Nearly everyone has heard that you can determine the age of a tree by counting its rings. Now, researchers think trees can reveal other secrets, too, such as the timing of specific events dating back thousands of years. Scientists at Oxford University say that trees capture evidence of radiation bursts from solar storms in the form of “time markers” that could help researchers date significant events in world history. This discovery could help archaeologists pinpoint milestones in ancient civilizations.

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The Oxford research team discovered unusually high levels of the radioactive isotope carbon-14 in the rings of certain trees. The isotope stems from severe solar storms, and its enduring presence in tree-rings may help scientists more accurately date ancient events. Researchers believe that major solar storms sent bursts of radiation down to Earth in 775 and 994AD, which became trapped inside the rings of trees growing at that time. Catalogs of tree-ring data around the world include the growth year for each corresponding tree, so identifying the year in which a tree was exposed to elevated radioactivity becomes a relatively simple task.

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Until now, archaeologists have had only vague ideas of when culturally significant events have taken place, such as milestones in ancient Egyptian and Mayan civilizations. With this new insight, radiocarbon dating of even just a few events can help frame future studies of ancient history. Oxford researchers point out that the radiation time-markers will also exist in every living plant or tree that grew during such a solar storm event, so the markers will be evident wherever those materials were used, such as an ancient building constructed from lumber or baskets woven from local plants.

The findings were recently published in the Proceedings of the Royal Society A.


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