Understanding Rock Age Through Dating Techniques

Some rocks have a built-in atomic clock. Before we had this tech,

geologists used common sense. In a stack of rock layers, the one at the bottom

is the oldest. That's superposition. And if something like a river cuts through those layers,

the river is younger than the rock. But the real game-changer is radiometric dating. Radioactive elements

inside minerals, like uranium, decay into other elements at a perfectly steady rate.

By measuring how much has decayed, scientists can calculate a rock's actual age in millions

or even billions of years. It’s how we know the Earth is 4.6 billion years old.