Reactivation of Stromboli's summit craters at the end of the 2007 effusive eruption detected by thermal surveys and seismicity

Abstract

This work arises from the field observations made during the civil protection emergency period connected to the 2007 Stromboli eruption. We observed changes in the shallow feeding system of the volcano to which we give a volcanological interpretation and the relative implications. Here we describe the processes that occurred in the upper feeding system from the end of the 2007 effusive eruption on 3 April to the renewal of the strombolian explosive activity at the summit craters (30 June), interpreted using multidisciplinary data. We used thermal camera data collected both from helicopter and from a fixed station at 400 m to retrieve the evolving summit crater activity. These data, compared with seismic signals and published geochemical records, allowed us to detail the shifting of the degassing activity within the crater terrace from NE to SW, occurred between 15 and 25 April 2007 prior to the resumption of the strombolian activity. In particular, from mid‐April, a gradual SW displacement in the maximum apparent temperatures was recorded at the vents within the summit craters, together with a change in the very long period location and confirmed by variations in geochemical indicators (CO2/SO2 plume ratios and CO2 fluxes) from literature. The shallow feeding system experienced a major readjustment after the end of the effusive activity, determining variations in the pressure leakage of the source, slowly deepening and shifting toward SW. All these data, together with the framework supplied by previous structural surveys, allowed us to propose that the compaction of debris accumulated in the uppermost conduit by inward crater collapses, occurred in early March, produced the observed anomalies. At Stromboli, major morphology changes, taking place in the following years, were anticipated by these small and apparently minor processes occurred in the upper feeding system. Other studies are relating similar changes to modifications of the eruptive activity also at other open‐conduit volcanoes, so we believe that it may be important to have a constant monitoring of these phenomena in order to better understand their shallow feeding systems.

Overflows and Pyroclastic Density Currents in March-April 2020 at Stromboli Volcano Detected by Remote Sensing and Seismic Monitoring Data

“…Conversely, the decrease of explosive activity following the lava flow output suggests that the drainage of the uppermost conduit was efficient, requiring a certain amount of time (of the order of h, Figure 3a) in order to allow the magma level to rise again after drainage in order to restore the persistent Strombolian activity at the summit craters. This is consistent with similar events, which were observed during the much longer 2002-2003 and 2007 effusive phases [19,39,[89][90][91]. Satellite data allowed us to obtain the map of the lava flows expanding on the SdF slope between 28 March and 1 April, which was estimated at 94,500 ± 3380 m 2 (Figure 6), the radiant heat flux over time (Figure 3e), and, consequently, the TADR ( Figure 5), providing an estimation of the cumulative erupted lava flow volume at 37-69 × 10 3 m 3 DRE.…”

Thermal Energy Release Measurement with Thermal Camera: The Case of La Solfatara Volcano (Italy)

“…For each point, we measured the surface temperature by means of a handheld thermal camera FLIR SC640 kept at about 1 m over the soil using a tripod and shallow gradients using a graduated thermocouple inserted at various depths into the ground (for details on the usage of FLIR SC640 thermal camera, see, e.g., Marotta et al [40]; a summary of its technical characteristics is reported in Table 1). Surface thermal images were taken just before the insertion of the thermocouple to avoid perturbations to the shallow thermal system due to the presence of the thermocouple itself.…”

Integration of Ground-Based Remote-Sensing and In Situ Multidisciplinary Monitoring Data to Analyze the Eruptive Activity of Stromboli Volcano in 2017–2018

“…During both the 2002-2003 and 2007 effusive eruptions the persistent summit explosive activity stopped or significantly decreased, as a result of magma drainage from the eruptive fissure [5,13,14]. After the 2007 effusive eruption, the persistent explosive summit activity of Stromboli resumed [48], but the eruptive activity changed, displaying several unusual overflows from the crater zone, a more than doubled number of major explosions, and absence of paroxysms [32,49,50]. The enhanced monitoring network allowed us to recognize that the effusive phases were preceded by a few weeks of increment of amplitude and occurrence rate of Very Long Period events (VLP) and associated number of explosions, which are related to the magma level within the shallow conduit [1,5,13,35].…”