozen maple syrup!). No one knows why the plates move. (p. 114)

4. Why are most earthquakes and volcanoes located near plate boundaries? … (think!) Most earthquakes and volcanoes occur near plate boundaries because this is where the plates come into contact with one another (pushing together and pulling apart).