Just a few days ago, we were laying a fiber-optic cable across the shallow, sandy seafloor of Paleochori Bay, Milos, to determine whether we could detect vibrations associated with escaping gas bubbles. Now, we are preparing to take that technology into a very different environment: the crater of an active submarine volcano.

Our destination is Kolumbo, located approximately seven kilometers (4.3 miles) northeast of Santorini, Greece. Unlike the shallow hydrothermal fields of Milos, Kolumbo is a submarine volcanic edifice with a crater reaching water depths of 500 meters (1,640 feet). Its hydrothermal system releases hot fluids and gases through the seafloor, making it a fascinating natural laboratory for investigating processes occurring within active submarine volcanoes.

The HYDROSENSE expedition, led by Mariacristina Prampolini from the Institute of Marine Sciences of the National Research Council of Italy (CNR-ISMAR), brings together scientists and engineers with expertise in marine geology, geophysics, hydrothermal systems, and underwater technology. Our objective is to investigate how different observational methods can be combined to better understand the volcanic structure, fluid circulation, and hydrothermal activity at Kolumbo.

One of the technologies we will be testing is distributed acoustic sensing (DAS), building on our recent experiment in Milos. In Paleochori Bay, divers helped us position the fiber-optic cable across the seabed at depths of approximately 20 meters (65 feet). At Kolumbo, the challenges are considerably greater. We will need to deploy the cable in much deeper water, position it using an underwater vehicle, and investigate whether it can record signals associated with volcanic and hydrothermal activity.

DAS is only one part of the investigation. We also plan to carry out detailed acoustic and geophysical surveys to map the volcanic crater and investigate its subsurface structure. The MiniROV, equipped with sensors and algorithms developed by MBARI’s CoMPAS Lab, will allow us to examine geological features at very fine spatial scales, while sediment and fluid sampling will provide information about the physical and chemical processes occurring beneath the seabed.

We are now in transit towards Kolumbo, having completed mobilization aboard the Italian research vessel Gaia Blu in Catania, Sicily. Over the past few days, the scientific team has been busy loading equipment, assembling instruments, checking connections, and preparing the various systems needed for the expedition. Bringing together so many different technologies requires considerable coordination, particularly when working within the limited space and tight schedule of a research vessel.