Read the questions first. Then answer them while watching this episode of "Earth Revealed". If you miss it in class you are still responsible for the viewing this segment and answering the questions. The video is available online at http://www.learner.org/vod/video.html?sid=78&po=3 . The index for these programs is online at http://www.learner.org/resources/series78.html# . If you do not have an internet connection at home, view it after school or during study hall in the media center. Each segment is 30 minutes long.

1. How deep have we drilled into the earth, relative to it's size?
2. What information can geophysicists get from the study of seismic waves?
3. Describe reflection and refraction.
4. Describe the internal structure of the earth.
5. Describe the two fundamentally different types of crustal rock.
6. What is an ophiolite? Describe in detail.
7. Why are ophiolites of special interest to geologists?
8. Describe the two basic types of seismic waves.
9. How do geophysicists use this difference to study the interior of the earth?
10. What happens to P and S-waves when they reach the core of the earth?
11. How is earth's magnetic field used to study the earth?
12. What are paleomagnetism and magnetic field reversals?
13. How often does earth's magnetic field reverse?
14. What concerns do geologists have about future field reversals?