Small meteoroids that enter Earth’s atmosphere often go unnoticed; their detection and characterisation rely on human observations, introducing observational biases in space and time. Acoustic shockwaves from meteoroid ablation convert to infrasound and seismic energy, enabling fireball detection using seismoacoustic methods. We analysed an unreported fireball in 2022 near the Azores, recorded by 26 seismometers and two infrasound arrays. Through polarisation analyses, array methods, and 3-D ray-tracing, we determined that the terminal blast occurred at 40 km altitude, ~60 km NE of São Miguel Island. This location matches an unidentified flash captured by a lightning detector aboard the GOES-16 satellite. The estimated kinetic energy is ~10-3 kT TNT equivalent, suggesting a 10-1 m object diameter, thousands of which enter the atmosphere annually. Our results demonstrate how geophysical methods, in tandem with satellite data, can significantly improve the observational completeness of meteoroids, advancing our understanding of their sources and entry processes.

<p>On September 19, 2021, a volcanic eruption began at the west flank of Cumbre Vieja, La Palma, the most northwestern of the Canary Islands. The lava flows caused the evacuation of thousands of residents living in the vicinity of the volcano, and 1,219 hectares were covered by lava flows. After 85 days of activity, the eruption ended on December 13, 2021. Since visible volcanic gas emissions (fumaroles, hot springs, etc.) do not occur at the surface environment of Cumbre Vieja, the geochemical program for the volcanic surveillance has been focused mainly on diffuse (non-visible) degassing studies. Since 2001, diffuse CO<sub>2</sub> emission surveys have been yearly performed in summer periods to minimize the influence of meteorological variations. Measurements of soil CO<sub>2</sub> efflux have been performed following the accumulation chamber method in about 600 sites and spatial distribution maps have been constructed following the sequential Gaussian simulation (sGs) procedure to quantify the diffuse CO<sub>2</sub> emission from the studied area. In the period 2001-2016, the diffuse CO<sub>2</sub> output released to the atmosphere from Cumbre Vieja volcano ranged between 320 to 1,544 t·d<sup>-1</sup>. During pre-eruptive period (2016-2021), time series of the diffuse CO<sub>2</sub> emission showed a change with an increasing trend from 788 t·d<sup>-1 </sup>up to 1,870 t·d<sup>-1</sup>, coinciding with the beginning of the seismic swarms. This increase of diffuse CO<sub>2</sub> emission is interpreted as a geochemical precursory signal of volcanic eruption of Cumbre Vieja, on September 19, 2021. The observed increase on the diffuse CO<sub>2</sub> emission during this time window suggests that in October 2017 a process of magma ascent began from the upper mantle to depths between 35-25 km, at which the seismic swarms were recorded for four years. During eruption period, diffuse CO<sub>2</sub> emission showed strong temporal variations with a minimum value of the diffuse CO<sub>2</sub> emission in October 21, followed by an increase trend of up to 4,435 t·d<sup>-1 </sup>on December 14, the highest of time series and coinciding with the end of the eruption. During the post-eruptive period, the diffuse CO<sub>2</sub> emission has shown a descending trend. Our results demonstrate that periodic surveys of diffuse CO<sub>2</sub> emission are extremely important in the volcanic surveillance tools of Cumbre Vieja to improve the detection of early warning signals of future volcanic unrest episodes.</p><p> </p><p> </p><p> </p>

