Askja is an active volcano in Central Iceland that has experienced ~ 45 cm of uplift since August 2021, marking an abrupt end to decades of gradual deflation. We have operated a dense local seismic network around Askja since 2007, providing an exceptionally long time series of seismic data within which to search for patterns that relate to this sudden change in behaviour. Here we focus on spatiotemporal changes in microseismicity associated with the switch to inflation. Understanding what seismicity can tell us about the ongoing unrest at the volcano is crucial, because it is one of the few monitoring tools that is available year-round. Furthermore, joint interpretation of seismic and geodetic data is key to overcoming ambiguities in the interpretation of surface deformation measurements alone.

Our catalogue of microseismicity in Askja spanning July 2007 to August 2022 contains more than 25,000 events detected and located with QuakeMigrate¹. Increases in seismicity rate are clearly observed in August 2021, corresponding to the start of inflation as measured by a GPS station close to the centre of uplift. However, a strong spatial variation across the caldera is observed in the magnitude and duration of the seismicity rate increase. To investigate this further, we cross-correlate earthquake waveforms and calculate relative relocations. Combined with cluster analysis, this divides the seismicity into sharply resolved structures, with markedly different temporal evolution. We identify new clusters of events not seen in the 14 years preceding the current inflation, as well as previously persistent clusters which have now shut off, and areas of microseismicity which are seemingly unaffected by the inflation. Combined with analysis of tightly-constrained earthquake focal mechanisms covering the same time period, these results provide new insight into both the mechanism linking the observed deformation and seismicity rate changes, and the role of caldera fault slip in facilitating the ongoing inflation at Askja.

1: Winder, T., Bacon, C., Smith, J., Hudson, T., Greenfield, T. and White, R., 2020. QuakeMigrate: a Modular, Open-Source Python Package for Automatic Earthquake Detection and Location. https://doi.org/10.1002/essoar.10505850.1

How to cite: Winder, T., Siggers, I., Rawlinson, N., White, R., and Brandsdóttir, B.: Earthquake cluster analysis reveals the complex response of microseismicity to the ongoing 2021-2023 inflation at Askja caldera, Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13838, https://doi.org/10.5194/egusphere-egu23-13838, 2023.

Volcanic hazard is still an issue in the French Massif Central (FMC) because the last eruptions are dated 6700 yrs BP. Indeed, seismic bursts and geodetic uplift related to volcano-magmatic activity have recently been detected in the Eifel region (Germany), which belongs to the same European Cenozoic rift system as the FMC. However, geophysical knowledge of the sources of FMC volcanism is limited to the mantle-plume hypothesis, which dates from the last seismological experiment performed >30 years ago. To improve our knowledge on the deep structures of the FMC and the sources of volcanism, a multidisciplinary team of geophysicists, geologists, and volcanologists has set up the MACIV project, in a context of solid synergy with ongoing and future research initiatives in France and Europe (e.g. AdriaArray). Between 2023-2026, we will deploy several hundreds of seismic instruments in a multiscale configuration to probe the different scales and depths of the FMC volcanic systems with optimal spatial resolution. The entire FMC will be covered with broadband seismic stations in a 2-D array (spacing ~35 km) and three transverse profiles (spacing 5-20 km) for durations of 1.5-3 yrs. These arrays will provide information on the causes of mantle melting at depth, their links with the expression of volcanism at the surface, and the influence of Variscan and Cenozoic lithospheric structures. On a smaller scale, dense large-N arrays of ~650 short-period stations will provide images of the upper crust below the volcanoes and illuminate their plumbing systems. The enhanced earthquake detection power of the dense arrays will illuminate active faults and possible plumbing systems of the youngest volcanoes. The MACIV project will help better evaluate the volcanic hazard and provide a framework for a monitoring strategy scaled to a currently dormant volcanic province. The resulting seismological dataset will be used for years to come to yield essential information on intraplate volcanism.

