Scientists were able to accurately date, in the year 1021, the presence of Vikings in the North American continent after their crossing of the Atlantic, thanks to the dating of cosmic radiation, of which they detected traces in pieces of wood.
It has long been known that Scandinavian sailors were the first Europeans to land there, around the year 1000, long before Christopher Columbus arrived further south and nearly five centuries later.
To this day, the only known site of its occupation remains Anse aux Meadows, a bay on the northern tip of the island of Newfoundland, where the wooden foundations of eight buildings remain.
But as the study published in Nature on Wednesday notes, the traditional carbon-14 dating carried out in the last century is more than inaccurate, at more than 250 years. However, everything indicates a brief and sporadic occupation of the site, according to archeological remains and the “Sagas”, semi-endual texts that narrate the epics of the Vikings.
The team led by Michael Dee and Margot Kuitems, respectively professor of isotopic chronology and archaeologist at the Center for Isotopic Research at the Dutch University of Groningen, got around the hurdle with an original method.
The Earth is constantly subjected to cosmic radiation, “which continually produces carbon-14 (a heavier and much rarer form than the carbon atom) in the upper atmosphere,” explained Margot Kuitems to AFP. This form of carbon “will enter the carbon cycle, which is taken up by plants through photosynthesis.”
Sometimes radiation is much more powerful: these cosmic radiation “events” abruptly raise the carbon-14 level in the atmosphere.
– Solar storm –
A Japanese study isolated two of these “events” in 775 and 993, the remains of which remain in trees of a well-known age. The sudden increase in carbon-14 was found on the dates in question in its growth rings, those circles we see on a cut trunk that help determine the age of the tree.
Margot Kuitems’ team searched, using a mass spectrometer, for the trace of the 993 event in three samples of pieces of wood taken from the site of Anse aux Meadows. Canadian experts determined that these parts were worked there by the occupants with iron tools.
“When we measured the carbon-14 concentration in a series of rings, we found a sharp increase in one of them and we were sure that it corresponded to the year 993,” the scientist said. It was enough then to count the number of rings between the ring of the “cosmic event” and the last one located before the bark, to determine the date when the tree was felled. Answer: the year 1021.
The measurement worked for two pieces of wood, of which the scientists were even able to specify that one belonged to a tree felled in spring and the other in summer-fall.
The Isotopic Research Center is at the forefront of this unique method of archaeological dating. He signed a first study on the subject in 2020, precisely dating an archaeological structure in southern Siberia using the cosmic event of 775.
According to Kuitems, there is now a “consensus” to explain these peaks of cosmic radiation by a “solar event, like a solar storm”.
Another peak in the year 660 was recently confirmed and could, in turn, serve as a time “marker” thanks to the continuous improvement in the accuracy of mass spectrometers.
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