Carbon dating the process
Here on Earth, Carbon is found in the atmosphere, the soil, the oceans, and in every living creature. C-12, so-named because it has an atomic weight of 12 – is the most common isotope, but it is by no means the only one.Carbon 14 is another, an isotope of carbon that is produced when Nitrogen (N-14) is bombarded by cosmic radiation.It can be used on objects as old as about 62,000 years. Atoms of the same element that have different numbers of neutrons are called isotopes. Most carbon on Earth exists as the very stable isotope carbon-12, with a very small amount as carbon-13.Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.Radiocarbon present in molecules of atmospheric carbon dioxide enters the biological carbon cycle: it is absorbed from the air by green plants and then passed on to animals through the food chain.Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food.Plants and animals absorb both C-12 and C-14 in the course of their natural lifetimes simply by carrying out these basic functions.When they die, they cease to consume them, and the isotope of C-14 begins to revert back to its Nitrogen state at an exponential rate due to its radioactive decay.
A detailed description of radiocarbon dating is available at the Wikipedia radiocarbon dating web page.
This plot shows the level of carbon-14 in the atmosphere as measured in New Zealand (red) and Austria (green), representing the Southern and Northern Hemispheres, respectively.
Aboveground nuclear testing almost doubled the amount of carbon-14 in the atmosphere. The black arrow shows when the Partial Test Ban Treaty was enacted that banned aboveground nuclear tests. A special kind of radiocarbon dating: Bomb radiocarbon dating.
Among the significant events that caused a temporary but significant spike in the atmospheric carbon-14 to carbon-12 ratio were above-ground nuclear test detonations in the two decades following World War II.
is a term for radiocarbon dating based on timestamps left by above-ground nuclear explosions, and it is especially useful for putting an absolute age on organisms that lived through those events.