One method or relative dating
Unlike observation-based relative dating, most absolute methods require some of the find to be destroyed by heat or other means.
This family of dating methods, some more than a century old, takes advantage of the environment’s natural radioactivity.
Thermoluminescence: Silicate rocks, like quartz, are particularly good at trapping electrons.
Researchers who work with prehistoric tools made from flint — a hardened form of quartz — often use thermoluminescence (TL) to tell them not the age of the rock, but of the tool.
The uranium-thorium method is often helpful for dating finds in the 40,000- to 500,000-year-old range, too old for radiocarbon but too young for K-Ar or Ar-Ar.
Over time, certain kinds of rocks and organic material, such as coral and teeth, are very good at trapping electrons from sunlight and cosmic rays pummeling Earth.
Whenever possible, researchers use one or more absolute dating methods, which provide an age for the actual fossil or artifact.Measuring carbon-14 in bones or a piece of wood provides an accurate date, but only within a limited range.Says Shea: “Beyond 40,000 years old, the sample is so small, and the contamination risk so great, that the margin of error is thousands of years.It would be like having a watch that told you day and night.” Single crystal fusion: Also called single crystal argon or argon-argon (Ar-Ar) dating, this method is a refinement of an older approach known as potassium-argon (K-Ar) dating, which is still sometimes used.Both methods date rock instead of organic material. But unlike radiocarbon dating, the older the sample, the more accurate the dating — researchers typically use these methods on finds at least 500,000 years old.
Both plants and animals exchange carbon with their environment until they die.