What role does radioactivity play in geological dating?

Radioactivity plays a crucial role in geological dating by providing a method to determine the age of rocks and fossils.

Radioactivity, or radioactive decay, is a natural process where unstable atomic nuclei lose energy by emitting radiation. This process is fundamental to geological dating, specifically radiometric dating, which is used to date rocks and fossils. Radiometric dating relies on the properties of isotopes, which are different forms of the same element that have the same number of protons but different numbers of neutrons.

The key to this method is the half-life of the radioactive isotopes. The half-life is the time it takes for half of the atoms in a sample to decay. It is a constant rate for each isotope, unaffected by external conditions such as temperature or pressure. This makes it a reliable 'clock' to measure the age of geological samples.

For example, the isotope Uranium-238 decays into Lead-206 with a half-life of about 4.5 billion years. By comparing the ratio of Uranium-238 to Lead-206 in a rock sample, scientists can estimate the time that has passed since the rock formed. Similarly, Carbon-14 dating is used to date organic material, like fossils, up to about 60,000 years old. Carbon-14 decays into Nitrogen-14 with a half-life of about 5,730 years.

In summary, radioactivity is a powerful tool in geological dating. By understanding the properties of radioactive isotopes and their half-lives, scientists can accurately determine the age of rocks and fossils, providing valuable insights into the history of our planet.