A dating method based on the decay of the radio-isotope K40 (potassium) to a daughter isotope Ar40 (argon). The rocks of volcanic origin that are dated using this method are assumed to have been initially free from argon since it is removed by heating, and thus the ratio of the K40 to any Ar40 decay product driven off the sample in the laboratory is a function of the age of the sample. This method is used mostly for samples formed in the last 30 million years but is limited to samples greater than 100,000 years old due to the half-life of K40. See Bradley (1985), Ch. 3.
A form of isotope dating that relies on the extremely long half-life of radioactive isotopes of potassium, which decay into isotopes of argon, to determine the age of rocks in which argon is present. Potassium-argon dating is used for rocks between 100,000 and 4 billion years old.
geological dating that relies on the proportions of radioactive potassium in a rock sample and its decay product, argon
A technique for determining the age of rock and mineral samples by measuring the amounts of radioactive potassium ( 40 K) and its daughter element, a form of argon ( 40 Ar) in a sample. Because 40 K decays relatively slowly, this technique typically only yields reliable ages for samples that are more than about 100,000 years old.
Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. 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 and evaporites.