A study reveals a new volcano imaging method that creates high-resolution pictures of seismic wave patterns. Researchers have detected a sizable, previously unseen body of mobile magma beneath Columbo, an active underwater volcano near Santorini, Greece. The presence of this magma chamber increases the chance of a future eruption and could pose risks to nearby populations within the next century and a half.
About four centuries ago, in AD 1650, Columbo breached the sea surface and erupted, claiming the lives of about 70 people on Santorini. This event, associated with the Theran volcanic system, was driven by magma accumulating beneath Columbo. Current findings suggest the molten material inside the chamber has reached a similar scale to that ancient event.
Geophysical research described in a recent Geochemistry, Geophysics, Geosystems report marks the first use of full-waveform inverse seismic imaging to monitor changes in subsurface magmatic activity along one of the submarine volcanoes on the Hellenic Arc where Columbo sits.
Full waveform inversion technology analyzes seismic profiles that span kilometers and highlights velocity differences in underground rocks. The results indicate where moving magma bodies may reside and provide estimates of their size and melting rates.
Seismic data were collected after researchers fired air cannons from a research vessel operating above the volcanic area. The generated seismic waves were captured by ocean-floor seismometers positioned along the arc.
“Full waveform inversion is like a medical ultrasound,” explained a volcanologist from Imperial College London and a study coauthor. “It uses sound waves to render an image of a volcano’s subterranean structure.”
Lower seismic velocities beneath the seafloor point to a circulating magma chamber beneath Columbo.
Lead author Kajetan Chrapkiewicz, a geophysicist at Imperial College London, noted that existing submarine data in the region were sparse and uncertain. The diverse seismic profiles and the application of full waveform inversion enabled much clearer images than before. The newly described large magma chamber has been accumulating at roughly 4 million cubic meters per year since Columbo’s last eruption in 1650 AD.
A large explosive eruption in 150 years
The study estimates the total melt stored in the lower Columbo magma reservoir at about 1.4 cubic kilometers. If growth continues at the current pace, Columbo could reach two cubic kilometers of molten material, potentially surpassing the 1650 eruption in scale within the next 150 years. While melt volumes can be estimated, precise timing of the next eruption remains uncertain.
Findings suggest that the magmatic system at Columbo could trigger an eruption of substantial violence, reminiscent of the Hunga Tonga-Hunga Ha’apai event but with possible greater impact due to proximity to Santorini’s population center. Greece lies about 7 kilometers from Columbo, underscoring the risk to nearby communities.
Columbo sits in a relatively shallow portion of the Mediterranean at a depth near 500 meters, and current estimates indicate rising explosivity potential. Researchers anticipate a tsunami and an ash-laden eruption column extending tens of kilometers as events unfold.
Jens Karstens, a geophysicist at the GEOMAR Helmholtz Centre for Ocean Studies in Kiel, stressed the value of these findings. “With studies like this, more can be learned about how volcanic structures operate, what to expect from them, and where to anticipate an eruption. That knowledge can guide underwater volcano monitoring systems.”
The ongoing research adds to the growing understanding of Columbo, the most active underwater volcano in the Mediterranean, and the dangers it poses. The team notes that full waveform inversion could help identify similar magma reservoirs beneath other active submarine volcanoes. However, the method can be spatially limiting and slow, suggesting it should be used alongside techniques such as sediment drilling and seismographic monitoring to form a clearer picture of submarine volcanic activity.
Underwater observatory
In recent years, an international team has established Santorini’s seabed volcanic observatory, SANTORY, equipped with instruments capable of tracking Columbo’s activity. SANTORY is still developing, but its design serves as a blueprint for potential underwater monitoring stations.
As noted by researchers, terrestrial monitoring networks for land-based volcanoes outnumber those at sea. Monitoring beneath the ocean is more complex and costly, yet essential for early warning and public safety.
Alongside data from SANTORY and sediment cores from the International Ocean Exploration Program’s Expedition 398, the team hopes this work convinces policymakers of the critical need for real-time monitoring at submarine volcanoes.
“We need better data on what’s really going on beneath these volcanoes,” explained the lead author. “Continuous monitoring systems enable earlier warnings and safer evacuation planning.”
Reference work: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GC010475
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Environmental authorities seek to advance monitoring capabilities and public safety planning in response to these insights, with a focus on strengthening early-warning networks for coastal communities.