Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source potassium-argon dating A method of radiometric dating, involving analysis of the ratio of potassium 40 (a radioactive isotope of potassium) to argon (the product of radioactive decay of potassium 40) in a given sample.
Potassium–Argon dating or K–Ar dating is a radiometric dating method used in geochronology and archaeology.
That is, a fresh mineral grain has its K-Ar "clock" set at zero.
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 is relatively small because of its escape to the atmosphere during processes associated with volcanism.
Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).
One out of every 10,000 Potassium atoms is radioactive Potassium-40 (K-40).
The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.
Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.The rock sample to be dated must be chosen very carefully.Any alteration or fracturing means that the potassium or the argon or both have been disturbed.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.and the ages of fossil hominids, molecular dating and divergence times for mammalian lineages, meteorites and the age of the solar system, and the use of color-magnitude diagrams for assessing ages of collections of stars.