Radiocarbon dating is a technique used by geologists to determine the age of certain materials, such as wood, bone, and shell, based on the decay of the radioactive isotope carbon-14. This method relies on the fact that carbon-14 is constantly being produced in the Earth's atmosphere through the interaction of cosmic rays with nitrogen atoms. Once an organism dies, it stops absorbing carbon-14, and the carbon-14 that it has absorbed begins to decay at a predictable rate. By measuring the amount of carbon-14 remaining in a sample, geologists can calculate how long it has been since the organism died.
There are two substances that geologists use in radiocarbon dating: organic material and inorganic material.
Organic material, such as wood, bone, and shell, contains carbon atoms that were absorbed from the atmosphere while the organism was alive. Geologists can extract these carbon atoms and measure the amount of carbon-14 they contain using a mass spectrometer. The amount of carbon-14 in the sample is compared to the known decay rate of carbon-14 to determine how long it has been since the organism died.
Inorganic material, such as sediment or rock, does not contain carbon atoms that were absorbed from the atmosphere. However, geologists can still use radiocarbon dating to determine the age of inorganic material by measuring the amount of carbon-14 in organic material that is found in the same layer of sediment or rock. For example, if a layer of sediment contains a fossilized shell, geologists can measure the amount of carbon-14 in the shell to determine the age of the sediment.
In conclusion, geologists use two substances in radiocarbon dating: organic material and inorganic material. Organic material, such as wood, bone, and shell, contains carbon atoms that were absorbed from the atmosphere while the organism was alive. Inorganic material, such as sediment or rock, does not contain carbon atoms that were absorbed from the atmosphere, but the age of inorganic material can still be determined by measuring the carbon-14 in organic material that is found in the same layer.