Researchers have discovered an extensive hydrothermal vent system near the Greek island of Milos, revealing previously unknown activity along active fault lines. The find, made during a recent expedition, highlights the island's role as a key site for studying tectonic and volcanic processes in the Mediterranean. Depths of the vents range from 100 to 230 meters, reshaping understandings of regional geology.
A team of scientists, led by Solveig I. Bühring from the MARUM Center for Marine Environmental Sciences at the University of Bremen, made the surprising discovery during the METEOR expedition M192. Using underwater mapping tools, autonomous vehicles, and remotely operated vehicles, they surveyed the seafloor around Milos and identified three main vent regions: Aghia Kiriaki, Paleochori-Thiorychia, and Vani.
These vents are aligned with active fault zones within the Milos Gulf-Fyriplaka graben, a tectonic depression that has sunk parts of the seafloor to depths of up to 230 meters. The positioning underscores how tectonic forces channel hot, gas-rich fluids to the surface, creating diverse features like boiling fluids and microbial mats on chimneys.
"We never expected to find such a large field of gas flares off Milos," Bühring said. "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."
Paraskevi Nomikou, the study's first author from the National and Kapodistrian University of Athens, noted the precise correlation with fault patterns. "Our data clearly show that the gas flares follow the patterns of the major fault systems around Milos," she explained. "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 discovery positions Milos as one of the Mediterranean's largest shallow to intermediate-depth hydrothermal systems. It stems from collaboration between Greek and German institutions, including the University of Athens, MARUM, and others. The findings, published in Scientific Reports in 2025, pave the way for future expeditions to nearby sites like the Kolumbo submarine volcano near Santorini and Nisyros, advancing knowledge of tectonics, volcanism, and hydrothermal interactions.