Labels:bulletin board | reckoner | sky OCR: Dating rocks using so called radioactive clocks allows geologists to work on old terrains that do not contain fossils The hands ofa radioactive clock are isotopes atoms of the same element that have different atomic weights and geologic time is measured by the rate decay of one isotope into another [see "The Earliest History of the Earth by Derek York; SCIENTIFIC AMERICAN January 1993] Among the many clocks, those based on the decay of uranium 238 into lead 206 and of uranium 235 into lead 207 are special Geochronologists can determine the age of samples by analyzing only the daughter product in this case, lead of the radioactive parent, uranium Isotope geology has permitted geologists to determine that the accretion of the earth culminated in the differentiation of the planet: the creatio ...
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