GMPV8.6 | Volcano monitoring and imaging with networks
Volcano monitoring and imaging with networks
Co-organized by NH2
Convener: Jurgen Neuberg | Co-conveners: Luca De Siena, Thomas R. Walter, Catherine Hayer
| Thu, 27 Apr, 10:45–12:30 (CEST)
Room -2.91
Posters on site
| Attendance Thu, 27 Apr, 08:30–10:15 (CEST)
Hall X2
Orals |
Thu, 10:45
Thu, 08:30
Over the past few years, major technological advances significantly increased both the spatial coverage and frequency bandwidth of multi-disciplinary observations at active volcanoes. Networks of instruments, both ground- and satellite-based, now allow for the quantitative measurement of geophysical responses, geological features and geochemical emissions, permitting an unprecedented, multi-parameter vision of the surface manifestations of mass transport beneath volcanoes. Furthermore, new models and processing techniques have led to innovative paradigms for inverting observational data to image the structures and interpret the dynamics of volcanoes. Within this context, this session aims to bring together a multidisciplinary audience to discuss the most recent innovations in volcano imaging and monitoring, and to present observations, methods and models that increase our understanding of volcanic processes.
We welcome contributions (1) related to methodological and instrumental advances in geophysical, geological and geochemical imaging of volcanoes, and (2) to explore new knowledge provided by these studies on the internal structure and physical processes of volcanic systems.
We invite contributors from all geophysical, geological and geochemical disciplines: seismology, electromagnetics, geoelectrics, gravimetry, magnetics, muon tomography, volatile measurements and analysis. The session will include in-situ monitoring and high- resolution remote sensing studies that resolve volcanic systems ranging from near-surface hydrothermal activity to deep magma migration.

Orals: Thu, 27 Apr | Room -2.91

Chairpersons: Jurgen Neuberg, Luca De Siena
On-site presentation
Michael Heap, Claire Harnett, Jamie Farquharson, Patrick Baud, Marina Rosas-Carbajal, Jean-Christophe Komorowski, Marie Violay, Albert Gilg, and Thierry Reuschlé

The rocks forming a volcano are typically saturated or partially-saturated with liquid. However, most experiments aimed at better understanding the mechanical behaviour of volcanic rocks have been performed on dry samples, and therefore most large-scale models designed to explore volcanic stability have used parameters representative for dry rock. We present a combined laboratory and modelling study in which we (1) quantify the influence of water on the mechanical behaviour of variably altered dome rocks from La Soufrière de Guadeloupe (Eastern Caribbean) and (2) use these new laboratory data to investigate the influence of water on dome stability. Our laboratory data show that the ratio of wet to dry uniaxial compressive strength (UCS) and Young's modulus are ~0.95–0.30 and ~1.00–0.10, respectively. In other words, the rocks were all weaker when saturated with water. We also find that the ratio of wet to dry UCS decreases with increasing alteration (the wt% of secondary minerals). Micromechanical modelling suggests that the observed water-weakening is the result of a decrease in fracture toughness (KIC) in the presence of water. We also find that the ratio of wet to dry KIC decreases with increasing alteration, explaining why water-weakening increases with alteration. To explore the influence of water saturation on dome stability, we numerically generated lava domes using the experimental data corresponding to dry unaltered and altered rock, in Particle Flow Code. The strength of the dome-forming rocks was then reduced to values corresponding to wet conditions. Our modelling showed that, although the stability of the unaltered dome was not influenced by water saturation, large displacements were observed for the altered dome. Additional modelling in which we modelled a buried alteration zone within an unaltered dome showed that higher displacements were observed when the dome was water saturated. We conclude that (1) the presence of water reduces the UCS and Young's modulus of volcanic rock, (2) larger decreases in UCS in the presence of water are observed for altered rocks, and (3) large-scale dome stability modelling suggests that the stability of a dome can be compromised by the presence of water if the dome is altered or contains an altered zone. These conclusions highlight that the degree of alteration and water saturation should be monitored at active volcanoes worldwide, and that large-scale models should use values for water-saturated rocks when appropriate.

