Explained: What is Carbon dating? Can rocks be carbon dated?

Updated on Oct 14, 2022 03:11 PM IST

Carbon dating is the measurement of the amount of C-14 radioactive leftover. After determining this, the scientist estimates the time that has passed since that thing died, although it comes with certain assumptions.

Carbon dating utilizes the radioactive decay to estimate time.(Photo by Kilian Karger on Unsplash)
Carbon dating utilizes the radioactive decay to estimate time.(Photo by Kilian Karger on Unsplash)
By | Edited by Aryan Prakash

The Varanasi court hearing the Gyanvapi mosque case on Friday rejected the plea of five women petitioners seeking carbon dating of Shivling like structure found inside the Gyanvapi mosque complex.

What is carbon dating?

According to a research paper published in the scientific journal Nature, all living objects absorb carbon from the surrounding environment. This assimilated carbon also comprises a certain amount of natural, radioactive carbon-14 (C-14).

Not all but some isotopes have an unstable nucleus, which means this unstable isotope will change its number of protons, neutrons, or both. This variation over time is termed as radioactive decay.

The presently living organisms would constitute the same proportion of carbon-14 as what is present in the atmosphere. On the other hand, excessively ancient dead sources would have decayed all.

Thus, assuming this, the age of organic objects of intermediate ages could be predicted by measuring the extent of carbon-14 present in the sample and correlating this against the established half-life of carbon-14 of 5,730 years. This means that 5,730 years after a living creature dies, half of its carbon-14 atoms have decayed to nitrogen atoms.

The paper explains that when the plant or animal dies, the absorption of carbon stops. But as carbon-14 is radioactive carbon, the accumulated portion continues to decay. This creates a time-capsule with a steadily decreasing carbon-14 count.

Carbon dating is the measurement of the amount of this radioactive leftover. After determining this, the scientist estimates the time that has passed since that thing died, although it comes with certain assumptions.

Can rocks be carbon dated?

Geologists, however, don’t generally use carbon dating to establish the age of rocks as organic material presence is required. According to Dr. Christopher S. Baird, a physics professor at West Texas A&M University, carbon dating is used mostly to date trees, plants, and animal remains that are younger than about 50,000 years.

Then how do geologists find the age of rock?

Carbon dating is just one form of radiometric dating. Radiometric dating determines the age of geologic materials by measuring a short-life radioactive element. Of them, carbon-14 and potassium-14/argon-40 dating methods are most developed.

So if the rock under test lacks C-14 isotope, it can be dated based on other radioactive isotopes present in it. Also, readers should note, radiometric dating is one of the many techniques available for estimation of age of rocks.

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