GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.3 267 dense-rock equivalent masses during the first paroxysm were of 10 9 kg and the second 10 8 kg or 3.5 x 10 5 m 3 e 3.5 x 10 4 m 3 , respectively. However, masses and volumes related to the second paroxysm could be largely underestimated. Volumes of the pyroclastic deposits of VOR have been estimated at 7.1 x 10 6 m 3 (Corsaro et al. , 2017). Volumes of lava flows emitted by NSEC on December 2015 display a minimum at 2 x 10 6 m 3 and a maximum at 2.6 x 10 6 m 3 . The total average volumes erupted during the three main eruptive episodes (May 2015, December 2015 and May 2016) are therefore the following: (1) May 2015: 3.9 x 10 6 m 3 ; (2) December 2015: 9.7 x 10 6 m 3 ; and (3) May 2016: 5.6 - 8.8 x 10 6 m 3 (Branca, personal communication). This allow estimating a total average erupted volume of magma of about 2.0 x 10 7 m 3 over the considered period. Considering the total volume of degassed magma on 31 May 2016 (1.2 x 10 8 m 3 ), the balance between the degassed and erupted magma yields a volumetric ratio of about 6:1, which imply a volume of intruded and not erupted magma of about 1.0 x 10 8 m 3 . Conclusions. We investigated the correlation between the daily bulk flux of SO 2 and the eruptive activity at Mt. Etna during the period March 2015 - May 2016. The SO2 emission displayed changes in connection with eruptive activity at both temporal and magnitude scale. Balance between the volumes of degassed magma and erupted magma reveals an unbalance of 6:1. This ratio implies two scenarios in (i) which intruded magma are confined at depth with the crust (Francis et al. , 1993, Allard et al. , 1996) or (ii) potential remobilization upward of degassed magma through a flushing processes or gas-rich magma injections from depth (Giuffrida et al. , 2018). References Allard, P. (1997), Endogenous magma degassing and storage at Mount Etna , Geophys. Res. Lett., 24 , 2219–2222, doi:10.1029/97GL02101 Cannata A., Di Grazia G., Giuffrida M., Gresta S., Palano M., Sciotto M., Viccaro M. and Zuccarello F.; 2018: Space-time evolution of magma storage and transfer at Mt. Etna volcano (Italy): The 2015-2016 reawakening of Voragine crater . Geochem. Geophys. Geosyst., 19 , 471-495, doi 10.1002/2017GC007296. Corsaro R.A., Andronico D., Behncke B., Branca S., Caltabiano T., Ciancitto S., Cristaldi A., De Beni E., La Spina A., Lodato L., Miraglia L., Neri M., Salerno G., Scollo S. and Spata G.; 2017: Monitoring the December 2015 summit eruptions of Mt. Etna (Italy): Implications on eruptive dynamics . J. Volcanol. Geotherm. Res., 341 , 56-69, doi 10.1016/j.jvolgeores.2017.04.018. Francis P., Oppenheimer C., Stevenson D., 1993; Endogenous growth of persistently active volcanoes . Nature, 366 (6455), 554. Giammanco S., M. Neri, G.G. Salerno, T. Caltabiano, M.R, Burton, V. Longo: 2013; Evidence for a recent change in the shallow plumbing system of Mt. Etna (Italy): gas geochemistry and structural data during 2001-2005. J. Volcanol. Geotherm. Res . , 251 , 90-97. Giuffrida M., Viccaro M. and Ottolini L.; 2018: Ultrafast syn-eruptive degassing and ascent trigger high-energy basic eruptions . Scientific Reports, 8 , 147, doi 10.1038/s41598-017-18580-8 Oppenheimer C.; 2003: Volcanic degassing . Treatise in Geochemistry, 3-9 , 123-166. Salerno G.G., Burton M., Oppenheimer C., Caltabiano T., Tsanev V.I. and Bruno N.; 2009: Novel retrieval of volcanic SO 2 abundance from ultraviolet spectra . J. Volcanol. Geotherm. Res., 181 , 141-153, doi 10.1016/j. jvolgeores.2009.01.009. Spilliaert, N., P. Allard, N. Métrich, and A. V. Sobolev (2006), Melt inclusion record of the conditions of ascent, degassing, and extrusion of volatile- rich alkali basalt during the powerful 2002 flank eruption of Mount Etna (Italy) . J. Geophys. Res., 111 , B04203, doi:10.1029/2005JB003934 Shinohara H. and Witter J.; 2005: Volcanic gases emitted during mild Strombolian activity of Villarrica volcano, Chile . Geophys. Res. Lett., 32 , L20308, doi 10.1029/2005GL024131.