Morpho-acoustic characterization of a shallow-water mud volcano offshore Scoglio d'Affrica (Northern Tyrrhenian Sea) responsible for a violent gas outburst in 2017

New Approaches for the Observation of Transient Phenomena in Critical Marine Environment

“…In this area, the seabed is mainly sandy with scattered rocky blocks. from the point of view of morphology, the area is characterized by multiple lobate mudflows on the side of the mound, some of which have a fresh-looking morphology and most not colonized by Posidonia oceanica meadows, suggesting a repetition of eruptive events in recent times, supported by an overall smooth morpho-acoustic facies (FSS) [40]. In this area, emission activity consisted in trains of bubbles of centimeter size coming out intermittently from small holes of centimeter size.…”

“…The data collected using the e-URoPe ROV were acquired in a sub-area of the area investigated by the ITS Magnaghi, that is part of an elongated main NNW-SSE ridge that rises 30 m from the surrounding seabed, not far from the Scoglio d'Affrica site, already observed in the high-resolution bathymetric data collected subsequent to the 2017 gas outburst. The ridge is made up of two mounds whose tops are located at about 8 m and 10 m water depths, respectively [40]. The ROV collected Moreover, three analog cameras installed at the stern and bow offered the pilot a subjective panoramic view of the operating environment.…”

“…One of the main results obtained by analyzing the videos acquired with the ROV was the possibility not only to characterize the environment in support of the traditional geochemical and morphological analyses but also to observe degassing processes extremely localized in space and study their evolution over time, opening a window to the dynamics of the emission processes also in spatial terms. To this end, a table (Table 2) that summarizes the main features of the points of interest, obtained by integrating the ROV data with the morphological data from [40] and the geochemistry of the area known in the literature [44,45], was created in order to give hints of the mechanisms that originate some of the observed phenomena. 11: position coordinates (WGS84-EPSG 4326), depth of the seabed (m), seabed type, presence or not of gas emission, and the image of the area extracted from the video.…”

“…11: position coordinates (WGS84-EPSG 4326), depth of the seabed (m), seabed type, presence or not of gas emission, and the image of the area extracted from the video. * = morphology data as indicated in [40]; ** = geochemistry data as indicated in [44,45].…”

“…In this area, emission activities consisted of small bubbles, intermittent and originating from the sediment. Going up the slope of the western side of this mound, the morphological structures are of a lower and smooth slope (LSS) divided in sub-facies according to the density of the blocks [40]. In this area, there is the F point, located at the boundary of the top part of the mound, in a shallow water area (about −12 m).…”