GMPV9.3 | Geochemical monitoring of volcanic systems: methods, findings, and perspectives.
Geochemical monitoring of volcanic systems: methods, findings, and perspectives.
Convener: Marcello Liotta | Co-conveners: Fátima Viveiros, Carlo Cardellini
Orals
| Mon, 24 Apr, 14:00–18:00 (CEST)
 
Room D2
Posters on site
| Attendance Mon, 24 Apr, 10:45–12:30 (CEST)
 
Hall X2
Posters virtual
| Attendance Mon, 24 Apr, 10:45–12:30 (CEST)
 
vHall GMPV/G/GD/SM
Orals |
Mon, 14:00
Mon, 10:45
Mon, 10:45
The understanding of geochemical processes occurring in volcano systems is the driver for the scientific community and Civil Protection agencies towards an effective geochemical monitoring of volcanic activity. Volatile emissions provide the opportunity to infer information on magma degassing that drives the unrest, the eruption activity and its style. In light of this, scientists study the chemical and isotope composition of different types of gas emissions (volcanic plumes, fumaroles and soil emissions) and waters (groundwater, crater lakes, geysers etc.). Many valuable monitoring activities are carried out all around the world by the members of the scientific community thus contributing to the volcanic risk mitigation. In addition, the study of volcanic gases represents a valuable tool to evaluate the impact of volcanic emissions into the atmosphere, characterize the geothermic potential of the areas, identify and characterize outdoor and indoor gas hazard.
We are seeking contributions from any geochemical studies on various topics including (but not limited to):
Soil degassing;
Fumaroles emissions;
Volcanic plumes;
Dissolved gases;
Thermal waters;
All methodological approaches, from the most traditional to the most innovative ones are welcome.

Orals: Mon, 24 Apr | Room D2

Chairpersons: Marcello Liotta, Fátima Viveiros, Carlo Cardellini
14:00–14:05
14:05–14:35
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EGU23-4308
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GMPV9.3
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solicited
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Highlight
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On-site presentation
Giovanni Chiodini, Giulio Bini, and Stefano Caliro

The ratio between fumarole gas species of predominant magmatic origin (i.e., CO2, He) and CH4, which is typically produced in the hydrothermal environment, is a powerful indicator of the upflow of magmatic fluids towards the surface. The analysis of time series of fumarolic composition from different dormant volcanoes (e.g., Campi Flegrei, Vesuvius, Vulcano, Panarea, Nisyros, Mammoth Mt) reveals similar anomalous peaks of the CO2/H2O, CO2/CH4, and He/CH4 ratio during unrests, suggesting recurrent events of magma degassing. The sudden upflow of deep magmatic fluids causes pressure buildup and heating of the hydrothermal systems, earthquakes and ground deformations, which precede the fumarole gas compositional anomalies. These anomalies, once normalized to the time and to the amplitude of the curve, show the same shape: a rapid increase in the geochemical indicator followed by an exponential decrease.

An intriguing consideration based on these examples (almost all the volcanoes for which a long time series of fumarolic compositions are available) is that episodes of magma degassing probably reflect the normal background activity of volcanoes, making the interpretation of volcanic unrests challenging. Concurrently with magma degassing events, a significant increase in the CO2 degassing process was either measured or qualitatively observed in these systems. A better knowledge of these degassing episodes is needed to improve our understanding of the volcanic behavior and to better constrain the release of CO2 from quiescent volcanoes.  

How to cite: Chiodini, G., Bini, G., and Caliro, S.: The hidden activity of volcanoes: magma degassing events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4308, https://doi.org/10.5194/egusphere-egu23-4308, 2023.

14:35–14:45
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EGU23-4205
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GMPV9.3
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ECS
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On-site presentation
Giulio Bini, Giovanni Chiodini, Stefano Caliro, Franco Tassi, Orlando Vaselli, Andrea Rizzo, Silvio Mollo, Georgios Vougioukalakis, and Olivier Bachmann

The Nisyros caldera is located in the easternmost part of the South Aegean Volcanic Arc (SAVA), which formed in the seismically active region of the Aegean and has been site of violent explosive eruptions in the last 160 ky. Two 2–3 kmdense-rock equivalent silicic explosions caused the collapse of the Nisyros volcanic edifice 60 ka, and were followed by effusive eruptions until 20 ka. More recently, the interplay between an upper-crustal magma reservoir and an active hydrothermal fluid circulation has led to hydrothermal explosions (the most recent in 1887), concurrently with periods of enhanced seismicity. In 1996–1997, a cluster of earthquakes at shallow depth (<10 km) affected the Nisyros area, growing concern for new hydrothermal/volcanic activity. Here, we compare new fumarole chemical and isotopic compositions (2018–2021) with previous data to gain new insights into the state of the magmatic-hydrothermal system and reconstruct its dynamics during the 1996–1997 seismic crisis. New N2, He, and Ar contents and isotopes show that Nisyros gases are mixtures of magmatic fluids typical of subduction zones, groundwater (or air saturated water, ASW), and air. The composition of the magmatic endmember is calculated through reverse mixing modeling, and shows N2/He = 31.8 ± 4.5, N2/Ar = 281.6, δ15N = +7 ± 3‰, 3He/4He = 6.2 Ra (where Ra is air 3He/4He), and 40Ar/36Ar = 552 ± 20. Although N2/He is significantly low with respect to typical values for arc volcanoes (1,000–10,000), the contribution of subducted sediments to the SAVA magma generation is reflected by the positive δ15N values of Nisyros fumaroles. Hence, we suggest that the low N2/He ratio is not ascribed to the absence of subducted sediments, as previously thought, but to a N2-depletion due to solubility-controlled differential degassing of an upper-crustal silicic (dacitic/rhyodacitic) reservoir at high-crystallinity. N2, He, and Ar data reveal clear additions of both magmatic fluid and ASW during the unrest. In the same period, fumarolic vents display a significant increase in magmatic species relative to hydrothermal gas, such as CO2/CH4 and He/CH4 ratios, an increase of ~50 °C in the equilibrium temperature of the hydrothermal system (up to 325 °C), and greater amounts of vapor separation, estimated through the H2O-H2-CO-CO2-CH4 gas system. These variations reflect an episode of magmatic fluid expulsion during the seismic crisis. The excess of heat and mass supplied by the magmatic fluid injection is then dissipated through boiling of deeper and peripheral parts of the hydrothermal system, without culminating in hydrothermal eruptions. Gas chemistry and reverse mixing modeling of N2, He, and Ar have therefore important implications for monitoring magmatic-hydrothermal systems, as enable us not only to better understand the state of upper-crustal magma reservoirs, but also to track episodes of magmatic outgassing.

How to cite: Bini, G., Chiodini, G., Caliro, S., Tassi, F., Vaselli, O., Rizzo, A., Mollo, S., Vougioukalakis, G., and Bachmann, O.: Tracking episodes of outgassing from upper-crustal magma reservoirs through fumarole gas chemistry: the case of the Nisyros caldera (Aegean Arc, Greece), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4205, https://doi.org/10.5194/egusphere-egu23-4205, 2023.

14:45–14:55
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EGU23-5995
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GMPV9.3
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On-site presentation
Eleazar Padrón, Gladys V. Melián, María Asensio-Ramos, Pedro A. Hernández, Nemesio M. Pérez, Fátima Rodríguez, Cecilia Amonte, Alba Martín, Luca D'Auria, and Hirochika Sumino

Monitoring the volcanic activity of Teide, the only active stratovolcano in Tenerife, the largest island of the Canary Islands, is extremely important for the prevention and reduction of the volcanic disasters of the island. As part of the geochemical monitoring of the Teide volcanic activity, during the last three decades the volcano has been the subject of a geochemical monitoring of the fumarole discharges, characterized by low flux emission of fluids with temperatures of ∼83°C, located at the Teide summit crater (Pérez et al., 1992 and 1996; Melián et al., 2012). Teide fumaroles show chemical compositions typical of hydrothermal fluids, i.e., meteoric steam dominates the gas composition, followed by CO2, N2, H2, H2S, HCl, Ar, CH4, He, and CO (Pérez et al., 1992). The temporal variations in fumarole gas chemistry at Teide volcano was useful to detect significant changes in the chemical composition of the Teide fumarole, including the appearance of SO2, and increases in the HCl and CO concentrations, one year before a seismic crisis that occurred in Tenerife Island between April and June 2004, what suggested that the associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are unequivocally related (Melián et al., 2012). The average of the air-corrected 3He/4He ratio during the period 1991-2022 was 6.80 RA (being RA the atmospheric ratio), with the maximum value of the time series (7.57 RA) measured in August 2016, when an input of magmatic fluids triggered by an injection of fresh magma and convective mixing took place beneath Teide volcano (Padrón et al., 2021). After such input of magmatic fluids, increases in the CO2/H2O, C/S and He/CO2 ratios, a decrease in the CO/CO2 ratio were observed together with a significant increase in the seismic activity recorded in the island of Tenerife. This work highlights the important role of volcanic gases in the monitoring of volcanic activity, paying attention to different chemical and isotopic species in the fumarolic discharges.

 

Melián G.V. et al., (2012), Bull. VolcanoL. 74, 1465–1483.

Padrón E. et al., (2021), J. Geophys. Res. 126, e2020JB020318.

Pérez N.M. et al., (1992), Actas de las sesiones científicas. III Congreso Geológico de España, 1, 463–467.

Pérez N.M. et al., (1996), Geophys. Res. Lett. 23(24), 3531–3534.

 

 

How to cite: Padrón, E., Melián, G. V., Asensio-Ramos, M., Hernández, P. A., Pérez, N. M., Rodríguez, F., Amonte, C., Martín, A., D'Auria, L., and Sumino, H.: Temporal variations in fumarole gas chemistry at Teide volcano, Tenerife, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5995, https://doi.org/10.5194/egusphere-egu23-5995, 2023.