How to cite: Heap, M., Harnett, C., Farquharson, J., Baud, P., Rosas-Carbajal, M., Komorowski, J.-C., Violay, M., Gilg, A., and Reuschlé, T.: The influence of water-saturation on the strength of volcanic rocks and the stability of lava domes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1248,, 2023.

On-site presentation
Torsten Dahm and the Eifel Large-N team

The Quaternary east (EEVF) and west Eifel volcanic fields consist of hundreds of distributed scoria cone and explosive maar-diatreme volcanoes fed from reservoirs in the upper mantle and lower crust. Uplifting of the larger EVF region of up to 2 mm/yr is resolved today with modern GNSS and InSAR processing, and the distribution of deformation rates correlate with seismic anomalies and topography at Moho level. The EEVF developed additionally explosive volcanic centres, with a VEI 6 Plinean eruption at the Laacher See volcano (LSV) only 13,000 years ago. The LSV is the second youngest silicic-carbonatitic magma system in the world, with CO2-rich melt erupting from a long-lived (>30.000 years) zoned silicic reservoir at a depth of 5-6 km. The phonolitic centres are today characterised by high CO2 fluxes, fossil CO2-driven diatremes and short-term short wavelength uplift and subsidence. Deep low-frequency earthquakes have been observed beneath the LSV since 2013, suggesting a channel-like connection between the upper mantle and the suspected LSV reservoir, through which magmatic volatiles and possibly fresh melts could migrate upwards.

As a uniquely accessible site in central Europe, the Eifel is a prime location to study the transcrustal magma system of intraplate distributed volcanic fields and their appearance in seismological and geodetic data. Therefore, in September 2022 we started a large-scale field experiment with more than 350 temporary seismological stations (Eifel Large-N) complementing the permanent seismic networks, a 100 km long dark fibre DAS campaign for a period of three months, and further densified the network of continuous GNSS and multiparameter stations at the LSV. We report on pre-studies to design the Large-N experiment, the logistical and technical approach to handle the network and data, and show first examples for selected earthquakes, local noise conditions and ambient noise correlations.

How to cite: Dahm, T. and the Eifel Large-N team: A large-N passive seismological experiment to unravel the structure and activity of the transcrustal magma system of the Eifel Volcanic Field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2590,, 2023.

On-site presentation
Adriana Iozzia, Leighton Watson, Massimo Cantarero, Emanuela De Beni, Giuseppe Di Grazia, Gaetana Ganci, Jeffrey B Johnson, Eugenio Privitera, Cristina Proietti, Mariangela Sciotto, and Andrea Cannata

Over the last 20 years, infrasound signals have been used to investigate and monitor active volcanoes during eruptive and degassing activity. In particular, infrasound amplitude information has been used to estimate eruptive parameters such as plume height, magma discharge rate and lava fountain height. Active volcanoes are characterized by pronounced topography and, during eruptive activity, the topography can change rapidly, affecting the observed infrasound amplitudes. While the interaction of infrasonic signals with topography has been investigated by several authors over the past decade, the impact of changing topography on the infrasonic amplitudes has not yet been explored. In this work, the infrasonic signals accompanying 57 lava fountain paroxysms at Mount Etna (Italy) during 2021 were analyzed. In particular, the temporal and spatial variations of the infrasound amplitudes were investigated. During 2021, significant changes in the topography around the most active crater (the South-East Crater) took place and were reconstructed in detail through unoccupied aerial system surveys. Through analysis of the observed infrasound signals and numerical simulations of the acoustic wavefield, we demonstrate that the observed spatial and temporal variation in the infrasound signals can be explained by the combined effects of changes in the location of the acoustic source and changes in the near-vent topography. This work demonstrates the importance of accurate source locations and high-resolution topographic information, particularly in the near-vent region where the topography is most likely to change rapidly. Changing topography should be considered when interpreting local infrasound observations over long time-scales.

How to cite: Iozzia, A., Watson, L., Cantarero, M., De Beni, E., Di Grazia, G., Ganci, G., Johnson, J. B., Privitera, E., Proietti, C., Sciotto, M., and Cannata, A.: How topographic changes influenced infrasound amplitude during Mt. Etna’s 2021 lava fountains, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3158,, 2023.

