Radiometric dating
Radiometric dating estimates the time since a material formed or changed by measuring radioactive parent isotopes and their daughter products.
Radioactive decay: The spontaneous transformation of unstable atomic nuclei into more stable nuclei, often releasing particles or energy. Dating relies on predictable decay to convert parent isotopes into measurable daughter products.
Uranium–lead dating: A radiometric dating method that uses uranium isotopes decaying to lead isotopes, especially in zircon. Its long-lived decay chains can date ancient igneous rocks and constrain Earth history.
Parent isotope: A radioactive isotope that decays into another isotope, called its daughter product. Its abundance is one half of the isotope ratio used to calculate a radiometric age.
Relative dating: A method of placing events or materials in chronological order without assigning numerical ages. It establishes older–younger relationships, whereas radiometric dating can provide numerical age estimates.
Geologic time scale: A chronology of Earth’s history divided into eons, eras, periods, and smaller units. Radiometric measurements calibrate many boundaries and durations in the scale.
Half-life: The time required for half the radioactive atoms in a sample to decay. A known half-life translates a measured parent-to-daughter ratio into elapsed time.
Potassium–argon dating: A method that dates rocks by measuring radioactive potassium-40 and the argon-40 produced by its decay. It is widely used to date volcanic rocks and geological events across millions of years.
Daughter isotope: An isotope produced by the radioactive decay of a parent isotope. Its abundance records decay, provided the sample’s initial amount and later movement are accounted for.
Stratigraphy: The study of rock layers, their sequence, and their spatial and temporal relationships. Layer order supplies relative chronology that radiometric ages can calibrate.
Age of Earth: The time elapsed since Earth formed, estimated at about 4.54 billion years. Radiometric dating of meteorites and terrestrial materials established this estimate.