Patterns in the recent 2007–2008 activity of Mount Etna volcano investigated by integrated geophysical and geochemical observations

Abstract

[1] Seismic, deformation, and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment. In spite of their wide use, there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques. Here we combine seismic (volcanic tremor and long-period seismicity), deformation (GPS), and geochemical (volcanic gas plume CO 2 /SO 2 ratios) measurements in an attempt to interpret trends in the recent (2007)(2008) activity of Etna volcano. We show that each eruptive episode occurring at the Southeast Crater (SEC) was preceded by a cyclic phase of increase-decrease of plume CO 2 /SO 2 ratios and by inflation of the volcano's summit captured by the GPS network. These observations are interpreted as reflecting the persistent supply of CO 2 -rich gas bubbles (and eventually more primitive magmas) to a shallow (depth of 1-2.8 km asl) magma storage zone below the volcano's central craters (CCs). Overpressuring of the resident magma stored in the upper CCs' conduit triggers further magma ascent and finally eruption at SEC, a process which we capture as an abrupt increase in tremor amplitude, an upward (>2800 m asl) and eastward migration of the source location of seismic tremor, and a rapid contraction of the volcano's summit. Resumption of volcanic activity at SEC was also systematically anticipated by declining plume CO 2 /SO 2 ratios, consistent with magma degassing being diverted from the central conduit area (toward SEC).

Ten years of soil CO2 continuous monitoring on Mt. Etna: Exploring the relationship between processes of soil degassing and volcanic activity

“…These are not included in the graph in order to simplify Figure 8a. These observations are coherent with those made in Aiuppa et al [2010] and Cannata et al [2010]. Furthermore, È…”

“…If the batch of magma continues to move toward the surface, the depressurization determines a rapid decrease in the SO 2 solubility in magma and a consequent decrease of the CO 2 /SO 2 ratio in the plume gases; this trend is shown with a red line in Figure 7b and is consistent with the cycles of the plume CO 2 /SO 2 ratios during the 2007-2009 volcanic activity on Mt. Etna [Aiuppa et al, 2010]; soil CO 2 flux also follows the same trend (green line of Figure 7b). Although CO 2 is continuously released from magma, the source (magma) moves to the top of the edifice and does not supply the peripheral areas where the CO 2 monitoring stations are located.…”

“…[40] The following five intervals (III-VII in black), with the exception of the third, coincided with increase-decrease CO 2 /SO 2 plume ratio cycles, described in Aiuppa et al [2010]. Of these, it is particularly clear that intervals IV, V, and VI show a good correlation between the plume and the È 11 Norm signal.…”

“…[48] As pointed out in Aiuppa et al [2010], cycles of increase-decrease of CO 2 /SO 2 plume ratios are very closely linked to volcanic activity. These authors, using a multidisciplinary approach, showed that the resumption of volcanic activity at SEC was systematically anticipated by a complete CO 2 /SO 2 plume cycle (increasing-decreasing) and marked by sharp increases in tremor.…”

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

“…As anticipated, this accords with the previous source modeling obtained by the analysis of the strain changes . For the lava fountains of NSEC, several geochemical and geophysical studies (Aiuppa et al, 2010;Bonaccorso et al, 2011a,b;Calvari et al, 2011;Ganci et al, 2012;Corsaro et al, 2017) supported the interpretation that these events were violent releases of bubble-rich magma layers previously decoupled from the melt and trapped at shallow depths close to sea level. The observed behavior for the NSEC lava fountains is a cyclic process of charge/discharge.…”