The eruption of the underwater volcano Columbo in the Aegean Sea in 1650 caused a devastating tsunami described by historical eyewitnesses. Dr. from the Helmholtz Center for Ocean Research at GEOMAR, Kiel. A group of researchers led by Jens Carstens explored the underwater crater Columbus and reconstructed historical events using modern imaging techniques.

They found that eyewitness accounts of the disaster could only be identified by the combination of a landslide followed by an explosive explosion. Their findings were published today in the journal Nature Communication.

The eruption was visible from the Greek island of Santorini for several weeks. In the late summer of 1650, people reported that the water had changed color and was boiling. About seven kilometers northeast of Santorini, an underwater volcano rose from the sea and began spewing bright rocks.

Fire and lightning were visible and clouds of smoke darkened the sky. The water then suddenly receded, and after a few seconds it rose to the shoreline and crashed into the shore with waves up to 20 meters high. The powerful explosion was heard from more than 100 kilometers away, pumice and ash fell on the surrounding islands, and the deadly poisonous gas cloud claimed many lives.

Dr. D., an expert in marine geophysics at GEOMAR at the Helmholtz Center for Ocean Research in Kiel. “We know these details of the historic Columbus eruption because there are contemporary reports collected and published by a French volcanologist in the 19th century,” says Jens Carstens. .

So how did these devastating events happen? To find out, he and his German and Greek colleagues traveled to Greece’s Aegean Sea in 2019 to explore the volcanic crater using special technology. “We wanted to understand how the tsunami occurred at that time and why the volcano erupted so powerfully,” says Carstens.

Aboard the now-decommissioned research vessel POSEIDON, the team used 3D seismic techniques to create a three-dimensional image of the crater, located 18 meters below the water surface. One of the authors of the study, Dr. “This allows us to look inside the volcano,” says Gareth Crutchley.

Not only did the 3D image show that the crater was 2.5 kilometers in diameter and 500 meters deep, indicating a truly powerful explosion, but seismic profiles also showed that one side of the cone was severely deformed.

“This part of the volcano has definitely slipped,” says Crutchley. The researchers then took a detective approach, comparing various mechanisms that could have caused the tsunami with historical eyewitness accounts. They concluded that only the combination of a landslide and subsequent volcanic eruption could explain the tsunami.

Combining three-dimensional seismic data with computer simulations, the researchers were able to reconstruct how high the waves would have been if they had been caused solely by the explosion. “Accordingly, waves of 6 meters can be expected in a particular place, but we know from eyewitnesses that there were waves of 20 meters,” says Carstens.

It is also said that the sea receded at a different point first, but in computer simulations the crest of the wave reaches the shore first. Therefore, an explosion alone cannot explain the tsunami. However, when drift was included in the simulations, the data were consistent with historical observations.

Jens Carstens explains: “Part of Columbo consists of pumice with rather steep slopes. It is not very stable. During the eruption, which lasted several weeks, lava constantly erupted. Underneath, a tremendous pressure was created in the magma chamber, which contains a lot of gas. When one of the slopes of the volcano slid, “The effect was like uncorking a bottle of champagne: the sudden drop in pressure allowed the gas in the magma system to expand, leading to a massive explosion.”

Something similar could happen during the 2022 eruption of the underwater volcano Hunga Tonga, whose volcanic crater has a similar shape to the Columbus crater.

Therefore, the study was conducted by Prof. from the National and Kapodistrian University of Athens (NKUA). Dr. It provides valuable information for the development of active underwater volcanic activity monitoring programs such as SANTORY, led by Paraskevi Nomikou. “We hope that we can use our results to develop new approaches to monitoring volcanic disturbances,” says Jens Carstens, “and perhaps even for an early warning system that will collect real-time data.” That would be my dream.” Source