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24 Cards in this Set
- Front
- Back
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absolute age
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actual age of an object
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amber
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hardened tree sap in which fossils may be trapped
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angular unconformity
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boundary between horizontal and tilted layers of rock
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bedding plane
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boundary between two sedimentary rock layers
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coprolite
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fossilized waste material from an animal
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disconformity
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boundary between layers of rock that have not been deposited continuously
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evolution
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change of living things over time
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gastrolith
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fossilized stone found within the digestive of a dinosaur or other reptile
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half-life
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time required for half the mass of a radioactive element to decay into its daughter element
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index fossil
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guide fossil, fossil found in the rock layers of only one geologic age and is used to establish the absolute age of the rock layers.
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law of crosscutting relationships
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principal that a fault or intrusion is always younger than the rock layers it cuts through.
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mummification
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preservation of a dead organism by drying
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nonconformity
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when stratifed rock rests upon unstratified rock.
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Paleontologist
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scientist who studies fossils
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Paleontology
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the study of fossils
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petrification
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process in which organic materials are replaced by new materials
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principal of uniformitarianism
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theory that geologic processes at work in the present were also at work in the past
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relative age
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age of an object compared with the ages of other objects
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trace fossil
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fossil trace left by an ancient organism, such as a track, footprint, boring or burrow.
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unconformity
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break in the geologic record created when rock layers are removed by erosion.
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varve
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annual layer of sedimentary deposit on a lake bed
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radioactive isotopes
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have nuclei that emit particles and energy at a constant rate. rocks often contain radiocactive isotopes
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starts with U-??? turns in to Th-???
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238, 234
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half life for U-238 is??
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4.5 billion years
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