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Chapter 18: Geologic Time Multiple Choice 1. In 1869, ____________, who was later to head the U.S. Geological Survey, led a pioneering expedition down the Colorado River and through the Grand Canyon. a. James Ussher b. John Wesley Powell c. William Smith 99 d. John Playfair e. James Hutton 2. Approximately how old is Earth currently thought to be? a. 4 to 5 million years b. 6000 years c. 40 billion years d. 90 million e. none of the above 3. The subdivisions of the geologic time scale that represent the greatest expanse of time are called ____________. a. epoch b. era c. period d. stage e. none of the above 100 4. Which one of the following represents the greatest expanse of time? a. Mesozoic b. Cenozoic c. Precambrian d. Paleozoic 5. By applying the law of superposition, ____________ dates can be determined. a. numerical b. radiometric c. relative d. isotope e. both numerical and radiometric 6. The era of "ancient life" is the _________ era. a. Cenozoic 101 b. Precambrian c. Neolithic d. Mesozoic e. none of the above 7. The era of "recent life" is the _________ era. a. Cenozoic b. Precambrian c. Neolithic d. Mesozoic e. none of the above 8. About 85 percent of geologic time is repre- sented by the time span called the ____________. a. Paleozoic b. Stone Age c. Precambrian 102 d. Cretaceous e. Ordovician 9. When a beta particle is emitted during radioactive decay ____________. a. the atomic number remains the same b. the atomic number decreases by 1 c. the atomic number increases by 1 d. the mass number drops by 1 and the atomic number remains unchanged e. none of the above 10. If a radioactive isotope (atomic number 90, mass number 232) emits 6 alpha particles and 4 beta particles during the course of radioactive decay, what is the atomic number and mass number of the stable daughter product? a. atomic number 100, mass number 256 103 b. atomic number 82, mass number 208 c. atomic number 98, mass number 222 d. atomic number 74, mass number 208 e. none of the above Geologic Time 11. If the half-life of a material x is 1000 years and you found a specimen with equal amounts of material x and material z (the daughter product) the specimen would be about ____________. a. 500 years old b. 1000 years old c. 1500 years old d. 2000 years old 104 e. it is not possible to determine from the information given 12. Abundant fossil evidence did not appear in the geologic record until about _________ years ago. a. 5 billion b. 6 million c. 600 million d. 300 million e. 3 billion 13. Of 5 undeformed horizontal beds of sedi- mentary rock, we can say that _________. a. the top layer is oldest b. the lowest layer is oldest c. the third layer from the bottom is older than the second layer from the bottom 105 d. there is no way of knowing which layer is oldest 14. An unconformity is a(n) ____________.... View Full Document

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