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Radioactive dating
Radioactive dating is also called radiometric dating. This is an age-old method for determining the ages of geological materials (rocks and minerals) as well as fossils and ancient artefacts using radioactive isotopes.
Radiometric dating has also been used to date not only natural but aslo man-made materials. The basic logic here is that a acomparisson is made between the natural abundance of a radioactive isotope on earth, that of its daughter product in a sample (decayed product) and its half-life i.e its decay rates.
For accurate determination of ages of materials by radioactive dating, the following conditions are necessary;
- The half-life of the parent nuclide should be long enough so that the parent nuclide will be of significant amount at the time of measurement
- The unique half0life of the parent nuclide should be accurately known
- Sufficient amount of daughter product is produced so as to enable its accurate measurement and there should be clear distinction between nuclide produced and the initial amount of the daughter known to be present in the material
The number of atoms
We can also derive the equation for determining the population of daughter nuclide. Now by letting the number of daughter nuclides at t=0 be
=
The above equation gives the population of daughter nuclide base on
=
=
Where t = age of the sample,
Carbon-14 and Radiocarbon dating
Carbon-14 commonly referred to as radiocarbon is an unstable and weakly radioactive isotope of carbon with half-life of 5730 years.Other isotopes of carbon i.e carbon 12 and carbon 13 are stable and therefore are not radioactive.
Carbon-14 dating also known as radiocarbon (
Age of materials is estimated by determining the amount of radiocarbon in a sample and campare it against international reference standard. It is suitable for determining the ages of organic materials between 500 to 50,000 years old, beyond 50000 years, the amount of
Carbon-14 dating is based on carbon-14 decaying to nitrogen. Carbon-14 is continually replenished in the atmosphere when neutrons in cosmic rays bombard nitrogen-14. Living organisms generally take in carbon from the atmosphere in form of carbon dioxide, in most instances, green plants absorb carbon-dioxide and pass the radiocarbon to animals along the food chain.
Carbon-14 is continually added to living organisms as long as they take in air and food. Absorption of carbon-14 stops immediately the organism dies and the amount in their tissues start to decay. The rate of decay is constant, thus, the date the organism died can be determined by measuring the amount of residual radiocarbon carbon.
Other dating methods
Potassium-argon dating- used to determine ages of rocks by measuring the ratio of radioactive argon to radioactive potassium within it.it is based on decay of solid
Uranium-lead dating - A dating technique that measures the ratio of uranium isotopes
Chlorine-36 dating- method used to date old ground water (100000-1 million years old), this method involves calculating the amount of
Luminescence dating-Dates crystalline materials to the time they were heated by sun or human-made fires.
There are other methods such fission-track, samarium-neodymium, rubidium-strontium, and uranium-thorium, all these methods depend on aspects of radioactive decay to estimate ages of rocks
REFERENCE
1.Strunk, A., Olsen, J., Sanei, H., Rudra, A., & Larsen, N. K. (2020). Improving the reliability of bulk sediment radiocarbon dating. Quaternary Science Reviews, 242, 106442.
2. Goh, K. M. (1991). Carbon dating. Carbon Isotope Techniques, 1, 125.
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