14:55–15:05
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EGU23-14757
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GMPV9.3
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On-site presentation
Giancarlo Tamburello, Marcello Bitetto, Dario Delle Donne, and Alessandro Aiuppa

Gas-sensor-based monitoring stations (aka MultiGAS) near degassing volcanic vents sensibly increased the sampling rate of gas composition measurements. In particular, the CO2/SO2 gas molar ratio was demonstrated to be a good indicator of magma depth thanks to the CO2 and SO2 contrasting solubilities in magma. Numerous high CO2/SO2 gas transients recorded days before an effusive/explosive eruption have been reported in the literature (e.g. Etna, Villarrica, Masaya, Poas). The successful detection of a precursor gas signal in these volcanoes has been favoured by the presence of open or highly permeable closed-conduit (as in the case of Poas) and the instrument’s vicinity to a high-flux degassing vent (high signal/noise ratio). Volcanic gas monitoring in Stromboli represents a particular case. Stromboli is characterised by degassing from multiple vents, which exhibit simultaneous different molar gas ratios during quiescent degassing. The gas emissions during transient strombolian explosions are also different, with higher CO2 contents. Stromboli occasionally exhibits major explosions and paroxysms of greater energy which have often shown a substantial variation of the gas bulk composition weeks before their onset. Finally, the safest sites for a monitoring station in Stromboli are located hundreds of meters from the crater terrace, implying that the detected gas concentrations depend on the wind direction and speed. All these features make the analysis and interpretation of the volcanic CO2/SO2 challenging. This work presents a 2-year-long CO2/SO2 time series recorded at the Stromboli’s summit. We discuss different types of analysis that can be performed to enhance the variations before major and paroxysmal eruptions. We apply an iterative algorithm to estimate the time, number and magnitude of abrupt changes within the CO2/SO2 time series and discuss the origin of such variations. We use an algorithm for finite mixture models on the whole dataset to characterise the source of different gas phases. Finally, we compare the measured CO2 and SO2 concentrations with the wind parameters obtained for the area of Stromboli from the ERA5 reanalysis dataset. Hence, we determine the best conditions for gas ratio measurements and how meteorological conditions may affect the measurements' quality.

How to cite: Tamburello, G., Bitetto, M., Delle Donne, D., and Aiuppa, A.: Insights from  CO2/SO2 gas molar ratio variations and distribution at Stromboli volcano, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14757, https://doi.org/10.5194/egusphere-egu23-14757, 2023.

15:05–15:15
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EGU23-16823
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GMPV9.3
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On-site presentation
Charles Balagizi, Niche Mashagiro, Marcellin Kasereka, and Peter Kelly

Nyiragongo Volcano is located in the western branch of the East African Rift, in eastern Democratic Republic of Congo (DRC). Nyiragongo has gained fame thanks to its long-lived lava lake and the significant hazards it presents to the >1.5 million people living within <30 km, particularly the inhabitants of Goma (DRC) and Gisenyi (Rwanda).  These hazards include fast-moving lava flows produced during effusive eruptions (e.g., in 1977, 2002, and 2021) and regional environmental and health impacts from the persistent volcanic gas plume.

Continuous gas emissions at Nyiragongo present an opportunity for geochemical monitoring of the volcano during changes in activity, such as the recent 2021 flank eruption.  From late 2019 to the present (early 2023), we monitored plume H2O-CO2-SO2-H2S compositions at the summit and at the May 2021 flank vent using a portable multi-GAS (multiple Gas Analyzer System). Pre-eruption measurements from 2019 on the crater rim of Nyiragongo reveal two geochemical end-members: the lava lake gas plume characterized by CO2/SO2 ratios of 50-60 and crater fumaroles characterized by CO2/SO2 ratios up to 300 and a trace of H2S. Overall, the bulk composition of the summit gases was 39.31-70.34% H2O, 29.52-59.93% CO2 and 0.14-0.76% SO2, within the range of plume compositions reported by Gerlach (1979). At the May 2021 eruptive vent, located ~3 km from the summit on the volcano’s southern flank, measurements in August 2021 (after the eruption had ceased) reveal more C-poor gases with a CO2/SO2 ratio of 21.90 and a bulk composition of 95.41% H2O, 4.35% CO2 and 0.32% SO2. The reappearance of the lava lake in the main summit crater in late September 2021 was accompanied by a decrease in the CO2/SO2 ratio to 5 at the May 2021 eruptive vent.  These results show that measuring the changes in plume composition by multi-GAS improves monitoring of Nyiragongo. In the future, we plan to deploy a permanent multi-GAS station at the summit of Nyiragongo to carry out much needed continuous geochemical monitoring. 


Key words: Nyiragongo Volcano, volcanic gases, volcano monitoring, multi-GAS, Plume chemistry

How to cite: Balagizi, C., Mashagiro, N., Kasereka, M., and Kelly, P.: Pre- and post-eruptive gas composition measurements at Nyiragongo Volcano, East Africa, using a portable Multi-GAS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16823, https://doi.org/10.5194/egusphere-egu23-16823, 2023.

15:15–15:25
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EGU23-7410
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GMPV9.3
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ECS
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Virtual presentation
Cecilia Amonte, Eleazar Padrón, Gladys V. Melián, María Asensio-Ramos, Fátima Rodríguez, German D. Padilla, José Barrancos, Luca D'Auria, Pedro A. Hernández, and Nemesio M. Pérez

Tenerife is the largest (2,034 km2) and highest (3,718 m) island of the Canarian archipelago and is the only one hosting an active stratovolcano (Teide-Pico Viejo volcanic system). Its structure is controlled by a volcanotectonic rift-system with NW, NE and NS directions, with the Teide-Pico Viejo volcanic system located in the intersection. The last eruption Teide-Pico Viejo volcanic system occurred in 1798 through an adventive cone. Although Teide volcano shows a weak fumarolic system, volcanic gas emissions observed in the summit cone consist mostly of diffuse CO2 degassing (Hernández et al., 1998; Mori et al., 2001).

More than 200 diffuse CO2 efflux surveys have been performed in the summit crater of Teide Volcano during the period 1999-2023. During each survey, diffuse CO2 emission was estimated in 38 sampling sites, homogeneously distributed inside the crater, by means of a portable non dispersive infrared (NDIR) CO2 fluxmeter using the accumulation chamber method. CO2 emission rates was estimated after spatial distribution maps constructed by sequential Gaussian simulation (sGs) algorithm. During 23 years of the studied period, CO2 emissions ranged from 2.0 to 346 t/d. The most remarkable feature of the temporal evolution of diffuse CO2 emission rate was an important increase that began few weeks after the occurrence of a seismic swarm of long period events was recorded on Tenerife in 2 October 2, 2016, a followed by a general increase of the seismic activity in and around the island (D’Auria et al., 2019). Several geochemical parameters showed significant changes during ∼June–August of 2016 and 1–2 months before the occurrence of the October 2, 2016, long-period seismic swarm (Padrón et al., 2021). Since then, anomalously high diffuse CO2 emission rates has remained in the crater of Teide. This change might be explained as an input of magmatic fluids triggered by an injection of fresh magma and convective mixing after the 2 October 2016 seismic swarm (D'Auria et al., 2019; Padrón et al., 2021). This work reflects how useful are the diffuse studies to understand the behaviour of the volcanic system and to forecast future volcanic activity. Monitoring the diffuse degassing rates has demonstrated to be an essential tool for the prediction of future seismic–volcanic unrest and has become an important monitoring tool to reduce volcanic risk in Tenerife.

D'Auria, L., et al. (2019). J. Geophys. Res.124,8739-8752

Hernández, P., et al. (1998). Geophys. Res. Lett. 25, (17) 3311-3314

Mori, T., et al. (2001). Chem. Geol. 177, 85–99

Padrón, E., et al. (2021). J. Geophys. Res.126,e2020JB020318

How to cite: Amonte, C., Padrón, E., Melián, G. V., Asensio-Ramos, M., Rodríguez, F., Padilla, G. D., Barrancos, J., D'Auria, L., Hernández, P. A., and Pérez, N. M.: Anomalous diffuse CO2 emission from the summit crater of Teide volcano and changes of seismic activity in and around Tenerife, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7410, https://doi.org/10.5194/egusphere-egu23-7410, 2023.

15:25–15:35
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EGU23-9895
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GMPV9.3
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ECS
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On-site presentation
Víctor Ortega-Ramos, Nemesio M. Pérez, Daniel Dinardo, Lía Pitti, Cecilia Amonte, Maria Asensio-Ramos, Mathew J. Pankhurst, José Barrancos, Gladys V. Melián, Pedro A. Hernández, Sonia Silva, Eurico J. Montrond, and Nadir Cardoso

The Cape Verde Islands are a group of 10 intraplate oceanic islands of which 3 show significant levels of recent volcanic activity: Fogo, Santo Antao and Brava. Of these, Fogo is the only historically active volcano with intense activity up to 1725 AD followed by less frequent, mainly effusive eruptions in the last 280 years. The last eruption began on 23 November 2014, and continuing until 8 February 2015. This eruption occurred 19 years after the previous eruptive event, but on the contrary of the 1995 eruption, when there was not monitoring program for the Cape Verde volcanic surveillance, a simple and multidisciplinary volcanic monitoring program, based on a collaborative research volcano monitoring program between Cape Verde and Spanish scientists, was operative to face volcanic unrest such as the 2014 eruption. As part of this volcano monitoring program, from May 2007 to January 2015, forty eight diffuse CO2 emission surveys were performed at the summit crater of Pico do Fogo, covering homogeneously an area of about 0.142 km2. Measurements of diffuse CO2 emission were performed at the surface environment following the accumulation chamber method. The emission rate was calculated after the construction of spatial distribution maps following the sequential Gaussian simulation (sGs) algorithm. The emission rate showed a first anomalous peak in the diffuse CO2 emission, suggesting the occurrence of a first magmatic reactivation likely due to a deep magma intrusion beneath Pico do Fogo volcano between November 2008 and February 2009. Diffuse CO2 emission data suggest the occurrence of a second magmatic intrusion that trigger the eruption process as can be observed by the significant increase of CO2 emission on March 2014. The increment of the diffuse CO2 emission rate shows a good temporal correlation with the satellite-based long-wavelength infrared data reported by Girona et al., (2021). The diffuse CO2 emission data and satellite-based thermal infrared radiance measurements prior the 2014-15 Fogo eruption demonstrate the importance of measuring both parameters to identify and evaluate changes in the volcanic activity of Pico do Fogo volcano.

