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24. Some of the oldest fossils are about how many years old? 34. The numerical dates associated with events on the geologic time
a. 4.55 billion scale were determined by
b. 3.5 billion a. relative dating of the rate of sediment deposition.
c. 250 million b. radiometric dating using radioactive decay.
d. 10,000 c. the temperature of Earth.
25. According to the evidence, a human footprint found preserved in d. the rate that salt is being added to the ocean.
baked clay is about 5,000 years old. According to the definitions 35. Which of the following is not a fossil?
used by paleontologists, this footprint is a (an) a. Dinosaur footprints
a. fossil since it is an indication of former life. b. Petrified wood
b. mold since it preserves the shape. c. Saber-toothed tiger bones
c. actual fossil since it is preserved. d. Pieces of ancient Native American pottery
d. None of the above is correct. 36. An early record about the discovery of fossils and connection of
26. A fossil of a fly, if found, would most likely be fossils to living organisms comes from the
a. a cast. a. ancient Greeks.
b. formed by mineralization. b. ancient Romans.
c. preserved in amber. c. Babylonians.
d. Any of the above is correct. d. Vikings.
27. Which of the basic guiding principles used to read a story of geologic 37. Signs of activity that are a type of fossil preservation include all but
events tells you that layers of undisturbed sedimentary rocks have a. tracks.
progressively older layers as you move toward the bottom? b. footprints.
a. Superposition c. burrows.
b. Horizontality d. shells.
c. Crosscutting relationships 38. The observation that sediments are commonly deposited in
d. None of the above is correct. flat-lying layers is called the
28. In any sequence of sedimentary rock layers that has not been a. principle of uniformity.
subjected to stresses, you would expect to find b. principle of superposition.
a. essentially horizontal stratified layers. c. principle of original horizontality.
b. the oldest layers at the bottom and the youngest at the top. d. principle of crosscutting relationships.
c. no faults, folds, or intrusions in the rock layers. 39. A geologic feature that cuts across or is intruded into a rock
d. All of the above are correct. mass must be younger than the rock mass. This is based on the
29. An unconformity is a a. principle of uniformity.
a. rock bed that is not horizontal. b. principle of superposition.
b. rock bed that has been folded. c. principle of original horizontality.
c. rock sequence with rocks missing from the sequence. d. principle of crosscutting relationships.
d. All of the above are correct. 40. Criteria for a geologic clock process do not include that the
30. Correlation and relative dating of rock units are made possible a. process must have been operating since Earth began.
by application of the b. process must be measurable.
a. principle of crosscutting relationships. c. process must be uniform or subject to averaging.
b. principle of faunal succession. d. process must include humans.
c. principle of superposition. 41. How many eons has there been since the birth of Earth?
d. All of the above are correct. a. 2
31. The geologic time scale identified major blocks of time in Earth’s b. 4
past by c. 16
a. major worldwide extinctions of life on Earth. d. Over 100
b. the beginning of radioactive decay of certain unstable 42. The geologic eon that is known for abundant fossil records and
elements. living organisms is called
c. measuring reversals in Earth’s magnetic field. a. Precambrian.
d. None of the above is correct. b. Postcambrian.
32. You would expect to find the least number of fossils in rocks c. Phanerozoic.
from which era? d. Post-Phanerozoic.
a. Cenozoic 43. The earliest abundant fossils are found in what era?
b. Mesozoic a. Cenozoic
c. Paleozoic b. Mesozoic
d. Precambrian c. Paleozoic
33. You would expect to find fossils of life very different from d. Phanerozoic
anything living today in rocks from which era? 44. Dinosaurs first appeared in what era?
a. Cenozoic a. Cenozoic
b. Mesozoic b. Mesozoic
c. Paleozoic c. Paleozoic
d. Precambrian d. Phanerozoic

21-17 CHAPTER 21 Geologic Time 537