The historic underwater explosion of the Kolumbo volcano in the Aegean, which occurred in 1650 causing a devastating tsunami, was reconstructed by researchers from the German GEOMAR institute in collaboration with the National and Kapodistrian University of Athens and the University of Hamburg. The 3D imaging provided new information about the event and opens new avenues for monitoring volcanic eruptions.

The team of researchers, led by Jens Carstens from the GEOMAR Helmholtz Center for Ocean Research in Kiel, explored the underwater Columbus Crater with state-of-the-art imaging technology and reconstructed the historical events using 3D seismic profiles for the first time. The findings are published in the journal Nature Communications.

The eruption was visible in Santorini for several weeks. In September 1650 people reported that the color of the water had changed and the water was boiling. About seven kilometers northeast of Santorini an underwater volcano had risen from the sea and started spewing red-hot rocks. Clouds of smoke darkened the sky and fires and lightning could be seen. The water then suddenly receded to rush towards the coastline a few minutes later, “lashing” it with waves up to 20 meters high. A huge bang was heard more than 100 kilometers away, pumice and ash fell on the surrounding islands and a deadly cloud of poisonous gases claimed the lives of several people in Santorini.

The details of the historic eruption were collected and published by a 19th century French volcanologist, and there are also historical descriptions from the island’s inhabitants. But how did these catastrophic events come about?

To provide answers, the research team studied the volcanic crater of Columbus with special marine technology machines. “We wanted to understand how the tsunami occurred at that time and why the volcano erupted so violently,” notes Jens Carstens.

The research team then used 3D seismic methods to create a 3D image of the crater, the shallowest part of which is 18 meters below the surface of the water.

3D seismic imaging is a geophysical technique that takes advantage of the fact that sound waves are partially reflected at layer boundaries. This makes it possible to create cross-sectional profiles of geological structures beneath the sea floor. Unlike 2D reflection seismic, 3D marine reflection seismic uses multiple measurement cables (receivers) that are towed in parallel behind the research vessel. The result is a three-dimensional image, known as a seismic volume, which allows us to look below the seabed and analyze the geology of the area in detail.

Three-dimensional imaging during this investigation showed that the crater was two and a half kilometers in diameter and 500 meters deep, suggesting a truly massive eruption, while seismic profiles also revealed that one side of the cone had been severely deformed.

The researchers then decided to compare the various mechanisms that could have caused the tsunami with historical eyewitness accounts. As Evi Nomikou, associate professor of EKPA and one of the authors of the study, explains to APE-MPE, it was found that “only the combination of a landslide followed by a volcanic eruption could explain the tsunami”. “The explosion alone cannot explain the creation of the tsunami. However, when landslides were included in the simulations, the data agreed with historical observations,” she adds.

The study provides valuable information for the development of programs to monitor active underwater volcanic activity, such as the “Santory” program, led by Ms. Nomikou.

“We hope to be able to use our results to develop new approaches to monitoring volcanic disturbances. Our dream is to create an early warning system by collecting data in real time. Now we have placed innovative undersea sensors in the active Columbus hydrothermal field and data is collected every six months,” points out Ms. Nomikou.

Maria Kouzinopoulou

S.S. Related photos are attached.

Photo2: 3D seismic dataset of Columbus Volcano, showing the deposits of the 1650 eruption (the orange translucent overlay) and the crater formed by a large eruption. Credit: Karstens et al. 2023

Photo Kolumbo: Photo of the undersea volcano Kolumbo. Credit: SANTORY