Rubidium strontium dating
In some parent-daughter pairs, the daughter is still radioactive and subject to further decay to a new daughter.
In other cases, decay yields a daughter that is non-radioactive (stable) and will remain unchanged for the rest of time.
The half-life of rubidium-87 is 48.8 billion years, meaning it can accurately measure rocks as old as the Earth itself.
Uranium-lead dating is one of the most complicated of all dating techniques.
For example, an object with a quarter of its original amount (2x1/2) should be roughly 11,460 years old.
In all radiometric procedures there is a specific age range for when a technique can be used.
The transformation occurs either by loss of particles from, or addition of particles to, the parent nucleus.
Numerous chemical analyses of crustal rocks have revealed that radioactive isotopes of elements such as uranium, thorium, potassium, and rubidium occur naturally in these rocks and account for their radioactivity.
The precise half-lives of these isotopes have been measured experimentally.
The isotope potassium-40 (k-40) decays into a fixed ratio of calcium and argon (88.8 percent calcium, 11.2 percent argon).
Since argon is a noble gas, it would have escaped the rock-formation process, and therefore any argon in a rock sample should have been formed as a result of k-40 decay.
It can be determined experimentally or by using the half-life, and is equivalent to the fraction of atoms that decays per some interval of time.