In 1257 A.D., a massive volcano erupted, spreading ash all over the world. The explosion was so big that scientists can see its chemical signal as far away as the Arctic and Antarctic. Medieval manuscripts from the time describe a sudden change of weather, failed harvests and confusion. But scientists had no idea where the eruption happened.

Now, one group thinks they’ve solved the mystery. A recent paper in the journal PNAS suggests that the offending volcano was probably Samalas volcano on Lombok Island in Indonesia. Jonathon Amos at the BBC reports:

The team has tied sulphur and dust traces in the polar ice to a swathe of data gathered in the Lombok region itself, including radiocarbon dates, the type and spread of ejected rock and ash, tree-rings, and even local chronicles that recall the fall of the Lombok Kingdom sometime in the 13th Century.

Not much remains of the mountain today—just a crater lake—but the researchers suggest that the volcano was big and fierce. It could have belched out as much as 10 cubic miles of ash, as high as 25 miles into the sky. According to National Geographic, the eruption was eight times bigger than the Krakatau eruption that you might have heard about, and twice as large as the 1815 Tamobra eruption.

The researchers themselves write:

Based on ice core archives of sulfate and tephra deposition, one of the largest volcanic eruptions of the historic period and of the past 7,000 y occurred in A.D. 1257. However the source of this “mystery eruption” remained unknown. Drawing on a robust body of new evidence from radiocarbon dates, tephra geochemistry, stratigraphic data, a medieval chronicle, this study argues that the source of this eruption is Samalas volcano, part of the Mount Rinjani Volcanic Complex on Lombok Island, Indonesia. These results solve a conundrum that has puzzled glaciologists, volcanologists, and climatologists for more than three decades. In addition, the identification of this volcano gives rise to the existence of a forgotten Pompeii in the Far East.

But unlike Pompeii, this volcano left behind no preserved cities or bodies. Just a mystery that might finally be solved.

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