Radioactive dating of rocks
Other radiometric dating techniques are available for earlier periods.One of the most widely used is potassium–argon dating (K–Ar dating).For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.
In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young (radiocarbon dating with Radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes.
There's a small amount of radioactive carbon-14 in all living organisms.
When they die no new carbon-14 is taken in by the dead organism.
Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide.
Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. It takes 5,730 years for half the carbon-14 to change to nitrogen; this is the half-life of carbon-14.
It is possible, particularly in dry, desert climates, for organic materials such as from dead trees to remain in their natural state for hundreds of years before people use them as firewood or building materials, after which they become part of the archaeological record.