In addition to CO₂ and sulphur dioxide (SO₂), volcanic plumes also contain reactive halogen species. Bromine monoxide (BrO) can reliably be quantified by remote sensing measurements and is known to catalyse ozone (O₃) destruction. Therefore, local O₃ depletion is commonly assumed inside volcanic plumes.
Contrary to popular belief, a calculation comparing atmospheric turbulent mixing with the rate of O₃ destruction inside the (young) plume suggests no significant halogen catalysed O₃ loss (1% or less) in the plume.

So far, however, O₃ and its concentration distribution in volcanic plumes have only been insufficiently determined since commonly used short-path ultraviolet (UV) absorption O₃ monitors show a severe, positive interference with SO₂, an abundant volcanic gas.
This interference problem can be overcome by using a chemiluminescence (CL) O₃ monitor, a standard technique for O₃ measurements in the 1970s (and still the standard instrument for air pollution monitoring), which shows no interference with trace gases in volcanic plumes and therefore allows reliable O₃ measurements in volcanic plumes.
However, field measurements with existing CL O₃ monitors are challenging, since they are usually heavy and bulky. We therefore designed an improved and lightweight version of the CL O₃ instrument (1kg, shoebox size), which can be easily carried or mounted onto a drone, thus opening up completely new measurement possibilities.

After test measurements in Heidelberg, including ground-based as well as drone-based measurements, during which we determined vertical O₃ profiles, we performed drone-based O₃ measurements in the plume of Etna volcano. The latter data show an anti-correlation between O₃ and simultaneously determined SO₂, suggesting an O₃ depletion of up to ~60% in the plume of Etna. This raises the question which – probably unknown - process leads to this observed O₃ depletion.

How to cite: Rüth, M., Karbach, N., Bobrowski, N., Platt, U., Geil, B., Hoffmann, T., Bräutigam, E., and Kuhn, J.: Reliable Ozone Measurements in Volcanic Plumes: A Way to Resolve the Volcanic Ozone Enigma, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16322, https://doi.org/10.5194/egusphere-egu24-16322, 2024.

Nyiragongo (D.R. Congo) is an active volcano known for its impressive persistent lava lake within its crater, and it is recognized as one of the most dangerous volcanoes in the world because more than two million people live on its slopes. Suddenly, on 22 May 2021, Nyiragongo produced three different lateral lava flows from the southern lower flanks, and significant amounts of volcanic gas and ash were emitted from the summit crater following the collapse of the crater floor. For a few weeks, the ash fallout impacted the main city of Goma and the numerous villages located in the vicinity of the volcano. 22 samples of volcanic ashes and 135 samples of drinking water (springs, rivers, rainwater, roof runoff) were collected before, during and after the eruption. From the leaching of the ashes and their direct observation through a field emission scanning electron microscope (FE-SEM), large quantities of soluble salts (e.g. sulphates, chlorides) on their surface were identified. The results showed that most of the drinking waters collected in the downwind villages (like Rusayo, Kingi, Sake) were heavily contaminated by volcanic emissions. In fact, fluoride, chloride, sulphur, and many potentially toxic elements (PTEs), including Al, As, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb, Se, Te, Tl, and V, exceeded the suggested World Health Organization (WHO) drinking water limits during the eruptive period, exposing the population living in villages downwind of the preferential direction of the volcanic plume, to high health risks.

How to cite: Calabrese, S., Habakaramo Macumu, P., Bellomo, S., Bobrowski, N., Boudoire, G., Brugnone, F., Giuffrida, G. B., Brusca, L., D'Alessandro, W., Gouhier, M., Lentini, S., Li Vigni, L., Randazzo, L., and Tedesco, D.: Nyiragongo eruption 2021 and its environmental impact: volcanic ash fallout and high levels of trace metals in drinking water, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7479, https://doi.org/10.5194/egusphere-egu24-7479, 2024.

