A little over 3,500 years ago, Greece's Mount Thera erupted, devastating perhaps the era's greatest civilization and throwing others into chaos. However, archaeologists have been puzzled by contradictory indications of the event's date, leaving big question marks over the timelines of numerous historical events influenced by this disaster. Now a study of tree rings on the other side of the world may have settled the question.
Around 1600 BCE, the Minoan civilization was the most advanced in the world. When Thera blew its top, it largely wiped out the island and left a layer of ash and pumice 40 meters (130 feet) deep across the remnants, now called Santorini. Tsunamis destroyed Minoan cities on other islands and possibly inspired the legend of Atlantis. However, attempts to date the event using different methods have produced conflicting results.
The capacity for the eruption to anchor dates is so important that Dr Charlotte Pearson of the University of Arizona said entire conferences have been devoted to resolving it.
"The volcano erupts and represents one short moment in time," Pearson said in a statement. "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."
Archaeological records from Egypt place the eruption after the start of the New Kingdom, suggesting it occurred between 1570 and 1500 BCE. However, radiocarbon dating of plant material in Santorini's ash placed it earlier – before 1600 BCE.
So much ash was injected into the atmosphere by Thera that the Sun was dimmed and plants stunted, similar to the “year without a summer” 3,400 years later when Mount Tambora caused much of the world to starve. Pearson found the event was recorded in the tree rings of California's high-altitude bristlecone pines, as well as Irish oaks closer to the event.
Pearson reports in Science Advances that she found four years of low growth that could have been triggered by the eruption. By carbon dating the rings laid down on either side of these bad years, she estimated the first occurred in 1597 BCE and the last in 1544, overlapping with the archaeological evidence. Even allowing for modest margins of error, all these dates are inconsistent with the most common radiocarbon estimates produced at Santorini.
The work was facilitated by advances in mass spectrometry that require much smaller wooden samples. This allowed Pearson to measure the age of a single ring, rather than 10-20 years' worth, as was required previously for slow-growing trees like the bristlecone. The new precision is overturning many dates based on less reliable radiocarbon techniques, potentially straightening out many questions on the timing of historic events.