How to cite: Paul, A. and Mordret, A. and the MACIV Team (1, 2, 3, 4): MACIV: a new project on multiscale seismic imaging of Massif Central (France) focusing on recent intraplate volcanism, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3565, https://doi.org/10.5194/egusphere-egu23-3565, 2023.

Merapi is a strato-volcano rising at 2900 m a.s.l, located on the South coast of Java island, Indonesia. Only 30 km north to the city of Yogyakarta (2 millions inhabitants), it is considered one of the most dangerous dome building stratovolcanoes, as summit domes almost continuously grow and destruct. Merapi is therefore closely and routinely monitored by InSAR (Interferometric Synthetic Aperture Radar) to track ground deformation. To retrieve ground deformation from the full wave path, the delay due to the radar wave crossing the atmosphere needs to be corrected. In the case of Sentinel-1, interferograms are mostly biased by the tropospheric variations. Tropospheric variations are expected to be stronger in tropical regions and where topographic gradient is high, which is the case at Merapi. They can be estimated thanks to various methods, including global weather models (ERA-5 and GACOS), a linear model regarding topography, and GNSS networks.

In this work, we compare the performance of atmospheric corrections derived from two weather-based models, ERA-5 and GACOS, and those derived from the empirical method based on a linear phase-elevation correlation. The aim is to evaluate the efficiency of each model in correcting this tropospheric bias. To this end, we choose to study a period between 2016 and 2018 during which no deformation occurred on the Merapi, so that most of the phase delays corresponds to tropospheric signals.

We use three criteria to evaluate the performance: i) the reduction of the standard deviation, ii) the reduction of the sill of the semi-variogram, iii) the slope reduction of the phase-elevation correlation. We show that corrections with ERA and GACOS are efficient on only half of the interferograms.

Finally, we also use the local network of 5 GNSS stations to rely on an independent dataset. We show there is a linear relation between the GNSS tropospheric delays and the global weather models delays. However, the GNSS network at Merapi is too small to provide an efficient correction on the whole volcanic edifice. For this reason, a similar workflow has been carried on the Piton de la Fournaise, Réunion island, using a wider GNSS network. The final aim of this study would be to implement a strategy on which the most suitable tropospheric model is chosen routinely based on the evaluation of the performance criteria to obtain atmospheric-free interferograms during volcanic unrest.

How to cite: Gremion, S., Pinel, V., Albino, F., and Beauducel, F.: InSAR tropospheric corrections on Merapi using global weather models and local GNSS network, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5757, https://doi.org/10.5194/egusphere-egu23-5757, 2023.

In the Caribbean Netherlands, the islands of Saba and St. Eustatius host the active but quiescent volcanoes Mt. Scenery and The Quill. To mitigate volcanic risk to the islands, robust monitoring is essential. Therefore in the past five years the Royal Netherlands Meteorological Institute (KNMI) significantly expanded the volcano monitoring network on both islands.

The seismic monitoring network was expanded from seven to 11 broadband seismometers located across the islands. Seismic data are sent to and stored at KNMI and Observatories and Research Facilities for European Seismology (ORFEUS). Eight permanent continuous Global Navigation Satellite System (GNSS) stations were newly installed, where possible co-located with the broadband seismometers. GNSS data are sent to and stored at KNMI and UNAVCO. On a daily basis we run an automatic earthquake detection system and coincidence trigger to identify seismic events and create GNSS time series using both network and Precise Point Positioning (PPP) solutions.

The installation of new instruments was challenging due to the remoteness of the envisioned locations which were needed to monitor all sides of the volcanoes.  Local governmental and military assistance was key to the success of the mission. At the most remote locations instruments are operated on solar power and data are transmitted using  Very-Small-Aperture Terminal (VSAT) technology. Ensuring the operability of the monitoring network remains demanding due to the harsh tropical conditions (hurricanes, UV-radiation, sea spray, lightning) as well as network and power outages. 

Apart from seismic and GNSS instruments, we also deploy three temperature sensors and four cost-effective GNSS units to extend our monitoring network. Furthermore, in collaboration with Delft University of Technology (TU Delft) we test the feasibility of the use of Interferometric Synthetic Aperture Radar (InSAR) for the monitoring of these islands.