 

Girona, T. et al., (2021). Nature Geoscience 14, 238–241.

How to cite: Ortega-Ramos, V., Pérez, N. M., Dinardo, D., Pitti, L., Amonte, C., Asensio-Ramos, M., Pankhurst, M. J., Barrancos, J., Melián, G. V., Hernández, P. A., Silva, S., Montrond, E. J., and Cardoso, N.: Diffuse CO2 degassing and low-temperature anomalies prior the 2014-15 Fogo eruption, Cape Verde, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9895, https://doi.org/10.5194/egusphere-egu23-9895, 2023.

15:35–15:45
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EGU23-6185
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GMPV9.3
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Virtual presentation
María Asensio-Ramos, José M. Santana, Maud Smit, Daniela Matias, Nemesio M. Pérez, Fátima Viveiros, Luca D'Auria, Monika Przeor, Gladys V. Melián, Eleazar Padrón, Pedro A. Hernández, Catarina Silva, and Fátima Rodríguez

São Jorge is one of the nine islands of the Azores Archipelago. On March 19, 2022, a seismic crisis began in the island, with more than 32,300 earthquakes recorded until May 2022, of which nearly 300 were felt by the population. On April 5, 2022, an INVOLCAN team travelled to the Azores and, in collaboration with CIVISA/IVAR of the Universidade dos Açores, carried out a soil gas and CO2 diffuse efflux survey to monitor the activity in this volcanic island. The absence of visible volcanic gas emissions (fumaroles, hot springs, etc.) at the surface environment of Manadas volcanic system -the most recent volcanic system in São Jorge- makes this type of studies an essential tool for volcanic surveillance purposes.

Soil CO2 efflux was measured in 400 observation points on the island following the accumulation chamber method using a non-dispersive infrared LICOR-830 CO2 analyzer. Soil gas samples were taken at 40 cm depth to study the chemical composition of diffuse emanations. The chemical composition of the gas samples (He, Ne, H2, CO2, CH4, N2 and O2) was analyzed daily on the island by means of a micro-gas chromatograph (micro-GC).

The results reported herein are related to the soil He and H2 degassing. The former has exceptional characteristics as a geochemical tracer while the second is one of the most abundant trace species in volcanic systems and it is fundamental in many redox reactions occurring in the reservoir gas. Mapping He and H2 soil effluxes may be useful to detect hidden tectonic structures. In addition, detection of significant changes in the diffuse emission of both gases in volcanically active areas, as well as changes in their spatial distribution, is usually linked to movements of magma in the subsoil and/or changes in seismic-volcanic activity. These variations may be excellent early warning signals of changes in the activity of the system.

Spatial distribution maps of the diffuse flow of He and H2 in the 237.59 km2 area of the island were constructed following the sequential Gaussian simulation (sGs) procedure to quantify the diffuse He and H2 emission from the studied area. He fluxes varied from 0 to 3.7 mg·m-2·d-1 (mean value, 0.4 mg·m-2·d-1), while H2 fluxes ranged between 0 and 4.7 mg·m-2·d-1 (mean value, 0.15 mg·m-2·d-1). He and H2 diffuse emission was estimated in 101 and 28 kg·d-1, respectively, with diffuse degassing values of 0.369 and 0.102 kg·km-2·d-1.

The principal H2 flux anomaly is in the central part of the island and coincides with the ground deformation obtained by synthetic aperture radar data acquired by the ESA Sentinel-1 satellite at the beginning of the crisis. He highest fluxes are dispersed in different areas and most of the highest values are located in the Manadas volcanic system, where most of the seismicity focused. The spatial distribution maps of He and H2 fluxes seem to show the existence of areas that could be acting as preferential zones of vertical permeability allowing the migration of deep source gases, which is very important to follow any seismic-volcanic crisis.

How to cite: Asensio-Ramos, M., Santana, J. M., Smit, M., Matias, D., Pérez, N. M., Viveiros, F., D'Auria, L., Przeor, M., Melián, G. V., Padrón, E., Hernández, P. A., Silva, C., and Rodríguez, F.: Soil He and H2 degassing during the recent seismic crisis of São Jorge Island, Azores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6185, https://doi.org/10.5194/egusphere-egu23-6185, 2023.

Coffee break
Chairpersons: Fátima Viveiros, Carlo Cardellini, Marcello Liotta
16:15–16:25
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EGU23-9703
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GMPV9.3
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On-site presentation
Boglarka-Mercedesz Kis, Antonio Caracausi, László Palcsu, Roland Szalay, Andreea-Rebeka Zsigmond, Fátima Viveiros, Alessandro Aiuppa, Paolo Randazzo, and Szabolcs Harangi

The Eastern Carpathians are characterized by CO2-dominated, intense, cold gas emissions starting from the Neogene to Quaternary volcanic structures, the youngest dormant volcano, Ciomadul, but occurring also quite far away from these, in the Cretaceous flysch units.

The gases are often transported to the surface through groundwater and appear in the form of bubbling mineral water springs. The major components of these cold gas emissions are: CO2, CH4, N2 and sometimes H2S. This is the most intensive degassing area from Romania. The gas emissions often appear in inhabited areas, representing a natural risk for locals.

In the recent years we performed detailed geochemical surveys, in which the chemical composition of the free gases, the origin of the different gas species and also the quantification of fluxes from diffuse emissions from the soil and dissolved gas was investigated. We have used different approaches and methods, starting with a specially designed Multi-GAS instrument for low-temperature gases, towards different monitoring experiments.

Our results show that the chemical and isotopic compositions of the investigated fluids throughout the Carpathians are strongly influenced by processes that characterize the geotectonic setting of the study area, such as the former volcanic activity and the subduction. In the present the occurrence of the gas emissions and the high flux areas are dependent on the tectonic structures, namely the nappe systems of the Carpathians and related faults, which represent a pathway for the deep fluids towards the surface.

All our investigations gave us a general view on the quantity, flux, geochemistry and origin of the fluids in the study area and helped us to select the most suitable and appropriate sites for future gas monitoring projects.

This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2019-1908, within PNCDI III, contract number TE 63/2020.

How to cite: Kis, B.-M., Caracausi, A., Palcsu, L., Szalay, R., Zsigmond, A.-R., Viveiros, F., Aiuppa, A., Randazzo, P., and Harangi, S.: The volcano-tectonic setting of the Eastern Carpathians: from detailed gas-geochemical surveys towards gas monitoring planning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9703, https://doi.org/10.5194/egusphere-egu23-9703, 2023.

16:25–16:35
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EGU23-17277
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GMPV9.3
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ECS
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On-site presentation
Letícia Ferreira, José Virgílio Cruz, Fátima Viveiros, Nuno Durães, Rui Coutinho, César Andrade, and José Francisco Santos

Rainwater samples were collected at Furnas and Fogo volcanoes (São Miguel, Azores) in order to characterize their chemical signatures and to investigate a possible interaction with fumarolic gases. Marine aerosols contribute significantly to the chemistry of the rainwaters. The marine inputs ranges from 17.72 to 100 % for Cl-, 9.81 to 100 % for SO42-, 3.79 to 30.31 % for Ca2+, 34.09 to 48.12 % for Mg2+ and 17.29 to 81.09 % for K-. This suggests other sources beyond marine aerosols influencing the hydrochemistry of rainwater, which can be ascribed to two additional components: mineral and volcanic aerosols. The majority of the samples shows an influence of dust particles from North Africa, which can be found in the north Atlantic atmosphere. It is also possible to notice inputs of fumarolic fluids over the hydrochemistry of at least two samples, namely the ones collected near the Caldeiras fumarolic field in Furnas volcano.
Most of the rainwater samples showed 87Sr/86Sr ratios (0.70849 ± 21 - 0.71027 ± 45) similar to the seawater (87Sr/86Sr= 0.70918 ± 1), suggesting that sea salts are the main source of the strontium isotopic ratios. The results are within the range of values presented by rainwater in mainland Portugal (87Sr/86Sr = 0.708965 ± 31 – 0.710345 ± 38). One sample that is exposed to the fumarolic fluids deviates from these values, depicting a lower strontium isotopic ratio (0.70701), confirming the influence of fumarolic fluids already deduced from the major ion hydrogeochemistry.

How to cite: Ferreira, L., Cruz, J. V., Viveiros, F., Durães, N., Coutinho, R., Andrade, C., and Santos, J. F.: Chemical composition and 87Sr/86Sr signatures of rainwaters from São Miguel, Azores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17277, https://doi.org/10.5194/egusphere-egu23-17277, 2023.

