Ferdinandea Island and Graham Bank, Sicily Channel: An Integrated Historical, Geological and Geomorphological Synthesis of a Shallow Submarine Monogenetic Volcanic Field

Ferdinandea Island, part of a shallow-water submarine volcanic field, emerged in the Sicily Channel between Italy and Tunisia in July 1831 and was eroded below sea level within months; its submerged remnant forms the shallowest water depth region of Graham Bank. Here, we review nearly two centuries of historical accounts, geological interpretations and geomorphological data analysis and reassess them against high-resolution multibeam bathymetry, sub-bottom profiles (CHIRP) and published multichannel seismic data. The field comprises six volcanic edifices (V1–V6), 100–170 m high, located along structural trends characteristic of the Sicily Channel Rift. V3, the shallowest edifice, is the remnant of Ferdinandea Island formed during the 1831 Surtseyan eruption. Its flat summit, wave-reworked terrace and steep flanks record rapid post-eruptive modification. Historical observations and hydrographic surveys document the destruction of the emergent island and a further ~6 m lowering of its shallowest point between 1883 and 2012–2015; the separate contributions of wave erosion, subsidence and gravitational adjustment cannot be resolved from the available data. The same regional structural framework appears to have governed the distribution of the other volcanic centres, pockmarks, erosional escarpments and mass-transport deposits of the study area. Seventeen pockmarks, up to ~540 m wide and 22 m deep, occur as isolated, clustered and locally aligned depressions; they are associated with subsurface concave-upward reflectors and local water-column acoustic anomalies, consistent with focused fluid escape. Failures of volcanic and sedimentary slopes are widespread, with the largest debris-avalanche deposit covering ~2.2 km2. Taken together, these observations indicate that tectonics, volcanism, fluid migration, wave- and bottom-current reworking, and gravitational instability have operated over different timescales to shape Graham Bank. Ferdinandea thus offers a rare historical and geological reference for investigating the rapid construction, degradation and long-term evolution of shallow-water volcanic edifices and highlights the still-open questions regarding the evolution and fate of ephemeral volcanic islands.