Because 39 Ar has a very short half-life, it is guaranteed to be absent in the sample beforehand, so it's a clear indicator of the potassium content. Use dmy dates from May Andrew Alden is a geologist who writes extensively about all aspects of geology, and leads research expeditions for professional organizations. It is based on measurement of the product of the radioactive decay of an isotope of potassium K into argon Ar. Thermoluminescence Dating National Nuclear Data Center. Time since recrystallization is calculated by measuring the ratio of the amount of 40 Ar to the amount of 40 K remaining.
Potassium-argon (K-Ar) dating
Potassium K is one of the most abundant elements in the Earth's crust 2. All rights reserved. And in the next video I'll actually go through the mathematical calculation to show you that you can actually date it.