K 40 dating
Potassium-Argon Dating Potassium-Argon dating is the only viable technique for dating very old archaeological materials.Geologists have used this method to date rocks as much as 4 billion years old.Potassium occurs in two stable isotopes (Ar atoms trapped inside minerals.What simplifies things is that potassium is a reactive metal and argon is an inert gas: Potassium is always tightly locked up in minerals whereas argon is not part of any minerals. So assuming that no air gets into a mineral grain when it first forms, it has zero argon content.A second problem is that for technical reasons, the measurement of argon and the measurement of potassium have to be made on two different samples, because each measurement requires the destruction of the sample.
For every 100 K-40 atoms that decay, 11 become Ar-40.
K has a half-life of 1.248 billion years, which makes it eminently suitable for dating rocks.
Potassium is chemically incorporated into common minerals, notably hornblende, biotite and potassium feldspar, which are component minerals of igneous rocks.
And it'll get a little bit mathy, usually involving a little bit of algebra or a little bit of exponential decay, but to really show you how you can actually figure out the age of some volcanic rock using this technique, using a little bit of mathematics.
So we know that anything that is experiencing radioactive decay, it's experiencing exponential decay.
Search for k 40 dating:
The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.