Scientists Got the Date of One of Europe's Biggest Volcanic Eruptions Wrong

The date of the last eruption of a huge volcano in Germany called Laacher See has been changed after scientists realized the original calculations were wrong.

The volcano was originally thought to have last erupted 13,077 years ago, 2021 research in the journal Nature found, but now, according to a new study—also in Nature—this date might be 130 years off, with the volcano actually erupting 12,880 years ago.

The previously estimated date was based on radiocarbon dating of the trees that had been preserved in the pyroclastic flow sediment. However, researchers think that carbon dioxide from the volcano's magma chamber may have filtered through the soil and become absorbed by the trees. This incorporated carbon has no radiocarbon isotopes in it, so will make the trees appear to be inaccurately old.

"The Laacher See eruption (LSE) in Germany ranks among Europe's largest volcanic events of the Upper Pleistocene," the authors of the 2021 paper wrote in the study. Thought to have been 250 times larger than the eruption of Washington state's Mount St. Helens in 1980, Laacher See's eruption had a Volcanic Explosivity Index (VEI) value of 6.

The VEI is a logarithmic scale where each value represents an eruption 10 times as powerful as the last. The eruption of Vesuvius was only a VEI 5, while Krakatoa's 1883 eruption and Mount Pinatubo in 1991 were VEI 6. Yellowstone is considered a VEI 8.

Trees around the volcano were flattened by the blast up for several miles, with a massive plume of smoke and ash reaching around 20 miles high, sending ash across Europe and spreading sulfur around the globe. Pyroclastic flows are thought to have suffocated the nearby area, wiping out plants and animals, and its ash was so thick that it stopped the flowing of the Rhine.

"Our new study notes that the recent date for the eruption does not consider dead carbon which is emitted by the volcano and is absorbed by trees," lead author James Baldini, a professor of Earth Sciences at Durham University, said in a statement.

"Therefore, the trees used in the Reinig et al. (the 2021 paper) were contaminated by this volcanic carbon, producing an age that was around 130 years too old."

The updated estimate of 12,880 years ago is backed up by a newly discovered spike of sulfur in the Greenland ice sheet, thought to have been a result of the eruption. This sulfur spike has been dated to around 12,870 years ago, closely matching the new eruption date estimate.

"This perspective is supported by the presence of a very large sulfur spike found in the Greenland ice sheet with all the characteristics of the Laacher See eruption, dated 130 years after the new Reinig et al., date," Baldini said.

Laacher See, which has lain still since this last eruption, is still an active volcano, and today has a lake inside its caldera. Magma activity has been recently detected below the caldera, as well as seismic activity, German news outlet DW reported, although experts don't anticipate another eruption occurring any time soon.

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