Uranium–Lead Dating
A radiometric method that determines the age of very old rocks from the ratio of uranium to its lead decay products.
Formula / equation
²³⁸U → ²⁰⁶Pb (4.47 Ga)
Unit
years
In depth
Two independent uranium decay chains with different half-lives run simultaneously, so agreement between them provides an internal check on the result. Zircon crystals are ideal because they incorporate uranium but exclude lead when they form.
Examples in the real world
Dating Earth's oldest zircons at 4.4 billion years and meteorites that fix the age of the solar system.