How to cite: de Zeeuw-van Dalfsen, E., Sleeman, R., and Krietemeyer, A.: The installation and operation of a multi-parameter volcano monitoring network on the islands of Saba and St. Eustatius in the Caribbean Netherlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6925, https://doi.org/10.5194/egusphere-egu23-6925, 2023.

We present initial positioning results obtained by analyses of data from four cost-effective Global Navigation Satellite System (GNSS) units installed on the island of Saba. The island hosts the active but quiescent stratovolcano Mt. Scenery which reaches an elevation of 887 metres and was last active around 1640. The cost-effective GNSS units were installed around the volcano in February 2022 and house all necessities for autonomous, continuous monitoring. The overall equipment cost per unit is about 1000 Euros, a fraction of the material costs of a conventional, permanent continuously monitoring GNSS station. Furthermore, the typical installation time of permanent stations takes multiple days whereas the installation time required for our cost-effective units can be undertaken within a few hours. We demonstrate that the performance of the cost-effective GNSS units for daily positioning estimations is comparable with the performance of permanent stations. We investigate the precision and accuracy of the time series of kinematic and static positioning solutions using geodetic positioning estimation algorithms. For direct comparison we placed one cost-effective GNSS unit next to a permanent, conventional GNSS station. Furthermore, we investigate if results improve after applying a minimum-effort calibration of the cost-effective antenna using a permanently installed GNSS station. We demonstrate that cost-effective GNSS units are i) well-suited to extend an existing volcano monitoring network of permanent GNSS stations and ii) can potentially even be used independently for basic volcano monitoring when funding is limited. We also envisage the use of cost-effective GNSS units for rapid deployment in hazardous or risk-prone areas where installations of conventional GNSS stations could be deemed too costly.

How to cite: Krietemeyer, A., de Zeeuw-van Dalfsen, E., and Sleeman, R.: The use of cost-effective GNSS units as a volcano monitoring tool on Saba, Caribbean Netherlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7122, https://doi.org/10.5194/egusphere-egu23-7122, 2023.

During the last decades, explosive activity of Mt. Etna (Italy) has increased. Those events produced powerful lava fountains which form high eruption columns rising up to 15 km above sea level and low intensity and long-lasting explosive activity producing weak plumes of few kilometres above the summit craters. During Etna explosive activity, the estimation of the eruption column height is very important for several reasons. This value is inserted in the Volcano Observatory Notices for Aviation (VONA) messages sent by the Istituto Nazionale di Geosifica e Vulcanologia, Osservatorio Etneo (INGV-OE) as monitoring and surveillance duties. The column height is also one of the main eruption source parameters needed to run volcanic tephra dispersal models. Luckily, the column height is one of the easiest features that can be detected in real time using different ground-based instruments (e.g. cameras, radar and lidar) and satellite spectrometers. In this work, we analyse images of two visible calibrated cameras of the permanent video-surveillance system of INGV-OE. They are installed on the south and west sectors of Etna volcano flanks and the column height is estimated also considering the prevailing wind direction above the Etna summit craters. Data cover the period between 2014 and 2022 and were selected on the base of the VONA messages sent by INGV-OE. For the first time, this new database includes the time-variation of the column height for each explosive event. Our analysis, now free available, could be used in future to: i) analyse each explosive activity at Etna volcano; ii) validate new techniques aimed at estimating the eruptive column heights; iii) improve the modelling of eruption column; iv) estimate the mass eruption rate, another key parameter characterizing the explosive activity. 

How to cite: Scollo, S., Prestifilippo, M., and Mereu, L.: Estimations of eruption column height during Etna eruptions: a new database based on visible calibrated cameras, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13071, https://doi.org/10.5194/egusphere-egu23-13071, 2023.

