Chronometric dating definition
This process frees electrons within minerals that remain caught within the item.Heating an item to 500 degrees Celsius or higher releases the trapped electrons, producing light.Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated.Argon, a noble gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay.
Many factors can spoil the sample before testing as well, exposing the sample to heat or direct light may cause some of the electrons to dissipate, causing the item to date younger.
Particular isotopes are suitable for different applications due to the types of atoms present in the mineral or other material and its approximate age.
For example, techniques based on isotopes with half lives in the thousands of years, such as carbon-14, cannot be used to date materials that have ages on the order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments.
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.
K–Ar dating was used to calibrate the geomagnetic polarity time scale.