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.

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.

radioactive isotope dating rocks-5

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.

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, we start out with two isotopes of uranium that are unstable and radioactive.

They release radiation until they eventually become stable isotopes of lead.

The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.

The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.

However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.