Start Archaeology chronometric dating

Archaeology chronometric dating

Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated.

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.

Thermoluminescence testing also dates items to the last time they were heated.

This technique is based on the principle that all objects absorb radiation from the environment.

The technique often cannot pinpoint the date of an archeological site better than historic records, but is highly effective for precise dates when calibrated with other dating techniques such as tree-ring dating.

An additional problem with carbon-14 dates from archeological sites is known as the "old wood" problem.

This process frees electrons within minerals that remain caught within the item.

Heating an item to 500 degrees Celsius or higher releases the trapped electrons, producing light.

Particular isotopes are suitable for different applications due to the type of atoms present in the mineral or other material and its approximate age.

For example, techniques based on isotopes with half lives in the thousands of years, such as Carbon-14, cannot be used to date materials that have ages on the order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments.

In archaeology, absolute dating is usually based on the physical, chemical, and life properties of the materials of artifacts, buildings, or other items that have been modified by humans and by historical associations with materials with known dates (coins and written history).