When we hear “Aegean Sea”, it often conjures up images of Ancient Greece, relaxing beach holidays, or sparkling blue waters. But underneath the glittery surface lies Kolumbo, an active submarine volcano that in 1650, erupted and triggered a destructive tsunami. Thanks to modern imaging technology, researchers have now successfully reconstructed the event, finally solving the “why” and “how” of what happened nearly 400 years ago.
The 1650 Kolumbo eruption
Like many historical events, up until now our understanding of the 1650 Kolumbo eruption and tsunami came primarily from eyewitness accounts. According to these reports, in the late summer of 1650 fire and lightning could be seen to the northeast of Santorini. Suddenly, there was a massive bang, one that could be heard over 100 kilometers (62 miles) away, and pumice, ash, and poisonous gas began to fall on the Aegean islands.
As if that wasn’t bad enough, moments before, the sea had rapidly receded, returning in the form of tsunami waves that were reportedly up to 20 meters (66 feet) high. "We know these details of the historic eruption of Kolumbo because there are contemporary reports that were compiled and published by a French volcanologist in the 19th century," explained Dr Jens Karstens, an author of a paper detailing the event’s reconstruction, in a statement.
The issue with contemporary reports is that they don’t explain the reasons behind the eruption and the tsunami that followed. "We wanted to understand how the tsunami came about at that time and why the volcano exploded so violently,” said Karstens.
Solving the mystery
The research team first used seismic imaging technology to create a 3D image of Kolumbo’s crater, which revealed the signs of a huge eruption; the crater was 2.5 kilometers (1.55 miles) long and 500 meters (1,640 feet) deep. One side of the volcano’s cone had also been severely deformed, which indicates that there was a landslide.
But what triggered the tsunami in 1650 – the landslide, or the eruption itself? A combination of the 3D images and computer simulations revealed that it was, in fact, both. Matching historical accounts of when the waters receded versus when the loud bang was heard, the researchers concluded that the combination of both the landslide and the violent eruption that followed was the likely explanation for the huge waves. Simulated waves weren’t as high when it was just one or the other.
"Kolumbo consists partly of pumice with very steep slopes. It is not very stable,” Karstens explained. “During the eruption, which had been going on for several weeks, lava was continuously ejected. Underneath, in the magma chamber, which contained a lot of gas, there was enormous pressure. When one of the volcano's flanks slipped, the effect was like uncorking a bottle of champagne: the sudden release of pressure allowed the gas in the magma system to expand, resulting in a huge explosion."
The researchers think that something similar could’ve happened during last year’s Hunga Tonga-Hunga Ha’apai eruption, which was the largest natural explosion in a century and had significant impacts on the surrounding seabed and the ozone layer above.
As a result, they think their research could potentially be used to lay the groundwork for new ways of monitoring active submarine volcanoes. "We hope to be able to use our results to develop new approaches to monitor volcanic unrest," said Karstens, "Maybe even an early warning system, collecting data in real-time. That would be my dream."
The study is published in Nature Communications.