Radioactive dating is also called
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.
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.When the isotope is halfway to that point, it has reached its half-life.There are different methods of radiometric dating that will vary due to the type of material that is being dated.These two uranium isotopes decay at different rates. The half-life of the uranium-238 to lead-206 is 4.47 billion years.The uranium-235 to lead-207 decay series is marked by a half-life of 704 million years.
In fact, this form of dating has been used to date the age of rocks brought back to Earth from the moon.