Surprise magma chamber found under Mediterranean Sea volcano near popular tourist destination

A new study has uncovered a previously undetected magma chamber beneath Kolumbo, an active submarine volcano in the Mediterranean Sea near Santorini, Greece.

A group of international researchers used a novel imaging technique for volcanoes that produces high-resolution images of seismic wave properties, according to a Jan. 12 release from the American Geophysical Union (AGU).

The study was published in the AGU journal Geochemistry, Geophysics, Geosystems, and the authors noted that the presence of the chamber “poses a serious hazard as it could produce a highly explosive, tsunamigenic eruption in the near future.”

Researchers are recommending real-time hazard monitoring stations near other active submarine volcanoes to improve estimations of when an eruption might be likely to occur.


“The current state of the reservoir indicates that an explosive eruption of high societal impact in the future is possible (though not imminent), thus we suggest establishing a permanent observatory involving continuous earthquake monitoring… and seafloor geodesy,” they wrote.

The indicated eruption would be similar to but of a lesser magnitude to the recent Hunga Tonga-Hunga Ha’apai eruption, bringing a predicted tsunami and an eruptive column tens of kilometers high.

Maxar satellite imagery shows the Hunga Tonga-Hunga Ha’apai volcano on Dec. 24, 2021, before the eruption on Jan. 14, 2022, in the Hunga Tonga-Hunga Ha’apai Islands, Tonga.
(Maxar via Getty Images)

The study was reportedly the first to use full-waveform inversion seismic imaging to look for changes in magmatic activity beneath the surface of submarine volcanoes along the Hellenic Arc, where the volcano is located.

Submarine volcanic activity along a section of the Kolumbo crater on the seafloor, observed with SANTORY monitoring equipment.

The technology is applied to seismic profiles, or recordings of ground motions along kilometers-long lines, and assesses differences in wave velocities that may indicate subsurface anomalies. The group found that full-waveform inversion technology can be used in volcanic regions to find potential locations, sizes and melt rates of mobile magma bodies.


The seismic profiles were constructed after the scientists fired air-gun shots from aboard a research vessel cruising over the volcanic region, triggering seismic waves that were recorded by ocean-bottom seismometers located along the arc.

A significantly decreased velocity of seismic waves that travel beneath the seafloor indicated the presence of a mobile magma chamber underneath Kolumbo, according to the study, with the characteristics of the wave anomalies used to better understand the potential hazards the magma chamber may present.

Images helped to identify a large magma chamber that has been growing at an average rate of roughly 4 million cubic meters per year since Kolumbo’s last eruption in 1650 C.E., nearly 400 years ago.

A view of the town of Oia with its lime-washed houses and churches with blue domes on Santorini in the Aegean Sea.
(Marcos del Mazo / LightRocket via Getty Images / File)

The last time Kolumbo erupted, it killed 70 people in Santorini.

The study’s lead author noted that if the current rate of magma chamber growth continues, sometime in the next 150 years the volcano could reach the 2 cubic kilometers of melt volume that was estimated to be ejected during the 1650 C.E. eruption.

Although volcanic melt volumes can be estimated, there is no way to tell for sure when Kolumbo, which lies at around 500 meters deep, will erupt next.


“We need better data on what’s actually beneath these volcanoes,” Kajetan Chrapkiewicz, a geophysicist at Imperial College London and the lead author of the study, said in a statement. “Continuous monitoring systems would allow us to have a better estimation of when an eruption might occur. With these systems, we would likely know about an eruption a few days before it happens, and people would be able to evacuate and stay safe.”

For the past few years, scientists have worked on establishing SANTORY (Santorini’s seafloor volcanic observatory) that will be able to measure progressions in Kolumbo’s volcanic activity. It is still under development.