The isotopic compositions of boron (δ¹¹B‰) and strontium (⁸⁷Sr/⁸⁶Sr) were measured, for the first time, in 10 rainwater samples from Mt. Etna, Italy. The samples were collected during the paroxysmal sequence of 2021-2022. The chemical composition was determined using an ICP-MS, while the isotopic ratios of B and Sr were measured using a mass spectrometer MC-ICP-MS (Neptune Plus™), after specific pre-concentration procedures in clean rooms (class 100 - 1000). In the analysed rainwater samples, the concentrations of B and Sr were between 4.6 µg L^-1 and 42.2 µg L^-1, and between 9.7 µg L^-1 and 541 µg L^-1, respectively. Overall, the isotopic composition of B ranging from +1.29‰ ± 0.30‰ to +42.9‰ ± 0.20‰, with a median value of +22.0‰ ± 0.19‰. The lowest δ¹¹B‰ values were measured in the site closest to the main active craters (3.6 km), with a median value of +11.4‰ ± 0.21‰; the highest was measured in the site close to the Ionian Sea (Zafferana Etnea), with a median value of +38.1‰ ± 0.21‰. Strontium (⁸⁷Sr/⁸⁶Sr) ratios were between 0.703728 ± 0.000008 and 0.710363 ± 0.000006, with a median of 0.707328 ± 0.000007. The highest and the lowest ⁸⁷Sr/⁸⁶Sr ratios were measured in the sites most and less affected by the contribution of the volcanic emissions, with median values of 0.704339 ± 0.000007 and 0.709583 ± 0.000007, respectively. Although exists few data of isotopic ratios of boron and strontium on fluids in volcanic systems (δ¹¹B‰ between -9.3 to 21.4‰), there are no studies on rainwater influenced by volcanic emissions. Nevertheless, the data available in the literature are sufficient to attribute Etna's volcanic source as the major contributor to B and Sr emissions in the atmospheres of this area. The rainwater chemistry of the Zafferana Etnea site was partly influenced by the volcanic source, but the measured isotopic ratios at this site showed a strong contribution from the marine source. The results provide the first comprehensive study of B and Sr isotopes in Mt. Etna rainwater. Two main sources of atmospheric emissions of B and Sr were recognised: sea-salt aerosols and volcanic gases. This research also adds to the potential for the use of B and Sr isotopes as volcanic emissions contribution tracers.

How to cite: Brugnone, F., Salvadori, M., Pennisi, M., D'Alessandro, W., Brusca, L., Parello, F., and Calabrese, S.: Boron and strontium isotopic signature in rainwaters from Mt. Etna, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17761, https://doi.org/10.5194/egusphere-egu24-17761, 2024.

Within the framework of SANTORY (SANTORini’s seafloor volcanic observatorY) project, funded by the Hellenic Foundation for Research and Innovation and with the financial support of the Municipality of Thira, three oceanographic cruises were performed in December 2022 and June and October 2023, with the research vessels PHILIA and AEGAEO of the HCMR at the submarine volcano Kolumbo, 7 km NE of Santorini. Kolumbo is considered to be one of the most active submarine volcanic complexes in the Eastern Mediterranean Sea, while being easily accessible from land.. The oceanographic surveys were mainly aimed at the deployment of a new generation observatory along with several multiple innovative sensors such as temperature sensors, inclinometers, pressure gauges, optical cameras, multispectral and stereo camera, radioactivity sensor gSniffer and the γ-radiation imager. During the surveys, several water column profiles were also performed in order to collect seawater samples for chemical analysis. At the bottom of the Kolumbo crater (500m depth), acidic and slightly reducing conditions prevail, due to the presence of several active hydrothermal vents. This agrees with previous studies and with the data recorded by the deployed observatory. Collected samples have been analyzed for the chemical and isotope (carbon, helium and argon) composition of the dissolved gases as well as for the major, minor and trace element concentrations. The results indicate that the morphology of the crater allows the buildup of persistent anomalies that extend from the bottom up to the lowest crater-rim level at about 250-meter depth. We will discuss the temporal variability of the Kolumbo venting dynamics and the explore in detail the resulting vertical gradients in the crater funnel.

How to cite: Longo, M., D'Alessandro, W., Grassa, F., Heimbürger-Boavida, L. E., Lazzaro, G., Scirè Scappuzzo, S. S., Nomikou, P., Polymenakou, P., and Rizzo, A. L.: Impact of the hydrothermal activity on the seawater chemistry above the Kolumbo volcano (southern Aegean Sea - Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15859, https://doi.org/10.5194/egusphere-egu24-15859, 2024.