16:35–16:55
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EGU23-15309
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GMPV9.3
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solicited
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On-site presentation
Cinzia Federico, Antonio Paonita, Sergio Bellomo, Roberto Maria Rosario Di Martino, Alessandro Gattuso, Leonardo La Pica, Gianluca Lazzaro, Manfredi Longo, Giovannella Pecoraino, Antonino Fabio Pisciotta, and Francesco Sortino

The INGV monitoring system operating in the volcano Island since three decades, recorded a new phase of unrest at the La Fossa volcano since September 2021. The main set of the crisis was the central hydrothermal system, deeply affected by the input of heat and chemicals from the magmatic source. The Levante Bay, located northwest of the La Fossa edifice, is a thermal area, where the vapor, coming from a local hydrothermal aquifer, is emitted from several low temperature (100°C) fumaroles along the beach and in the near off shore. The composition of the gas is typical of hydrothermal systems, and indicates equilibrium at temperature close to 200°C. By the onset of the crisis, in September 2021, the composition of the gas emitted from these fumaroles showed a smooth trend of increasing contribution of the magmatic gas. In May 2022, a sudden release of gas occurred in the Levante Bay, which was testified by the whitening of the seawater in the bay, due the formation of sulfur flakes, and by the appearance of typical pockmark structures on the seafloor. The drastic increase of the gas flux from the underwater gas vents, coupled to the presence of the pockmarks, suggested that an explosive emission of gas occurred in May 2022. The chemical and isotopic composition (He and C isotopes) of the gas emitted from the fumaroles revealed the prevailing presence of the magmatic component, closely approaching the composition of the gas emitted from crater fumaroles. This episode drove the attention of the scientific community to this area, currently affected by a significant input of the magmatic vapor, because of the risk related to the huge gas emission and the eventual overpressurization of the local hydrothermal aquifer.

How to cite: Federico, C., Paonita, A., Bellomo, S., Di Martino, R. M. R., Gattuso, A., La Pica, L., Lazzaro, G., Longo, M., Pecoraino, G., Pisciotta, A. F., and Sortino, F.: When a hydrothermal system is shaken by the magmatic fluids: the thermal area of Levante Bay during the 2021-22 unrest of La Fossa volcano (Vulcano Island, Aeolian Archipelago), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15309, https://doi.org/10.5194/egusphere-egu23-15309, 2023.

16:55–17:05
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EGU23-2291
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GMPV9.3
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On-site presentation
Franco Tassi, Francesco Capecchiacci, Orlando Vaselli, and Stefania Venturi

In summer 2021, a progressive increase of seismic activity and ground deformation was recorded at Vulcano (Aeolian Islands), followed by a strong change in fumarolic gas emission started in September 2021. New gas vents appeared on the crater rim and along the northern outer flank of the La Fossa crater with outlet temperatures up to 350 °C, and a general increase of CO2 and SO2 fluxes was measured.

In this study, we report the results of a geochemical monitoring, including gas and water samples collected during 5 field campaigns, carried out from November 2021 to October 2022. The main aim was to verify the evolution of the plumbing system feeding the fluid discharges of the Vulcano summit crater and those located in the Baia di Levante area. The geochemical dataset also includes the chemical and isotopic composition of thermal and cold wells located in the Vulcano Village. The analytical results have shown that in November 2021 and February 2022 the 9 selected crater fumaroles were affected by a strong increase, compared to the previous decade, of the (i) concentrations of acidic gases of marked magmatic origin (SO2, HCl and HF) and temperature-dependent gases (H2 and CO) (ii) gas/vapor and (iii) SO2/H2S ratios. In this period, the chemistry of waters and dissolved gases from the wells located at the foothill of the volcanic cone, and that of the gas discharges at Baia di Levante did not show significant anomalies.

Since June 2022, the SO2/H2S ratios as well as the concentrations of magmatic gases, H2, and CO decreased, concurrent with a general decrease of the fumarolic flux. At Baia di Levante an opposite evolution was observed mainly consisting of a significant increase in H2S, H2, and CO accompanied by a decrease in CH4 concentrations. Such compositional changes were marked by the occurrence of seawater whitening events caused by enhanced emission of sulfur-rich fluids. In this period, the temperature, as well as the SO4/Cl ratios and the concentrations of dissolved CO2 in the thermal wells of the Vulcano Village also increased. The chemical-physical evolution of the crater fumaroles, culminated in February 2022, was likely related to a strong pulse of magmatic fluids occurred in summer 2021. The fluid reservoir feeding the discharges at the periphery of the magmatic fluid plumbing system, the latter being directly connected to the crater fumaroles, seems to have buffered the pulse until May 2022, when the heat and magmatic fluids fed by the deep source partially bypassed the hydrothermal aquifer. Further observations related to the continuation of the geochemical and geophysical monitoring of the Vulcano hydrothermal-magmatic system in the next months could provide fundamental insights to confirm the decline of the volcanic crisis as suggested by the recent evolution of the crater gas chemistry.

How to cite: Tassi, F., Capecchiacci, F., Vaselli, O., and Venturi, S.: The 2021-2022 unrest phase of Vulcano Island volcanic system (Aeolian islands): chemical and isotopic evolution of low-to-high temperature fluid discharges and waters from thermal and cold wells., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2291, https://doi.org/10.5194/egusphere-egu23-2291, 2023.

17:05–17:15
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EGU23-11463
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GMPV9.3
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On-site presentation
Roberto M. R. Di Martino and Sergio Gurrieri

Monitoring volcanic gases have provided valuable information in recognizing variations of the magma outgassing at depth. The increase of magmatic volatile compounds in either crater plumes or fumarole emissions can help in tracking transitions from dormancy to unrest which can progress further in a volcanic eruption. The volcanic degassing has renewed at Vulcano since September 2021 as the result of an increase of the magma degassing at depth. This event created concerns among civil defense authorities because the CO2 concentration rose in the air, although the unrest has not produced an eruption.

This study examines the air CO2 at Vulcano Porto from the early summer to autumn of 2021, when the volcanic degassing achieved the climax at La Fossa volcano. Five surveys enabled exploring lateral variations for CO2 in the air at Vulcano Porto based on measurements for stable isotope compositions of both oxygen and carbon. In addition, the continuous stable isotopes surveying at a fixed point of interest (i.e., the Centro Carapezza - INGV) enabled studying the time variations for CO2 in the air.

The surveys captured a remarkable increase of the volcanic CO2 in the air throughout the settled zone of Vulcano Porto from October to November 2021. At Vulcanello, which lies a few kilometers far from the crater cone, the isotopic signature of the air CO2 revealed also an increased volcanic degassing. Several variations for the volcanic CO2 in the air occurred during the same period and some estimations of the CO2 flux from the crater plume were obtained through continuous stable isotope surveying.
The results of this study represent a step forward in providing volcano monitoring techniques that enable estimating the CO2 emission in the air from active vents.

How to cite: Di Martino, R. M. R. and Gurrieri, S.: Stable isotope surveys reveal variations in the air CO2 during the unrest event at Vulcano, Italy, in 2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11463, https://doi.org/10.5194/egusphere-egu23-11463, 2023.

17:15–17:25
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EGU23-16462
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GMPV9.3
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On-site presentation
Iole Serena Diliberto, Gaetana Ganci, Annalisa Cappello, Maria Grazia Di Figlia, and Giuseppe Bilotta

Here we present methodologies and practices resulting from the integration, comparison, and validation of thermal monitoring data collected on the close conduit volcano (on the Island of Vulcano, Aeolian Archipelago, Italy). The last unrest phases of La Fossa volcano, manifest since September 2021, allowed us to closely follow the time variations of ground surface temperatures, through the permanent monitoring network, operating since 1991. Our ground control data were used to verify the systematic quantification of time and space variation of thermal anomalies retrieved by the Visible Infrared Imaging Radiometer Suite (VIIRS). The ground-based permanent monitoring network generally provides almost continuous time coverage and higher accuracy, but with limited aerial coverage. On the other hand, satellite data are a powerful tool to study surface thermal anomalies, providing a useful way to monitor the thermal evolution of restless volcanoes by remote platforms. The main applications of thermal remote sensing studies are related mostly to active lava flows and explosive eruptions, whereas the first attempts to remotely track the thermal evolution of quiescent volcanoes are generally lacking ground control reference data. For this reason, those former applications may result in more qualitative than quantitative surface effects of endogenous processes, sometimes including the underestimation of biases of external origin.

This near real-time evaluation of the thermal behavior of the close conduit volcano (La Fossa crater) has been based on three series of long-term monitoring data, independently acquired: the time series of ground temperatures measured within the High-Temperature Fumaroles (a); the depth variation of the convective front rising below the diffuse degassing area (b) and the thermal variations tracked from January 2021 onwards, by the VIIRS images (c). The contact sensors registered the intensity and duration of some periodical modulations of surface temperatures and highlighted other intervals of times when the dynamic equilibrium, usually represented by the gentle emission of fluids in the condition of stationary convection, was critically altered. The radiant flux, retrieved by the nighttime images of VIIRS, confirmed the wider extension of the altered thermal state of the La fossa crater, out of the High-temperature fumaroles, registered from June 2021, up to date.

The complementary nature of the two techniques (direct and remote thermal sensing) has been confirmed by the correlation among the time-series of thermal data. Moreover, the radiant heat remotely sensed by the VIRSS, resulted more closely related to the mild thermal anomaly of the steam-heated ground. Many papers have already presented other monitoring data supporting the same evidence of this volcanic unrest, defined by a significant, and long-lasting phase of pressure buildup, driven by the enhanced supply of magmatic gases in the hydrothermal system (e.g. Diliberto 2021; Inguaggiato et al., 2022a, 2022b; Federico et al., 2023).

How to cite: Diliberto, I. S., Ganci, G., Cappello, A., Di Figlia, M. G., and Bilotta, G.: The combined approach to Ground-based and Satellite Monitoring techniques applied on a close conduit volcano (La Fossa cone, Vulcano, Aeolian Islands, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16462, https://doi.org/10.5194/egusphere-egu23-16462, 2023.

