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20 Cards in this Set
- Front
- Back
isotopes
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atoms of the same elements that have the same number of protons in their nuclei but a different number of neutrons, iotopes of the same element have different masses
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geologic time scale
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the division ofgeologic time into intervals in chronological ordr, based largelt on fossil evidence and on evidence of significant geologic events
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halflife
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the time required for one-half of an unstable atoms in a radiocative sample to decay to a different isotope
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Paleozoic Era
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the time period represents about 85% of Earth's geologic history
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unconformity
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a gap in rock record caused by the burial of an erosional surface by younger rocks or sediments
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index fossils
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fossils that are useful in correlating and dating rocks because of its wide geographic distribution and small vertical distribution
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orginal horizontality
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a principle that states that sedimentary rocks are originally formed in horizontal layers
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mesozoic era
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the time period represents abour 3.5% of Earth's geologic history
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outgassing
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the release of gasses from the interior of Earth due to internal heat and chemical reaction
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bedrock
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the solid, unweathered portion of the lithosphere
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radiocactive decaay
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the breakdown or the nuclei of unstable atomes into more stable atoms of the samer or other elements
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Precambrian
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the time period represents the first 85% of Earth's history
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principle of superposition
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the principle that states that in layered rocks the youngest layer is on top and the age of the other layers increases with depth
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variations
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natural changes within species
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correlation
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the matching or rock units or events in seperate rock formations
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volcanic ash
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small pieces of volcanic rock dispersed into the air during a volcanic eruption
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cenozoic era
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This era represents the most recent 3% of Earth's geologic history
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absolute age
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the actual age of a rock or event
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geologic history
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determined from fossil evidence, the age of the rocks, and the erosional record in the rocks
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free oxygen
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oygen not combined with other elements
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