Thermal Emissions of Active Craters at Stromboli Volcano: Spatio-Temporal Insights From 10 Years of Satellite Observations

Open-vent volcanoes continuously emit magmatic products and frequently feature multiple adjacent craters. Temporal shifts of thermal emissions between craters are especially detectable by InfraRed satellites. Here, SENTINEL-2 and LANDSAT-8/9 Short Wave InfraRed (SWIR) high-spatial resolution satellite data, are combined to investigate 10 years (2013-2023) of thermal activity at Stromboli volcano (Italy). The correlation between Volcanic Radiative Power (VRP, in Watts) and Volcanic Radiative Energy (VRE, in Joules), retrieved by moderate MODIS and VIIRS Middle InfraRed (MIR) data, with the Thermal Index SWIR (TISWIR) data, allows us to quantify long-term series of heat fluxes (VRPSWIR) and energy (VRESWIR). Combining moderate and higher spatial resolution data and fitting cumulative trends of TISWIR with VREMIR allows to measure thermal activity sourced by single craters during Strombolian activity. Long-term results highlight that thermal emissions are clustered in the northern and southern parts of the crater terrace, with total energy emitted (similar to 12 x 1014 J) equally distributed. The thermal increase since April 2017 marked a reactivation of shallow magma transportation and an intensification of the activity after the 2014 eruption. Distinct thermal behaviors are shown by the NE, C, and SW craters, related to mechanisms of explosions. We found that short-term thermal variations match well those resolved by ground-based signals, and the NE crater as the most sensitive to the transition to higher-intensity activity. Our multispatial/multisensory investigation allows, for the first time, the long-term quantification of heat flux from Stromboli's craters, with an improved understanding of open-vent dynamics and a new approach to monitor multiple active craters. Stromboli is a volcano in southern Italy, historically well-known, considered unique and fascinating for its persistent emission of magma and gas through multiple adjacent craters lasting for millennia. This study focuses on tracking the thermal activity of Stromboli using modern satellite data over 2013-2023, with unprecedented levels of detail able to distinguish the heat released by single craters. The analysis revealed that most thermal emissions at Stromboli were concentrated in two primary sectors of the summit terrace. Notably, a significant increase in thermal activity was observed since April 2017, indicating a resurgence in volcanic activity after a period of relatively calm following the previous eruption. Distinct thermal behaviors of the three historically active craters of Stromboli have been recognized and reconciled with different styles of volcanic explosions. Furthermore, the study identified patterns of heat release within Stromboli's main craters which agreed with the fluctuations in gas emissions and explosive activity characterizing the volcano. Overall, this comprehensive analysis provides valuable insights to scientists and volcano-involved communities into the long-term quantification of heat flux from multiple craters at Stromboli, contributing to a better understanding of open-vent eruptive dynamics and enhancing continuous monitoring of Stromboli and similar volcanoes. Ten years (2013-2023) quantification of heat flux VRPSWIR from active craters at Stromboli using Sentinel-2 and Landsat-8/-9 SWIR images Two main thermal clusters emitting similar to 12 x 1014 J. Thermal increase since April 2017 marks a reactivation of intense Strombolian activity NE, C, and SW craters show distinct thermal behavior, with the NE as the most energetic. VRPSWIR tracks transition to more explosive phases