potassium-argon dating

/peuh tas"ee euhm ahr'gon/, Geol.
a method for estimating the age of a mineral or rock, based on measurement of the rate of decay of radioactive potassium into argon.
[1965-70]

* * *

Method for determining the age of igneous rocks based on the amount of argon-40 in the rock.

Radioactive potassium-40 decays to argon-40 with a half-life of about 1.3 billion years, making this method useful for dating rocks that are billions of years old. A more sophisticated method, called argon-argon dating, provides a more accurate estimate of the original potassium-40 content by means of the ratio of argon-40 to argon-39 in the rock, thus yielding a more accurate age determination. See also dating.

* * *

      method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40. Thus, the ratio of argon-40 and potassium-40 and radiogenic calcium-40 to potassium-40 in a mineral or rock is a measure of the age of the sample. The calcium-potassium age method is seldom used, however, because of the great abundance of nonradiogenic calcium in minerals or rocks, which masks the presence of radiogenic calcium. On the other hand, the abundance of argon in the Earth is relatively small because of its escape to the atmosphere during processes associated with volcanism.

      The potassium-argon dating method has been used to measure a wide variety of ages. The potassium-argon age of some meteorites is as old as 4,500,000,000 years, and volcanic rocks as young as 20,000 years old have been measured by this method.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Potassium-argon dating — or K Ar dating is a radiometric dating method used in geochronology and archeology. It is based on measuring the products of the radioactive decay of potassium (K), which is a common element found in materials such as micas, clay minerals, tephra …   Wikipedia

  • potassium-argon dating — [pō tas΄ē əmär′gän΄, pə tas΄ē əm är′gän΄] n. an indirect method of dating fossils, esp. those in very ancient volcanic rock, by using potassic minerals in the same strata as a reference: a natural radioactive isotope of potassium, K 40, decays… …   English World dictionary

  • potassium-argon dating — noun geological dating that relies on the proportions of radioactive potassium in a rock sample and its decay product, argon • Hypernyms: ↑dating, ↑geological dating * * * /peuh tas ee euhm ahr gon/, Geol. a method for estimating the age of a… …   Useful english dictionary

  • potassium-argon dating — /pəˌtæsiəm ˈagɒn deɪtɪŋ/ (say puh.taseeuhm ahgon dayting) noun a method of dating rocks which depends on the ratio of potassium 40 to radiogenic argon 40 which they contain …   Australian English dictionary

  • potassium-argon dating — noun A method of estimating the age of igneous rocks or of archaeological objects by measuring the amount of argon that has built up through the radioactive decay of potassium …   Wiktionary

  • potassium-argon dating — potas′sium ar′gon dat ing n. gel a method for estimating the age of a mineral or rock, based on measurement of the rate of decay of radioactive potassium into argon • Etymology: 1965–70 …   From formal English to slang

  • potassium - argon dating — …   Useful english dictionary

  • Argon–argon dating — Argon argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassium argon (K Ar) dating in accuracy. In this technique, the decay of 40K to 40Ar* (* indicates radiogenic) is used to date geological events,… …   Wikipedia

  • potassium-argon — adjective Date: 1953 being or relating to a method of dating paleontological or geological materials based on the radioactive decay of potassium to argon that has taken place in a specimen …   New Collegiate Dictionary

  • potassium-argon — po·tas·si·um ar·gon (pə tăs ē əm ärʹgŏn ) adj. Of, relating to, or being a geologic dating method relying on the percentage of potassium in a specimen that has radioactively decayed to argon. * * * …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.