Integration of Remote Sensing and Offshore Geophysical Data for Monitoring the Short-Term Morphological Evolution of an Active Volcanic Flank: A Case Study from Stromboli Island

The Sciara del Fuoco (SdF) collapse scar at Stromboli is an active volcanic area affected by rapid morphological changes due to explosive/effusive eruptions and mass-wasting processes. The aim of this paper is to demonstrate the importance of an integrated analysis of multi-temporal remote sensing (photogrammetry, COSMO-SkyMed Synthetic Aperture Radar amplitude image) and marine geophysical data (multibeam and side scan sonar data) to characterize the main morphological, textural, and volumetric changes that occurred along the SdF slope in the 2020–2021 period. The analysis showed the marked erosive potential of the 19 May 2021 pyroclastic density current generated by a crater rim collapse, which mobilized a minimum volume of 44,000 m3 in the upper Sciara del Fuoco slope and eroded 350,000–400,000 m3 of material just considering the shallow-water setting. The analysis allowed us also to constrain the main factors controlling the emplacement of different lava flows and overflows during the monitored period. Despite the morphological continuity between the subaerial and submarine slope, textural variations in the SdF primarily depend on different processes and characteristics of the subaerial slope, the coastal area, the nearshore, and “deeper” marine areas

Isidella elongata (Cnidaria: Alcyonacea). First report in the Ventotene Basin (Pontine Islands, western Mediterranean Sea)

A mono-specific population of Isidella elongata in the Ventotene Basin (Pontine Islands, western Mediterranean Sea) was recently revealed by ROV survey. This vulnerable marine community was found on top of a 3.6 km long morphological high, in water depths between 510 and 560 m. Side scan sonar data showed the presence of several trawl marks suggesting a high anthropogenic impact of the study area. Furthermore, multibeam and high-resolution seismic data revealed the presence of widespread pockmarks, indicating occurrence of fluids in the sub-seafloor

Study of mass-wasting processes offshore NE Vulcano (Aeolian islands): A multidisciplinary approach

Vulcano is the southernmost island of the Aeolian Archipelago in the Southern Tyrrhenian Sea and represents the tip of a large stratovolcano that rises from ≈ 1000 mbsl. Its northern sector is dominated by La Fossa Caldera, whose northeastern part lies underwater and has been deeply eroded and breached. The dismantling of the caldera rim and infill has fed a large volcaniclastic fan in the offshore through repeated mass-wasting events. A multi-disciplinary approach was used to infer the main sedimentary processes acting in this submarine sector through the integration of a large dataset of marine geophysical data (multibeam, side scan sonar and seismics) and the results of sedimentological and micropaleontological analyses of seafloor samples. Overall, the northeastern submarine flank of Vulcano is mostly covered by relatively coarse-grained volcaniclastic sediments, resulting from sediment-laden gravity flows; this high-energy sedimentary system is able to transport fine and medium sand over 1100 mbsl down to the Stromboli Canyon. In detail, three morpho-sedimentary zones were recognized from the coastal sector to the offshore, each of them characterized by one (or more) prevalent reworking and transport processes: the first one corresponds to the highly incised submerged prosecution of La Fossa and is characterized by rock falls/avalanches and granular inertial flows. The second zone is represented by the wide Baia di Levante Fan system, where turbiditic sedimentation prevails, whereas the third zone encompasses most part of the lower submarine flank of Vulcano and the sedimentary highs located both inside and outside the BLF system, being dominated by hemipelagic deposition

Small-scale slope instability on the submarine flanks of insular volcanoes: the case-study of the Sciara del Fuoco slope (Stromboli).

