6.4  Plate  Tectonics:  Continental  Drift       7  Science  Matters    

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Name ______________________

Video Review Directions: While watching the video, answer the “You Decide” questions as they are presented in the video. Answer the Video Quiz questions at the end of the video. You Decide: 1. What is the longest mountain range in the world?

Answer ________________

2. What is a tectonic plate?

Answer ________________

3. What force formed these volcanic mountains?

Answer ________________

4. Where is most of earth’s new crust found?

Answer ________________

Video Quiz:

1. Wegner introduced the idea of continental __________________.

2. The largest mountain range in the world is the ______________ ridge.

3. Oceanic rocks are ____________ than rocks on continents.

4. Sea-floor spreading is the process of plates _______________.

5. Tectonic plates consist of the _______________ and the upper mantle.

6. The largest plate is the _____________________ plate.

7. A _____________________ boundary occurs where two plates collide.

8. ____________________ occurs when one plate thrusts under another.

9. The San Andreas Fault is a ___________________ fault.

10. Iceland straddles the _____________________ ridge.

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6.4  Plate  Tectonics:  Continental  Drift       10  Science  Matters    

Answers Video Review (pg. 22) 1. Mid-ocean ridges make up the longest mountain range in the world.

2. Tectonic plates consist of the crust and upper mantle, which when combined make

up the lithosphere.

3. The movement of lithospheric plates is responsible for forming these volcanic

mountains.

4. Most of the earth’s new crust is found on the ocean floors where molten rock rises to

the surface as plates separate.

Video Quiz (pg. 22) 1. drift 2. mid-ocean 3. younger 4. separating 5. crust 6. Pacific 7. convergent 8. subduction 9. transform 10. mid-Atlantic  

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Reader’s Theater:

Alfred Wegener and Pangaea What is Pangaea? Scientist Alfred Wegener (1880-1930) believed that long ago the seven continents were joined together, forming a supercontinent he called Pangaea. Characters:

• Alfred Wegener

• The Seven Continents: Africa, Antarctica, Asia Australia, Europe, North America, South America

The setting is planet Earth, and Wegner is taking the stage. Wegener (to audience): Good afternoon, I am a German scientist Alfred Wegener. Europe (aside): His name is pronounced “VAY-guh-ner.” Wegener: My friends and I are here to present my theory of continental drift, which I published in the year 1915. North America (shocked): Did you say “continental drift?” Are you suggesting the continents move? Wegener: Don’t act so surprised! Surely you know that continents move during earthquakes and volcanic eruptions. North America: Yes, but- Wegener (holding up one hand at North America): Let me tell you my story. Then you will understand. It all started when I was a young man fascinated by maps. One day I noticed that the coasts of two continents appear to fit together, like pieces of a jigsaw puzzle. Africa and South America, will you demonstrate? Africa (moving toward South America): If I turn a little this way, and South America rotates that way… South America: Yes, we could fit together, couldn’t we? Wegener: Yes! That got me thinking. I found out that nearly identical fossils have been discovered on both sides of the Atlantic Ocean, as well as identical rock layers. There are similar pairs of mountain ranges, too, such as the Scottish Highlands in Europe and in the Appalachians in North America.

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Asia: What are you driving at? Are you saying that some of the continents were once joined? Wegener: Not some of the continents---all of the continents! That’s my theory. Antarctica: Incredible! Wegener: Isn’t it? I called this joined continent Pangaea. That’s Greek for “all the Earth.” Might the seven of you demonstrate what Pangaea looked like? Wegener waves directions. The continents move together to form Pangaea. Australia (stumbling): This is terribly disorienting. Am I still down under? South America: Hey, someone’s stepping on my Galapagos Islands! Antarctica: It’s getting a bit too warm around here. Wegener: Stop right there! Perfect! As you can see, the continents fit together into one supercontinent. According to my theory, this is how Earth looked about 200 million years ago. Africa: So animals could wander from me to South America, is that right? South America: Plant seeds could travel easily, too. Wegener: Right and right. But over the years, slowly but surely, the continents drifted apart. Wegener gestures at the continents. They drift apart, back to their modern-day positions. Australia: Well, it was fun while it lasted! Europe (to the others): Maybe I’ll see you again in another 200 million years or so. Wegener: Perhaps, perhaps. My theory about Pangaea explains a great deal about Earth’s geography. For example, have you noticed that mountain ranges are found mostly near the edges of continents? South America: Now that you mention it, I have a rugged mountain range running along my west coast. North America: That’s funny, so do I!

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6.4  Plate  Tectonics:  Continental  Drift       17  Science  Matters    

Wegener: According to my theory, mountains arise when continents move into each other. For example, the Himalayas rose when India slammed into the rest of Asia. Asia: Ouch! North America: Well, Mr. Wegener, you seem to have solved all the mysteries of our planet. So tell us: Just how did continents move around the planet? Wegener (shaking his head): Well, you’ve hit upon the weakness of my theory. I could only guess at how the continents moved. Many of my critics enjoyed pointing this out. Continents gather around Wegener and pat him on the back in consolation. Wegener: It’s okay. After my time, people decided that I was correct. You see, scientists began studying the ocean floor. Asia: What do oceans have to with anything? Wegener: A great deal. Scientists have discovered giant mountain chains, called mid-ocean ridges, in the ocean’s depths. In these ridges, molten rocks rise from below Earth’s surface and become part of the ocean floor. Europe: So what does that mean? Wegener: It means that the ocean floors are moving, too! Oceans and continents move in giant slabs that scientists call tectonic plates. If I’d lived long enough, I would have studied tectonic plates myself. Australia: I’d like to thank Mr. Wegener for proposing new ideas that challenged old ones. That’s very important in science. Africa: Plus, he used evidence from many different branches of science. North America: A keen observer and a logical thinker—that’s our Mr. Wegener! Wegener: Why thank you, my friends, I am truly—moved! All laugh.

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