In September 2022 we launched a large-scale seismic experiment in Germany with more than 350 seismological stations (Eifel large-N), to study the Eifel volcanic system. The temporary network is complementing the permanent seismic networks in the region. The deployed instruments used include both 4.5 Hz 3C, 1 Hz short-period, and broadband instruments. DIEGOS Cube³ digitizers are used for data sampling and 9 V electrical fence batteries provide autarch energy at each site. Most of the instruments were borrowed from the GFZ GIPP Instrument Pool for 1 year. In a second phase of the project, half of the installed stations will be re-deployed along linear profiles with a station spacing of 1 km. In 2023, continuous distributed acoustic sensing measurements along a 100 km dark telecommunication fiber optical cable will begin, for a period of three months. These measurements will complete the campaign. We report on preliminary studies on the design of the Large-N experiment, the logistical and technical approach to handling the network and the data, and show first examples for selected local earthquakes, local noise conditions and noise correlations.

The Eifel region in Germany is characterized both as a recreational area with villages, agriculture, forestry and parks, as well as with cities, industrial centers, motorways, railway lines, windmill energy parcs and quarries. The site selection phase was carried out with up to three groups, and began half a year before the network deployment. At the same time, the district administrators and mayors of cities and municipalities who provide valuable support for the project were contacted.

Site selection information was organized in a geo information system (GIS). The fieldwork was orchestrated using the mobile QField App. In September 2022, we started to install the large-N network, which covers an area of ​​approximately 150 x 110 km². Around the scientific target, the Laacher See, is a high station density with inter-station distance of less than 1 km, the inter-station distances increase with distance from the Laacher See. During the installation phases in September and October 2022, the international project partners formed up to 8 groups that installed the nodal stations in the sectors. Each group was equipped with a smartphone or tablet running the QField app also, updating the station information database independently. The QField app provided instant information about the network status via online synchronization.

How to cite: Milkereit, C., Isken, M., Sens-Schönfelder, C., and Dahm, T.: The planning and field work for the large-N passive seismological experiment in the Eifel Volcanic Field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13558, https://doi.org/10.5194/egusphere-egu23-13558, 2023.

Detection of geophysical signatures associated with a geologic event, such as a volcanic eruption, is key to understanding the underlying physical processes and making an accurate hazard assessment. Magma reservoirs are the main repositories for eruptible magma, and understanding them requires the ability to detect and interpret changes in the magmatic system from surface measurements. Traditionally, monitoring for these changes has been done with seismic and geodetic approaches, both of which require dynamic ‘active’ changes within the magmatic system. Seismic monitoring relies on the number and location of earthquakes, to indicate magma migrating within the magmatic system. In contrast, geodetic efforts rely on identifying ground inflation events which have traditionally been interpreted to represent recharge of magma from a deep parental source into shallower crustal reservoirs. Neither of these techniques is sensitive to the petrology or temperature of the magma though. Thus, additional monitoring techniques able to detect ‘static’ phase changes in the evolving magma and the thermal structure of the magma reservoir are needed. The magnetotelluric method, measures subsurface electrical properties and is sensitive to both ‘magma on the move’ and these petrological changes that occur within the magma reservoir itself. Using Mount St Helens where a detailed magnetotelluric survey was completed during the most recent dome building eruptive phase 2005-06, and is now in a period of quiescence, we compare the original measurements from 2005-06 to repeated measurements in the same locations in 2022 to develop the temporal analysis approaches required for monitoring application. In addition to the repeat campaign we have deployed 4 long-term monitoring stations with continuous data observation and telemetry to local servers. First, qualitative, comparisons of the data from different time periods indicate some significant changes in subsurface conductivity. We will present an overview of the newly acquired data and the monitoring setup and discuss where the most significant changes occur.

How to cite: Hill, G., Moorkamp, M., Avram, Y., Hogg, C., Mateschke, K., Gahr, S., Schultz, A., Bowles-Martinez, E., Peacock, J., Karcioglu, G., Chen, C., Cimarelli, C., Carrichi, L., and Ogawa, Y.: Probing the 4D evolution of active magmatic systems through magnetotelluric monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2969, https://doi.org/10.5194/egusphere-egu23-2969, 2023.