Small-scale landslides affecting insular and coastal volcanoes are a relevant geohazard for the surrounding infrastructures and communities, because they can directly impact them or generate local but devastating tsunamis, as demonstrated by several historical accounts. Here, a review of such landslides and associated predisposing/triggering mechanisms is presented, with particular reference to the submarine volcanic flanks. We take into account, as a case study, the instability phenomena occurring on the Sciara del Fuoco (SdF, hereafter), a 2-km wide subaerial-submarine collapse scar filled by volcaniclastic products, which form the NW flank of the Stromboli volcano. Because of its steepness (>\u200930\ub0) and the high amount of loose volcanic material funneled from the summit crater towards the sea, the submarine part of the SdF is prone to instability phenomena recurring at different spatial and temporal scale. Particularly, landsides with a volume of some millions of cubic meters, as the 2002 tsunamigenic landslide, can repeatedly affect the submarine slope. Based on the integration of 11 years (2002\u20132013) of morpho-bathymetric monitoring of the SdF with geotechnical characterization of volcaniclastic and lava flow materials, stability analyses of the subaerial and submarine slope and previous literature studies, we analyze the role of different triggering mechanisms in controlling the occurrence and size of submarine slope failures at the SdF, such as dykes intrusion as occurred in 2002 or the emplacement of a large delta as occurred in 2007

Study of Recent Small-Scale Landslides in Geologically Active Marine Areas Through Repeated Multibeam Surveys: Examples from the Southern Italy

Repeat multibeam surveys are used to investigate recent submarine landslides in three different areas on southern Italy, i.e. Stromboli, Southern Messina Strait and Puma Alice. High-resolution Digital Terrain Models (DTMs) depict the morphology of mass-wasting events, while residual maps of the difference between successive bathymetric surveys indicate failure volumes ranging from tens of thousands to millions of cubic meters. A tentative estimate of recurrence time for the slope failures was based on chronological constraints and historical reports, and gave values ranging from tens to hundreds of years. Characterizing mass-wasting events and their recurrence time is a necessary step for geo-hazard assessment of densely populated coastal areas

Il canyon di Gioiosa Marea (Sicilia nord-orientale). Hazard presente e futuro della fascia costiera antistante.

Numerosi studi attribuiscono ai canyon sottomarini l’importante ruolo di captatore delle correnti di fondo cariche di sedimenti, con maggiore effetto quando è minore la loro distanza da costa. Tale processo determina un definitivo allontanamento dei sedimenti dalla fascia costiera ed un deficit sedimentario lungo costa che si manifesta sotto forma di erosione costiera. Questo è il caso del canyon di Gioiosa Marea, posto ad ovest di Capo Calavà (Sicilia nord-orientale). Questo canyon ha una testata larga circa 900 m, dista dalla costa 40 m ed è caratterizzato da numerosi lineamenti erosivo-deposizionali ben evidenti nei dati morfobatimetrici multibeam. Lo studio di immagini multi-temporali da Google Earth ha evidenziato una veloce evoluzione morfologica (spostamento di circa 10 m, prima verso terra e poi verso mare) di parte della testata del canyon, in funzione di periodi di erosione più o meno intensa. Tale evidenza mette in stretta relazione erosione costiera ed attività del canyon e sottolinea anche la pericolosità del canyon per la sua vicinanza a costa. Per questo motivo sono state effettuate ulteriori indagini in relazione al possibile sviluppo di futuri eventi di franamento presso la testata del canyon, ipotizzando un evento “dimensionato” sulle frane attuali ed un evento estremo legato ad un trigger sismogenetico, considerato che si tratta di un’area ad alta sismicità. Applicando le relazioni semiempiriche disponibili in letteratura, è stata tentativamente stimata un’onda anomala di 0,9 m sulla verticale del baricentro della frana ed un’onda di 1,8 m a costa per un evento di frana “dimensionato”; un’onda anomala di 5,4 m sul baricentro della frana e di 11,3 m a costa per un evento estremo. Oltre al rischio tsunamigenico, sono stati presi in considerazione anche i possibili scenari di inondazione della costa in relazione all’eventuale sollevamento relativo del livello del mare nell’area secondo l’approccio di Antonioli et al., 2020, che è la sommatoria di eustatismo, isostasi e tettonica (Sulli et al., 2013), risultando nell’ordine di 0,18 m al 2050 e 1,15-1,21 m al 2100, utilizzando le stime previsionali dell’IPCC 2019 e Rhamstorf 2007. Tali dati, applicati al territorio, potrebbero determinare un arretramento della linea di costa di circa 4-10 m