‘Secret Clocks’ In Tree-Rings Could Date Events From Thousands of Years Ago

Trees that grew during intense radiation bursts hold "secret clocks" that could pinpoint historical events in world history, scientists said.

According to researchers at Oxford University, massive solar storms caused intense radiation bursts to impact the Earth sometime in 775 and 994 AD, which caused large concentrations of radiocarbon to be trapped inside the trees growing during that period.

"Variations in atmospheric radiocarbon concentration are largely the result of carbon dioxide emissions from activity from volcanoes and the ocean, but they are also influenced by changes in solar activity," Michael Dee from the School of Archaeology at the University of Oxford and lead author of the study said in a press release.

"The spikes in 775 and 994AD were almost vertical and of comparable magnitude all around the Earth. Such markers can be easily identified in known-age tree-rings and are fixed in time.

The researchers found unusually high levels of the radioactive isotope carbon-14 seen in tree-rings of certain trees, and that the presence of isotope in these tree-rings could help archaeologists date ancient events more accurately.

The scientists outlined how they could find these distinct spikes in isotope or "time markers" from thousands of years' worth of tree-ring data around the world, suggesting that they could pinpoint the year in which a certain tree was exposed to high levels of radioactivity and create a dating framework for important civilizations.

Archaeologists today rely on vague evidence in dating important civilizations, such as significant events in ancient Egyptian and Mayan civilizations. While standard radiocarbon measurements provide estimates, these data are only accurate from 200 to 300 calendar years.

However, the researchers said that if the high levels of radiocarbon in the tree-ring data were also found in archaeological items taken from specific historical periods, such as timber, papyri, baskets made of living plants and other organic materials, the time markers could be used to point exactly when these events occurred.

"In the past, we have had floating estimates of when things may have happened," Dee said. "But these secret clocks could reset chronologies concerning important world civilizations with the potential to date events that happened many thousands of years ago to the exact year."

The study was published in the journal Proceedings of the Royal Society A.