Argon, a noble gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay.
The date measured reveals the last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice.
In each of these disintegration systems, the parent or original radioactive substance gradually decays into daughter substances.
Scientists compared one fossil to another and tried to decide if that fossil was from the same time period as the original.
Absolute dating provides a numerical age or range in contrast with relative dating which places events in order without any measure of the age between events.
One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains.
K–Ar dating was used to calibrate the geomagnetic polarity time scale.
Thermoluminescence testing also dates items to the last time they were heated.
The development of accelerator mass spectrometry (AMS) dating, which allows a date to be obtained from a very small sample, has been very useful in this regard.
Other radiometric dating techniques are available for earlier periods.