Volcanic gases are a main trigger of explosive eruptions, but the largest amounts are emitted through passive, non-eruptive, degassing during quiescence. It is thus necessary to accurately map bubble clouds, and to monitor their dynamics, to reduce volcanic risks.

Contrary to atmosphere, gases are easily detected in water column, particularly using hydro-acoustic methods (Vandemeulebrouck et al., 2000). Two pioneering studies have monitored gas venting into Kelud Crater Lake (Indonesia) from a hydroacoustic station shortly before a Plinian eruption in 1990 [1] and, nearly two decades later, by empirically quantifying CO2 fluxes using acoustic measurements in the same lake just before a non-explosive eruption [2]. However, despite hydroacoustic detection capabilities, fundamental advances are limited by technology performances. Overall acoustic detection of a bubble field is easy, while its quantification remains complex due to the 3D structure of clouds and the acoustic interactions between bubbles.

We present results from near-surface geophysics of sedimentary deposits and water column gas seepage at the Laacher See (Eifel, Germany), using Exail Seapix 3D multibeam echosounder & Echoes high-resolution sub-bottom profiler. Backscatter profiles of water column elements distinguish macrophytes, gas bubbles and fishes and highlight several bubble plumes. Target Strength (TS) of bubbles is centered around -70 dB, suggesting they are of very small size (35 μm), much smaller than observed elsewhere using single beam echosounders. This would explain why, in the same spot, we did not observe any gas bubbling using camera mounted on ROV. Recent measurements at the nadir of a gas flare, in static positioning, using the steerable mills cross multibeam capability of the SeapiX, offered a 4D observation of the gas bubbling. It also provided an equivalent TS of the bubbling we observed two years earlier. We will also present CO2 flow rates that were also extracted from backscatter of gas bubbling in 4D. These calculations are currently being constrained using different backscatter models and represent the last technical aspect before developing an efficient early warning system. Meanwhile, Echoes 10 000 provides high-resolution paleoenvironmental reconstruction using 3D modeling of remobilized materials, and gas diffusion through the sediment. Fusion of all geophysical data using Delph Roadmap allows 3D modeling of gas flare dynamic from 40m in sediment to water-atmosphere interface. Our scientific approach contributes to improve forecasting of volcanic and limnic eruptions and participates to improve early warning systems by constant collaborations with academic research.

[1] Vandemeulebrouck et al (2000) J. Volcanol. Geotherm. Res 97, 1-4: 443-456

[2] Caudron et al (2012) JGR: Solid Earth 117, B5

How to cite: Jouve, G., Caudron, C., Matte, G., Mosca, F., Gauthier, T., and Veloso, M.: Monitoring underwater volcanic degassing using Exail (iXblue) SeapiX volumetric sonar, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5035, https://doi.org/10.5194/egusphere-egu23-5035, 2023.

The Solfatara-Pisciarelli area, within the Campi Flegrei caldera, represents the site of small phreatic, phreatomagmatic and effusive eruptions, which emplaced domes and crypto-domes. Despite a significant number of scientific studies devoted to such an area, the deeper feeding system of the Pisciarelli hydrothermal field, its relation to the Solfatara system, and the main structures governing the fluid rising still represent open problems.