On-site presentation
Mie Ichihara, Takao Ohminato, Kostas Konstantinou, Kazuya Yamakawa, Atsushi Watanabe, and Minoru Takeo

The accelerating growth of seismic unrest before eruptions has been observed at many volcanoes and utilized for eruption forecasts. However, there are still many eruptions for which no precursory unrest has been identified, even at well-monitored volcanoes. The recent eruptions of Shinmoe-dake, an active cone of Kirishima volcano, Japan, had been another negative example of this kind. Here we present seismological evidence that the eruption preparation had been ongoing at the shallow depths beneath Shinmoe-dake for several months to a year.

We investigated the seismic background level (SBL) of eleven-year data recorded around the volcano, including two stations about 1 km from the eruptive crater. We searched for persistent weak signals, focusing on low-amplitude time windows recorded during quiet nighttime. Then the spectra of daily background noise were classified by clustering analysis. The SBL analysis successfully revealed very weak precursory tremors from more than several months before the eruption, and residual tremors to the end of the eruptive period. The precursory signals grew acceleratory in a similar way as is assumed in the material failure forecast method applied to eruption forecasts. However, their growth was significantly slower and longer compared to previous cases. Such slow and quiet preparations would not be captured by conventional seismological methods but could be a common feature at volcanoes with developed hydrothermal systems. It is also noted that the SBL monitoring is potentially useful to judge the end of an eruption period. Further studies are necessary for clarifying the source locations and mechanisms of the SBL noise.

How to cite: Ichihara, M., Ohminato, T., Konstantinou, K., Yamakawa, K., Watanabe, A., and Takeo, M.: Seismic background level growth can reveal slowly developing long-term eruption precursors – A case study at Kirishima volcano, Japan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5226,, 2023.

On-site presentation
Jifei Han, Nicholas Rawlinson, Tom Winder, Tim Greenfield, Robert White, and Bryndís Brandsdóttir

Askja caldera is a large central volcano located in the Northern Volcanic Zone in Iceland. It has experienced a number of eruptions in modern history with one of the largest taking place in 1875, from which tephra managed to travel as far as Germany. After its most recent erup- tion in 1961, GPS measurements have shown that deflation has continued since the 1970s, which may primarily be caused by the cooling of a magma body at a depth of around 2 km below sea level, as suggested by geodetic modelling. In ~September 2021, the Askja caldera switched from deflation to inflation. This has caused a lot of excitement in the seismology and volcano communities, with increased monitoring and data collection beginning in earnest in an attempt to better evaluate the progress and potential outcomes of this interesting phenomenon.

My study aims to image the magmatic plumbing system beneath the top ~10 km of the Askja caldera and the surrounding region using seismic tomography. The dataset consists of the first arrival picks of P- and S-waves from local earthquakes. The initial dataset is sourced from Greenfield et al. (2016), but additional picks from more recently collected data are also incorporated to enhance ray coverage. These arrival times are inverted using the FMTOMO package, which jointly constrains hypocenter location and 3-D Vp, Vs and Vp/Vs structure using an iterative non-linear approach, in which the forward problem of traveltime prediction is solved using the Fast Marching Method (Rawlinson et al., 2005).

The final tomographic results yield a variety of wavespeed anomalies that can be associated with the volcanic plumbing system. Of particular note is a low Vp, low Vs and high Vp/Vs anomaly at around 2 km depth below the caldera, a feature that has previously not been observed in seismic imaging results. A low wavespeed anomaly also connects the mid-crust with the surface below the edifice, which is consistent with the flux of melt through the crust. Synthetic checkerboard and spike tests indicate that these features are constrained by the data.


Rawlinson, N. and Sambridge, M. (2005). The fast marching method: an effective tool for tomographic imaging and tracking multiple phases in complex layered media. Exploration Geophysics, 36(4):341.

Greenfield, T., White, R. S., and Roecker, S. (2016). The magmatic plumbing system of the Askja central vol- cano, Iceland, as imaged by seismic tomography. Journal of Geophysical Research: Solid Earth, 121(10):7211– 7229.

