Carbon dating method


26-Jan-2020 17:04

Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.As a rule, carbon dates are younger than calendar dates: a bone carbon-dated to 10,000 years is around 11,000 years old, and 20,000 carbon years roughly equates to 24,000 calendar years.The problem, says Bronk Ramsey, is that tree rings provide a direct record that only goes as far back as about 14,000 years.Marine records, such as corals, have been used to push farther back in time, but these are less robust because levels of carbon-14 in the atmosphere and the ocean are not identical and tend shift with changes in ocean circulation.Stratigraphy and biostratigraphy can in general provide only relative dating (A was before B), which is often sufficient for studying evolution.This is difficult for some time periods, however, because of the barriers involved in matching rocks of the same age across continents.The more accurate carbon clock should yield better dates for any overlap of humans and Neanderthals, as well as for determining how climate changes influenced the extinction of Neanderthals.“If you have a better estimate of when the last Neanderthals lived to compare to climate records in Greenland or elsewhere, then you’ll have a better idea of whether the extinction was climate driven or competition with modern humans,” says Paula Reimer, a geochronologist at Queen’s University in Belfast, UK.

If a fossil is found between two layers of rock whose ages are known, the fossil’s age is thought to be between those two known ages.Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive.By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.Carbon dating is used to work out the age of organic material — in effect, any living thing.

The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.The researchers collected roughly 70-metre core samples from the lake and painstakingly counted the layers to come up with a direct record stretching back 52,000 years.



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