The present contribution aims to detail the surface and buried volcano-tectonic structures and their interaction with hydrothermal fluids in the Solfatara-Pisciarelli area and characterize the presently unknown feeding zones. Geological-structural field surveys permitted the reconstruction of the geological map of the area and the implementation of the fault and fracture orientation and kinematic dataset. Additionally, a series of Electrical resistivity tomographies (ERT), carried out along profiles of different lengths, detailed the structure up to about 100 m depth. The detected patterns of electrical resistivity anomalies helps to define the main structural lineaments of the investigated sector, particularly the presence of normal faults, which results in the presence of sub-vertical resistivity discontinuities. The combination of the ERT and the geo-volcanological and structural survey results allowed the reconstruction of geological sections showing the main structures that characterize the Solfatara and Pisciarelli area. Finally, an Audio-MagnetoTelluric (AMT) survey was carried out in the central sector of the Campi Flegrei caldera to obtain information on the deeper feeding system of the Pisciarelli fumarolic field and its relations with that of the Solfatara and the volcano-tectonic structures of the area. The AMT survey comprised a series of electromagnetic measurements in 47 different sites. The subsequent data inversion produced a 3D model, which identified the electrical resistivity pattern of the investigated structure down to a depth of 2.5 km below sea level. Such a 3D model, which represents the first three-dimensional electromagnetic image of the first few kilometres of the central sector of the Phlegraean area, highlights the presence of significant anomalies related to distinct processes and physical conditions in the system. Remarkably, the main volcano-tectonic structures already hypothesized by shallower electrical surveys are detected by the AMT survey, which results describe their development in depth, identifying at the same time the main structures playing a significant role in the ongoing dynamics of the investigated area.

The proposed combination of shallow ERT, deeper AMT and geological-structural field surveys suggests a possible paradigm for studies on the volcano-tectonic characterization of hydrothermal systems,  due to the good capability to shed light on their evolution. Furthermore, although the intensive monitoring already realized by the INGV-OV surveillance system in the Solfatara-Pisciarelli area, the reiteration of the proposed combination of surveys could reveal helpful to detect changes in the relationships between the faults and the hydrothermal fluid circulation. Our approach could also be of interest to other similar systems, which could steer toward unrest states compatible with impulsive events, such as hydrothermal and phreatic explosions, as recorded worldwide in several cases, also recently. 

How to cite: Isaia, R., Di Giuseppe, M. G., Natale, J., Troiano, A., and Vitale, S.: Volcano-tectonic, electrical and electromagnetic investigations to highlight the structure of the most active sector of Campi Flegrei caldera, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7714, https://doi.org/10.5194/egusphere-egu23-7714, 2023.

Strokkur geyser in Iceland is located in the Haukadalur valley and features jetting water fountains of hot water every few minutes. In earlier studies we found that Strokkur geyser passes through typical phases: eruption, conduit refilling with water, gas accumulation in a bubble trap and regular bubble collapses at depth in the conduit (Eibl et al. 2021).

In this presentation we focus on the blue bulge that forms at the beginning of an eruption and the following jetting and drifting of the water fountain. We analysed video camera data from 2017, 2020 and 2022 from the ground and from drones to assess the bulge heights and formation speeds. We find that an up to 0.5 m high water bulge forms within 0.7 s at an average speed of 0.6 m/s. Following the bulge burst, we subdivide the eruption phase into a water jet phase and a water drift phase. The water jet reaches a mean height of 16.2 m rising at a maximum average speed of 10.2 m/s. 5 s after maximum jet height is reached the water has drifted to a mean height of 25.6 m at a constant drift speed of 2.0 m/s. We find that eruptions that feature larger bulges also feature larger jet heights and discuss whether there is a link between eruption height and waiting time after eruptions.

How to cite: Karmacharya, S., P. S. Eibl, E., Shevchenko, A., Walter, T., and Páll Hersir, G.: Bulge Formation, Water Jetting and Drifting at Strokkur Geyser, Iceland, derived from Video Camera Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12201, https://doi.org/10.5194/egusphere-egu23-12201, 2023.

Sangay is a 5286 m high stratovolcano located in the southern part of the Ecuadorian Andes, about 200 km south of the capital city of Quito. Sangay is the last active volcano to the south of the Northern Andes, and has been characterized by an almost constant and continuous activity with variable periods of quiescence. During historical times, the written reports describe at least 9 major eruptions since 1628. Sangay has been instrumentally monitored by the Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) since 2013. In May 2019, Sangay began a new eruptive period, which is still ongoing and has been categorized as the most intense in the last six decades. The main phenomena produced during this period are small explosions, ash and gas emissions, lava fountaining, lava flows and associated pyroclastic currents and secondary lahars.