How to cite: Han, J., Rawlinson, N., Winder, T., Greenfield, T., White, R., and Brandsdóttir, B.: Imaging the Magmatic Plumbing System beneath Askja Caldera, Iceland with Seismic Tomography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5638,, 2023.

On-site presentation
Nicola Pergola, Nicola Genzano, Simon Plank, and Francesco Marchese

On 27 November 2022, an eruption started at the Mauna Loa (Hawaii; USA) volcano after about 38 years of quiescence. The eruption took place at the summit caldera; the day after, it migrated to the upper Northeast Rift Zone, where lava effusion initially occurred from three fissure vents. In this work, we investigate the Mauna Loa 2022 eruption, ending on 13 December, by means of a virtual network of multi-sensor infrared satellite observations. In particular, we show the results achieved by implementing the Normalized Hotspot Indices (NHI) on GOES-R ABI data, at 10 min temporal resolution, and by using Sentinel-2 MSI and Landsat-8/9 OLI/OLI-2 observations at mid-high spatial resolution via the Google Earth Engine tool developed to map volcanic thermal anomalies at global scale.. Both the eruption onset and the short-term variations of thermal activity were well identified by NHI, using GOES-R ABI data. Moreover, an accurate mapping and characterization of active lava flows was performed. These results confirm that SWIR (short wave infrared) observations, at different temporal and spatial resolution, if properly analysed, may support the monitoring and surveillance of active volcanoes from space.

How to cite: Pergola, N., Genzano, N., Plank, S., and Marchese, F.: Investigating Mauna Loa (Hawaii) eruption of November-December 2022 from space: recent results from GOES-R, Sentinel-2, and Landsat 8/9 observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7776,, 2023.

On-site presentation
Freysteinn Sigmundsson, Michelle Parks, Halldór Geirsson, Páll Einarsson, Vincent Drouin, Benedikt G. Ófeigsson, Kristín Jónsdóttir, Kristín S. Vogfjörd, Andrew Hooper, Yilin Yang, Sonja H. M. Greiner, Siqi Li, Chiara Lanzi, Sigrún Hreinsdóttir, Ronni Grapenthin, Erik Sturkell, Elske de Zeeuw van Dalfsen, Mathijs Koymans, and Sara Barsotti

Precursors to volcanic eruptions vary widely between volcanic systems and their individual eruptions. Volcanic systems in Iceland undergoing unrest include the Reykjanes, Svartsengi, Fagradalsfjall, and Krísuvík systems on the obliquely spreading Reykjanes Peninsula. Main precursors prior to the Fagradalsfjall eruptions in 2021 and 2022 were signals associated with the formation of dikes releasing stored tectonic stress over weeks and days, respectively. If volcanic activity occurs at Fagradalsfjall in coming years it may be associated with shorter warning time, as less stored tectonic stress remains. In contrast, the nearby Svartsengi system experienced cumulative uplift of about 15 cm in multiple inflation episodes during 2020 to 2022, modeled as repeating sill intrusions. Prior to, in-between, and following the intrusive events, the surface subsided. We find that the onset of diking accompanied by a sudden increase in seismicity and deformation rates is a likely scenario prior to future eruptions on the Reykjanes Peninsula. A decline in seismicity and/or deformation may occur as unrest activity progresses, as experienced prior to the 2021 and 2022 eruptions. In other areas of Iceland, since 2020 magma storage areas with increasing pressure have been identified at the Askja, Grímsvötn, Krafla, and Bárðarbunga calderas, as well as at Hekla volcano. Increasing pressure buildup in the roots of these volcanoes, is expected to a varying degree prior to next eruption, with different amounts of inflation and seismicity. Tectonic stress release as observed during the 2014/15 Bárðarbunga rifting event may occur or not. The largest capacity for pressure increase is expected at the Askja caldera, where the surface over the magma chamber subsided by more than 1 m from 1983 to 2021, but since August 2021 over 45 cm of uplift has occurred and deformation continues. The amount of subsidence prior to present uplift may indicate the scale of further inflation needed to reach critical conditions, assuming that the current inflation is sourced in a similar crustal volume as the deflation, and the strength of the surrounding material remains similar (e.g., no new faulting/fracturing). Examples of intermittent flow of magma to shallow depth, or pressure increase beneath calderas, occurred during 2017-2018 at Öræfajökull, where a slight increase in seismicity has been detected in recent months, and inflation 2018-2019 at Torfajökull caldera. It remains a challenge to promptly identify seismic swarms that may be indicative of formation of magma feeding conduits versus those indicating intermittent increases in seismic activity due to high stress levels, e.g., caused magma recharging, changes in geothermal activity, or glacial retreat. Experience from the Northern Volcanic Zone and the Reykjanes Peninsula oblique rift, suggest precursory activity may take place simultaneously over wide parts of plate boundary areas, indicating to some extent coupled activity of nearby volcanic systems.

