Scientists Lower Fibre-Optic Cable Into Santorini’s Kolumbo Volcano

Scientists are turning the Kolumbo volcano off Santorini into a listening post, laying about 500 metres of fibre-optic cable in its crater to track volcanic activity.

Researchers from the National and Kapodistrian University of Athens (NKUA) are taking part in the HYDROSENSE mission. They work alongside the US-based Monterey Bay Aquarium Research Institute (MBARI) and Italy’s National Research Council (CNR).

Operations take place from the CNR research vessel Gaia Blu.

The aim is to capture faint vibrations and sounds that could reveal hidden processes on the seabed.

Located north-east of Santorini, the Kolumbo volcano is an active underwater volcano and a key site for monitoring geological hazards. It also offers a natural testing ground for new technology.

In early 2025, a volcanic and seismic crisis hit the area for about a month, with more than 30,000 earthquakes. During that period, the activity shifted quickly north-east of the Kolumbo volcano, towards the islet of Anydros.

Evi Nomikou, a professor of geological oceanography at NKUA, said the new method marks “a real scientific leap for underwater volcanology and oceanography in the Aegean”.

How the fibre-optic cable listens

HYDROSENSE uses Distributed Acoustic Sensing (DAS), which turns a single fibre into a long chain of sensors.

Laser pulses travel along the fibre while the system measures tiny changes in the light that bounces back. As a result, it can detect vibrations and sound at hundreds of points along the cable.

Specifically, the researchers want to know if the noise of gas bubbles shows how much gas the Kolumbo volcano releases. They also want to see how those emissions change over time.

To check the readings, the team is using an underwater stereo camera and temperature sensors. A hydrophone also records the sound of the escaping gas.

Nomikou said land-based seismic networks struggle to detect many of these processes.

Once linked to the Geo-Sense system, the cable will record underwater tremor, bursts of tiny earthquakes and the paths that fluids take, she said.

Tested first on Milos

The team first tested the method on Milos, home to one of the world’s largest known shallow underwater geothermal systems.

There, the vents sit in shallow water close to shore, said Aaron Micallef, lead researcher at the MBARI Seafloor Processes Lab. So the team kept the laser system on land, while local divers laid about 500 metres of cable.

By comparison, divers cannot work inside the Kolumbo volcano, where the cable will sit at depths of almost 500 metres. Instead, the crew will lower the cable from the ship, guided by a remotely operated MiniROV.

Micallef said the site presents a different and particularly interesting scientific challenge.

After the mission, the team will retrieve the cable. If the method works, it could one day provide constant monitoring of large areas of seabed.

Nomikou also wants every instrument of the SANTORY observatory back at the Kolumbo volcano, with state funding and help from the Municipality of Thira.

Permanent monitoring cannot rely only on periodic research projects, she said.

Source: Ta Nea

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