Click on the "Show Movie" button below to view this animation.
K-Ar Decay Profile Clicking on the "Show Movie" button below will bring up an animation that illustrates how a K-Ar sample is processed and the calculations involved in arriving at a date.
When rocks are heated to the melting point, any Ar-40 contained in them is released into the atmosphere.
When the rock recrystallizes it becomes impermeable to gasses again.
The answer reveals one of the peculiarities of the nuclear forces.
From potassium 40 to argon 40The electron capture which causes potassium 40 to transform into argon 40 in its ground state takes place in only 0.04% of cases.
As the K-40 in the rock decays into Ar-40, the gas is trapped in the rock.
Quite remarkable also is the very long half-life of 1;251 billion years, exceptional for a beta decay.Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).One out of every 10,000 Potassium atoms is radioactive Potassium-40 (K-40).With a half-life of 1,251 billion years, potassium 40 existed in the remnants of dead stars whose agglomeration has led to the Solar System with its planets.The two decay channels of potassium 40The decay scheme of potassium-40 is unusual.