potassium–argon dating
potassium–argon dating A dating technique for certain rocks that depends on the decay of the radioisotope potassium–40 to argon–40, a process with a halflife of about 1.27 × 10^{10} years. It assumes that all the argon–40 formed in the potassiumbearing mineral accumulates within it and that all the argon present is formed by the decay of potassium–40. The mass of argon–40 and potassium–40 in the sample is estimated and the sample is then dated from the equation: ^{40}Ar = 0.1102 ^{40}K(e^{λ}^{t} – 1),
where λ is the decay constant and t is the time in years since the mineral cooled to about 300°C, when the ^{40}Ar became trapped in the crystal lattice. The method is effective for micas, feldspar, and some other minerals.
Cite this article
Pick a style below, and copy the text for your bibliography.

MLA

Chicago

APA
"potassium–argon dating." A Dictionary of Biology. . Encyclopedia.com. 17 Jan. 2018 <http://www.encyclopedia.com>.
"potassium–argon dating." A Dictionary of Biology. . Encyclopedia.com. (January 17, 2018). http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating1
"potassium–argon dating." A Dictionary of Biology. . Retrieved January 17, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating1
potassium—argon dating
potassium—argon dating (K—Ar method) Geologic dating technique based on the radioactive decay of potassium (^{40}K) to argon (^{40}Ar). This potassium isotope has a halflife (see DECAY CONSTANT) of 1.3 billion (10^{9}) years, making this a valuable dating method. The minimum age limit for this dating method is about 250 000 years.
Cite this article
Pick a style below, and copy the text for your bibliography.

MLA

Chicago

APA
"potassium—argon dating." A Dictionary of Earth Sciences. . Encyclopedia.com. 17 Jan. 2018 <http://www.encyclopedia.com>.
"potassium—argon dating." A Dictionary of Earth Sciences. . Encyclopedia.com. (January 17, 2018). http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating
"potassium—argon dating." A Dictionary of Earth Sciences. . Retrieved January 17, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating
potassium–argon dating
potassium–argon dating(K–Ar method) A dating technique based on the radioactive decay of potassium (^{40}K) to argon (^{40}Ar). This potassium isotope has a halflife of 1.3 billion (10^{9}) years, and the minimum age limit for this dating method is about 250 000 years.
Cite this article
Pick a style below, and copy the text for your bibliography.

MLA

Chicago

APA
"potassium–argon dating." A Dictionary of Ecology. . Encyclopedia.com. 17 Jan. 2018 <http://www.encyclopedia.com>.
"potassium–argon dating." A Dictionary of Ecology. . Encyclopedia.com. (January 17, 2018). http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating0
"potassium–argon dating." A Dictionary of Ecology. . Retrieved January 17, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionariesthesaurusespicturesandpressreleases/potassiumargondating0