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radiometric dating

radiometric dating(radioactive dating) The most precise method of dating rocks, in which the relative percentages of ‘parent’ and ‘daughter’ isotopes of a given radioactive element are estimated. Early methods relied on uranium and thorium minerals, but potassium–argon, rubidium–strontium, samarium–neodymium, and carbon-14–carbon-12 are now of considerable importance. Uranium-238 decays to lead-206 with a half-life of 4.5 billion (109) years, rubidium-87 decays to strontium-87 with a half-life of 50.0 billion years, and potassium-40 decays to argon-40 with a half-life of 1.5 billion years. For carbon-14 the half-life is a mere 5730 ± 30 years (see radiocarbon dating). It is important that the radioactive isotope be contained within the sample being dated. Carbon-14 is contained within plant material, but potassium-40, argon-40, and uranium-238 are contained satisfactorily only within crystals. Igneous rocks are the most suitable for dating. Fossils occur mostly in sedimentary rocks, however, so absolute dates can be calculated for them less commonly than might be supposed. The only exceptions are fossils occurring in glauconite, a clay mineral containing potassium and argon which forms authigenically on the bottom of shelf seas.

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"radiometric dating." A Dictionary of Ecology. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

"radiometric dating." A Dictionary of Ecology. . Encyclopedia.com. (August 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiometric-dating-0

"radiometric dating." A Dictionary of Ecology. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiometric-dating-0

radiometric dating

radiometric dating (radioactive dating) The most precise method of dating rocks, in which the relative percentages of ‘parent’ and ‘daughter’ isotopes of a given radioactive element are estimated. Early methods relied on uranium and thorium minerals (see URANIUM-LEAD DATING), but potassium-argon, rubidium-strontium, samarium-neodymium, and carbon-14—carbon-12 are now of considerable importance. Uranium-238 decays to lead-206 with a half-life of 4.5 billion (109) years, rubidium-87 decays to strontium-87 with a half-life of 50.0 billion years, and potassium-40 decays to argon-40 with a half-life of 1.5 billion years. For carbon-14 the half-life is a mere 5730 ± 30 years (see RADIOCARBON DATING), and beyond about 70 000 years the amount of carbon-14 remaining in organic matter is beyond accurate measurement. Compare INITIAL STRONTIUM RATIO.

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"radiometric dating." A Dictionary of Earth Sciences. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

"radiometric dating." A Dictionary of Earth Sciences. . Encyclopedia.com. (August 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiometric-dating

"radiometric dating." A Dictionary of Earth Sciences. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiometric-dating

dating, radioactive

dating, radioactive (radiometric dating) Any of several methods using radioactive decay to assess the ages of archaeological remains, fossils and rocks. The specimens must contain a very long-lived radioisotope of known half-life (time taken for one half of its nuclei to decay), which, with a measurement of the ratio of radioisotope to a stable isotope (usually the decay product), gives the age. In potassium-argon dating, the ratio of potassium-40 to its stable decay product argon-40 gives ages more than 10 million years. In rubidium-strontium dating, the ratio of rubidium-87 to its stable product strontium-87 gives ages to several thousand million years. In carbon dating, the proportion of carbon-14 (half-life 5730 years) to stable carbon-12 absorbed into once-living matter gives ages to several thousand years.

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"dating, radioactive." World Encyclopedia. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

"dating, radioactive." World Encyclopedia. . Encyclopedia.com. (August 22, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/dating-radioactive

"dating, radioactive." World Encyclopedia. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/dating-radioactive

radiometric dating

radiometric dating (radioactive dating) See dating techniques; radioactive age.

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"radiometric dating." A Dictionary of Biology. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

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"radiometric dating." A Dictionary of Biology. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiometric-dating-1

radioactive dating

radioactive dating See radiometric dating.

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"radioactive dating." A Dictionary of Ecology. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

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"radioactive dating." A Dictionary of Ecology. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radioactive-dating

radioactive dating

radioactive dating: see dating.

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"radioactive dating." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 22 Aug. 2017 <http://www.encyclopedia.com>.

"radioactive dating." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 22, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/radioactive-dating

"radioactive dating." The Columbia Encyclopedia, 6th ed.. . Retrieved August 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/radioactive-dating