How radioactive dating works chemically dating for country people
This technique has become more widely used since the late 1950s.
Its great advantage is that most rocks contain potassium, usually locked up in feldspars, clays and amphiboles.
those that form during chemical reactions without breaking down).
The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.
This technique is used on ferromagnesian (iron/magnesium-containing) minerals such as micas and amphiboles or on limestones which also contain abundant strontium.
However, both Rb and Sr easily follow fluids that move through rocks or escape during some types of metamorphism. The dual decay of potassium (K) to 40Ar (argon) and 40Ca (calcium) was worked out between 19.
The rate of decay (given the symbol λ) is the fraction of the 'parent' atoms that decay in unit time.
This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
The amount of 14C present and the known rate of decay of 14C and the equilibrium value gives the length of time elapsed since the death of the organism.
This method faces problems because the cosmic ray flux has changed over time, but a calibration factor is applied to take this into account.
This technique is good for iron meteorites and the mineral molybdenite.
This system is highly favoured for accurate dating of igneous and metamorphic rocks, through many different techniques.
Some techniques place the sample in a nuclear reactor first to excite the isotopes present, then measure these isotopes using a mass spectrometer (such as in the argon-argon scheme).