17:25–17:35
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EGU23-15112
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GMPV9.3
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On-site presentation
Salvatore Inguaggiato, Fabio Vita, Claudio Inguaggiato, Agnes Mazot, Iole Serena Diliberto, and Marianna Cangemi

The Active cone of La Fossa caldera is a close conduit volcano affected by solphataric activity, manifested in the hot fluids released from fumaroles and the associated thermal anomalies in groundwater and exposed ground.

The evaluation of the volcanic activity changes are inferred by the near real-time monitoring of soil CO2 fluxes diffused at the La Fossa Cone and the peripheral areas of Palizzi and Levante Bay and by the discontinuous monitoring of CO2 fluxes diffused by soil in areas around the CO2 continuous monitoring stations, La Fossa Cone, Palizzi and Levante Bay. 

In particular, from June 2021 to February 2023 we evaluated in near real time the level and duration of the exhaling crisis affecting the Island of Vulcano, by measuring the changes in mass and energy carried by the fluid release.

The first summit volatiles increase degassing (VSCS station) started in June 2021 reaching in September 2021 the value of 34,000 g m2 d-1 more of one order of magnitude higher respect to the background values (1000 g m2 d-1).

While, the first great increase of CO2 output in the peripheral area, measured with the soil CO2 survey, have been recorded at Levante Bay in May 2022 (17 t d-1) higher respect to the base values recorded in the past (2-4 t d-1). At November 2022 a new strong increase of soil CO2 degassing, have been estimated at Levante Bay area, reaching a values of 46 t d-1.

The strong and deep input of volatiles released from the underlying magma batch strongly modified the chemical composition of the shallow plumbing system, bringing the system to a higher level of CO2 total pressure than the average background recorded in recent decades.

How to cite: Inguaggiato, S., Vita, F., Inguaggiato, C., Mazot, A., Diliberto, I. S., and Cangemi, M.: Abrupt output increase of soil CO2 emissions from summit and peripheral areas of Vulcano Island 2021-2023, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15112, https://doi.org/10.5194/egusphere-egu23-15112, 2023.

17:35–17:45
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EGU23-15400
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GMPV9.3
|
Virtual presentation
Luca Tarchini, Maria Luisa Carapezza, Domenico Granieri, Nicola Mauro Pagliuca, Antonio Patera, Lucia Pruiti, Massimo Ranaldi, Cosimo Rubino, and Francesco Sortino

La Fossa volcano on Vulcano island is the type-location for Volcanian eruptions. Last eruption dates back to 1888-’90. Since then, the quiescent state of La Fossa has been affected both by persistent fumarolic activity and by diffuse CO2 degassing either at the crater and in areas on the flanks (Forgia vecchia) at the base (Palizzi) of the cone, but also in inhabited areas of Vulcano porto (Levante beach, Faraglione). Normal quiescence has been punctuated by potential unrest crises mainly characterized by increase in magmatic degassing, in fumarole temperatures and in diffuse CO2 degassing. We have been monitoring the diffuse degassing area of La Fossa crater since 1995 and Palizzi, Levante beach and Vulcano porto zones since 2004.

The ongoing crisis started in 2021 and showed a huge unprecedented increase in fumarolic degassing associated to ground deformation and episodic anomalous seismicity. For monitoring purposes, we performed since October 2021 two general surveys at the crater of La Fossa (soil CO2 flux and temperature), monthly surveys of diffuse soil CO2 flux in the areas of Palizzi, Levante Beach, Forgia vecchia and an extensive CO2 flux survey (~1000 measurements over 1 km2) in the inhabitated area of Volcano Porto in October 2021. From this wide survey we identified a new diffuse-degassing structure which was apparently inactive during the most recent unrest crises. Since November 2021, this area has been monthly surveyed too. This degassing structure is associated to shallow aquifer thermalism and the area is spotted by some mofetes. During the 1988-’93 crisis, it has been the site of some lethal accidents to animals caused by exposure to high CO2 concentration in air. There have been accidents during this crisis too, with the death of some cats and many birds caused by lethal concentrations of CO2 inside the yard of a house. Fortunately, there were no human casualties due to the prompt evacuation of the zone.

Monthly repetition of soil CO2 flux from the target areas, showed that, at the early stage of the crisis, diffuse CO2 degassing equalled or even exceeded the high-flux rates measured during the previous crisis of 2004-’05 both at the crater area and at the crater base. In 2022-‘23 soil CO2 fluxes have slowly decreased, but the pre-crisis conditions have not yet been reached.

How to cite: Tarchini, L., Carapezza, M. L., Granieri, D., Pagliuca, N. M., Patera, A., Pruiti, L., Ranaldi, M., Rubino, C., and Sortino, F.: Soil CO2 flux monitoring of the ongoing Vulcano crisis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15400, https://doi.org/10.5194/egusphere-egu23-15400, 2023.

17:45–17:55
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EGU23-4492
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GMPV9.3
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On-site presentation
Matteo Lelli, Stefano Caliro, Evelina Dallara, Giovanni Chiodini, and Luigi Marini

Volcanic and/or geothermal gases provide essential information on the activity of a volcanic system, on magma degassing and on the origin and evolution of fluids. Their study represents one of the most powerful technique to understand the dynamics of systems and to monitor the volcanic activity (dormant state, but also unrest and/or eruption phase).

Volcanic/geothermal gases are complex mix of chemical elements and compounds. Starting from the study of their chemical composition, many equilibrium reactions in gas phase were introduced in the past as possible geothermometers and geobarometers, and they actually used to estimate the thermodynamic conditions in deep system (both in volcanic or geothermal area) and in volcanic surveillance. However, depending on the system, known geothermal-barometric reactions are not able to accurately describe the thermodynamic conditions of reservoirs, highlighting the need for new geothermometric reactions. Of course, the opportunity to develop new “geothermometers/geobarometers functions” depends to the availability of analytical techniques able to detect and quantify new chemical compounds of interest, often at low to very low concentration levels (ppb).

The GC-ICP-MS (gas chromatography-inductively coupled plasma-mass spectrometry), one of the most useful hyphenated method (Michalski R. et al., 2006; Easter R.N. et al., 2010), combines the high separation capacity of the GC with the high sensitivity and specificity of the ICP-MS. Chemical compounds containing C, S and O are abundant in volcanic/geothermal gases and they can be detected at low levels via GC-ICP-MS technique. The development of new specific analytical methods for volcanic/geothermal gas analysis (in particular for what concern new compounds) may provide the chance to introduce new gas equilibrium as a “key” to better understand thermodynamic and redox conditions at depth.

Dry gas samples from fumaroles of the La Solfatara di Pozzuoli (Bocca Grande, Bocca Nuova and Pisciarelli) and for crater area in the Vulcano island were analysed, studying the distribution of sulphur-bearing species. The results obtained are very satisfactory in terms of chromatographic separation and detection limits, making the GC-ICP-MS method very promising in the study of volcanic/geothermal gases.

How to cite: Lelli, M., Caliro, S., Dallara, E., Chiodini, G., and Marini, L.: Sulphur trace components in La Solfatara and Vulcano volcanic gases: searching for suitable new geo-indicators, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4492, https://doi.org/10.5194/egusphere-egu23-4492, 2023.

17:55–18:00

Posters on site: Mon, 24 Apr, 10:45–12:30 | Hall X2

Chairpersons: Carlo Cardellini, Marcello Liotta
X2.142
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EGU23-16114
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GMPV9.3
Antonio Paonita, Cinzia Federico, Sergio Bellomo, Roberto Maria Rosario Di Martino, Alessandro Gattuso, Leonardo La Pica, Giovannella Pecoraino, Antonino Fabio Pisciotta, and Francesco Sortino

In September 2021, the La Fossa volcano entered a new phase of unrest. The monitoring system, operating in the island since late ‘80s, recorded a sudden variation in seismicity, ground deformation, fumarole temperatures, soil and plume degassing. These variations were interpreted as due to the fast vaporization and expansion of the hydrothermal system (Federico et al., submitted), hypothesized at depth > 1.5 km bsl. At the same time, fumarole chemistry showed clear-cut variations, related to the dominant contribution of the magmatic gas over the hydrothermal one. The CO2 content and the helium isotope composition of the magmatic source revealed the appearance of a more primitive magma, compared to that feeding the fumaroles in the previous period, during the climax of the unrest. The signs of the enhanced contribution of magmatic gases in the fumarolic gases was already evident since 2018, so the 2021 unrest appears to have been the outcome of a long lasting preparatory phase. The systematics of gas species together with C and He isotopes, emitted from fumaroles after the first months of the unrest, revealed the appearance of a different magmatic component, poorer in N2, 3He and richer in He, S and 13C. The magmatic contribution is persistently overwhelming the hydrothermal one by the time of this communication.

How to cite: Paonita, A., Federico, C., Bellomo, S., Di Martino, R. M. R., Gattuso, A., La Pica, L., Pecoraino, G., Pisciotta, A. F., and Sortino, F.: The 2021-22 unrest of La Fossa volcano (Vulcano Island, Aeolian Archipelago) by the side of fumarole chemistry: clues on the magmatic source in the precursory and ongoing phases, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16114, https://doi.org/10.5194/egusphere-egu23-16114, 2023.

X2.143
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EGU23-14729
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GMPV9.3
Fabio Vita, Benedetto Schiavo, Claudio Inguaggiato, and Salvatore Inguaggiato

The volatiles emitted in different way from the active volcanoes have been responsible of the increases of gases in the atmosphere like H2O, SO2, CO2, and H2S.

The volatiles are exsolved from the magma batch located below the volcano edifice, during the rising towards the surface interacts with surficial fluids, and come out from the soils, the aquifers, the fumaroles and the main conducts.

Near continuous plume SO2 fluxes, measurements have been carried out by a network system of SO2 measurements at Vulcano Island, Italy. Two Scan-DOAS stations belonging to the NOVAC Project are located respectively at NE and SW of volcanic cone. This configuration allowed tracking over 80% of plume emission during the solar year.

