How does potassium argon dating work
Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites.
In these materials, the decay product Ar is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).
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.
By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined.Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology.It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar).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.
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That is, a fresh mineral grain has its K-Ar "clock" set at zero.