Scientists think they have found the volcano responsible for a huge eruption that occurred in AD1257. The mystery event was so large its chemical signature is recorded in the ice of both the Arctic and the Antarctic. European medieval texts talk of a sudden cooling of the climate, and of failed harvests.
An international team indicates it was the Samalas Volcano on Lombok Island, Indonesia. Little remains of the original mountain structure - just a huge crater lake. 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.
"The evidence is very strong and compelling,"said Prof Clive Oppenheimer, from Cambridge University. Co-worker Prof Franck Lavigne, from the Pantheon-Sorbonne University, France, added: "We conducted something similar to a criminal investigation.
"We didn't know the culprit at first, but we had the time of the murder and the fingerprints in the form of the geochemistry in the ice cores, and that allowed us to track down the volcano responsible."
The team's studies on Lombok indicate that as much 40 cubic kilometres (10 cubic miles) of rock and ash could have been hurled from the volcano, and that the finest material in the eruption plume would likely have climbed 40km (25 miles) or more into the sky. It would have had to be this big in order for material to be carried across the entire globe in the quantities seen in the Greenland and Antarctic ice layers.
The impact on the global climate would have been significant. Medieval texts describe atrocious weather the following summer in AD1258. It was cold, and the rain was unrelenting, leading to flooding. Archaeologists recently put a date of AD1258 on the skeletons of thousands of people who were buried in mass graves in London.
"We cannot say for sure these two events are linked but the populations would definitely have been stressed," according to Prof Lavigne.
In comparison with recent catastrophic blasts, Samalas was at least as big as Krakatoa (AD1883) and Tambora (AD1815), the researchers believe. The ice cores do hold clues to yet another colossal event in about 1809, but, like Samalas before it, finding the source volcano has been difficult.
Prof Oppenheimer said: "It's outstanding that we haven't come across evidence for it." There doesn't seem to be any recorded historic proof of it nor any written independent witness accounts. Where in the world could you bury such bad news? This eruption was a super volcanic event that had global impact.
Could this happen again? It could. With the extreme climate changes in response to global warming, it is not unreasonable to say the odds are increasing.