Geologic Time Scale Practice Test – Flashcards
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Which of the following ideas do geologists use as they study Earth? a. the rock record provides evidence of past geological events and life forms b. processes in the present acted in the past c. Earth is very old and has changed over time d. All of the above
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D
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In what type of rocks would geologists most likely find evidence of past life forms? a.metamorphic rocks b.igneous rocks c. volcanic rocks d. sedimentary rocks
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D
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The geologic process that shape Earths Surface today __________. a. are basically the same as they were in the geologic past b. are much different than thousands of years ago c. did not operate in the distant past d. became important only several hundred years ago
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A
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What scientist is credited with proposing the principle of uniformitarianism? a. James Hutton c. John Wesley Powell b. William Smith d. Nicolaus Steno
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A
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The physical, chemical, and biological laws that operate today have also operated in the geologic past. This statement relates to the principle of ____. a. superposition c. uniformitarianism b. cross-cutting relationships d. correlation
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C
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The present is the key to the past. This statement rephrases the ____. a. principle of cross-cutting relationships b. law of gravity c. principle of uniformitarianism d. principle of original horizontality
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C
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According to the principle of cross-cutting relationships, an intrusive rock body is ____. a. deposited as sedimentary layers b. always made of the same materials as rock around it c. older than the rocks into which it intrudes d. younger than the rocks into which it intrudes
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D
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Nicolaus Steno proposed the most basic principle of relative dating, the law of ____. a. correlation c. superposition b. fossil succession d. gravity
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C
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The dating process that places geologic events in proper sequence is referred to as a ____. a. radiometric dating c. numerical dating b. relative dating d. temporary dating
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B
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In general, the law of superposition states that in an undeformed sequence of sedimentary rocks, each layer is ____. a. basically the same age c. older than the one below it b. older than the one above it d. thicker than the one above it
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B
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If a mass of granite is in contact with a layer of sandstone that contains small pieces of the granite, which rock is older? a. the sandstone b. the granite c. Both are the same age. d. It is not possible to determine which rock is older from this information.
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B
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A break that separates older metamorphic rocks from younger sedimentary rocks immediately above them is a type of unconformity called a(n) ____. a. disconformity c. angular unconformity b. nonconformity d. conformity
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B
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What type of unconformity consists of tilted sedimentary rocks that are overlain by younger, more flat-lying sedimentary rocks? a. angular unconformity c. nonconformity b. disconformity d. conformity
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A
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Which type of geologic event has to occur to create an angular conformity? a. uninterrupted deposition of sediment b. igneous intrusion into layered rock c. sediment deposited on older, eroded igneous rock d. folding or tilting of rock layers, followed by renewed deposition
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D
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An unconformity is a(n) ____. a. layer of sedimentary rocks c. intrusion b. gap in the rock record d. layer of rocks with unusual fossils
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B
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After examining a sequence of horizontal sedimentary rocks, you determine that there is a considerable span of time for which no sedimentary rock layers exist at this location. You have discovered a(n) ____. a. angular unconformity c. nonconformity b. disconformity d. sequence of correlated strata
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B
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Fossils are the ____. a. oldest layers of rock in a region b. remains or traces of prehistoric life c.living creatures with habitats in or around rock d. objects that people of long ago left behind as artifacts
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BA
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what type of rocks are most fossils found? a. sedimentary rocks c. metamorphic rocks b. igneous rocks d. granite and marble
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A
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Which of the following environments would most likely NOT contain fossils? a. sediment deposited in a riverbed b. a thick deposit of dried mud c. layers of sand that accumulate over thousands of years d. intrusive rock formed from cooled magma
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D
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What determines the type of fossil that is formed? a. the conditions under which the organism was metamorphosed and how it was buried b. the conditions under which the organism died and how it lived c. the conditions under which the organism died and how it was buried d. the conditions under which the organism lived and how it was buried
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C
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The footprints of a dinosaur are an example of what type of fossil? a. unaltered remains c. carbonized remains b. mold d. trace fossil
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D
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Which of the following is important if an organism is to become a fossil? a. slow burial and soft parts c. rapid burial and soft parts b. rapid burial and hard parts d. slow burial and hard parts
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B
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Organisms with hard parts stand a good chance of being fossilized if they are ____. a. rapidly decomposed by bacteria c. rapidly eaten by scavengers B.slowly buried by sediments d. rapidly buried by sediments
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C
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which of the following environments would the shell of an organism most likely be preserved as a fossil? a. on a beach b. on the top of a hill c. at the bottom of a lake buried by a landslide d. on the banks of a dry river bed
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C
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Why would a worm stand a poor chance of being fossilized? a. Worms did not exist in the geologic past. b. Worms have been rare during the geologic past. c. Worms have no hard parts. d. all of the above
