Abstract
The three volcanoes that are the object of this paper show different types of activity that are representative of the large variety of volcanism present in the Central Mediterranean area. Etna and Stromboli are sub-aerial volcanoes, with significant part of their structure under the sea, while the Marsili Seamount is submerged, and its activity is still open to debate. The study of these volcanoes can benefit from multi-parametric observations from the seafloor. Each volcano was studied with a different kind of observation system. Stromboli seismic recordings are acquired by means of a single Ocean Bottom Seismometer (OBS). From these data, it was possible to identify two different magma chambers at different depths. At Marsili Seamount, gravimetric and seismic signals are recorded by a battery-powered multi-disciplinary observatory (GEOSTAR). Gravimetric variations and seismic Short Duration Events (SDE) confirm the presence of hydrothermal activity. At the Etna observation site, seismic signals, water pressure, magnetic field and acoustic echo intensity are acquired in real-time thanks to a cabled multi-disciplinary observatory (NEMO-SN1 ). This observatory is one of the operative nodes of the European Multidisciplinary Seafloor and water-column Observatory (EMSO; www.emso-eu.org) research infrastructure. Through a multidisciplinary approach, we speculate about deep Etna sources and follow some significant events, such as volcanic ash diffusion in the seawater.
Highlights
The Mediterranean area is characterized by the convergence between the Eurasian and African plates, with contemporary collisional and extensional processes occurring along plate margins [1,2].In this framework, volcanic phenomena have taken place in the Central Mediterranean region since the Oligocene [3], and starting from the Tortonian, the Tyrrhenian basin has opened with the development of the Magnaghi and Vavilov oceanic basins (4.3–2.6 Ma)
We focus on data acquired on the seafloor in the proximity of the volcanoes (Figure 1) by: (1) An ocean bottom seismometer placed at 1500 m b.s.l. (Beyond the Sea Level) at the toe of Stromboli Volcano; (2) A multidisciplinary observatory deployed at ~3300 m b.s.l. at the NW
A couple of scalar and vectorial magnetometers are placed on a separate module (Figure 2B) that is moved some tens of meters away by the Remotely-Operated Vehicle (ROV) after the deployment, in order to avoid interference from the other devices
Summary
The Mediterranean area is characterized by the convergence between the Eurasian and African plates, with contemporary collisional and extensional processes occurring along plate margins [1,2]. Seafloor fixed-point multidisciplinary observatories offer new possibilities to detect signals on a longer time scale They allow for extensive and long-term synchronous measurements of signals from different sensors (multi-parameter). They are present worldwide, and their number is increasing with time [18], providing useful information on little-known oceanic areas and, in particular, on volcanic structures and activity (e.g., [19,20]). A sub-product of these measurements is the echo intensity, which can be used to infer scatterer concentration in the water column [35,36,37] This feature is mostly used to monitor sediment and turbidity fluxes in rivers and coastal areas, but it can be used to detect ash fallout in seawater from volcanic explosive activity. We focus on data acquired on the seafloor in the proximity of the volcanoes (Figure 1) by: (1) An ocean bottom seismometer placed at 1500 m b.s.l. (Beyond the Sea Level) at the toe of Stromboli Volcano; (2) A multidisciplinary observatory deployed at ~3300 m b.s.l. at the NW base of the Marsili Seamount; (3) A multidisciplinary observatory deployed offshore of the eastern coast of Sicily, at a depth of ~2100 m, in proximity to the submerged flank of Etna Volcano
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