<p align="justify"><span lang="en-US">Located in the middle of the North Atlantic Ocean, São Jorge is a volcanic island that belongs to the central group of the Azores Archipelago, Portugal. Very steep, with 54 km long and 7 km wide, São Jorge is different from all the other archipelago’s islands, being itself a WNW-ESE oriented fissure volcanic system composed of four volcanic units.</span></p> <p align="justify"><span lang="en-US">Since March 19, 2022, a seismovolcanic crisis has been ongoing beneath the active Manadas Volcanic Fissure System on the western half of the island, where historical eruptions occurred in 1580 and 1808. </span><span lang="en-GB"> This unrest, characterized by the occurrence of several thousands of low magnitude earthquakes and some ground deformation, </span><span lang="en-US">is being monitored by IVAR/CIVISA teams using several techniques </span><span lang="en-GB">(seismology, geodesy, infrasound, ground water geochemistry and CO</span><sub><span lang="en-GB">2</span></sub><span lang="en-GB"> and </span><sup><span lang="en-GB">222</span></sup><span lang="en-GB">Rn emissions). </span></p> <p align="justify"><span lang="en-GB">Infrasound detections were based on data from the IMS IS42 infrasound station located on the Graciosa Island (Azores) and a portable infrasound array (SJ1) that was deployed in the northwestern part of the island </span><span lang="en-US">at ~7 km from the main epicentral area.</span></p> <p align="justify"><span lang="en-GB">We describe the actual procedures to correlate seismic and infrasonic data, based on epicentral locations and infrasound back-azimuths and the main </span><span lang="en-GB">results obtained</span><span lang="en-GB"> so far. </span></p>

<p>With the advent of civil aviation and growth in air traffic, the problem of volcanic ash encounter has become an issue of importance as a prompt response to volcanic eruptions is required to mitigate the impact of the volcanic hazard on aviation. Many volcanoes worldwide are poorly monitored, and most of the time notifications of volcanic eruptions are reported mainly based on satellite observations or visual observations. Among ground-based volcano monitoring techniques, infrasound is the only one capable of detecting explosive eruptions from distances of thousands of kilometers. On July 3 and August 28, 2019, two paroxysmal explosions occurred at Stromboli volcano. The events, that are similar in terms of energy and size to the peak explosive activity reported historically for the volcano, produced a significant emission of scoria, bombs and lapilli, that affected the whole island and fed an eruptive column that rose almost 5 km above the volcano. The collapse of the eruptive column also produced pyroclastic flows along the Sciara del Fuoco, a sector collapse on the northern flank of the volcano.</p> <p>Being one of the best-monitored volcanoes of the world, the 2019 Stromboli paroxysmal explosions were observed in real-time and Civil Protection procedures started immediately. However, notification to the Toulouse Volcanic Ash Advisory Centre (VAAC) was not automated, and the VAA was issued only long after the event occurrence. The two explosions produced infrasound signals that were detected by several infrasound stations as far as Norway (IS37, 3380 km) and Azores islands (IS42, 3530 km). Despite of the latency due to the propagation time, infrasound-based notification arrays precedes the Volcanic Ash Advisories (VAAs) issued by Toulouse VACC. Following the same procedure applied for the Volcano Information System developed in the framework of the ARISE project, we show how infrasound array analysis could allow automatic, near-real-time identification of these eruptions with timely reliable source information. We highlight the need for an integration of the CTBT IMS infrasound network with local and regional infrasound arrays capable of providing a timely early warning to VAACs. This study opens new perspectives in volcano monitoring and could represent, in the future, an efficient tool in supporting VAACs activity.</p>

<p>Stromboli is one of the most active volcanoes on Earth with a continuous explosive activity and persistent degassing since at least 3-7 AD (Rossi et al., 2000). Being an open conduit volcano, its spectacular basaltic explosions interspersed by lava fountains occurring every ≈10 minutes (Ripepe et al., 2002) make it probably the world's best-know and best-monitored volcano.</p><p>On 3<sup>rd </sup>July 2019 at the 14:45:43 UTC a paroxysmal explosion occurred with an ash column that rose almost 5 km above the volcano. This very strong explosive event was detected in several IMS infrasound stations, including IS42, located in the Azores islands in the middle of the North-Atlantic, at a distance of about 3,700 km.</p><p>We present the long-range infrasound detections that allowed us to locate the source based only in infrasound with an estimated error of less than 55 km from the ground truth event.</p><p><strong>Keywords:</strong> Stromboli volcano, paroxysm, infrasound, IMS, IS42</p>