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The 285 samples of annual tree rings were analyzed for radiocarbon at the UA AMS lab.Co-author Gregory Hodgins, director of the UA AMS lab, said, “Charlotte’s redoing the calibration curve at an annual scale.The radioactive carbon-14 within an annual tree ring starts decays at a steady rate and can act as a clock indicating when the tree grew that ring.She and her colleagues used two different tree-ring chronologies from long-lived trees that were alive at the time of the Thera eruption but were growing 7,000 miles apart.“The volcano erupts and represents one short moment in time,” she said.“If you can date precisely when that moment is, then whenever you find evidence of that moment at any archeological site, you suddenly have a very precise marker point in time — and that’s really powerful for examining human/environmental interactions around that time period.” Archeologists have estimated the eruption as occurring sometime between 15 BC by using human artifacts such as written records from Egypt and pottery retrieved from digs.
At that time, the scientists needed to use chunks of wood that combined 10 to 20 years of a tree’s annual rings to have enough wood to test for radiocarbon.
There’s a kind of revolution in the radiocarbon community to revise the calibration curve using these more precise measurements.” Other research teams are also finding discrepancies between their radiocarbon measurements using annual tree rings and the current radiocarbon calibration curve, he said.
Pearson, still fascinated by Thera, hopes future research can nail the eruption down to a particular year.
Other researchers estimated the date of the eruption to about 1600 BC using measurements of radiocarbon, sometimes called carbon-14, from bits of trees, grains and legumes found just below the layer of volcanic ash.
By using radiocarbon measurements from the annual rings of trees that lived at the time of the eruption, the UA-led team dates the eruption to someplace between 16, a time period which overlaps with the 1570-1500 date range from the archeological evidence.Work conducted at the UA Accelerator Mass Spectrometry Laboratory contributed substantially to the radiocarbon calibration curve currently in use worldwide.