“a real scientific leap for underwater volcanology and oceanography in the Aegean”, Evi Nomikou declared.
Researchers are deploying a 500-meter fiber-optic cable into the Kolumbo underwater volcano near Santorini, transforming it into a high-tech listening post for geological threats, tovima.com reported.
The mission, dubbed HYDROSENSE, is a collaborative effort involving scientists from the National and Kapodistrian University of Athens (NKUA), the Monterey Bay Aquarium Research Institute (MBARI) in the U.S., and Italy’s National Research Council (CNR). The work is being conducted aboard the CNR research vessel Gaia Blu.
From Milos to the Kolumbo Crater: A Technological Stress Test
The project’s methodology, known as Distributed Acoustic Sensing (DAS), is not new to the Aegean. Greek City Times reports that the technology was field-tested off the island of Milos. There, researchers laid about 500 meters of cable in shallow water, keeping the laser-based detection system on land and using local divers for deployment.
Kolumbo presents a vastly more formidable challenge. The volcano’s crater, at depths approaching 500 meters, is a complex and active geological environment. Unlike the Milos test, divers cannot assist with the installation due to the extreme depth and treacherous terrain. The team will instead use a specialized deployment system, guided by a remotely operated vehicle (MiniROV) equipped with advanced sensors from MBARI’s CoMPAS Lab.
Scientists Lower Fibre-Optic Cable Into Santorini’s Kolumbo Volcano Greek, US and Italian scientists lay 500 metres of cable in the Kolumbo volcano off Santorini to listen for gas and tremors.#GreekCityTimes #AaronMicallef #Anydros #Athens #Cnr #Eart…https://t.co/6UubbolPbD
What This Means for Subsurface Sensing
DAS works by sending laser pulses down a fiber-optic cable and measuring the minuscule changes in the light that is reflected back. These changes, caused by vibrations and acoustic disturbances, allow the system to function as a dense network of thousands of virtual sensors along the cable’s length. This creates an unprecedented ability to listen to the seafloor, capturing faint signals that traditional land-based seismic networks often miss.
The primary objective at Kolumbo is to analyze the acoustic signatures of gas bubbles escaping from the hydrothermal vents. The researchers aim to determine if this “sound” can quantify the volume of gas being released and track how these emissions fluctuate over time. To validate the DAS data, the mission also employs an underwater stereoscopic camera, temperature sensors, and hydrophones for direct sound recording.
The 30,000-Earthquake Catalyst
The urgency for this advanced monitoring system stems directly from a geological crisis in early 2025. During a one-month period, the region experienced a volcanic and tectonic crisis that generated over 30,000 earthquakes. This seismic activity rapidly shifted northeast from the Kolumbo volcano towards the islet of Anydros, showing how the fault system changes unpredictably.
While research has progressed, scientists still lack a comprehensive understanding of the underwater pathways through which hot fluids and gases escape, and many weak acoustic signals associated with microseismic activity go undetected.
The SANTORY Observatory and the Future of Continuous Monitoring
Professor Nomikou stressed that continuous monitoring cannot rely on periodic research voyages. She identified the reinstallation of all instruments from the SANTORY underwater volcanic observatory at Kolumbo as a critical priority. This would require sustained state funding and support from the Municipality of Thira, which administers Santorini, to build a permanent, institutional monitoring capability.
Architectural Breakdown: How DAS Functions Under Pressure
The core of this mission is the DAS system, which repurposes existing fiber-optic infrastructure. The architecture involves a laser source injecting coherent light pulses into the cable. As these pulses travel down the fiber, they encounter microscopic imperfections in the glass, which cause a tiny amount of light to scatter back towards the source.
When an acoustic wave or vibration from the surrounding water passes the cable, it minutely alters the density and strain of the fiber. This strain changes the optical path length, causing a detectable shift in the phase of the backscattered light. By analyzing these phase shifts at a high sampling rate, the system can reconstruct a detailed acoustic profile of the environment along the entire length of the cable.
Aaron Micallef, lead researcher at the MBARI Seafloor Processes Lab, said the vents in Milos sit in shallow water close to shore, which allowed the team to keep the laser system on land while local divers laid the cable. Micallef described the Kolumbo site as a different and particularly interesting scientific challenge.
Turning a simple cable into a dense sensor array advances the technology. It effectively creates a line-array sonar with thousands of elements, offering spatial resolution that was previously unattainable with sparse arrays of individual, expensive sensors.
Why This Matters: The Broader Implications for Geohazard Tech
The HYDROSENSE mission demonstrates the practical application of advanced telecommunications technology (fiber-optics) in the field of earth science.
Fiber-Optic Cable Monitors Santorini Volcano Activity
A 500-meter fiber-optic cable is being turned into a sensor array to listen to a sleeping giant beneath Santorini. This isn’t just about listening for earthquakes; it’s about decoding the language of a volcano to build a real early-warning system.
