Multiple eruptive events at Etna volcano in a short time (Dec 2025 – Jan 2026) captured by high-precision borehole strain and tilt

Between late 2025 and early 2026, Mt. Etna exhibited a highly diversified eruptive activity characterized by shifting eruptive styles. Occurring during a period of severe weather conditions, these different eruptive phases were captured by high-resolution signals recorded by borehole strainmeters and tiltmeters, whose joint analysis enabled the precise tracking of the evolving volcanic processes and the constraining of the related magmatic sources. Starting on 24 December, the recorded signals showed a trend change that anticipated the subsequent eruptive phases. In the evening of 26 December, an effusive vent opened on the upper eastern flank of the Voragine crater. Later, during the same day, two lava fountains occurred at the North-East Crater, which had not generated paroxysms in the last 28 years. From 29 December, strain and tilt signals showed a slope change accompanying effusive activity from new vents opened in the eastern flank at ∼2,100 m above sea level. After a few days, the signals indicated an attenuation of the decompression trend accompanied by a gradual decreasing of the effusion rate. The strain and tilt networks detected clear signal changes associated with the paroxysmal events and the effusive phase, enabling analytical modeling to constrain the underlying magmatic sources. These findings reaffirm the exceptional capacity of borehole strain and tilt in capturing complex eruptive dynamics and providing critical real-time insights of ongoing volcanic processes.