What is carbon dating? How many forms of dating do you know about? How does carbon dating work? Let’s dig in and find out more.
LEARNING OBJECTIVES
By the end of this topic, you are expected to;
Carbon-14 refers to a weakly radioactive isotope of Carbon, which is also referred to as radiocarbon. It is an isotopic chronometer.
Carbon-14 dating can only be applied to organic and some inorganic materials. It is important to note that, this method of dating is not applicable to metals. The three principal radiocarbon dating methods are accelerator mass spectrometry, liquid scintillation counting, and gas proportional counting.
WHAT IS RADIOCARBON DATING
Radiocarbon dating refers to a method that provides objective age estimates for carbon-based materials that originated from living organisms. Age can be estimated by measuring the amount of carbon-14 that is present in the sample and comparing it against an internationally used reference standard.
The impact that this technique of radiocarbon dating has on modern man has made it among the most significant discoveries of the 20th century. There is no other scientific method that has managed to revolutionize the understanding of man not only of his present but also of events that already took place thousands of years ago.
Archeology as well as other human sciences, make use of radiocarbon dating to either prove or disprove theories. Over the years, carbon 14 dating has found applications in paleoclimatology, oceanography, atmospheric science, geophysics, geology, and hydrology.
BASIC PRINCIPLES OF CARBON DATING
Radiocarbon (carbon 14) is an isotope of the element carbon. It is unstable and weakly radioactive. The stable isotopes of carbon are carbon 12 and carbon 13.
Carbon 14 is always being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms. It is oxidized rapidly in air to form carbon dioxide and enters the global carbon cycle.
Animals and plants assimilate carbon 14 from carbon dioxide throughout their lifetimes. When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts decreasing at a rate that is determined by the law of radioactive decay.
Radiocarbon dating is basically a method that is designed to measure residual radioactivity.
MEASURING RADIOCARBON
There are three major techniques that are used to measure the content of carbon 14 of any given sample, they are; accelerator mass spectrometry, liquid scintillation counting, and gas proportional counting.
Gas proportional counting is a conventional radiometric dating technique that counts the beta particles that are emitted by a given sample. Beta particles are products of radiocarbon decay.
Liquid scintillation counting is a technique of radiocarbon dating where the sample is in liquid form and a scintillator is added. A flash of light is produced when this scintillator interacts with a beta particle.
Accelerator mass spectrometry is a modern method of radiocarbon dating considered to be the more efficient way of measuring the content of radiocarbon in a sample. This method does not count beta particles but the number of carbon atoms that are present in the sample and proportion of the isotopes.
CARBON 14 DATABLE MATERIALS
Not all materials can be dated by radiocarbon dating. Almost all organic compounds can be dated. Some inorganic matter such as shell’s aragonite component can also be dated provided that the mineral’s formation involved assimilation of carbon 14 in equilibrium with the atmosphere.
Samples that have been radiocarbon dated since the inception of this method include wood, charcoal, shells, bones, peat, hair, blood residues, water, corals, among others.
Physical, as well as chemical pretreatments, are done on these materials to remove possible contaminants before they are analyzed for their radiocarbon content.