NOVAC is a permanent network for the measurement of volcanic gas emissions, born in 2005 from a European project to creating and installing automated prototypes capable to monitor gases by volcanic plumes, around the world. The main objective was to quantify global volcanic gas emissions and increase knowledge on changes in volcanic activity by estimating the gases emitted by each individual volcanic system.

The fluxes of SO2 plume acquired by the UV-scanning DOAS network showed, in the study period (2021 – 2022), monthly average values between 20 and 121 t d-1. Starting from June 2021 onwards, the SO2 output showed a positive trend with an abrupt increase reaching the highest monthly value in September 2021 (monthly average value= 121 t d-1) and the highest daily measurement 16 November 2021 (daily average = 248 t d-1).

The atmospheric dispersion model (AERMOD), designed for simulate the dispersion of air pollutant from stationary anthropogenic and natural emission source, have been utilized to produce the dispersion SO2 maps and evaluate the air SO2 concentrations in the neighboring areas of the Vulcano island. These maps have been constructed using environmental parameters such as wind speed and direction measured by the local network installed in different points of the island and at different altitudes. These SO2 iso-concentration maps compared with the limit values shown in the human health tables have made it possible to identify the most harmful areas.

How to cite: Vita, F., Schiavo, B., Inguaggiato, C., and Inguaggiato, S.: Increase of volatiles output in the atmosphere at Vulcano Island inferred by SO2 plume monitoring in the 2021-2022 period., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14729, https://doi.org/10.5194/egusphere-egu23-14729, 2023.

X2.144
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EGU23-4517
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GMPV9.3
Daniel Di Nardo, William Hernández, Claudia Rodríguez, Fátima Rodríguez, José Barrancos, Eleazar Padrón, Gladys V. Melián, Germán D. Padilla, Nemesio M. Pérez, María Asensio-Ramos, and Pedro A. Hernández

El Hierro (278 km2) is one of the eight islands of the Canary Islands archipelago. It is an oceanic island formed ~1.2 Ma ago and one of the most active from a volcanic point of view of all the Canary Islands. Its last historical eruption was submarine eruption that began on 12 October, 2011 until 5 March, 2012, off its southern coast, which was the first to be monitored in the Canary Islands. Since 1998, periodic diffuse CO2 surveys have been carried out (except for the 2011-2012 seismic-volcanic unrest and eruptive periods, when the surveys frequency increases, Melián et al., 2014) by means of the accumulated chamber method measuring the diffuse CO2 emission at 601 points distributed homogeneously throughout the emerged 278 km2 of El Hierro. CO2 emission rate measured in the entire island has been varying over time, registering highest values in the pre-eruptive and eruptive periods where a significant increase of this gas emission rate was registered. Soil CO2 efflux values for the 2022 survey ranged between non-detectable (<0.5 g·m−2·d−1) to 38.0 g·m−2·d−1, with an average value of 2.6 g·m−2·d−1. Diffuse CO2 output from the studied area was estimated in 616 ± 26 t·d-1 for El Hierro Island, a value above the background average of CO2 emission estimated on 412 t d-1, but within background range of 181 t·d-1 (−1σ) and 930 t·d-1 (+1σ) calculated at El Hierro volcano during the quiescence period 1998-2010 (Melián et al., 2014). The monitorization of the diffuse CO2 emission has demonstrated that contributes to detect early warning signals of volcanic unrest, especially in areas where visible degassing is non-existent as in the El Hierro Island.

 

Melián et al. (2014), J. Geophys. Res. Solid Earth, 119, 6976–6991, DOI 10.1002/2014JB011013

How to cite: Di Nardo, D., Hernández, W., Rodríguez, C., Rodríguez, F., Barrancos, J., Padrón, E., Melián, G. V., Padilla, G. D., Pérez, N. M., Asensio-Ramos, M., and Hernández, P. A.: Twenty four years of geochemical monitoring of the oceanic active volcanic island of El Hierro, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4517, https://doi.org/10.5194/egusphere-egu23-4517, 2023.

X2.145
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EGU23-4414
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GMPV9.3
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ECS
David Martínez van Dorth, Daniel Di Nardo, Germán D. Padilla, Pedro A. Hernández, Fátima Rodríguez, Gladys V. Melián, María Asensio-Ramos, Eleazar Padrón, and Nemesio Pérez

Lanzarote (795 km2) is a volcanic island with 58 km long and 21 km wide located in the eastern part of the Canary Islands and it is approximately 130 km away from the African coast. The island has experienced the longest historical eruption occurred in the Canarian archipelago, Timanfaya eruption, from 1730 to 1736. It created more than 30 volcanic cinder cones along several NE – SW fissures and produced voluminous amounts of lava flows that covered an area of 200 km2, which corresponds to almost a quarter of the island. Nowadays, several thermal anomalies remain active in the Islote de Roque Hilario. The latest eruption recorded in the island was in 1824, known as Tinguatón eruption, along an ENE – WSW fracture.

Since there are not visible gas emanations at the surface environment of Timanfaya Volcanic Field (TVF), diffuse degassing surveys became a useful tool to monitor the volcanic activity. Among degassing phenomena, soil CO2 efflux is important because of the characteristics of CO2: it is the major gas species after water vapor in both volcanic fluids and magmas and it is an effective tracer of subsurface magma degassing due to its low solubility in silicate melts at low to moderate pressures (Gerlach and Graeber, 1985). To do so, since 1999, diffuse CO2 emission surveys have been yearly undertaken in and around the TVF. Between September and October 2022, a new survey was performed with 410 sampling sites, covering an area of 252 km2 in order to have a homogeneous distribution. Soil CO2 efflux was measured following the accumulation chamber method. Soil temperature was determined by inserting a thermocouple at each sampling site at a depth of 40 cm. Soil CO2 efflux values ranged from non-detectable (<0.5 g·m-2·d-1) to 43.1 g·m-2·d-1, with an average of 2.0 g·m-2·d-1), while soil temperature ranged from 16.1 to 125 ºC. Statistical-graphical analysis of the data showed different geochemical populations; background (B) and peak (P), represented by 85.2 and 0.8 % of the total data, respectively, with geometric means of 0.32 and 26.2 g·m-2·d-1, respectively. Higher CO2 efflux values were measured at the north and south sectors of the TVF. Other relative high values were measured at the central part of TVF, where thermal anomalies occur. During this campaign, a period of rains took place, which may have influenced the measurement of higher values. Sequential Gaussian simulations (sGs) were applied to construct soil CO2 efflux and soil temperature distribution maps and to estimate the diffuse CO2 emission from the studied area, 519 ± 42 t·d-1. This value is of the same order as the maximum value of the time series, and registered in February 2011 (winter). This type of studies demonstrate the great utility of using diffuse CO2 degassing as a useful geochemical method to contribute to volcanic monitoring programs in systems where there are no visible geothermal surface manifestations.

How to cite: Martínez van Dorth, D., Di Nardo, D., D. Padilla, G., A. Hernández, P., Rodríguez, F., V. Melián, G., Asensio-Ramos, M., Padrón, E., and Pérez, N.: Diffuse CO2 emission from Timanfaya volcano (Lanzarote, Canary Islands) during the period 1999-2022, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4414, https://doi.org/10.5194/egusphere-egu23-4414, 2023.

X2.146
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EGU23-9916
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GMPV9.3
Violeta Tai Albertos, Pedro A. Hernández, Gladys V. Melián, Antonio J. Álvarez Díaz, Alba Martín-Lorenzo, Eleazar Padrón, and Nemesio M. Pérez

La Palma Island (708 km2) is located at the north-west and is one of the youngest (~2.0My) of the Canarian Archipelago. The current stage of shield-building is manifest by the construction of Cumbre Vieja volcano, at the southern part of the island, where volcanic activity has taken place exclusively in the last 123 ka. On September 19, 2021, a new volcanic eruption occurred at Cumbre Vieja volcanic system (Tajogaite eruption). The erupting fissure (~1.0 km-length) is characterized by lava effusion, strombolian activity, lava fountaining, ash venting and gas jetting. After 85 days, the eruption finished on December 13, 2021. The 2021 Tajogaite eruption, with a magnitude VEI=3 (Bonadonna et al., 2022), resulted in the longest volcanic event on the island during the last 600 years and the most important eruption of Europe during the last 75 years.

At the time of this study, the volcanic gas emissions observed at Tajogaite volcanic cone consisted mostly in diffuse CO2 degassing and residual fumarolic activity. Here we report the first diffuse CO2 and H2S emission surveys that have been carried out in Tajogaite volcanic cone.The measurements of soil CO2 efflux have been performed following the accumulation chamber method in 94 sites and the spatial distribution maps have been constructed following the sequential Gaussian simulation (sGs) procedure to show the location of CO2 and H2S diffuse degassing structures (DDS) and to quantify the diffuse CO2 and H2S emission from the studied area. The diffuse CO2 emission released to the atmosphere from Tajogaite volcanic cone ranged between 0 to 11.4 kgm-2·d-1 with an average of 0.90 kgm-2·d-1. The main DDS was located in the easternmost area of ​​the cone. Regarding the diffuse H2S emission, the data ranged between 0 to 44. 7 kgm-2·d-1 with an average value of 3.0 kgm-2·d-1. Two main DDS were identified: one coinciding with the CO2 DDS, in the easternmost zone, and other in the northern area of the cone. This study represents a starting point to study the degassing of the residual magma bodies beneath Tajogaite volcanic cone.

Bonadonna, C. et al. (2022), EGU22-11927, https://doi.org/10.5194/egusphere-egu22-11927.

