to go out on a narrow point with a jackhammer the tourist said no because the

# To go out on a narrow point with a jackhammer the

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to go out on a narrow point with a jackhammer, the tourist said no, because the rocks might fall off and slide down into the Canyon. When the professor pointed out the many places that rocks had fallen off and slid down, the quick­witted tourist figured out that the Canyon has been widened by such rockfalls as the river has cut downward. 6. The age of the Earth can be estimated in many ways. Which statement below is most accurate (remember that uniformitarian calculations involve looking at the thickness and type of sedimentary rocks, and similar things, but do NOT include radiometric dating or counting of annual layers)? A) Annual­layer counting shows that the Earth is more than about 100 million years old. B) Annual­layer counting shows that the Earth is more than about 100 thousand years old, uniformitarian calculations show that the Earth is more than about 100 million years old, but we don’t know how to estimate how Points Earned: 1.0/1.0 Correct Answer(s): C Points Earned: 1.0/1.0 Correct Answer(s): E Points Earned: 1.0/1.0 Correct Answer(s): D
11/3/2016 RockOn #10 3/8 much more than 100 million years the Earth is. C) Annual­layer counting shows that the Earth is more than about 100 thousand years old, uniformitarian calculations show that the Earth is more than about 100 million years old, and radiometric techniques tell us how old the Earth is. D) Annual­layer counting shows that the Earth is 4.6 billion years old. E) Uniformitarian calculations show that the Earth is 4.6 billion years old. 7. One practical radioactive system used to date lava flows involves: A) The gas argon­40, which decays to the gas potassium­40. B) The gas argon­40, which decays to solid potassium­40. C) The solid potassium­40, which decays to solid argon­40. D) The solid potassium­40, which decays to the gas argon­40. E) The solid potassium­40, which decays to the solid moosemossium­41. Feedback: Potassium­40 is common in solid minerals, and decays to produce the gas argon­40. And despite his great contributions to humanity, no one has named an isotope after moose moss (the favorite food of Thidwick, for you Dr. Suess fans). 8. You start with 400 parent atoms of a particular radioactive type, which decays to give stable offspring. You wait just long enough for three half lives to pass. You should expect to have how many parent atoms remaining (on average): A) 400. B) 200. C) 100. D) 50. E) 25. Feedback: After one half­life, you’ve gone from 400 parents to 200; after a second half­life you go from 200 parents to 100, and after a third half­life 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.) 9.

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• Fall '08
• ALLEY,RICHARDBANANDAKRISHNAN,SR
• Rockon 10, Quiz 10, Correct Answer