Earth and Space Chapter 12 – Flashcards
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What ideas do geologists use as they study Earth?
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the rock record provides evidence of past geological events and life forms, processes in the present acted in the past, Earth is very old and has changed over time
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In what type of rocks would geologists most likely find evidence of past life forms?
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sedimentary rocks
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The geological processes that shape Earth's features today...
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are basically the same as they were in the geologic past
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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...
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uniformitarianism
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According to the principle of cross-cutting relationships, an intrusive rock body is...
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younger than the rocks into which it intrudes
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The dating process that places geologic events in proper sequence is referred to as a...
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relative dating
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In general, the law of superposition states that in an undeformed sequence of sedimentary rocks, each layer is...
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older than the one above it
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Which type of geologic event has to occur to create an angular conformity?
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folding and tilting of rock layers, followed by renewed deposition
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An unconformity is a...
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gap in the rock record
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Fossils are the...
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remains and traces of prehistoric life
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In what type of rocks are most fossils found?
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sedimentary rocks
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What environment would NOT contain fossils?
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intrusive rock formed from cooled magma
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What determines the type of fossil that is formed?
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the conditions under which the organism died and how it was buried
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What is important if an organism is to become a fossil?
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rapid burial and hard parts
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Why would a worm stand a poor chance of being fossilized?
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worms have no hard parts
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The task of using fossils to match up rocks of similar ages in different areas is called...
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correlation
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Index fossils allow geologists to...
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match up rocks of the same age in different regions
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The process by which atomic nuclei spontaneously decay is called
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radioactivity
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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...
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a half-life
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According to the theory of evolution, organisms change over time because of a process called...
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natural selection
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Which two substances do geologists use in radiocarbon dating?
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carbon-14 and carbon-12
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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...
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geographical time scale
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What is the currently accepted age of Earth?
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about 4.6 billion years old
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The largest expanse of time on the geologic time scale is the...
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eon
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What is the division of the geologic time scale in order from longest to shortest?
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era, period, epoch
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About 88 percent of Earth's history is within the expanse of time before the Phanerozoic era called the...
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Precambrian
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Radiometric dating does not usually work with sedimentary rock because they
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form from many older rock particles
