Lab 8 dating of rocks fossils and geologic events answers
Half the original quantity of carbon-14 will decay back to the stable element nitrogen-14 after only 5,730 years.
Indeed, if all the atoms making up the entire earth were radiocarbon, then after only 1 million years absolutely no carbon-14 atoms should be left!
For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years.
Radiocarbon dating measures radioactive isotopes in once-living organic material instead of rock, using the decay of carbon-14 to nitrogen-14.
When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.
Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.