The Stromboli volcano, Aeolian Islands, Italy, is characterized by persistent Strombolian activity. It is a perfect case study to investigate the relationship between outgassing activity and paroxysmal events.

The discrete soil CO₂ degassing measurements, performed with the portable flux meter based on the accumulation chamber method, were carried out in the summit and peripheral zones. These measurements surveys allowed us to individuate the anomalous degassing areas (Scari, Piscità, and Pizzo Sopra La Fossa), coincident with the main structural faults respectively N64° and N41° as preferential paths for the rising of deep fluids.

Based on the information resulting from the discrete measurements a near-continuous (hourly frequency) geochemical network was installed on Stromboli Island and consists of three stations, one located in the summit part of the Pizzo Sopra La Fossa area (STR02), and two located in the peripheral zone STR01 and STR03 in the Scari and Piscità areas respectively. This network allowed us to acquire a large amount of soil CO₂ flux data to investigate and model the plumbing volcanic system. The analysis of a large dataset of soil CO₂ fluxes collected in the summit crater area (STR02), from 2000 to 2023, showed significant changes in degassing values and style before and in coincidence with major volcanic events like paroxysmal explosions caused by the rapid rise of volatile-rich magma and the changes from explosive to effusive eruptions. In particular, the soil degassing processes of CO₂ peaks showed three main and peculiar behaviors:

• A long-lasting modification, characterized by a slow and continuous increase in CO₂ flux;
• Transient changes, characterized by abrupt changes in the rate of CO₂ outgassing;
• Strong Increase in the Natural Daily Variation, highlighting drastic changes in the degassing style, a few months before the major paroxysmal events.

How to cite: Vita, F., Inguaggiato, C., Mazot, A., Corrao, M., Cangemi, M., and Inguaggiato, S.: Volatile degassing at Stromboli Volcano: Continuous soil CO2 fluxes monitoring network and soils discrete measurements. Volcanic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16170, https://doi.org/10.5194/egusphere-egu24-16170, 2024.

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, three main changes in degassing activity were recorded in 2009, 2021, and 2022 and allowed us to evaluate 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 strong and deep input of volatiles released, in the last decades, from the underlying magma batch strongly modified the chemical composition of the shallow plumbing system, leading the system to an increase in the level of CO₂ and energy over time.

How to cite: Inguaggiato, S., Vita, F., Inguaggiato, C., Mazot, A., and Cangemi, M.: Decadal monitoring of the soil CO2 outgassing activity of Vulcano Island, Aeolian Archipelago, Italy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18957, https://doi.org/10.5194/egusphere-egu24-18957, 2024.

The volcanic SO₂ flux is key indicator of magma influx into the shallower portions of magmatic plumbing systems, and as such is central to volcano monitoring. However, observations are challenged by a variety of technical and methodological caveats and limitations, requiring the use of a multiple-technique approach as a key to acquiring more robust SO₂ flux time-series. Here, we compare ~9 years (2014 to 2022) of SO₂ flux measurements at Stromboli obtained through (i) a near-vent SO₂ camera (UV1 system, managed by UNIPA) and (ii) a network of scanning-DOAS spectrometers (FLAME network, managed by INGV-OE). The UV1 system operates in close proximity to the summit craters (~500 m), while the FLAME network intercepts the volcanic plume from a greater distance (~2 km).

We find remarkable differences in the SO₂ flux time-series streamed by the two observational techniques, with the FLAME daily averages fluxes being up to ~200% higher than those seen by the SO₂ camera. By examining the individual components involved in the flux calculation, we find the SO₂ integrated column amounts (ICAs) to match one each other within a factor 30%. Hence, the large mismatch between the two SO₂ fluxes is primarily caused by large differences in the used plume speeds. By applying a simple dispersion model, we find the Stromboli’s plume to exhibit a non-Gaussian dispersion behaviour, in which in-plume SO₂ concentrations are non-linearly diluted (upon atmospheric dispersion) as a function of wind intensity. In the “puffing” plume conditions our model suggests for Stromboli, use of wind speed as a proxy for real gas velocity may not be appropriate, as it can lead to a net overestimation of SO₂ fluxes when observed by distally operating scanning-DOAS. In contrast, SO₂ camera observations can provide more accurate plume transport results, but are challenged by radiative transfer issues in the optically opaque, proximal plume.

