Bone age dating archaeology
After death the amount of carbon-14 in the organic specimen decreases very regularly as the molecules decay.Carbon-14 has a half-life of 5,730 ± 40 years, meaning that every 5,700 years or so the object loses half its carbon-14.We’ve never seen this before.”“This could indicate that there hasn’t been a comparable melting of the ice in the past 5,000 years,” he says.It could be an indication that something new is happening.While exposed wood usually rots and disappears, under the right conditions it can survive for millennia. Whereas regular glaciers consist of heavy sheets of ice that flow as much as tens of metres per year, snowdrifts that accumulate in a shady spot or depression can accumulate and turn into solid ice over the years that then stays put.This increases the chances of finding intact artefacts, now that warmer conditions are melting these mini-glaciers.
Under the right conditions some of these artefacts have been preserved in ice for thousands of years. (Photo: Åge Hojem and Martin Callahan/NTNU University Museum)Just a few years ago archaeologists figured the oldest objects anyone could expect to find in snowdrift glaciers would be about 2,000 years old.But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.Until this century, relative dating was the only technique for identifying the age of a truly ancient object.Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.
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This arrow, and a slightly younger one dating back 5,200 years, are among finds recently discussed in the publication Antiquity by archaeologist Martin Callanan of the Norwegian University of Science and Technology (NTNU).