Space- and Ground-Based Geophysical Data Tracking of Magma Migration in Shallow Feeding System of Mount Etna Volcano

Abstract

After a month-long increase in activity at the summit craters, on 24 December 2018, the Etna volcano experienced a short-lived lateral effusive event followed by a rapid resumption of low-level explosive and degassing activity at the summit vents. By combining space (Moderate Resolution Imaging Spectroradiometer; MODIS and SENTINEL-2 images) and ground-based geophysical data, we track, in near real-time, the thermal, seismic and infrasonic changes associated with Etna’s activity during the September–December 2018 period. Satellite thermal data reveal that the fissural eruption was preceded by a persistent increase of summit activity, as reflected by overflow episodes in New SouthEast Crater (NSE) sector. This behavior is supported by infrasonic data, which recorded a constant increase both in the occurrence and in the energy of the strombolian activity at the same crater sectors mapped by satellite. The explosive activity trend is poorly constrained by the seismic tremor, which shows instead a sudden increase only since the 08:24 GMT on the 24 December 2018, almost concurrently with the end of the infrasonic detections occurred at 06:00 GMT. The arrays detected the resumption of infrasonic activity at 11:13 GMT of 24 December, when tremors almost reached the maximum amplitude. Infrasound indicates that the explosive activity was shifting from the summit crater along the flank of the Etna volcano, reflecting, with the seismic tremor, the intrusion of a gas-rich magma batch along a ~2.0 km long dyke, which reached the surface generating an intense explosive phase. The dyke propagation lasted for almost 3 h, during which magma migrated from the central conduit system to the lateral vent, at a mean speed of 0.15–0.20 m s−1. Based on MODIS and SENTINEL 2 images, we estimated that the summit outflows erupted a volume of lava of 1.4 Mm3 (±0.5 Mm3), and that the lateral effusive episode erupted a minimum volume of 0.85 Mm3 (±0.3 Mm3). The results presented here outline the support of satellite data on tracking the evolution of volcanic activity and the importance to integrate satellite with ground-based geophysical data in improving assessments of volcanic hazard during eruptive crises.

Near Real-Time Monitoring of the Christmas 2018 Etna Eruption Using SEVIRI and Products Validation

“…By integrating the TADR time series, a maximum cumulative lava volume of 0.5 M m 3 is obtained. TADR and total volume retrieved are in good agreement with those obtained by Laiolo et al [44], which is derived from the analysis of the MODIS sensor on board the Terra/Aqua polar satellites, while significant discrepancies are found with the result obtained in Calvari et al [45] that uses the HOTSAT system [29,31,32]. Among the TADR computation, the methodology proposed by Lombardo et al [51], which provided the capability to use high temporal resolution data to predict erupting styles, has been applied.…”

Thermal Remote Sensing for Global Volcano Monitoring: Experiences From the MIROVA System

“…At basaltic volcanoes equipped with a large ground-based monitoring network, such as Stromboli, Etna, Piton de la Fournaise, etc., MIROVA is commonly used to estimate timeaveraged lava discharge rates (TADR) and erupted volumes in near real time Laiolo et al, 2019), to define imminent eruptive scenarios and to model the path and length of lava flows (Harris et al, 2017(Harris et al, , 2019.…”

“…According to the authors, these thresholds represent a critical magma flux (about 0.1-0.3 m 3 s −1 ) above which the ascending magma can no longer be recycled in the conduit, and must be partially or completely extruded through effusive activity. The definition of these thresholds (blue dashed lines in Figure 10), allows the separation of the different regimes of activity, making it possible to track the rise of magma within the conduit and to advise about potential transitions toward magma effusion (Valade et al, 2016;Ripepe et al, 2017;Laiolo et al, 2019). Valade et al, 2016 andLaiolo et al, 2019, respectively).…”

Volcanic Hot-Spot Detection Using SENTINEL-2: A Comparison with MODIS–MIROVA Thermal Data Series

“…In fact, there is a strong correspondence between the two analyzed thermal signals, both during the so-called "low thermal regime", related to strombolian and degassing activity at the summit craters (characterized by VRP < 10 8 W (cf. [37]) and S2Pix <~100, Figure 8c), and during the "high thermal regime" related to high-sustained strombolian activity or major lava effusion phases (Figure 8b,d and yellow bands in Figure 8a, characterized by VRP > 10 8 W and S2Pix > 100). Even if energetic events such as summit overflows or fountaining episodes at Etna are generally short-lived, each peak detected by MIROVA is also constrained by S2Pix hot pixels detections, also thanks to 2-3 days of revisit time of SENTINEL-2 above Etna.…”

“…Nevertheless, because of their recent availability, the SENTINEL-2 (hereafter S2) thermal dataset is partially still under-investigated in volcanological studies: a few works started to use these images, mainly for studying qualitatively a specific eruption or volcanic phase [37][38][39], mapping lava flows [40] or as a comparison dataset to calculate pixel-integrated temperatures or to infer thermal model of a specific volcanic phenomena [41,42].…”