One of history's great disaster mysteries may be solved—the case of the largest volcanic eruption in the last 3,700 years. Nearly 800 years ago, the blast that was recorded, and then forgotten, may also have created a "Pompeii of the Far East," researchers suggest, which might lie buried and waiting for discovery on an Indonesian island.

The source of an eruption that scattered ash from pole to pole has been pinpointed as Samalas volcano on Indonesia's Lombok Island. The research team, led by geographer Franck Lavigne of the Université Paris 1 Panthéon-Sorbonne, has now dated the event to between May and October of 1257. The findings were published today in the Proceedings of the National Academy of Sciences.

"It's been a long time that some people have been looking," said Lavigne. After glaciologists turned up evidence for the blast three decades ago, volcano experts had looked for the origin of the eruption everywhere from New Zealand's Okataina volcano to Mexico's El Chichón.

The previously unattributed eruption was an estimated eight times as large as the famed Krakatau explosion (1883) and twice as large as Tambora in 1815, the researchers estimate. (Related: "Tambora: The Greatest Explosion in History.") "Until now we thought that Tambora was the largest eruption for 3,700 years," Lavigne said, but the study reveals that the 1257 event was even larger.

Volcano Mystery Uncovered

To solve the mystery, the multidisciplinary team paired known clues with new radiocarbon-dating results, volcanic ejecta chemistry, stratigraphic data, and historical writings. "This eruption was known by many different disciplines, many researchers," Lavigne said, "but the main problem may be that they worked individually. I think this is a key point for work on other eruptions. We had geologists, geochemists, geographers, historians, radiocarbon-dating specialists, and many others—all these researchers from different specialties to combine facts."

The cataclysm blasted 10 cubic miles (40 cubic kilometers) of debris up to 27 miles (43 kilometers) high into the sky, producing fallout that settled around the world. Near the volcano itself, it settled into thick deposits that the team sampled in over 130 places to produce a stratigraphic and sedimentologic picture of the way the eruption unfolded.

The scientists refined the eruption date by sampling carbonized tree trunks and branches along the flanks of the Samalas and Rinjani volcanoes. The radiocarbon data was consistent with the mid-century eruption date and showed no samples younger than 1257. Those radiocarbon dates ruled out other likely candidates, such as El Chichón and Okataina, whose eruptions occurred outside this time frame. (Related: "Mega-eruptions Caused Mass Extinction, Study Finds.")

Further afield, the volcanic sulfate and tephra became locked in ice core samples taken from both Greenland and Antarctica. The eruption's geochemical "fingerprint" was uncovered two decades ago, Lavigne said. "We started with the ice cores," he said, "and we know from the [distribution near both poles] that the eruption was tropical."

That narrowed the field further. Ecuador's Quilotoa did produce a massive, caldera-creating eruption in roughly the same time period, and an enduring caldera much like the massive example at Segara Anak—but the findings from the ice samples ruled it out. Geochemical composition studies of glass shards found in both the Greenland ice sheet and Antarctica are much less of a match for the glass chemistry of Quilotoa tephra—but a very convincing match for Samalas glass.

"This just shows that there is a lot we don't know about volcanic eruptions, even what may seem like basic questions about some of these very big eruptions," said geologist Ben Andrews of the Smithsonian Institution's Global Volcanism Program, which maintains a public database chronicling 10,000 years of volcanic eruptions. "This international team of scholars did a huge amount of work to help us understand this one."

Impact Felt Around the World

Though the eruption was equatorial, its impact was felt and noted around the world. "The climate was disturbed for at least two years after the eruption," Lavigne said. Evidence of this was found in studies of tree rings that revealed abnormal growth rates, climate models, and historical records from as far afield as Europe."

Medieval chronicles, for example, describe the summer of 1258 as unseasonably cold, with poor harvests and incessant rains that triggered destructive floods—a "year without a summer." The winter immediately following the eruption was warmer in western Europe, however, as would be expected from high-sulfur eruptions in the tropics. The team cites historical records from Arras (northern France) that speak of a winter so mild "that frost barely lasted for more than two days," and even in January 1258 "violets could be observed, and strawberries and apple trees were in blossom."

In Indonesia records describe a catastrophe of a far more destructive and immediate sort. Found written on palm leaves, the Old Javanese texts of the Babad Lombok describe a massive volcanic blast that formed a caldera at Mount Samalas (read: rinjani), on Lombok Island. The writing describes the deaths of thousands of people due to deadly ashfall and pyroclastic flows that destroyed Pamatan, capital of the kingdom, and surrounding lands. While the records did not list an exact date, they narrowed the field considerably by stating that it took place before the end of the 13th century, lining up the historical record with the scientific evidence of the eruption.

Andrews noted that actual descriptions of such an enormous eruption are extremely rare because such eruptions happen only about once every 600 years. "This kind of chronicle could only be written if one of them happened near enough to where people were writing the records but not so near that the eruption clobbered them," he said.

In the case of Samalas, a far more tantalizing physical remnant than texts could await discovery—the ancient Lombok kingdom's capital of Pamatan, perhaps buried by the enormous blast. "Pamatan might represent a 'Pompeii of the Far East,'" the study authors note, but in what condition is anyone's guess.

"It's certainly intriguing," Andrews added. "Sometimes the effects of pyroclastic flow can be relatively gentle, like Pompeii where ash killed everyone but didn't obliterate the city. Other eruptions, like parts of Mount St. Helens in 1980, leveled areas of the countryside, so sometimes these flows just destroy everything. You really just do not know."

Original Source : National Geographic

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