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Abstract

During eruptive events, large amounts of volcanic ash are released into the atmosphere. However, the wind is not solely responsible for transport and dispersion of volcanic particles; in coastal areas, marine dynamics plays an interesting role in spreading and dropping ashes down to the seafloor impacting marine biogeochemistry, ocean fertilization and, overall, marine ecosystem. Unlike atmospheric monitoring with satellite technology, volcanic ash settling along seawater column is difficult to document, so understanding how marine processes can affect it, is still fraught with uncertainty. Here is presented a new perspective on how to catch volcanic fallout in marine areas, through several cases associated with different Mt. Etna eruptive events occurred between 2013 and 2015. The presence of a cabled multidisciplinary benthic observatory and a mooring system, both part of the EMSO ERIC Western Ionian node, allowed recording of ash deposits along the water column. The analysis of the ADCPs acoustic backscattering combined with other data, allowed to characterize each episode recorded from the evolution of the eruptive activity, up to the ash fallout into the sea, where volcanic particles settle through a more than 2 km thick water column. Data recorded show a surprisingly fast vertical transport, suggesting that intense ash aggregation processes may have occurred. The importance of a multidisciplinary infrastructure in particular areas, such as that of the western Ionian Sea, is confirmed by the possibility of monitoring key processes otherwise unexplored, carrying out multidisciplinary studies essential to explain the complex processes observed.