Volcanic CO ₂ tracks the incubation period of basaltic paroxysms

Abstract

Escalating CO2 emissions precede basaltic explosive eruptions on time scales of weeks to months.

Changes in the Eruptive Style of Stromboli Volcano before the 2019 Paroxysmal Phase Discovered through SOM Clustering of Seismo-Acoustic Features Compared with Camera Images and GBInSAR Data

“…In the period preceding the paroxysm of 3 July 2019, the predominance of cluster Blue in this dataset indicates a degassing activity that is not accompanied by an effective emission of juvenile material, consistently with the deflation or the absence of inflation in the crater area, therefore indicating a remarkable anomaly in the pattern of the persistent activity of Stromboli. The eruptive style change before the paroxysmal phase, which is clearly recognizable in the temporal evolution of the seismo-acoustic clusters found with the SOM analysis (Figures 11 and 13), is an important finding because it highlights hidden variations in the state of the volcano that may reveal undetected escalation of volcanic plume degassing and/or precursory leakage from deeply stored gas-rich magma (e.g., [62]). Actually, despite Stromboli being a well-monitored volcano, when the first paroxysm of the 2019 eruptive crisis occurred, it was considered to be in a state of normal activity.…”

“…Looking at the time evolution of the three main clusters, we discovered that the eruptive style of Stromboli was affected by significant changes in the three months preceding the 3 July 2019 paroxysm and that the gas explosions (Type 0; Leduc et al [26]) falling into cluster Blue dominated the persistent Strombolian activity, especially in the last month before this paroxysm, forecasting the ascent of gas-rich magma from a depth [62].…”

“…Therefore, this event occurred in a different condition compared with the first one, as also indicated by the temporal evolution of the seismo-acoustic clusters (Figures 11-13). Considering the models of Stromboli paroxysm triggering proposed in the literature, the first paroxysm (3 July 2019) could be explained by an increased supply of gas and magma from the depths (e.g., [39,62,63]). However, the neural analysis of the eruptive style and its comparison with the deformation of the summit area allowed us to discover that this paroxysm was preceded by a phase of decrease in the feeding of the persistent activity, which is highlighted by the decreased emission of pyroclastic material and by the deflation of the summit area accompanied by a greater release of degassing (Type 0 explosions of the Blue cluster).…”

The electrical signature of mafic explosive eruptions at Stromboli volcano, Italy

“…1 d). Although a posteriori analysis indicated the occurrence of anomalous seismic signals and heightened CO 2 emissions months before the paroxysm 48 , 49 , no clear precursory signals were detected by INGV and LGS at the time of the eruption. Both institutes classified the volcanic activity in the week preceding the paroxysm as “moderate”.…”

“…5 b, Table 1 ), which corresponds to the moment incandescent lava fragments emerged from the SWC zone and expanded radially (Fig. 1 d), based on the images of the INGV thermal cameras at Pizzo 49 . Within a second, small irregular electrical variations were detected, followed by the first electrical discharge at 14:45:44.85 UTC.…”