B 200 C 100 D 25 E 50 After one half life youve gone from 400 parents to 200

B 200 c 100 d 25 e 50 after one half life youve gone

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B. 200. C. 100. D. 25. E. 50. After one half-life, you’ve gone from 400 parents to 200; after a second half-life you go from 200 parents to 100, and after a third half-life you go from 100 parents to 50. (Typical studies of radioactive decay use many more atoms, to avoid statistical fluctuations, but the question says “on average”, so we asked you about 400 rather than 400,000,000,000,000 to make the math easier.) Points Earned: 1/1 Correct Answer: E Your Response: E 9. In age dating, geologists use: A. Cross-cutting relationships for absolute ages, and uniformitarianism for relative ages. B. Radiometric techniques and layer-counting for absolute dating of events that happened in the last 100,000 years, and other radiometric techniques for absolute dating of much older events. C. Radiometric techniques for relative dating of events that happened in the last 100,000 years, and layer-counting for relative dating of events that happened billions of years ago. D. Radiometric techniques and layer-counting for relative dating of events that happened in the last 100,000 years, and other radiometric techniques for relative dating of much older events. E. Radiometric techniques for absolute dating of events that happened in the last 100,000 years, and other radiometric techniques and layer-counting for absolute dating of much
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older events. If you want an absolute date (number of years) rather than older/younger, you can count layers for young things, or use radiometric techniques for young things or for old ones. Points Earned: 1/1 Correct Answer: B Your Response: B 10. What is indicated by the yellow lines in the image above? A. A great fault, where push-together action shoved the upper rocks over the lower ones. B. A great fault, where pull-apart action slid the upper rocks across the lower ones. C. A great unconformity, with sedimentary rocks above resting on older sedimentary rocks below. D. An intrusion, with melted rocks squirted along the yellow line and then hardened. E. A great unconformity, with sedimentary rocks above resting on metamorphic rocks below. John Wesley Powell, of the United States Geological Survey, and the leader of the first boat trip through the Grand Canyon, called the feature marked by the yellow lines “The Great Unconformity”. It separates horizontal Paleozoic sedimentary rocks, above, from inclined Precambrian sedimentary rocks, below. Points Earned: 1/1 Correct Answer: C Your Response: C
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11. In the photograph above, a portion of cliff about 30 feet high is shown. From what location in the Grand Canyon did Dr. Alley take this image? A. In the gift shop, where artists have painted the cliff to look like real rocks. B. Near the top, in sedimentary rocks that slumped downhill when they were soft, folding the rocks. C. Near the west end, where lava that came up pull-apart faults folded while flowing before hardening fully.
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