Forecasting Effusive Dynamics and Decompression Rates by Magmastatic Model at Open-vent Volcanoes

Abstract

Effusive eruptions at open-conduit volcanoes are interpreted as reactions to a disequilibrium induced by the increase in magma supply. By comparing four of the most recent effusive eruptions at Stromboli volcano (Italy), we show how the volumes of lava discharged during each eruption are linearly correlated to the topographic positions of the effusive vents. This correlation cannot be explained by an excess of pressure within a deep magma chamber and raises questions about the actual contributions of deep magma dynamics. We derive a general model based on the discharge of a shallow reservoir and the magmastatic crustal load above the vent, to explain the linear link. In addition, we show how the drastic transition from effusive to violent explosions can be related to different decompression rates. We suggest that a gravity-driven model can shed light on similar cases of lateral effusive eruptions in other volcanic systems and can provide evidence of the roles of slow decompression rates in triggering violent paroxysmal explosive eruptions, which occasionally punctuate the effusive phases at basaltic volcanoes.

Evolution of Conduit Geometry and Eruptive Parameters During Effusive Events

“…Still, it is worth noting that we considered a simplified system, where the temporal variations are limited to conduit geometry, water content, and reservoir overpressure, whereas several other kinds of magma source variations have been described for natural cases (Corsaro & Miraglia, ), which can alter the curves of effusion rate, exit velocity, and gas flow. Moreover, the occurrence of refilling cycles has been proposed as a typical mechanism controlling effusion rate (Coppola, Ripepe, et al, ; Ripepe et al, ). These processes are expected to depend on complex feedbacks between reservoir overpressure and the deeper feeding system, as well as on the characteristic times required for the displacement of large volumes of magma in the crust.…”

“…Evolution of effusive eruptions is mainly controlled by time-dependent variations of effusion rate, the dynamics of which are influenced by several processes related to magma source conditions and conduit geometry (Calvari et al, 2003;Harris et al, 2007Harris et al, , 2011Wadge, 1981). Temporal variations of composition and thermodynamic conditions of magma in the reservoir are often related to emptying and refilling cycles (Andronico et al, 2005;Coppola, Ripepe, et al, 2017;Dzurisin et al, 1984;Landi et al, 2006;Ripepe et al, 2017). Conduit geometry is strongly controlled by the coupled effect of erosion processes and elastic deformation, which are functions of the country rock and magma properties (Dragoni & Santini, 2007;Piombo et al, 2016).…”

Exploring the explosive‐effusive transition using permanent ultraviolet cameras

“…Considering that the total magma input rate (0.3 m 3 s −1 [ Allard et al ., ]) during regular explosive activity at Stromboli is 4 times our estimate (~0.07 m 3 s −1 ), our results indicate that a sustained (two months‐long) increase in the magma input rate to ~0.51 ± 0.13 m 3 s −1 is sufficient to trigger instability conditions that ultimately lead to vent opening and lava effusion. This value is consistent with the magma input rate measured during the last four major effusive eruptions at Stromboli [ Ripepe et al ., ; Valade et al ., ; Ripepe et al ., ].…”

“…The enhanced gas flux also raises the magma level in the conduit, thus increasing the probability of lava overflow events. The persistence of this high magma level may eventually produce flank instability, ultimately leading to opening of lateral effusive vents [Ripepe et al, 2017;Valade et al, 2016;Ripepe et al, 2015].…”

Thermal, Deformation, and Degassing Remote Sensing Time Series (CE 2000–2017) at the 47 most Active Volcanoes in Latin America: Implications for Volcanic Systems

“…Thermal data can be used to identify volcanogenic heating, variations in which have been related to pre‐eruptive activity (e.g., Dehn et al, ; Pieri & Abrams, ; Reath et al, ). During eruptions, thermal data have been used to estimate lava discharge rates (Coppola et al, ; Harris et al, , ) and, in some cases, to forecast the end of an effusive eruption (e.g., Bonny & Wright, ; Coppola et al, ; Ripepe et al, ). Interferometric SAR ( InSAR ) data are processed from Synthetic Aperture Radar (SAR) data, which measures changes in surface characteristics over time with all‐weather, day‐night capability.…”