Ultimately, we propose a new SO₂ flux record for Stromboli that combines DOAS and SO₂ camera and takes advantage of the specific advantages of both techniques. Our combined SO₂ fluxes is obtained by combining the SO₂ camera-derived plume velocities (obtained from the optical flow algorithm applied to high-frequency UV camera images in near-vent conditions) with the FLAME-derived ICAs, recalculated at source conditions using an experimentally derived plume dilution function. The resulting SO₂ flux exhibits a stronger correlation with volcanic activity than obtained using any of the two techniques alone. We emphasize that integrating near-vent measurements through UV cameras with distal scanning-DOAS measurements may significantly improve our understanding of volcano degassing dynamics and behaviour.

How to cite: Lo Bue Trisciuzzi, G., Aiuppa, A., Salerno, G., Delle Donne, D., Bitetto, M., Curcio, L., Vitale, A., Nogueira Lages, J. P., Lo Forte, F. M., Murè, F., Maugeri, R., and Principato, P.: Combining scanning-DOAS and SO2 camera observations leads to more robust volcanic SO2 flux records., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19466, https://doi.org/10.5194/egusphere-egu24-19466, 2024.

Assessing the pre-eruptive dynamic and volatile-saturation conditions of magmas of past eruptions at active volcanic systems is of paramount importance to understand the future behavior of volcanoes capable of high explosive events. Among all active volcanoes on the Earth, Campi Flegrei caldera (CFc) in southern Italy is a well monitored volcano considering the past highly explosive eruptions such as that of the Neapolitan Yellow Tuff (40 km³) occurred 15 ka ago. At the present, CFc has been undergoing through an unrest crisis consisting of a ~120 cm uplift of the central part of the caldera since 2005 (INGV, November 2023 bulletin), rising a debate relative to the origin of this crisis among scientists. The high volcanic risk is derived by the high degree of urbanization at CFc and the proximity to the city of Naples. For assessing the volcanic risk of CFc, scientists have selected the Agnano-Monte Spina (A-MS) eruption as a reference. The A-MS, in fact, represents the highest explosive event for the last 4.5 ka of CFc activity.

We studied 100 clinopyroxenes from pumices of air fall deposit associated to the A-MS, and we studied the petrography of their hosted melt and fluid inclusions (MI and FI respectively). The major and minor element compositions of the selected clinopyroxene were characterized based on electron-microprobe analysis. In addition, the volatile contents of the bubble of MI and FI were studied by using Raman microspectroscopy.

Two groups of clinopyroxene were identified based on mineral chemistry and petrography. On one hand, clinopyroxenes of one group show (1) a light green colour as hand specimen, (2) diopsidic composition (MgO=16-18 wt.%), and (3) resorbed margins. This group of clinopyroxenes was named as MgO-rich cpx. On the other hand, clinopyroxenes of the other group show (1) a showing a dark green colour as hand specimen, (2) salitic composition (MgO=12-14 wt.%), and (3) larger size grain relative to MgO-rich cpx. This group of clinopyroxenes was named as MgO-poor cpx. The most striking difference of these two groups of cpx are the types of MI and FI hosted in the crystals. Glassy MI are found exclusively hosted in the MgO-poor cpx. These glassy MI hosted in MgO-poor cpx show shrinkage bubbles (bubble-bearing MI). In contrast, MgO-rich cpx host MI and FI which were trapped heterogeneously together. Shrinkage bubbles of MI hosted in MgO-poor cpx did not show any Raman signals of volatile species, while FI and shrinkage bubbles of MI hosted in Mg-rich clinopyroxene showed CO₂, carbonate, and H₂S Raman signals.

Based on our results and data of MI and cpx from the literature, we suggest that a magma mush of relatively less evolved composition associated to MgO-rich cpx was present at shallow depth (~3 km). A deeper and more evolved magma ascended from deeper the plumbing system and mixed with a volatile-saturated mush triggering the A-MS eruption. We further suggested that the shallow magma mush was saturated with a CO₂-H₂S-rich magmatic fluids, while the deeper and more evolved magma did not present evidence of volatile saturation. 