How to cite: Sigmundsson, F., Parks, M., Geirsson, H., Einarsson, P., Drouin, V., Ófeigsson, B. G., Jónsdóttir, K., Vogfjörd, K. S., Hooper, A., Yang, Y., Greiner, S. H. M., Li, S., Lanzi, C., Hreinsdóttir, S., Grapenthin, R., Sturkell, E., van Dalfsen, E. D. Z., Koymans, M., and Barsotti, S.: Ongoing unrest at Icelandic volcanoes: What deformation and seismicity patterns to expect leading up to future eruptions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9696,, 2023.

On-site presentation
Chris Bean, Gareth O'Brien, and Ivan Lokmer

Despite advances in seismic instrumentation and seismic network densities, the ability to obtain detailed images of subsurface volcanic structure is still compromised. This leaves large uncertainties in the time evolution and nature of shallow magma emplacement, for example. Ideally it is desirable to see objects at the scale of individual sills, but strong wave scattering in volcanic settings makes this difficult to achieve and tomographic images smooth out objects at this scale. Multiple scattering creates a ‘fog’ through which it is difficult to pick singly scattered (reflected) events of interest. We use a Deep Learning approach to try capture information from this full wavefield and use that to build detailed images. Specifically we employ a Fourier Neural Operator (FNO) to model and invert seismic signals in heterogeneous synthetic volcano models. The FNO is trained using 40,000+ simulations of full wavefield elastic waves propagating through these 2D models. Once trained, the forward FNO network is used to predict elastic wave propagation and is shown to accurately reproduce the seismic wavefield. That is, the FNO can act as a fast and highly efficient forward full wavefield simulator. The FNO is also trained to predict highly heterogeneous velocity models given a set of seismograms. We show that this Deep Learning approach accurately predicts known synthetic velocity models based on surprisingly small sets of input seismograms, capturing details of the velocity structure that would lie outside the ability of current seismic methods in volcano imagery. This offers a potential new approach to imaging in volcanic environments. Although the upfront training cost of 40k simulations is very large, once trained the run times for the FNO are negligible.  

How to cite: Bean, C., O'Brien, G., and Lokmer, I.: Seismic imaging on volcanoes using Machine Learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13136,, 2023.

On-site presentation
Umberto Riccardi, Stefano Carlino, Tommaso Pivetta, Jacques Hinderer, and Severine Rosat

We report the results of about 20 years of relative gravity measurements acquired on Mt. Somma-Vesuvius INGV monitoring network, together with about 9 months of continuous gravimetric recordings collected with the new generation relative gravimeter gPhoneX#116, specifically designed for continuous gravity recording. We also present the outcomes of an intercomparison experiment of the gPhone#116 conducted at the J9 gravity observatory in Strasbourg (France). In this intercomparison, we were able to check the meter scale factor with a high degree of precision by comparing them with 2 superconducting gravimeters and a FG5-type absolute ballistic gravimeter. It was also possible to carry out a detailed study of instrumental drift, a crucial topic for reliable monitoring of the long-term gravity variations in active volcanic areas. In fact, a challenge in time lapse gravimetry is the proper separation of the instrumental variations from real gravity changes eventually attributable to recharge or drainage processes of magma or fluids in the feeding systems of active volcanoes.

