Deciphering the Cataclysm: The Enigma of a Volcanic Tsunami Unraveled After Centuries

Utilizing sophisticated imaging techniques, scientists have examined the eruption of the Kolumbo underwater volcano in 1650, discovering that the consequential tsunami was precipitated by a landslide followed by an eruption. These insights contribute significantly to the enhancement of monitoring for submarine volcanic activities.

In-depth study of a historic volcanic eruption accomplished with 3D seismic imaging by GEOMAR researchers.

The cataclysmic eruption of the Kolumbo submarine volcano, situated in the Aegean Sea in 1650, generated a devastating tsunami, historically documented by eyewitnesses. Dr. Jens Karstens from the GEOMAR Helmholtz Centre for Ocean Research Kiel spearheaded a team that investigated the submerged crater of Kolumbo using cutting-edge imaging technology to piece together the historical sequence of events. Their research, indicating that the accounts of this disaster correlate with a landslide and subsequent eruption, was disseminated in the journal Nature Communications on October 26.

Examining the Past

Witnesses on the Greek island of Santorini observed the eruption for several weeks. In late summer 1650, changes in water color and a boiling sea were reported. An underwater volcano erupted approximately seven kilometers northeast of Santorini, projecting incandescent rocks and creating sights of fire and lightning with smoke plumes that obscured the heavens. Subsequently, the sea withdrew abruptly and then surged back, creating waves reaching heights of up to 20 meters that struck the coast. A loud detonation was heard over 100 kilometers away, while pumice and ash showered neighboring islands, and toxic gases claimed lives.

Today’s serene Santorini caldera. Credit: Jonas Preine

“These details of Kolumbo’s historic eruption are known thanks to 19th-century compilations of contemporary reports by a French volcanologist,” Dr. Jens Karstens, a marine geophysicist at GEOMAR, states.

To discern the origins of these catastrophic events, Karstens and his team undertook a 2019 expedition to the Aegean Sea to study the volcanic crater with advanced equipment.

Karstens notes, “Our goal was to comprehend the genesis of the tsunami and the volcano’s violent explosion.”

A specialized technology involving two trawl doors, a signal source, and 15 measuring cables, also known as streamers, was deployed behind the research vessel to generate a three-dimensional representation of the Kolumbo volcano, now situated between 18 and 500 meters underwater. Credit: Thies Bartels

Scientific Scrutiny and Prospective Surveillance

Aboard the now-retired research vessel POSEIDON, the researchers employed 3D seismic technology to visualize the crater in three dimensions.

Co-author Dr. Gareth Crutchley elaborates, “With this technology, we can peer into the volcano.” The 3D imagery revealed a massive 2.5-kilometer wide and 500-meter deep crater, indicative of an immense eruption. Seismic profiles also showed substantial deformation of one side of the volcanic cone.

Crutchley points out, “This segment of the volcano appears to have collapsed.” By examining various mechanisms potentially responsible for the tsunami and comparing them with historical eyewitness reports, the team deduced that only a combination of a landslide followed by a volcanic eruption could account for the tsunami. These findings are featured in the journal Nature Communications.

Geological cross-sections from seismic data unveil the crater’s recorded history. Credit: Karstens et al. 2023

Using 3D seismic data alongside computer simulations, the researchers hypothesized the wave heights if produced solely by the explosion.

Karstens explains, “Based on this, one would anticipate waves of six meters at a specific location; however, historical accounts describe them as 20 meters high there.”

Moreover, there was an initial sea recession reported at another location, but the computer simulation shows a wave crest arriving first at the coast. This suggests that the eruption by itself is insufficient to explain the tsunami event. Including the landslide in the simulations, however, yielded results consistent with the historical accounts.

Karstens elaborates: “Kolumbo is composed in part of pumice with very steep inclines, making it structurally unsound. Over several weeks of eruption, lava was expelled continuously. Beneath, within the highly pressurized gas-laden magma chamber, when the volcano’s flank collapsed, it was akin to uncorking a champagne bottle: the abrupt pressure release allowed the magma’s gas to expand rapidly, causing a massive explosion.”

A similar event may have occurred during the 2022 Hunga Tonga underwater volcano eruption, which has a comparable structure to Kolumbo’s crater.

The penultimate mission of the now-retired RV POSEIDON focused on investigating the underwater volcano Kolumbo, which erupted in 1650. Credit: Paraskevi Nomikou

This investigation offers critical knowledge for developing monitoring systems for active submarine volcanoes, such as the SANTORY project led by co-author Prof. Dr. Paraskevi Nomikou of the National and Kapodistrian University of Athens. “We are hopeful that our findings will pave the way for novel methodologies to monitor volcanic unrest and possibly, in the future, an early warning system with real-time data collection. That is my aspiration,” states Jens Karstens.

Understanding 3D Marine Reflection Seismics

3D seismics is a geophysical method that utilizes the reflection of sound waves at layer boundaries, allowing for the creation of geological cross-sectional imagery beneath the seabed. In contrast to 2D seismics, the marine 3D approach employs multiple parallel receivers towed by the research vessel, resulting in a seismic volume that offers detailed geological analysis below the seafloor.

Reference: “Cascading events during the 1650 tsunamigenic eruption of Kolumbo volcano” by Jens Karstens, et al., 26 October 2023, Nature Communications.
DOI: 10.1038/s41467-023-42261-y

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More about Kolumbo volcanic eruption

• GEOMAR Helmholtz Centre for Ocean Research
• Nature Communications Journal
• National and Kapodistrian University of Athens
• 3D Seismic Imaging Technology
• History of the 1650 Kolumbo Eruption