How to cite: Albertos, V. T., Hernández, P. A., Melián, G. V., Álvarez Díaz, A. J., Martín-Lorenzo, A., Padrón, E., and Pérez, N. M.: Diffuse CO2 and H2S degassing from Tajogaite volcanic cone, La Palma, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9916, https://doi.org/10.5194/egusphere-egu23-9916, 2023.

X2.147
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EGU23-13349
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GMPV9.3
José Manuel Santana de León, Pedro A. Hernández, Gladys V. Melián, Germán D. Padilla, Antonio J. Álvarez Díaz, Cecilia Amonte, Fátima Rodríguez, María Asensio-Ramos, José Barrancos, Lia Pitti, Jaime Martín Díaz, and Nemesio M. Pérez

The eruption of the Tajogaite volcano occurred between September and December 2021, being the longest one recorded at La Palma Island. During the course of the eruption, the emission of gas and pyroclasts was constant, forming a cone of approximately 200m. Once the eruption ended, the gas emission has gradually decreased with fumaroles of low and high temperatures along craters. In situ sampling techniques, close as possible to the gas emission sources, are the most suitable tools to investigate the chemical composition of primary emitted volcanic gases. For this reason, we applied the sampling technique proposed by Noguchi & Kamita (1963) to monitor C/S, S/Cl, S/F and F/Cl ratios in the air inside the crater of Tajogaite by using alkaline traps (named JB1, JB3 and JB6) spatially distributed in order to access to different volcanic gas emission spots. This method gives the advantage of an integral monitoring of the acid gases during a certain sampling interval. Initially, two redundant sampling sites were use at three selected locations in April 2022 to study whether there were significant differences in the data from each pair of traps. The results indicated no significant differences in the results of the redundant sampling sites. The alkaline solutions, consisting of 2N KOH solutions, are analyzed using both volumetric and chromatographic methods. The carbon is analyzed by volumetric titrations, whereas Cl, S and F are analyzed by Ion Chromatography (IC). Samples are collected weekly for subsequent analysis.

Measured C/S ratios varied between 0.003-0.02, 0.001-002 and 0.002-4.1 for JB1, JB3 and JB6, respectively. S/Cl ratios varied between 11.5-62.3, 64.3-241.3 and 0.1-482.0 for JB1, JB3 and JB6, respectively. S/F ratios varied between 0.8-82.1, 6.3-78.9 and 0.01-74.4 for JB1, JB3 and JB6, respectively. F/Cl ratios varied between 0.4-17.8, 1.8-22.6 and 0.6-169.7 for JB1, JB3 and JB6, respectively. Results show a progress increase on the C/S ratio during all sampling period (April-November 2022), except for the JPB1 and JB3 during October and November 2022, which is explained in base of a observed slight decreasing trend in S content, which is to be expected since the post-eruptive activity should decrease as well as the decrease in the fumarolic output. However, the variations observed in the S/Cl, S/F and F/Cl ratios show a more chaotic behavior, depending on the alkaline trap and therefore its location. The fumaroles that come into contact with the alkaline traps are not the same, and the possible effects of external variables such as wind, can considerably reduce the transport of minor fumarolic gases from their source to the traps producing these variations. S/Cl ratio seems to show higher values during the first period of monitoring, that may be related to variations in the fumarolic activity whereas S/F and F/Cl do not show in general a clear temporal tendency. Direct sampling of plume/fumarolic gases by alkaline traps is a cheap and easy technique to monitor the relationship between various chemical species and volcanic activity.

Noguchi & Kamiya (1963). Bull. Volcanol., 24, 367-378.

How to cite: Santana de León, J. M., Hernández, P. A., Melián, G. V., Padilla, G. D., Álvarez Díaz, A. J., Amonte, C., Rodríguez, F., Asensio-Ramos, M., Barrancos, J., Pitti, L., Martín Díaz, J., and Pérez, N. M.: Monitoring of acid gases at the crater of Tajogaite volcano using alkaline traps, La Palma, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13349, https://doi.org/10.5194/egusphere-egu23-13349, 2023.

X2.148
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EGU23-17464
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GMPV9.3
Roberto Moretti, Vincent Robert, Séverine Moune, Manuel Inostroza, David Edward Jessop, Franco Tassi, Orlando Vaselli, Magali Bonifacie, Jens Fiebig, Jabran Labidi, Ivan Vlastelic, Eloide Chilin-Eusebe, Fausto Grassa, Abigali Metcalfe, and Patrick Allard

At volcanoes in unrest, the interpretation of geochemical time-series is a major issue for decrypting volcano dynamics and forecast eruptive scenarios. However, interpretation cannot be purely observational and demands the assessment of the main physicochemical features of the hydrothermal system. In the case of La Soufrière of Guadeloupe (FWI) andesitic volcano, a careful analysis of different techniques adopted historically for gas sampling and analysis by the local observatory has allowed us to model degassing and assess gas indicators from non-condensable species in the H2-N2-CH4-He-Ar system available since 2006. Here we report on the nature of discharged gases, resulting from the mixing of atmospheric component and a magmatic-hydrothermal gas evolving along a lineage connecting MORB-like upper mantle and arc-volcano components. We show that along this lineage we can track the hydrothermal build-up of pressure and temperature modulated by magmatic variations, particularly decompression. A careful analysis of inert gas fractionation allows recognizing two main regimes: one is about hydrothermal degassing conditions perturbed by the deep impulsive gas infiltration after magma refilling in a 4 to 8 km deep chamber; the other is determined by ascent of magma batches to a shallower (about 3 km deep) chamber. Further changes of the bulk permeability structure in the hydrothermal reservoir due to fracture sealing and clogging effect may exacerbate observed evolutions but do not represent the primary control of the degassing process. We also show that gas ratios in the H2-He-CH4 subsystem can effectively discriminate and anticipate such tendencies and, particularly, they can be turned into reliable precursors of magma-derived solicitations and set possible thresholds for next crises. The main test is made with reference to the 2013-2014 and 2018 episodes of accelerated unrest: we confirm that the latter is as an aborted phreatic eruption, triggered by the injection of hot magmatic fluids into the magmatic system. On the other hand, for the 2013-2014 period, poorly studied, we document for the very first time the ascent of a small batch of magma which refilled the 3 km deep shallow magma chamber. This triggered seismicity just on top of the brittle-ductile transition. Besides, our method reveals that in 2007-09 an unrest phase similar to the 2018 one occurred, although not marked by the same seismic activity likely because the volcanic system was more sealed and less fractured before the magmatic upward excursion of the 2013-14 phase. Our results and conclusions are suitable for all those volcanic systems at the hydrothermal stage and allow a better definition of unrest scenarios whenever sampling frequency of fumarolic fluids is compatible with the expected transit times of magmatic fluids from magma chambers to surface.

How to cite: Moretti, R., Robert, V., Moune, S., Inostroza, M., Jessop, D. E., Tassi, F., Vaselli, O., Bonifacie, M., Fiebig, J., Labidi, J., Vlastelic, I., Chilin-Eusebe, E., Grassa, F., Metcalfe, A., and Allard, P.: The geochemistry of magmatic solicitations on volcanic-hydrothermal systems: the long-standing unrest of La Soufrière de Guadeloupe dissected via non-condensable gases, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17464, https://doi.org/10.5194/egusphere-egu23-17464, 2023.

X2.149
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EGU23-15988
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GMPV9.3
The strengthening Stromboli’s geochemical monitoring: the advanced multi parameters stations for thermal wells
(withdrawn)
Alessandro Gattuso, Sergio Scirè Scappuzzo, Gianluca Lazzaro, Domenico Traina, Cinzia Federico, Francesco Italiano, Antonio Paonita, and Mauro Coltelli
X2.150
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EGU23-14226
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GMPV9.3
Jean Vandemeulebrouck, Romuald Daniel, Laurent Metral, Yann Do, Hervé Barrois, Simon Besancon, Tom Dumouch, Ted Luc, and Camille Bouvard

Our project aims at designing and realizing an autonomous hydroacoustic measurement system (“Bubblephone”) allowing to passively monitor the bubbling activity in underwater or lake degassing areas. Hydroacoustic activity is usually measured by the hydrophones of Ocean Bottom Seismometers (OBS) only at low frequencies (1-100 Hz) and in a band disturbed by turbulence, while bubbling emits energetic acoustic activity at higher frequencies (~ 1 kHz) that depend on the size of the bubbles. The station's functions are to filter the hydrophone signals to acquire the high-frequency signals emitted by the bubbles, to calculate and store their frequency spectra and also raw data sequences. The post processing will allow to evaluate the variations of the volume of the bubbles and thus of the degassing in the course of time. The electronics will have an autonomy of 6 months and will be installed in a hyperbaric chamber to be able to go to depths of kilometres.  It will be able to be deployed for several months near active volcanoes and to monitor the degassing of a submarine volcano.

How to cite: Vandemeulebrouck, J., Daniel, R., Metral, L., Do, Y., Barrois, H., Besancon, S., Dumouch, T., Luc, T., and Bouvard, C.: Development of an automatic station for acoustic measurements to continuously evaluate the underwater volcanic degassing., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14226, https://doi.org/10.5194/egusphere-egu23-14226, 2023.

X2.151
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EGU23-16282
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GMPV9.3
Mirko Messina, Marco Camarda, Sofia De Gregorio, Roberto M. R. Di Martino, and Vincenzo Prano

Periodic surveys for the measurement of the soil CO2 flux are regularly performed in three peripheral areas of the Mt Etna (Paternò, Zafferana-S. Venerina and Vena-Presa) for a whole of 140 measurement sites. It is widely demonstrated that anomalous emissions of CO2 in these areas are linked to magma supply dynamics. Herein we report the data of soil CO2 flux periodically recorded in these areas from 2015 to 2022. We processed and analyzed the data to reconstruct the magma supply dynamics over the considered period and showed as variations are related to the most significant eruptive phases which occurred through the investigated period.

