1. A) A B) B 2. Dr. Alley took this picture in Arches National Park. That is his
ID: 155103 • Letter: 1
Question
1.
A) A
B) 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 sample is hard stone now, but it once was soft sediment, and it records formation and
You are still a geologist, still wandering around in a fog with a tea-and-crumpets-toting student, and you walk into another cliff. This one turns out to be a hardened lava flow. Again, you look at a one-foot-square region, sketch pink arrows with A, B, C, and D on that region, and ask the student which of the pink arrows was pointing up just after the lava flow hardened. To help the student, you draw four additional arrows on the cliff; these are light blue (turquoise) arrows, pointing at bubbles. (If you are not able to distinguish pink from light blue, the four pink arrows are very close to the four letters A, B, C, and D, and the four light-blue arrows are not close to the letters.) You suggest that the student consider the behavior of bubbles in a liquid. These bubbles are within the lava flow, and not in the crust on top of the flow that was chilled very rapidly by the air. Your student is brilliant, and correctly tells you the answer. The pink arrow (close to a letter) that was pointing up when the lava flowed in and slowly cooled is the arrow that is closest to: You are a geologist. While walking in the fog one day, you bang into a cliff. After rubbing your sore nose, you inspect the cliff, and see what is shown in the picture, in a one-foot-square area. You recognize that this cliff is made of ??fossil sand dunes??, with wind-blown sand that was later glued together by hard-water deposits. You are accompanied by a student, who is carrying your tea and crumpets for you. You sketch four arrows on the cliff, label them as shown, and ask the student which of the arrows was pointing up when the loose sand was deposited. Your student is brilliant, and correctly tells you the answer. The arrow that was pointing up when the loose sand was deposited is the arrow that is closest to: Dinosaurs once stomped across the Yukon, leaving tracks in mud that were buried in more mud and hardened to stone. Some may have been turned on end or turned over by mountain building; others were split apart and turned over by humans looking for dinosaur tracks and putting them in museums. The light was shining in from the upper right, as indicated, making lighter-looking and darker-looking places depending on whether they were facing the light or in shadow; we have indicated a shadow of the human glove and of the dinosaur track to help guide your eye. Are you looking at the side that was down when the sediment was soft, or the side that was up? This block of rock fell off the Kaibab cliff near the top of the Bright Angel Trail, just below the South Rim of the Grand Canyon, and landed as shown. (No one was hurt by the fall.) Before the material in this block was hardened to rock, the material was soft sediment. Soft sediment often dries out, cracks, and then is buried by more sediment when the water returns. When a limestone is forming, such as this Kaibab Limestone, the drying and wetting may happen with the tides, or in other ways. The sun was high and hot when the picture was taken, but slanting in from the right as shown, and we have provided arrows to direct your eye to the shadow from Dr. Alley??s boot toe as well as to another useful shadow. Is the sample upside-down (you are looking at the side that was down when the sediment was soft) or right-side up (you are looking at the side that was up when the sediment was soft)? 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 sample is hard stone now, but it once was soft sediment, and it records formation and ??fossilization?? of mud cracks. Is this sample upside-down (you are looking at the side of this sample that was down when the sediment was soft) or right-side up (you are looking at the side of this sample that was up when the sediment was soft)? You are looking straight down at what remains of one moon-snail shell, in two different orientations. The pictures were taken with the light shining in from the left, as shown. This shell piece was found on a sandy beach at Cape Cod, and the shell had been moved around by waves on the beach. Based on what we know about shells in waves, which view (A or B) would you most likely have seen if you had been with Dr. Alley when he found this shell?Explanation / Answer
1=A
2=B
3=B
4=A
5=D
6=C
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