How to cite: Esposito, R., Pingitore, F., and Frezzoti, M.-L.: Evidence of pre-eruptive volatile-saturated magmas before the eruption of Agnano-Monte Spina (Phlegrean Fields, Southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20368, https://doi.org/10.5194/egusphere-egu24-20368, 2024.

Deep fluids and their isotopic signatures, especially He due to its inert nature, are powerful tools for investigating the processes occurring within the crust, as fluids- rocks interaction, storage and transfer mechanism. Numerous studies have emphasized the connection between local seismicity leading to widespread microfracturing processes and an increase in the release of ⁴He that was previously trapped within minerals. Thus, the episodic degassing of 4He through the crust can sustain the excess of He in natural reservoirs respect to the steady-state diffusion processes.

The aim of this study is to determine whether the quantity of He stored in the geothermal reservoir of Casaglia, an exploited mining concession located at the top of the Dorsale Ferrarese, which is a seismically active area in the Emilia-Romagna Region, can be attributable to long lasting diffusion process and to highlight the contribution that these geochemical approach can provide to enhance the understanding of underground phenomena, revealing changes in the stress field and related earthquakes.

We collect fluids from the reservoir and we analyse their chemical and isotopic composition. In particular, the helium abundance is very high, up to 3956 ppm. It is also characterised by a ³He/⁴He ratio of 0.02Ra, clearly indicating that the dominant component is attributable to radiogenic ⁴He produced by U and Th decay in the crust.

The measured total amount of He stored in Casaglia reservoir vary from 10⁷ to 10⁵ mol/km³ rocks, depending on the porosity. This data has been compared with the expected amount of helium accumulated over time under steady-state crustal degassing, which has been computed taking into account the local stratigraphy, the age of formation of the anticline hosting the reservoir (Upper Pliocene - Pleistocene) and the abundances of U and Th in the rocks. The preliminary result shows that there is at least an order of magnitude difference between the experimental evidence and the calculated data in terms of the amount of helium accumulated in the reservoir, even under the most conservative conditions, assuming that there are no losses of ⁴He due to advection or diffusion processes.

Our study demonstrates that the in-situ production of ⁴He in the crust and a long-lasting diffusion through the crust are not the main processes that rule the He degassing in the Casaglia reservoir but alternative and episodic processes controlling the transport mechanism act simultaneously.

Finally, exploiting the established association between rock deformation and helium degassing, monitoring helium flux in active tectonic settings may yield valuable insights into variations in the stress field and the occurrence of seismogenic processes. This aspect highlights the applicability of our findings in contributing to the understanding of underground phenomena, emphasizing the potential of geochemical approaches to reveal changes in the stress field and seismic activities.

How to cite: Balzan, S., Caracausi, A., Buttitta, D., and Coltorti, M.: Dissolved Helium Estimation in the Casaglia Geothermal Reservoir: a Geological Active Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18297, https://doi.org/10.5194/egusphere-egu24-18297, 2024.

Modeling magma ascent within volcanic conduits is not an easy task since it involves complex physical interactions between melt, crystals and gas. Since the evolution of gas content mainly controls the eruptive dynamics, we have to do our best to understand and quantify how and when this gas phase exsolves from the melt, expands and finds its way toward the surface, possibly independently from the melt. In order to follow these phenomena with time, we developed a new 1.5D two-phase system which takes, among others, effects of pressure, temperature, volatile exchanges (including diffusion and viscous relaxation) between the melt and gas phases into account. First tests with this numerical model have then been conduced in order to see if we manage to reproduce gas content and gas fluxes prior to the July 2013 vulcanian eruption at Tungurahua volcano in Ecuador.

How to cite: Collombet, M., Burgisser, A., Bresch, D., and Narbona Reina, G.: Do gas fluxes from numerical modeling and from field data match ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20543, https://doi.org/10.5194/egusphere-egu24-20543, 2024.

