Radiometric dating rock samples
Unlike people, you can’t really guess the age of a rock from looking at it.
To date a radioactive rock, geologists first measure the “sand grains” in the top glass bowl (the parent radioisotope, such as uranium-238 or potassium-40).
They also measure the sand grains in the bottom bowl (the daughter isotope, such as lead-206 or argon-40, respectively).
Part 2 explains how scientists run into problems when they make assumptions about what happened .
An hourglass is a helpful analogy to explain how geologists calculate the ages of rocks.
Free 5-day trial Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.