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.
The potassium-argon dating method has been used to measure a wide variety of ages.
Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral.
Potassium can be mobilized into or out of a rock or mineral through alteration processes.
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.
The Washington Post article Scientists discover hundreds of footprints left at the dawn of modern humanity describes the geological dating of stratified layers of mud by analyzing and dating minerals within each layer.
The Potassium 39 in the sample is irradiated to become Argon 39, then the ratio of the gas is compared.
However, the Argon, a noble gas, constitutes approximately 0.1-5% of the Earth's present day atmosphere.
But since floods jumble materials of different origins and ages together, that meant the scientists had to date dozens of different minerals.
The youngest crystal in the footprint layer would represent the oldest possible age for the prints; the oldest crystal in the layer above it would represent the youngest they could be.
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.