Isotopes used in radiometric dating
A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods.
More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years.
Relative dating is used to determine the relative ages of geologic strata, artifacts, historical events, etc.
In addition, the parent and daughter isotopes must remain together in a rock to use them to determine the rock's age.A sequence of paleomagnetic poles (usually called virtual geomagnetic poles), which are already well defined in age, constitutes an apparent polar wander path (APWP).Such a path is constructed for a large continental block.With the exception of the radiocarbon method, most of these techniques are actually based on measuring an increase in the abundance of a radiogenic isotope, which is the decay-product of the radioactive parent isotope.
A series of related techniques for determining the age at which a geomorphic surface was created (exposure dating), or at which formerly surficial materials were buried (burial dating).
The science of geochronology is the prime tool used in the discipline of chronostratigraphy, which attempts to derive absolute age dates for all fossil assemblages and determine the geologic history of the Earth and extraterrestrial bodies.