The eruption behavior of magmas depends strongly on the volatile content of the melt. Dissolved H₂O significantly affects magma ascent and the nature of volcanic eruptions. The formation and subsequent growth of fluid vesicles increases the magma volume and thus the internal pressure of the magma chamber. Consequently, the tensile strength of the overlying bedrock may be exceeded, triggering an eruption⁽¹⁾. Vesicle formation may be enhanced in volatile-rich bimodal magmatic systems, such as the Askja eruption in Iceland in 1875⁽²⁾ and the 16.5 Ma Yellowstone eruption⁽³⁾.

A bimodal magmatic system can result from a basaltic melt entering a volatile-rich rhyolitic magma chamber, leading to magma mixing, magma mingling, and magma ascent. Experimentally decompressed bimodal hydrous melts show a depletion of alkalis, especially Na₂O, in the hybrid zone⁽⁴⁾. This amplifies supersaturation of H₂O and subsequently the enhanced formation of H₂O vesicles in the hybrid zone, as H₂O solubility closely correlates with the alkali content of a silicate melt⁽⁵⁾.

In general, nucleation is considered as the driving mechanism for vesicle formation of volatiles in silicate melts⁽⁶⁾. Nucleation describes the process of the formation of a critical vesicle in the thermodynamically metastable range, which can increase in volume due to diffusion processes, thereby achieving near equilibrium conditions⁽⁶⁾. However, decompression rate independent vesicle number densities observed in experimentally decompressed phonolitic melts contradict the results of nucleation theory⁽⁷⁾. Instead, the phase separation of H₂O from the silicate melt may proceed in the thermodynamically unstable range, in which spontaneous spinodal decomposition is the controlling mechanism.

For further detailed investigation of the mechanisms behind enhanced H₂O vesicle formation in the hybrid zone of bimodal melts, we synthesized glass with the hybrid melt composition given in (4).  Subsequently, H₂O solubility experiments were conducted in the internally heated argon pressure vessel (IHPV). For this purpose, the hybrid melt was hydrated with H₂O excess for 96 h at 1523 K and 60, 80, 100 or 200 MPa, further equilibrated at 1323 K for 0.5 h and then isobarically quenched with 16 or 97 K·s^-1. The resulting solubility data are essential to conduct decompression experiments of initially slightly H₂O undersaturated melts at rates of 1.7-0.17 MPa·s^-1 to the final pressures of 60-100 MPa, followed by the analysis of the H₂O vesicle number density, spatial distribution and H₂O contents in the decompressed melts with quantitative image analysis and FTIR-spectroscopy and the calculation of the equilibrium porosity. A comparison of the data with the bimodal decompression experiments⁽⁴⁾ could provide decisive information on the melt degassing mechanism of hybrid melt zones.

(1) Sparks, R. S. J. (1978) Volcanol. Geoth. Res., 3(1-2), 1-37.

(2) Sigurdsson, H., & Sparks, R. S. J. (1981) Petrol., 22(1), 41-84.

(3) Huang, H. H., et al. (2015) Science, 348(6236), 773-776.

(4) Marks, P. L. et al. (2023) J. Mineral., 35(4), 613-633.

(5) Allabar A. et al. (2022) Mineral. Petr., 177(52).

(6) Navon, O. & Lyakhovsky, V. (1998) Soc., Spec. Publ., 145(1), 27-50.

(7) Allabar, A. & Nowak, M. (2018) Earth Planet. Sc. Lett., 501, 192-201.

How to cite: Luenenschloss, L., Marks, P. L., and Nowak, M.: H2O-vesicle formation in the hybrid region of a bimodal melt system. An experimental progress., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16089, https://doi.org/10.5194/egusphere-egu24-16089, 2024.

The Laacher See volcano in the Eifel region of western Germany caused one of the largest eruptions in Central Europe within the last 100,000 years. The Plinian eruptions lasted days to weeks and ejected about 6.3 km³ phonolitic magma. The ascent and subsequent discharge of magma is greatly influenced by the amount of dissolved H₂O. During the magma ascent the solubility of H₂O in the melt decreases while simultaneously the supersaturation of the melt increases. This is the prerequisite for phase separation, which leads to the formation of volatile bubbles.

