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23 Cards in this Set
- Front
- Back
Fossils
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preserved remains or traces living things.
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mold
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hollow area in sediment in the shape of an organism or part of and organism
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cast
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solid copy of the shape of an organism- opposite of a mold
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petrified fossils
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fossils in which minerals replace all or part of an organism
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Carbon film
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extremely thin coating of carbon on rock
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trace fossils
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provide evidence of the activities of ancient organisms
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Paleontologists
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scientists how study fossils
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evolution
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the gradual change in living things over long periods of time.
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Extinct
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a type of organism that no longer exists
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relative age
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The age of a rock compared to the age of other rocks.
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absolute age
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The number of years since the rock formed.
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Law of superstition
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determines the relative ages of sedimentary rock layers.
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extrusion
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Lava that hardens on the surface
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intrusion
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When magma hardens and cools under the surface
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Unconformity
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The surface where new rock layers meet a much older rock surface beneath them.
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Index Fossils
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Fossils that help geologist match rock layers
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Radioactive decay-
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when elements break down and decay by releasing particles and energy.
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half-life
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the rate of decay of an element
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Geologic time scale
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a record of the life forms and geologic events in Earth’s history.
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Periods
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Subdivisions in eras.
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Eras
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Time and present into three long units of time.
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mass extinction
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in which many types of living things became extinct at the same time
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mass extinction
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in which many types of living things became extinct at the same time
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