How Is Radioactive Dating Used to Date Fossils?
Radioactive Decay Many rocks and organisms contain radioactive isotopes, such as U-235 and C-14. These radioactive isotopes are unstable, decaying over time at a predictable rate. As the isotopes decay, they give off particles from their nucleus and become a different isotope. The parent isotope is the original unstable isotope, and daughter isotopes are the stable product of the decay. Half-life is the amount of time it takes for half of the parent isotopes to decay. The decay occurs on a logarithmic scale. For example, the half-life of C-14 is 5,730 years. In the first 5,730 years, the organism will lose half of its C-14 isotopes. In another 5,730 years, the organism will lose another half of the remaining C-14 isotopes. This process continues over time, with the organism losing half of the remaining C-14 isotopes each 5,730 years. Radioactive Dating of Fossils Fossils are collected along with rocks that occur from the same strata. These samples are carefully cataloged and analyzed w
