Growth of the submarine Paphsanias Volcanic Field within the Epidavros tectonic graben in the Western Saronikos Gulf, Aegean Sea

The Methana volcanic centre, located on the northwestern edge of the Aegean volcanic arc, formed owing to the Hellenic subduction zone. Submarine volcanic activity NW of the Methana Peninsula has created the Paphsanias Volcanic Field, comprising six volcanic edifices of varying morphology and heights of up to 185 m. These edifices lie within the eastern Epidavros Basin, a tectonic graben defined by WNW–ESE-, NE–SW- and NW–SE-trending faults, filled with 250–500 m of Plio-Quaternary sediments. Newly acquired 5 m resolution bathymetric data revealed a link between these submarine structures and onshore volcanism, through detailed morphometric analysis highlighting the initiation of NE–SW faulting and a subsequent tectonic phase characterized by east–west-trending faults. The orientation and distribution of the submarine edifices suggest a connection to extensional fault systems and magma ascent, with a general growth trend to the north. Moreover, between Methana and Agistri Island, a hummocky area with scattered and aligned blocks marks a multi-phase failure event. These debris avalanche deposits exhibit moderate mobility, differing from the high-mobility avalanches seen in other Aegean volcanic arc regions, such as Santorini and Nisyros.