ch 9 geol 100 – Flashcards
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What are the geologic features for which Siccar Point in Scotland is famous?
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a boundary between steep gray layers below and gently dipping red layer above
an unconformity
an ancient erosion surface
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If a rock started with 1,000 atoms of a parent but now contains 250 atoms, how many half lives have passed?
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2 half lives
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What is a principle we use to determine the age of a landscape surface?
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a surface with a well-developed soil is probably older than a surface with no soil
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In this photograph, Paleozoic sandstone rests depositionally on Precambrian granite. What events must have occurred before deposition of the sandstone?
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uplift of granite to the surface
solidification of granite at depth
formation of an erosion surface
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What factors are the most critical in determining whether a fossil is preserved?
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whether the creature had hard parts and how fast it was buried
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This figure shows two sections that partially overlap in age. Dashed lines show how the two sections correlate. What can you conclude from these correlations?
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the left section represents older rocks than the right section
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What would fossil ages from the geologic timescale tell us about the age of this unconformity?
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the unconformity is younger than the fossil ages on the tilted bed
the unconformity is older than the fossil ages in layers above the unconformity
the amount of time represented by the unconformity can be approximately bracketed by the ages of the fossils above and below
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Which of the following is evidence that Earth's history is not short?
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millions of layers of light- and dark-colored sediment that record yearly cycles
rates of seafloor spreading compared to the width of the Atlantic Ocean
a 4-billion-year age on a rock in Canada
thousands of isotopic ages measured by different methods
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What was the Cambrian explosion?
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a time when many different types of creatures appeared on Earth
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This figure shows two fault scarps, a lava flow, and erosion along one of the scarps. What is probably the oldest feature of those listed below?
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the scarp on the right
