Newly Discovered Hydrothermal Fields Off The Island Of Milos

The study identifies three major vent areas — Aghia Kiriaki, Paleochori–Thiorychia, and Vani — all located along active fault zones that run across the Milos shelf.

These faults belong to a large tectonic depression, the Milos Gulf–Fyriplaka graben, which has lowered the seafloor to depths of up to 230 meters. The close alignment of vents with these geological structures shows that tectonic activity plays a key role in determining where hydrothermal venting occurs.

“We never expected to find such a large field of gas flares off Milos,” says Solveig I. Bühring, senior author of the study and scientist at the MARUM – Center for Marine Environmental Sciences, University of Bremen, who led the expedition M192 during which the vents were discovered. “When we first observed the vents through the ROV cameras, we were stunned by their diversity and beauty — from shimmering, boiling fluids to thick microbial mats covering the chimneys.”

According to first author Paraskevi Nomikou of the National and Kapodistrian University of Athens, the spatial pattern of these vent clusters is closely controlled by the island’s tectonic fabric:

“Our data clearly show that the gas flares follow the patterns of the major fault systems around Milos,” Nomikou explains. “Different fault zones influence different vent clusters, especially where several faults meet. These tectonic structures strongly control how and where hydrothermal fluids reach the seafloor.”

The findings demonstrate how active faulting and ongoing geological processes have shaped the evolution of these vent fields. This discovery establishes Milos as one of the most significant natural laboratories in the Mediterranean for studying the interplay between tectonics, volcanism, and hydrothermal activity.

The results are also relevant for the MARUM-based Cluster of Excellence “The Ocean Floor – Earth’s Uncharted Interface.” A follow-up expedition to Milos, the Kolumbo submarine volcano off ,, and Nisyros is planned. The research is the result of close collaboration between Greek and German institutions, including the National and Kapodistrian University of Athens, MARUM – University of Bremen, Friedrich-Alexander-Universität Erlangen-Nürnberg, ICBM – Institute for Chemistry and Biology of the Marine Environment Oldenburg, and Constructor University Bremen.

Original publication:

Paraskevi Nomikou, Konstantina Bejelou, Andrea Koschinsky, Christian dos Santos Ferreira, Dimitrios Papanikolaou, Danai Lampridou, Stephanos P. Kilias, Eirini Anagnostou, Marcus Elvert, Clemens Röttgen, Joely M. Maak, Alissa Bach, Wolfgang Bach, Areti Belka, Evgenia Bazhenova, Karsten Haase, Charlotte Kleint, Effrosyni Varotsou, Palash Kumawat, Erika Kurahashi, Jianlin Liao, Eva-Maria Meckel, Ignacio Pedre, Wiebke Lehmann, Enno Schefuß, Michael Seidel, Sotiria Kothri & Solveig I. Bühring: Structural control and depth clustering of extensive hydrothermal venting on the shelf of Milos Island. Scientific Reports volume 15 (2025). DOI: https://doi.org/10.1038/s41598-025-26398-y

Ag. Kiriaki (A): a) water column depiction above the illustrated area, coordinates: 36°38.824’ N, 24°29.4516’ E, b) ROV photo above the seafloor at the area of Ag. Kiriaki with patches of bacterial mats on the sediments, c) AUV bathymetric map illustrating the morphology of the depressions formed due to hydrothermal activity. Paleochori-Thiorychia (B): d) water column depiction above the “Celestial Chimney”, coordinates: 36°42.0233’ N, 24°35.6548’ E, e) ROV photo of the “Celestial Chimney” partly covered with white bacterial mat (GeoB255-20), f) AUV bathymetry combined with multibeam data to illustrate the morphology of the seafloor east of Paleochori-Thiorychia. Vani (C): g) water column depiction above the illustrated active area of Vani, h) ROV photo above a highly active area with boulders covered partly with bacterial mat and yellow sulfur precipitated (GeoB255-36), coordinates: 36°46.6873’ N, 24°20.9174’ E, i) AUV bathymetric map illustrating the morphology of the vent field within the Vani graben. — Scientific Reports

Structural control and depth clustering of extensive hydrothermal venting on the shelf of Milos Island, Scientific Reports (open access)

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