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C
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Which of these organisms would have the best chance of becoming part of the fossil record? a. horse c. butterfly b. fish d. ant
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B
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The principle of fossil succession states that different types of fossil organisms ____. a. generally leave behind hard parts b. occur most often in sedimentary rock c. succeed one another in a definite order d. are younger in the deepest layers of rock
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C
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The task of using fossils to match up rocks of similar ages in different areas is called ____. a. succession c. geology b. correlation d. fossilization
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B
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Which of the following must be true for a fossil organism to be useful as an index fossil? a. The fossil organism must be widespread geographically. b. The fossil organism must be abundant. c. The fossil organism must be limited to a short span of geologic time. d. all of the above
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D
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Index fossils allow geologists to ____. a. match rocks of the same age in different regions b. determine the exact age of rocks c. identify organisms that did not leave fossil evidence behind d. determine why some organisms became extinct
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A
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Groups of fossil plants and animals succeed each other in a definite and determinable order, and any period of geologic time can be recognized by its respective fossils. This is a statement of the ____. a. law of superposition c. principle of original horizontality b. principle of cross-cutting relationships d. principle of fossil succession
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D
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Radioactivity is produced when unstable nuclei ____. a. bond together c. become cooler b. break apart d. expand
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B
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The process by which atomic nuclei spontaneously decay is called ____. a. relative dating c. erosion b. radioactivity d. deposition
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B
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The time it takes for 50% of the nuclei in a radioactive sample to decay to its stable isotope is called ____. a. the daughter product c. the half-life b. geologic time d. the half-time
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C
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Radiometric dating is possible because the rates of decay of radioactive isotopes ____. a. change over time c. are constant b. change from place to place d. vary widely
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C
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If the half-life of an unstable isotope is 10,000 years, and only 1/8 of the radioactive parent remains in a sample, how old is the sample? a. 10,000 years old c. 30,000 years old b. 20,000 years old d. 40,000 years old
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C
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Radiocarbon dating is used to date ____. a. recent geologic events up to 75,000 years ago b. recent geologic events up to 10,000 years ago c. distant geologic events more than one million years ago d. all geologic events of the past
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A
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Which two substances do geologists use in radiocarbon dating? a. carbon-12 and carbon-10 c. lead-206 and carbon-14 b. carbon-14 and uranium-238 d. carbon-14 and carbon-12
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D
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In living things, what is the source of the carbon-14 that is used in radiocarbon dating? a. carbon dioxide in rocks c. carbon dioxide in the atmosphere b. carbonic acid in caves d. carbon dioxide in water
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C
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Radiocarbon dating could be used to date which of the following? a. 65-million-year-old meteorite c. 60,000-year-old metamorphic rock b. 15-million-year-old lava flow d. 60,000-year-old mammoth bone
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D
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What length of time does the geologic time scale cover? a. 2.0 million years c. 20.5 billion years b. 4.6 billion years d. 10.1 million years
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B
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Based on interpretations of rock units and changes in fossil life forms, geologists have divided Earth's history into manageable units that are represented by the ____. a. geologic time scale b. fossil time scale d. Precambrian time scale c. geographical time scale
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A
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What is the currently accepted age of Earth? a. about 4.6 million years old b. about 10 billion years old c. about 4.6 billion years old d. about 5.6 billion years old
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C
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The largest expanse of time on the geologic time scale is the ____. a. eon c. era b. epoch d. period
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A
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Which eon of the geologic time scale means "visible life"? a. Phanerozoic b. Proterozoic c. Hadean d. Archean
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A
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The era of "ancient life" is known as the ____. a. Cenozoic b. Paleozoic c. Precambrian d. Mesozoic
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B
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Which of the following lists the divisions of the geologic time scale in order from longest to shortest? a. era, period, epoch c. era, epoch, period b. epoch, period, era d. period, era, epoch
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A
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About 88 percent of Earth's history is within the expanse of time before the Phanerozoic Era called the ____. a. Cambrian c. Cenozoic b. Paleozoic d. Precambrian
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D
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Which of the following is NOT an era of the Phanerozoic Eon? a. Paleozoic c. Mesozoic b. Cenozoic d. Hadean
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D
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When did abundant fossil evidence appear in the geologic record? a. 2.7 billion years ago c. 540 million years ago b. 1.0 billion years ago d. 100 million years ago
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C
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Radiometric dating does not usually work with sedimentary rocks because they ____. a. are too old b. form from many older rock particles c. never have particles that contain radioactive isotopes d. form too quickly to be accurately dated
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B
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The radiometric date of a metamorphic rock most likely represents when the rock was ____. a. originally formed c. heated during metamorphism b. deposited d. exposed at Earth's surface
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A
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62. Rocks record ____________________ and changing life forms of the past.
