Morphological evolution of the Salsa del Dragone mud volcano (Italy): historical data and modern investigations

Abstract

The Salsa del Dragone represents an emblematic example of a mud volcano in a complex geological setting, the northern Apennines of Italy, where fluid and mud emissions occur in poorly consolidated clayey soils and along permeable fracture systems. A modern reinterpretation of historical surveys allows the temporal range of study to be extended, providing new insights into the mud volcano’s dynamics. The surveys by Renato Biasutti (1906‑1907) document the site’s morphology, the arrangement of vents, and the characteristics of the mud, offering a valuable reference for comparison with the current situation.
Recent campaigns, carried out between 2023 and 2025 within the PROMUD (PROtocol for MUD volcanoes) project, produced detailed data on the affected surface using UAV (Unmanned Aerial Vehicle) photogrammetric surveys, generating precise orthophotos and maps. The integration of historical and modern data allowed common features to be identified and information to be aligned, comparing the surface distribution of 1906‑1907 with the present-day configuration.
Cross-referencing these data with geophysical measurements, obtained from both passive and active seismic surveys, enabled the formulation of a hypothesis on the evolution of the Salsa del Dragone, interpreted as a process of retreating terrain around the mud volcano, thus confirming hypotheses already suggested by Biasutti in 1907. These results also provide a solid starting point for future aerial and terrestrial survey campaigns.