Dating rocks using radioactive decay
So, we start out with two isotopes of uranium that are unstable and radioactive.
They release radiation until they eventually become stable isotopes of lead.
Uranium is not the only isotope that can be used to date rocks; we do see additional methods of radiometric dating based on the decay of different isotopes.
For example, with potassium-argon dating, we can tell the age of materials that contain potassium because we know that potassium-40 decays into argon-40 with a half-life of 1.3 billion years.
These differing rates of decay help make uranium-lead dating one of the most reliable methods of radiometric dating because they provide two different decay clocks.
This provides a built-in cross-check to more accurately determine the age of the sample.
So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive.
Because plants use carbon dioxide for photosynthesis, this isotope ends up inside the plant, and because animals eat plants, they get some as well.
When a plant or an animal dies, it stops taking in carbon-14.
Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes.
Different methods of radiometric dating can be used to estimate the age of a variety of natural and even man-made materials.