### D: Carbon Dating and Estimating Fossil Age - Biology LibreTexts

Scientists use carbon dating when determining the age of fossils that are are used in geochronology to establish the geological time scale. Radiocarbon dating is a method for determining the age of an object containing organic The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an .. To determine the degree of fractionation that takes place in a given plant, the amounts of both Radiocarbon dating has transformed our understanding of the past years. Radioactive decay can be used as a “clock” because it is unaffected by Unfortunately, neither are straightforward to determine. A huge amount of work is currently underway to extend and improve the calibration curve.

Professor Willard Libby produced the first radiocarbon dates in and was later awarded the Nobel Prize for his efforts. Radiocarbon dating works by comparing the three different isotopes of carbon.

Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons. This means that although they are very similar chemically, they have different masses.

The total mass of the isotope is indicated by the numerical superscript. While the lighter isotopes 12C and 13C are stable, the heaviest isotope 14C radiocarbon is radioactive. This means its nucleus is so large that it is unstable.

Over time 14C decays to nitrogen 14N. Most 14C is produced in the upper atmosphere where neutrons, which are produced by cosmic raysreact with 14N atoms. This CO2 is used in photosynthesis by plants, and from here is passed through the food chain see figure 1, below. Every plant and animal in this chain including us!

Dating history When living things die, tissue is no longer being replaced and the radioactive decay of 14C becomes apparent. Around 55, years later, so much 14C has decayed that what remains can no longer be measured.

In 5, years half of the 14C in a sample will decay see figure 1, below. Therefore, if we know the 14C: Unfortunately, neither are straightforward to determine. The difference between the concentration of carbon—14 in the material to be dated and the concentration in the atmosphere provides a basis for estimating the age of a specimen, given that the rate of decay of carbon—14 is well known. The length of time required for one-half of the unstable carbon—14 nuclei to decay i.

Libby began testing his carbon—14 dating procedure by dating objects whose ages were already known, such as samples from Egyptian tombs.

### Carbon dating is used to determine what

He found that his methods, while not as accurate as he had hoped, were fairly reliable. Libby's method, called radiocarbon or carbon—14 dating, gave new impetus to the science of radioactive dating. Using the carbon—14 method, scientists determined the ages of artifacts from many ancient civilizations. Still, even with the help of laboratories worldwide, radiocarbon dating was only accurate up to 70, years old, since objects older than this contained far too little carbon—14 for the equipment to detect.

## 18.5D: Carbon Dating and Estimating Fossil Age

Starting where Boltwood and Libby left off, scientists began to search for other long-lived isotopes. They developed the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method, all of which are based on the transformation of one element into another. They also improved the equipment used to detect these elements, and inscientists first used a cyclotron particle accelerator as a mass spectrometer. For example, they are not sufficiently precise and reliable for estimating when the groups that feature in the Cambrian explosion first evolved, and estimates produced by different approaches to this method may vary as well.

Carbon Dating Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale. The principle of radiocarbon dating is simple: This rate is represented by the half-life, which is the time it takes for half of a sample to decay.

### Explainer: what is radiocarbon dating and how does it work?

Radiometric dating is a technique used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. The half-life of carbon is 5, years, so carbon dating is only relevant for dating fossils less than 60, years old. Radioactive elements are common only in rocks with a volcanic origin, so the only fossil-bearing rocks that can be dated radiometrically are volcanic ash layers.