Tephra characterization and multi-disciplinary determination of Eruptive Source Parameters of a weak paroxysm at Mount Etna (Italy)

New insights into real-time detection of tephra grainsize, settling velocity and sedimentation rate

“…In addition, it is important to note that tephra particles are not spherical and their maximum density is often around 2700 kg m −3 for andesitic to basaltic compositions (e.g. Sakurajima 22 , Stromboli and Etna volcanoes in Italy 12 , 45 , 46 ). Hence, margin fallers can easily be filtered from LPM records using the Ganser 38 drag equation assuming densities of 2700 kg m −3 and a sphericity of 1 (Figs.…”

A Model for Buoyant Tephra Plumes Coupled to Lava Fountains With an Application to the 29th of August 2011 Paroxysmal Eruption at Mount Etna, Italy

“…Large particles that have fallen out are not supported by the outer plume and are, therefore, completely removed from the system when they fall from the lava fountain. The associated loss of mass, momentum and enthalpy from this process (Parfitt, 1998) and 2 Refers to (Freret-Lorgeril et al, 2021) results in the plume not reaching the same heights as the standard integral model despite having a hotter inner core. As the initial single-size GSD of the inner plume becomes finer, less fallout occurs leaving more mass, momentum and enthalpy in the whole plume system for it to go higher.…”

“…The observed lava fountain height is taken to be that of the saturated region in thermal camera images (Calvari et al, 2018). If the determined heights of the double plume region and the overall plume lie between the reported mean and maximum heights (Corradini et al, 2018;Calvari et al, 2018;Freret-Lorgeril et al, 2021) of the lava fountain and tephra plume, respectively, the simulation is recorded as a match. This procedure allows the range of initial MFRs that resulted in the observed plume and lava fountain heights to be determined.…”

“…This value is determined by the ratio between the estimated MFR of the cone deposit and the MFR of the cone deposit plus the MFR of the plume tephra deposit for the August 29, 2011 paroxysmal eruption of Mount Etna. The value of the MFR of the plume tephra deposit is reported in Freret-Lorgeril et al (2021). The MFR of the cone deposit is calculated by taking the reported cone volume and total lava fountaining duration between 2011 and 2012 from Behncke et al (2014), and assuming a density of the cone deposit of 1,800 kg m −3 (Mulas et al, 2016).…”

“…We demonstrate the clear difference between the height of the gas‐thrust region and the height of the lava fountain in Figure 2. The height of the gas‐thrust region is determined with the standard integral model as the height at which the modeled plume becomes less dense than the surrounding fluid (i.e., the point where the modeled plume becomes buoyant) for ESPs that reproduces the observed plume height (9–9.9 km a.s.l; Corradini et al., 2018; Freret‐Lorgeril et al., 2021) of the August 29, 2011 paroxysmal eruption at Mount Etna. The ballistic heights range between 287 and 2,039 m due to the velocity range in the parameter space.…”