Since 1980s the relative gravity network of Mt- Somma-Vesuvius has evolved over time becoming progressively larger and denser. We discuss the results of the time-lapse monitoring since 2003, when the INGV network reached an almost stable configuration. The retrieved field of time gravity change shows a pattern essentially related to the ground deformation detected by the permanent GNSS network. Vesuvius is currently experiencing subsidence at a variable rate. A clear topographic effect emerges with a strong correlation with altitude, whereby higher stations subside at a greater rate, up to 7 mm/year, than those at lower altitudes. Most of the observed gravity changes can be explained by this dynamics; only a residual positive gravity is detected in the western sector of the volcano, which could be likely due to hydrological effects. A reliable tidal gravity model was derived from the analysis of the gravity records. We believe that this result should help improve the accuracy of the volcano monitoring as it will be useful for the correct reduction of tidal effects for all relative and absolute gravity measurements acquired in the area.

How to cite: Riccardi, U., Carlino, S., Pivetta, T., Hinderer, J., and Rosat, S.: Catching the time-variable gravity at Mt. Somma-Vesuvius volcano (Southern Italy) by means of discrete and continuous relative gravity measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13361,, 2023.

On-site presentation
Luigi Carleo, Gilda Currenti, and Alessandro Bonaccorso

Lava fountains at Etna volcano are spectacular eruptive events characterized by powerful gas jets that expel lava fragments to several hundred meters and volcanic ash to several kilometers above the crater. Ash fall-out and dispersal cause critical hazards to both the vehicular traffic and the aviation, inducing the temporary closure of the southern Italy airports.

In 2020-2022, Etna experienced more than 60 lava fountains. The dynamics of such explosive events is usually a gradual process, starting with a strombolian activity that progressively evolves in an intense and continuous explosive activity with a sustained eruptive column. The duration, the degree of explosiveness, the portion of effusive flows, etc., are usually variable implying a different degree of involved hazard. Recently, researchers attempted to manually classify lava fountains at Etna on the basis of volcanological and geophysical data. However, manual classification is time consuming and prone to subjective biases.

We propose an automatic procedure to cluster the lava fountain events that occurred in 2020-2022 at Etna using unsupervised machine learning techniques. The clustering algorithm is applied on high precision strain signals recorded by the borehole dilatometer network deployed to monitor volcano deformation processes. In particular, the analysis focuses on the strain variations recorded during the lava fountain events to highlight similarities and differences among the eruptions in terms of induced ground deformation. The results disclose the main features of the strain signal effective to group the lava fountain events. Four well-separated and coherent clusters are identified improving the manual classifications performed by the experts. Moreover, the analysis reveals that the lava fountains clusters are grouped also over time showing possible transitions in the eruptive style.

How to cite: Carleo, L., Currenti, G., and Bonaccorso, A.: Clusters of lava fountain events identified on strainmeter data at Etna volcano, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12571,, 2023.

Posters on site: Thu, 27 Apr, 08:30–10:15 | Hall X2

Chairpersons: Jurgen Neuberg, Luca De Siena
Structure and tomography
Tom Winder, Isabel Siggers, Nicholas Rawlinson, Robert White, and Bryndís Brandsdóttir

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.

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,, 2023.

Anne Paul and Aurélien Mordret and the MACIV Team (1, 2, 3, 4)

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,, 2023.

Shan Gremion, Virginie Pinel, Fabien Albino, and François Beauducel

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,, 2023.

Elske de Zeeuw-van Dalfsen, Reinoud Sleeman, and Andreas Krietemeyer

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,, 2023.

Andreas Krietemeyer, Elske de Zeeuw-van Dalfsen, and Reinoud Sleeman

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,, 2023.

Simona Scollo, Michele Prestifilippo, and Luigi Mereu

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,, 2023.

Claus Milkereit, Marius Isken, Christof Sens-Schönfelder, and Torsten Dahm

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,, 2023.

Graham Hill, Max Moorkamp, Yann Avram, Colin Hogg, Kati Mateschke, Sofia Gahr, Adam Schultz, Esteban Bowles-Martinez, Jared Peacock, Gokhan Karcioglu, Chaojian Chen, Corrado Cimarelli, Luca Carrichi, and Yasuo Ogawa

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,, 2023.

Guillaume Jouve, Corentin Caudron, Guillaume Matte, Frédéric Mosca, Tehei Gauthier, and Mario Veloso

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,, 2023.

