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Lava overflows are highly hazardous phenomena that can occur at Stromboli. They can destabilize the crater area and the "Sciara del Fuoco" unstable slope, formed by several sector collapses, which can generate potentially tsunamigenic landslides. In this study, we have identified precursors of the October-November 2022 effusive crisis through seismic and thermal camera measurements. We analyzed the lava overflow on October 9, which was preceded by a crater-rim collapse, and the overflow on November 16. In both cases, seismic precursors anticipating the overflow onset have been observed. The analysis of the seismic and thermal data led to the conclusion that the seismic precursors were caused by an escalating degassing process from the eruptive vent, which climaxed with the overflows. Volcano deformation derived from ground-based InSAR and strainmeter data showed that inflation of the crater area accompanied the escalating degassing process up to the beginning of the lava overflows. The inflation of the crater area was especially evident in the October 9 episode, which also showed a longer seismic precursor compared to the November 16 event (58 and 40 min respectively). These results are important for understanding Stromboli's eruptive mechanisms and open a perspective for early warning of potentially dangerous phenomena. [ABSTRACT FROM AUTHOR]

In situ and remote-sensing measurements have been used to characterize the run-up phase and the phenomena that occurred during the August–November 2014 flank eruption at Stromboli. Data comprise videos recorded by the visible and infrared camera network, ground displacement recorded by the permanent-sited Ku-band, Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) device, seismic signals (band 0.02–10 Hz), and high-resolution Digital Elevation Models (DEMs) reconstructed based on Light Detection and Ranging (LiDAR) data and tri-stereo PLEIADES-1 imagery. This work highlights the importance of considering data from in situ sensors and remote-sensing platforms in monitoring active volcanoes. Comparison of data from live-cams, tremor amplitude, localization of Very-Long-Period (VLP) source and amplitude of explosion quakes, and ground displacements recorded by GBInSAR in the crater terrace provide information about the eruptive activity, nowcasting the shift in eruptive style of explosive to effusive. At the same time, the landslide activity during the run-up and onset phases could be forecasted and tracked using the integration of data from the GBInSAR and the seismic landslide index. Finally, the use of airborne and space-borne DEMs permitted the detection of topographic changes induced by the eruptive activity, allowing for the estimation of a total volume of 3.07 ± 0.37 × 106 m3 of the 2014 lava flow field emplaced on the steep Sciara del Fuoco slope. [ABSTRACT FROM AUTHOR]

Volcano slope instability manifests in many forms, ranging from steady state to punctuated movement, or shallow erosion to deep-seated spreading. The interplay of gravity, magmatic or hydrothermal fluids, and often active tectonics, results in complex spatial and temporal variations in deformation kinematics; deformation from magma rise or variations in hydrothermal systems may be inseparable from deep-seated and persistent flank motion. Similarly, shallow or localized ground motion may overlap with thermal contraction or subsidence of newly emplaced lava or tephra deposits. While this makes the recognition, assessment, and monitoring of volcano slope instability challenging, advancements in Synthetic Aperture Radar (SAR) technology have accelerated our knowledge of instability phenomena and our ability to assess their hazards. SAR amplitude images are powerful tools for mapping areas of geomorphological changes, which can be combined using Interferometric SAR (InSAR) to create multi-temporal deformation maps that provide unique information on the evolution of slope failures. Space-borne InSAR has become an economic way to detect changes at volcanoes at very high resolution. Ground-Based InSAR (GBInSAR) can produce frequent SAR images, propelling InSAR from monitoring to surveillance and early-warning applications. Various InSAR techniques have been used to measure persistent, transient, or surficial slope movement of at least ten volcanoes, some of which have had several periods or instances of flank motion. To highlight the utility of SAR for measuring and monitoring mass movements, studies at Stromboli (Italy) and Pacaya (Guatemala) volcanoes are reviewed in detail, where recent instability events, persistent volcanic activity, and ground truth constraints have resulted in excellent case-histories in applying SAR imagery to understand these potentially hazardous slope instabilities. At Stromboli, years of monitoring with GBInSAR has led to an operational approach to mitigate landslide risks by defining a relationship between measured displacement rates and associated instability and eruptive hazards. This aided in anticipating a flank eruption 11 hours in advance in 2014. At Pacaya, the combined use of aerial and satellite InSAR time series successfully measured a large transient co-eruptive event in 2010. This was determined to have initiated a new stage of rifting, implicating new potential hazards for future eruptions. Monitoring slope instability over the world's volcanoes will continue to increase with new radar satellites schedule to launch around 2020-2022, including ALOS-4 PALSAR by JAXA, NISAR by NASA-India, and SAOCOM by Argentine Space Agency. These satellites will provide more frequent images and improved coherence and coverage than previous sensors, with the potential to move from observing and explaining volcanic slope instability to tracking and forecasting failures. However, this enhanced mitigation potential relies on the manageability, rapidity, and fusing of these large datasets, and the integration of measured persistent or flank unrest into emergency planning. [ABSTRACT FROM AUTHOR]