Effects of tidal stresses on volcanic activity at Mount Etna, Italy

Abstract

Here we model quantitatively the stress and strain induced by tidal forces as possible triggers of Mount Etna eruptions during 1989, 2000 and 2001, by means of 2D numerical analysis by finite difference method applied to the volcano edifice. Spectral and vectorial analysis of tidal acceleration indicates that the quasi‐diurnal, semi‐diurnal and ter‐diurnal constituents may have induced decompressions up to some kPa in the shallow (i.e., 1,500 m) gas‐saturated magma reservoir, which controlled magma vesiculation and the timing of lava fountain activity from the South East Crater (SEC). We consider the geological heterogeneities in the volcanic edifice (i.e., rock geometries and properties, feeder conduit and vent systems, volcanic landforms), the magma properties (i.e., Bulk modulus, volatile content) and the ongoing volcano‐tectonic stresses (i.e., volcano flank deformations), which strongly influence the response of eruptive activity to tidal forces. Indeed, the tidal factor may act on flank deformation concomitant to shallow magma inflation. The implications of our model may help understand the eruptive behaviour and the disequilibrium state of the volcano and may be useful for hazard assessment at Mount Etna.

Is There an Influence of the Pole Tide on Volcanism? Insights From Mount Etna Recent Activity

“…Previous works (Bozzano et al, 2013;Sottili et al, 2007) brought evidences that, on hourly to daily timescales, the periodic decompression induced by tidal stresses on Mount Etna shallow plumbing system may act as a trigger mechanism for eruptive activity on condition that the eruptive system is already close to a critical state. At Mount Etna, this mechanism of tidal triggering of lava fountaining episodes is statistically more evident when the horizontal component of the quasi-diurnal tidal stresses acts in parallel with the ongoing eastern volcano flank instability (Sottili et al, 2007).…”

“…Through a simple time-predictable model, and by assuming a constant magma supply rate, it has been proposed that eruptions occur when the amount of stored magma reaches a critical value (Hill et al, 1998). Under these conditions, when the Mount Etna plumbing system is close to a critical state, the effects of decompression induced by external actions, as tidal forces (Sottili et al, 2007) and earthquakes (Bozzano et al, 2013) seem to affect the timing of eruptions at Mount Etna on short (days to hours) timescales. In our analysis, we considered the starting date and the magnitude of eruptions defined here as the logarithm of the erupted mass (in kg) of magma (e.g., Pyle, 2000).…”

“…Stress changes modulated by the LOD centrifugal forces-and estimated of the order of~400 kPa/year (Sottili et al, 2015)-have been reported to produce crustal deformations on multiyear scale (Wang et al, 2000). Active volcanoes are sensitive to other periodic crustal stress changes occurring over different timescales (see Table S2), as also reported for volcanoes along the "Ring of Fire" (Rymer & Brown, 1984;Kasahara et al, 2001;Palladino & Sottili, 2014); Stromboli, Italy (Johnston & Mauk, 1972;Sottili & Palladino, 2012); Kilauea, Hawaii (Brown, 1925;Dzurisin, 1980); Mayon, Philippines (Jentzsch et al, 2001); Ruapehu, New Zealand (Girona et al, 2018); and Mount Etna (Patanè et al, 1994;Sottili et al, 2007). Active volcanoes are sensitive to other periodic crustal stress changes occurring over different timescales (see Table S2), as also reported for volcanoes along the "Ring of Fire" (Rymer & Brown, 1984;Kasahara et al, 2001;Palladino & Sottili, 2014); Stromboli, Italy (Johnston & Mauk, 1972;Sottili & Palladino, 2012); Kilauea, Hawaii (Brown, 1925;Dzurisin, 1980); Mayon, Philippines (Jentzsch et al, 2001); Ruapehu, New Zealand (Girona et al, 2018); and Mount Etna (Patanè et al, 1994;Sottili et al, 2007).…”

Earth’s rotation variability triggers explosive eruptions in subduction zones

“…corresponding to ±45 Pa/h for typical annual ΔLOD values). For comparison, decompression rates related to glacio-eustatism and tidal forces, considered among possible controlling factors of volcanic eruptions, range in the order of a few Pa per year (Kutterolf, et al 2012) and 150 Pa/h (Sottili et al 2007), respectively, whilst magma volatile pressure build-up is reported around 400-720 Pa/h (Johnston and Mauk 1972;Jentzsch et al 2001). …”

“…due to global tectonism, glacio-eustatism and tidal forces; Kutterolf et al 2012;Sottili et al 2007). The recently described causal relationship between LOD changes and volcanic eruptions (Palladino and Sottili 2014) provides the background to understand how yearly LOD changes perturb the state of stress in specific geodynamic contexts.…”