Britannica Sources used in this answer

How do scientists use carbon-14 to date formerly living material?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Grand Canyon rock layering — geochronology The steep walls of the Grand Canyon contain a number of layers of sedimentary rock laid down over millions of years. The lower formations belong to the early Precambrian age, while the upper layers are of the Paleozoic age. The line between the two sets of formations is called the Great Unconformity.

Scientists use carbon-14 dating to determine the age of organic materials by measuring the decay of the radioactive isotope carbon-14.12

Carbon-14 is continuously produced in the atmosphere by cosmic rays and enters the carbon cycle, where it is absorbed by plants and subsequently consumed by animals. While an organism is alive, it maintains a stable ratio of carbon-14 to stable carbon isotopes because it is constantly replenishing its supply through food and air.132

Upon death, an organism ceases to intake carbon, and the carbon-14 in its tissues begins to decrease at a constant rate due to radioactive decay, with a half-life of 5,730 ± 40 years. By using an accelerator mass spectrometer to measure the remaining proportion of carbon-14, scientists can estimate how long ago the organism died. Because atmospheric carbon-14 levels have fluctuated over time, researchers often calibrate these raw dates using data from sources like dendrochronology to improve accuracy.1324