http://www.ck12.org Chapter 3. Chemical Interactions
3.64 Half-life and Radioactive Dating
- Define radioactive dating.
- Describe how radioactive dating works.
- Explain how carbon-14 dating can be used to date the remains of living things.
The Grand Canyon, pictured above, was carved by the rushing waters of the Colorado River over millions of years.
The exposed rocks at the bottom of the canyon are almost 2 billion years old. The youngest rocks near the top are
about 230 million years old. Therefore, from top to bottom, the rocks provide a continuous record of more than 1.5
billion years of geological history in this region.
Q:How have scientists been able to determine the ages of rocks in the Grand Canyon?
A:The ages are based on the gradual decay, or break down, of radioactive isotopes.
What Is Radioactive Dating?
Radioactive isotopes, or radioisotopes, can be used to estimate the ages of not only of rocks, but also of fossils and
artifacts made long ago by human beings. Even the age of Earth has been estimated on the basis of radioisotopes. The
general method is calledradioactive dating. To understand how radioactive dating works, you need to understand
radioisotopes and radioactive decay.
Radioisotopes and Radioactive Decay
A radioisotope has atoms with unstable nuclei. Unstable nuclei naturally decay, or break down. They lose energy
and particles and become more stable. As nuclei decay, they gain or lose protons, so the atoms become different
elements. This is illustrated in theFigure3.114. The original, unstable nucleus is called the parent nucleus. After it