A geologist uses relative dating methods to guess that a rock is between 1 million and 5 million years old. What is one radioactive isotope the geologist can use to learn the exact age of the rock?
Scientists usually use the potassium-argon method to date rocks that are older than about 1 million years. Uranium-238 is also used for radiometric dating. It has a half-life of 4.5 billion years. It decays to produce lead-206.