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Geologic events
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63. The principle of ____________________ states that physical, biological, and chemical processes we observe today have also operated in the geologic past.
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Uniformitariansm
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64. ____________________ tells geologists the sequence, or order, in which events occurred.
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Relative Dating
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65. To assume that rock layers that are tilted have been moved into that position by crustal disturbances is to apply a principle of relative dating known as ________________________.
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Original Horizontality
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66. A(n) ____________________ is a break in the rock record during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed.
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Unconformity
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67. An unconformity in which the sedimentary strata on either side of the unconformity are essentially parallel is referred to as a(n) ____________________.
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Disconformity
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68. The remains or traces of prehistoric life are called ____________________.
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Fossils
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69. Fossils rarely preserve the ____________________ parts of animals because scavengers often eat them and bacteria decompose them.
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Soft
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70. The principle of ____________________ states that fossil organisms succeed one another in a definite and determinable order, and that any time period can be recognized by its fossil content.
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Fossil Succession
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71. A half-life is the amount of time needed for one-half of the ____________________ in a sample to decay to form its stable isotope.
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Nuclei
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72. Using radioactive isotopes to calculate the ages of rocks and minerals is a procedure called ____________________.
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Radiometric dating
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73. ____________________ is used to date recent organic material.
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Carbon-14 dating OR Radiocarbon dating
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74. Eras are divided into ____________________, which can be further divided into ____________________.
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Periods, epochs
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75. Great worldwide changes in forms of ____________________ on Earth mark the boundaries of eras.
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Life
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76. The ____________________ is the era of "recent life" on Earth.
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Cenozoic era
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77. Although it can rarely be used to date ____________________ rocks directly, radiometric dating can help scientists estimate their absolute ages by comparison to igneous rock masses that are relatively older and relatively younger. Short Answer
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Sedimentary
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78. How do rocks allow geologists to interpret Earth's history?
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Rocks record geologic events and changes in life forms during Earth's History
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79. What is the principle of uniformitarianism?
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Uniformitarianism states that the processes and forces that we observe today have been functioning throughout geologic time.
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81. What is an unconformity?
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An unconformity is a break in the rock record that represents a long period of time during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed.
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82. What are the three types of unconformities?
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angular unconformities, disconformities, and nonconformities
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83. How are fossils useful to geologists?
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Fossils are used to determine the relative age of sedimentary rocks; to help correlate rock units in different areas; and to provide information on past environments, climates, and depositional settings.
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84. What conditions are important in determining whether an organism will be preserved as a fossil?
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rapid burial by sediments and the possession of hard parts that are more likely to be preserved
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85. What are the requirements for a fossil to be considered an index fossil?
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The fossil must have been widespread geographically, abundant, and limited to a short span of geologic time.
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86. Explain how natural selection works as the mechanism of evolution.
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Evolution occurs as organisms that are better adapted to their environment survive and reproduce, while organisms that are less well adapted become extinct.
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87. What are adaptations and how are they involved in evolution?
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Adaptations are traits that affect an organisms ability to survive and reproduce. Well adapted organisms survive and pass on their adaptations to later generations, allowing evolution to occur over time.
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88. What type of radiometric dating would be most useful in dating bones found in an Egyptian tomb?
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radiocarbon dating carbon-14 dating
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89. What is the geologic time scale?
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a scale that divides Earth's 4.56-billion-year history into units that represent specific amounts of time, based on geologic events and changes in ancient life forms
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90. What are the three eras in the Phanerozoic Eon?
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Paleozoic, Mesozoic, and Cenozoic
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91. What is the major problem in assigning specific dates to rocks or units of the geologic time scale? Essay
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The major problem is that not all rocks can be dated radiometrically; most of the rocks that contain fossils that were used to divide the units in the geologic time scale are sedimentary rocks, which usually cannot be dated radiometrically.
