1. You walk down the beach on Cape Cod, where waves have been bouncing shells around, including pieces of moon-snail shells, as shown here. You find 10 identical shell pieces. All 10 look either like A or like B, but not with 5 of each. Instead, 9 of the 10 shell pieces look like one of the pictures (either A or B), while only the 10th shell piece looks like the other picture. It is very likely that this 10th shell piece looks like: A) A B) B Feedback: The shell has a hollow side, shown turned upward toward you in B, while in A the hollow side is down. Waves tend to flip shells hollow-side-down, so moon-snail pieces on beaches usually look like A and only occasionally like B. Table for Individual Question Feedback Points Earned: 0.0/2.0 Correct Answer(s): B 2.
Dr. Alley took this picture in Arches National Park. That is his finger. The sun was shining along the arrow, as shown, casting the shadows you see. The picture shows hard stone that was once soft sediment. Examination of the sample tells a geologist that mud cracking was occurring where the sample formed. Are you looking at the side that was down when the sediment was soft, or the side that was up? A) Side that was down B) Side that was up Feedback: Mud cracks extend downward into soft sediment. When more sediment is washed in, this second layer will fill the cracks beneath. Later, after the layers have hardened, the rock may be turned upside-down and then the layers cracked apart (or, the layers cracked apart and then turned upside-down). If you see ridges in a mud-crack pattern, you are looking at the side of the second layer that originally was down. You can tell that this picture shows ridges, and not holes, by the shadows—ridges have a light on one side and a shadow on the other, as seen here, whereas holes have light and shadow on the same side.
You've reached the end of your free preview.
Want to read all 7 pages?
- Fall '08
- Correct Answer, Individual Question, geologist