Abstract

Submarine mud volcanoes (MVs) are seafloor features commonly found in tectonically active margins with high sedimentation and compressional regimes. This study reports the first discovery of a prominent crater-like mud volcano on the Chilean margin, named the Cucao Mud Volcano (CMV), located ?86 km offshore Chiloé Island (?42°S) at a depth of 1800 m. Multichannel seismic data reveal that the CMV is structurally emplaced along the crest of a faulted anticline within a transpressional setting, indicating that tectonic deformation governs both its morphology and fluid pathways. A strong, continuous Bottom Simulating Reflector (BSR), seismic blanking, bright spots, and chaotic facies in the shallow subsurface suggest the presence of gas hydrates, free gas, and active fluid migration. High-resolution multibeam bathymetry and backscatter mosaics show a caldera-like edifice with a central crater, dome-shaped flanks, and surrounding depressions. Comparative data from 2012 to 2018 indicate reduced surface activity, possibly reflecting a transition to a quiescent phase. Additionally, dome-shaped reflectors above the BSR suggest diapir-like intrusions and vertical conduits associated with gas hydrate dissociation and overpressure. These findings underscore the complex interplay between tectonics, gas hydrate systems, and mud volcanism, positioning the CMV as a key site for understanding fluid dynamics along convergent continental margins. © 2025 Elsevier Ltd