What describes absolute dating?

• A. A time range such as the Mesozoic era.
• B. Relative order of events.
• C. The number of years since a rock formed measured by radiometric dating.
• D. The color of minerals.

Answer: (C)

Absolute dating gives a numerical age in years for when a rock formed. This is done through radiometric dating, where scientists measure the amounts of a radioactive parent isotope and its decay product, then use the isotope’s known half-life to calculate how long it has been since the rock formed. The result is a specific age (for example, millions or billions of years), not just a general time frame or an ordered sequence. Radiometric methods like uranium–lead or potassium–argon are common, but they rely on having minerals that have remained closed to any loss or gain of isotopes and on careful calibration, so the reported ages come with uncertainty.