On 1 December 2021, from around 19:20 UTC, the seismic recordings of SAGA station began to show transient events occurring regularly. These events persisted for the next 13 hours with an irregularly accelerating rate of occurrence and increasing amplitude before merging into tremor at around 08:20 on 2 December. This sequence was rapidly followed by two explosive emissions, which were observed by the GOES-16 satellite, the first one at 09:02 and the second at 09:13. The emissions produced a 14.5 km-high gas-rich, ash-depleted eruptive column without any associated regional fallout reported. This drumbeat sequence was produced after a series of morphological changes observed through satellite images (Planet and Sentinel 2). Specifically, during the short time period considered in this study: 1) two new vents opened; 2) a landslide affected the northern flank of the volcano; 3) the first drumbeat sequence was recorded at Sangay; and 4) a new lava flow was emitted through the new northern vent. The drumbeat sequence is interpreted as being caused by the forced extrusion of this new lava flow through the new opening northern vent. Timely communication of this kind of volcanic events is favored by the creation and strict following of internal protocols within volcano observatories and the appropriate use of social networks allowing thousands of people to be reached in very short time period. The corresponding short report produced by the IG-EPN reached more than 300.000 people.

How to cite: Hidalgo, S., Vasconez, F., Battaglia, J., Bernard, B., Espin, P., Valade, S., Naranjo, M.-F., Campion, R., Salgado, J., Cordova, M., Almeida, M., Hernandez, S., Pino, G., Gaunt, E., Bell, A., Mothes, P., Ruiz, M., and Andrade, D.: Sangay volcano (Ecuador): multiparametric analysis of the December 2021 eruptive activity including the opening of new vents, a drumbeat seismic sequence and a new lava flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9354, https://doi.org/10.5194/egusphere-egu23-9354, 2023.

Volcanic SO₂ flux observations are relevant to understanding the magmatic processes that occur within the shallower portions of magmatic plumbing systems, and the mechanisms governing transition from open-vent quiescent degassing to explosive activity. Here, we review a SO₂ flux dataset acquired at Mt. Etna volcano from a permanent UV camera system during more than 7 years of observations, from June 2015 to December 2022. Our fully automated UV camera system, housed in the Montagnola INGV-OE hut, is designed to spatially resolve SO₂ emissions from the southern portion (SEC + Central Craters) of the summit craters’ terrace. The observed period encompasses a variety of eruptive phenomena, including the Voragine Crater (VOR) paroxysmal episodes in 2015-2016, several effusive and lateral eruptions (including the late 2019 “Christmas eruption”) and the two most recent paroxysmal sequences of the South-East Crater (SEC) in December 2020/April 2021 and May/October 2021. We find large temporal variations in the SO₂ flux in response to changes in volcanic activity style and vigour. Our results, in particular, demonstrate a clear acceleration in SO₂ degassing during effusive eruptions and paroxysmal episodes, relative to non-eruptive (quiescent) periods. Escalating SO₂ flux (>5000 t/d) is especially relevant prior (circa 1 month before) onset of the December 2020/April 2021 SEC paroxysmal sequence, whilst reduced degassing (<3000 tons/d) characterises the quiescent phases in between the paroxysmal sequences. This 2020-2021 paroxysmal sequences is characterised in more detail by complementing gas observations with volcanic tremor results and thermal output records (both ground- and satellite-based). Results are interpreted in view of a S degassing model lead that explain elevated SO₂ fluxes as caused by augmenting rate of magma transport into the shallow (< 5 km) Etna’s plumbing system.

How to cite: Lo Bue Trisciuzzi, G., Aiuppa, A., Bitetto, M., Delle Donne, D., Coltelli, M., Pecora, E., Alparone, S., and Ganci, G.: Seven years of UV camera-based SO2 flux observations at Mount Etna, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7824, https://doi.org/10.5194/egusphere-egu23-7824, 2023.