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8
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A general law stating that in any sequence of sediments or rocks that has not been overturned, the youngest sediments or rocks are at the top of the sequence and the oldest are at the bottom.
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9
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the beginning of an explosion of life forms
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11
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any method of dating material based on the decay of its constituent radioactive atoms, such as potassium-argon dating or rubidium-strontium dating Also called radioactive dating
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12
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the extinction of a large number of species within a relatively short period of geological time,
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16
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the theory that all geologic phenomena may be explained as the result of existing forces having operated uniformly from the origin of the earth to the present time.
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17
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A surface between successive strata representing a missing interval in the geologic record of time, and produced either by an interruption in deposition or by the erosion of depositionally continuous
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18
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The study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms.
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20
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Of or belonging to the geologic time period between Hadean Time and the Cambrian Period,
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21
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The vertical sequence of strata of various ages found in an area or region. Also known as column. The geologic time scale as represented by rocks.
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22
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the determination of the age of an object with reference to a specific time scale
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1
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the age of reptiles
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2
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The fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock or rock layer in which it is found. Also called guide fossil.
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3
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the age of the mammals
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4
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fossilized remains of a track, trail, footprint, burrow, etc., of an organism
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5
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the process of growth and development or the theory that organisms have grown and developed from past organisms.
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6
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a space of time between two events or a portion of time.
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7
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the time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes
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8
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An igneous rock, fault, or other geologic feature must be younger than any rock across which it cuts.
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10
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the shortest division of geological time
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13
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A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust.
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14
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a period of time marked by distinctive character, events
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15
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annual deposit usually consisting of two layers, one of fine materials and the other of coarse.
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19
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geologic age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years
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