One of the hallmarks eruptive episode occurred on 24th December 2018, from an eruptive fissure which opened on the New Southeast Crater (NCSE) flank. During this event both ash-rich plumes from the summit craters and intense strombolian activity along the fissure were observed. This episode was associated with intense seismic swarms. Mild strombolian activity, ash emission at summit craters, and constant inflation of the volcano edifice during autumn 2018 preceded the eruptive episode. The soil CO2 flux measured in the more distal peripheral areas reveal that, at least three episodes of magmatic supply into the deep system (7-13 km b.s.l.) occur in the Etna feeding system, since 2016. After November 2018, a remarkable increase in the soil CO2 emissions was recorded at Vena-Presa area, along the Pernicana fault, suggesting magma transfer into the shallower portions of the feeding system. The volcanic origin of this degassing event was confirmed also by isotopic signature of carbon of CO2.

Another notably eruptive phase occurred on 2021 at the NSEC, with a sequence of seventeen lava fountains from 16 February to 1 April 2021. Some of these events were the most intense among those which occurred at Mt. Etna in the last ten years. A few months earlier (July-December 2020) we detected a huge increase of CO2 emissions in the Paternò area, with the highest value ever recorded over the last 15 years.

 

How to cite: Messina, M., Camarda, M., De Gregorio, S., Di Martino, R. M. R., and Prano, V.: Recent magma supply dynamic at Mt Etna volcano inferred from periodic measurements of soil CO2 emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16282, https://doi.org/10.5194/egusphere-egu23-16282, 2023.

Posters virtual: Mon, 24 Apr, 10:45–12:30 | vHall GMPV/G/GD/SM

Chairpersons: Marcello Liotta, Fátima Viveiros, Carlo Cardellini
vGGGS.27
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EGU23-6561
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GMPV9.3
Lía Pitti, Gladys V. Melián, Fátima Rodríguez, Eleazar Padrón, Nemesio M. Pérez, María Asensio-Ramos, Alba Martín, Daniel Di Nardo, José Manuel Santana León, Víctor Ortega-Ramos, Rubén García-Hernández, David Martínez van Dorth, and Pedro A. Hernández

Tenerife (2,034 km2), the largest island of the Canarian archipelago, is characterized by three volcanic rifts NW-SE, NE-SW and N-S oriented, with a central volcanic structure, Las Cañadas caldera, hosting Teide-Pico Viejo volcanic complex. The North-West volcanic Rift Zone (NWRZ, 72 km2) is one of the youngest and most active volcanic systems of the island, where three historical eruptions (Boca Cangrejo in the 16th Century, Arenas Negras in 1706 and Chinyero in 1909) have occurred. The North-East volcanic Rift Zone (NERZ, 210 km2) has showed one historical eruptive activity during 1704 and 1705 across 13 km of fissuraleruption (Siete Fuentes-Arafo-Fasnia eruption). As part of the volcano monitoring program of NWRZ and NERZ, diffuse CO2 degassing surveys have been carried out yearly since 2000 at the NWRZ and since 2001 at the NERZ. In-situ measurements of CO2 efflux from the surface environment were performed according to the accumulation chamber method using a portable non-dispersive infrared (NDIR) sensor. Soil CO2 efflux contour maps were constructed to identify spatial-temporal anomalies and to quantify the total CO2 emission using the sequential Gaussian simulation (sGs) interpolation method. Previous studies in the NWRZ has shown a temporal correlation between long-term variations in the diffuse CO2 output with the occurrence of a seismic unrest in 2004 and the 2016 seismic swarm (Hernández et al., 2017). The last diffuse CO2 emission survey performed in the survey in the NWRZ in 2022 showed values between non-detectable ones and 32.1 g·m-2·d-1, with an average value of 5.6 g·m-2·d-1 for NWRZ. In the case of the NERZ, the last diffuse CO2 emission survey performed in 2022 showed values ranging between non-detectable values and 59.1 g·m2·d-1, with an average value of 6.7 g·m-2·d-1. Diffuse CO2 emission rate were estimated in 360 ± 15 t·d-1 for NWRZ and 1,444 ± 42 t·d-1 NERZ were obtained in the 2022 surveys. The normalized CO2 emission value by area was estimated in 5 t·d-1·km-2 for NWRZ and in 6.9 t·d-1·km-2 for NERZ. Temporal evolution of diffuse CO2 emission at both NWRZ and NERZ of Tenerife shows a clear relationship with the volcano seismic activity in and around Tenerife Island. These geochemical observations are clear evidence of changes of processes operating deep in the hydrothermal-magmatic system of Tenerife.

Hernández et al. (2017). Bull Volcanol, 79:30, DOI 10.1007/s00445-017-1109-9.

How to cite: Pitti, L., Melián, G. V., Rodríguez, F., Padrón, E., Pérez, N. M., Asensio-Ramos, M., Martín, A., Di Nardo, D., Santana León, J. M., Ortega-Ramos, V., García-Hernández, R., Martínez van Dorth, D., and Hernández, P. A.: Diffuse CO2 emission from NERZ and NWRZ Tenerife volcanic systems, Canary Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6561, https://doi.org/10.5194/egusphere-egu23-6561, 2023.

vGGGS.28
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EGU23-12305
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GMPV9.3
Sofia De Gregorio, Marco Camarda, Giorgio Capasso, Roberto M.R. Di Martino, and Vincenzo Prano

Water-gas interaction is an ordinary process occurring in volcanic areas because of gases released from magma reservoir at depth interact and dissolve in groundwater and/or are discharged from the soils or fumaroles. At the island of Vulcano (Aeolian Islands), both thermal and geochemical anomalies in groundwater were detected along lines of structural weakness in the volcanic edifice behaving as preferential pathways for up-flows of heat and fluids discharged by the deep magmatic system.

The interaction between deep volcanic/hydrothermal gases and groundwater can develop at various extent due to both local hydrogeological conditions and volcano-tectonic setting, resulting in different dissolved gas concentrations. Herein, we report a comprehensive study of chemical and stable isotope composition of dissolved gases in thermal groundwater at island of Vulcano.

The data were acquired with systematic sampling in four selected well since 2010, and include data on dissolved helium isotopes and carbon isotope composition of dissolved CO2. The chemistry and isotopic data (C and He) of dissolved gases reveal the magmatic origin of the gas interacting with the aquifer and point out as the pristine magmatic composition varies upon gas ascent because of either dilution by a soil-atmospheric component or fractionation processes during interaction with groundwater. Further we discussed dissolved gases variations recorded during the period of unrest which onset at Vulcano on September 2021 and is still ongoing. The period of unrest was characterized by huge increase, orders of magnitude over the background, of degassing activity both from main crater and in pericrateric area. The variations detected in the chemical and isotopic composition of the dissolved gases occurred at different times and intensities in relation to the location of the wells.

How to cite: De Gregorio, S., Camarda, M., Capasso, G., Di Martino, R. M. R., and Prano, V.: Dissolved gases in groundwater as tracer for gas-water interaction and volcanic system evolution: a case study at island of Vulcano (Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12305, https://doi.org/10.5194/egusphere-egu23-12305, 2023.

vGGGS.29
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EGU23-15720
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GMPV9.3
Massimo Ranaldi, Maria Luisa Carapezza, Andrea Fabbri, Marcello Liotta, Antonio Patera, Luca Pizzino, and Luca Tarchini

Repeated flooding episodes occurred from the crater lake of Albano until 398 B.C. These floods were probably caused by sudden injection of gas and warm waters on the lake bottom, or also by the overturn of the lake which would have brought to the surface the deep water rich in CO2. Since several years, we have been monitoring the crater lake chemical composition as well as its physico-chemical parameters and dissolved gas content, in order to assess evidences of possible deep fluid input in the lake water. The concentration of dissolved gases, and their isotopic composition (d13CTDIC, 3He/4He) suggest the presence of deep gases (CO2 and CH4) within the lake bottom layer. However, the total pressure of dissolved gases is presently, at any depth, much lower than the hydrostatic pressure. If, for any reason, a significant volume of deep water should rise to the surface, only limited phenomena of gas exsolution are to be expected. A density variation of shallow lake water due to cooling, in case of heavy rainfall in harsh winters (T<8.5°C), may produce water overturns. Such phenomena, as long as they happen with a certain frequency, would prevent the accumulation of dangerous quantities of CO2 in the deepest lake water strata. Apart from a volcanic unrest, the most dangerous condition is the occurrence of seismic swarms with hypocentres in the Lake Albano area, which could lead to an increase in the influx of hot gases and fluids in the lake. Currently, the conditions for a rapid release of significant quantities of CO2 from Lake Albano do not exist. To improve the knowledge of the Lake Albano  water circulation, we investigated also the isotopic 87Sr/86Sr composition of the lake water, comparing the results with those of the rocks hosting the aquifers. Results indicate that Lake Albano water samples well fit a binary mixing of a high 87Sr/86Sr ratios end-member (Colli Albani volcanites) and a low ratio end-member (carbonate basement) in a proportion of 75% and 25% respectively. Moreover, the landslide hazard of the internal slopes of Lake Albano has been assessed using Ordinary Least Squares and Empirical Likehood Ratio modelling functions. The presence of numerous dwellings and recreational activities along the internal slopes of the crater lake, makes the area of potentially-high risk, both because of the inner intense slope instability and for possible secondary effects due to tsunami waves that might be generated by the impact of sliding subaerial masses on the lake surface or by sub-aqueous landslides.

How to cite: Ranaldi, M., Carapezza, M. L., Fabbri, A., Liotta, M., Patera, A., Pizzino, L., and Tarchini, L.: Hazard assessment for gas emission and flank landslides at Albano crater lake (Rome), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15720, https://doi.org/10.5194/egusphere-egu23-15720, 2023.