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=23 . 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. What do glaciers leave behind when they retreat?
2. Describe how snow is converted to glacial ice.
3. What part of a glacier moves quickest? What part moves slowest?
4. What is basal slip?
5. Why do continental ice sheets flow away from their center?
6. What is the snowline?
7. What are striations?
8. What is till?
9. What are moraines?
10. Summarize the theories concerning the origin of ice ages.
11. Why do rivers often run faster during an ice age?
12. How do atmospheric CO₂ levels relate to ice ages?
13. How long ago did the last ice age end?
14. How much have atmospheric CO₂ levels increased since 1850? Why has this happened?