René Steinmann, Léonard Seydoux, Michel Campillo, Nikolai Shapiro, Cyril Journeau, and Nataliya Galina

Volcanic tremors are one of many seismic signals recorded on volcanoes and are associated with different pre- and co-eruptive processes. Therefore, they are widely used in volcano monitoring. The properties of the tremor signals such as duration, spectral content, or intermittency are very variable, reflecting the possible different tremor source mechanisms. In many cases, several tremor-generating processes can act simultaneously resulting in overlapping signals in the seismogram. Despite their complex signal characteristics and different source mechanisms, volcanic tremors are either treated as one seismic signal class or as a set of seismic signal classes. With a scattering network, we can access the information conveyed by volcanic tremors, even in the presence of short-term impulsive signals. We apply blind source separation methods and manifold learning techniques to continuous seismograms recorded at the Klyuchevskoy Volcanic Group (Kamchatka, Russia) and reveal the underlying patterns in the time series data dominated by volcanic tremors. The data-driven descriptors of the year-long seismogram reveal an ever-changing tremor signal, challenging the division of the observed volcanic tremors into a few distinct classes. The results highlight the complexity and non-stationarity of the volcanic tremors, suggesting a non-stationary volcanic system. Relating the data-driven patterns to the different underlying processes is the next step to understanding better the inner workings of a volcano.

How to cite: Steinmann, R., Seydoux, L., Campillo, M., Shapiro, N., Journeau, C., and Galina, N.: Non-stationarity of volcanic tremor signals revealed by blind source separation and manifold learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6328,, 2023.

Peter Makus, Marine Denolle, Christoph Sens-Schönfelder, Manuela Köpfli, and Frederik Tilmann

Mt. St. Helens is an explosively erupting volcano located in close vicinity to major metropolitan centres on the US Westcoast. In recent history, Mt. St. Helens erupted twice, in 2004 and 1980, causing more than 50 fatalities and over one billion USD of damage. Mt. St. Helens is also home to the only advancing glacier in the US, making it a unique site for geophysical measurements. Here, we present a seismic velocity change time-series (dv/v) of an unprecedented length covering the years 1998-2021. We quantify dv/v by applying the method of ambient seismic noise interferometry to waveform data recorded from a combination of various permanent and temporary seismic stations of the Pacific Northwest Seismic Network (PNSN). Due to its ubiquitous nature, ambient seismic noise allows for far denser temporal sampling than, e.g., active source or earthquake coda interferometry. However, source variability related, for example, to volcanic tremor activity affects the results retrieved by this method and can lead to decreased reliability. In this study, we focus on the impact of the complex dynamics at Mt. St. Helens on dv/v specifically by setting it into context with ground deformation, meteorological changes, and volcanic activity with the ultimate goal of unravelling the complex physical relationship between different forcings and the seismic velocity.

How to cite: Makus, P., Denolle, M., Sens-Schönfelder, C., Köpfli, M., and Tilmann, F.: The Complex Relationship between Seismic Velocity and Volcanic, Tectonic, and Environmental Forcings Illustrated by 23 Years of Data at Mt. St. Helens, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6757,, 2023.

Roberto Isaia, Maria Giulia Di Giuseppe, Jacopo Natale, Antonio Troiano, and Stefano Vitale

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,, 2023.

Sandeep Karmacharya, Eva P. S. Eibl, Alina Shevchenko, Thomas Walter, and Gylfi Páll Hersir

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,, 2023.

Silvana Hidalgo, Francisco Vasconez, Jean Battaglia, Benjamin Bernard, Pedro Espin, Sebastien Valade, Maria-Fernanda Naranjo, Robin Campion, Josue Salgado, Marco Cordova, Marco Almeida, Stephen Hernandez, Gerardo Pino, Elizabeth Gaunt, Andrew Bell, Patricia Mothes, Mario Ruiz, and Daniel Andrade

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,, 2023.

Giovanni Lo Bue Trisciuzzi, Alessandro Aiuppa, Marcello Bitetto, Dario Delle Donne, Mauro Coltelli, Emilio Pecora, Salvatore Alparone, and Gaetana Ganci

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,, 2023.