A set of high temperature decompression experiments with hydrous lower Laacher See phonolite (LLST) has recently been conducted at high temperature superliquidus conditions of 1323 K and starting pressure of 200 MPa showing spontaneous phase separation (Marks and Nowak 2024) at a final pressure of 80 MPa. In order to investigate the temperature dependence of vesicle formation, preparatory phase relation experiments were conducted in the cold seal pressure vessel at low temperature near liquidus conditions. Synthetic glass cylinders of the LLST composition were hydrated for 11 days with excess H₂O at 1123 K and 200, 90, and 70 MPa to obtain H₂O solubility data and pressure dependent liquidus conditions.

The hydrated and quenched sample at 200 MPa is a crystal-free homogeneous glass with residual H₂O fluid. The H₂O content of the glass was determined with FTIR-spectroscopy. The measured H₂O content of ~5.7 wt.% at 200 MPa and 1123 K is in good agreement with previous results of Schmidt and Behrens (2008).

In contrast, the samples hydrated at P <200 MPa are partially crystallized. Needle shaped crystals grew from the capsule walls towards the sample center indicating subliquidus conditions. Based on optical microscopy and Raman spectroscopy, the crystal phases are indicative of feldspar. For a detailed phase identification, the samples will be investigated with the electron beam microprobe.

The preparatory samples provide important information on planned low temperature decompression experiments: (1) At 1123 K, 200 MPa, and H₂O saturated conditions the melt is superliquidus, which is a prerequisite for homogeneous vesicle formation.  (2) Pressures conditions between 90 and 70 MPa are subliquidus, resulting in partial crystallization of the hydrous melt. This might induce crystal formation during decompression. However, (3) the planned decompression rates of 0.17 and 1.7 MPa·s^-1 and experimental run times <15 min are expected to be fast enough to inhibit partial crystallization (Brugger and Hammer, 2010). Therefore, we suggest that the determination of the low temperature near liquidus H₂O phase separation mechanism of the lower Laacher See phonolite will be successful.

Marks P. L. and Nowak M., 2024. Decoding the H2O phase separation mechanism as the trigger for the explosive eruption of the Lower Laacher See phonolite. EGU24-7723.

Schmidt, B.C., Behrens, H., 2008. Water solubility in phonolite melts: influence of melt composition and temperature. Chem. Geol. 256, 259–268.

Brugger, C. R. & Hammer, J. E., 2010 Crystal size distribution analysis of plagioclase in experimentally decompressed hydrous rhyodacite magma. Earth Planet. Sci. Lett. 300, 246–254.

How to cite: Hummel, F., Marks, P. L., and Nowak, M.: Preparatory experiments to investigate the vesicle formation of hydrous lower Laacher See phonolite at near liquidus conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19758, https://doi.org/10.5194/egusphere-egu24-19758, 2024.

Tenerife, the largest and highest island in the Canarian archipelago, houses the active Teide-Pico Viejo volcanic system. Its structure is shaped by a rift-system with various directions intersecting at this volcanic system. The system’s last eruption in 1798 expelled approximately 12 million m³ of lava across a three-month period, resulting in the formation of a distinct black surface that contrasts sharply with the surrounding. While Teide volcano exhibits a faint fumarolic system, the observed volcanic gas emissions mainly consist of diffuse CO₂ degassing.

Spanning from 1999 to 2024, over 200 surveys meticulously assessed CO₂ and H₂S emissions across 38 strategic sites within the Teide Volcano's summit crater. Portable fluxmeters, equipped with CO₂ and H₂S sensors, estimated emission rates via the accumulation chamber method. These rates fluctuated between 2.0 and 1,257 tons per day over a 25-year span. Following a seismic swarm in October 2016, there was a general marked escalation in CO₂ and H₂S emissions, aligning with heightened seismic activity. This shift led to relatively high CO₂ emissions, possibly attributed to fresh magma injection and convective mixing catalyzed by the seismic swarm.

It is pertinent to note a distinct event in the latter half of 2023, marked by a notable surge in CO₂ and H₂S emissions (ranging between 222 and up to 1,257 tons/day for CO₂, and 40 to 270 tons/day for H₂S), despite a relatively unchanged seismic activity compared to preceding years.

This study highlights the value of examining diffuse degassing in understanding volcanic behavior and forecasting potential volcanic activity. Monitoring these emissions has become a crucial tool in predicting seismic and volcanic unrest, contributing significantly to mitigating volcanic risks in Tenerife.

How to cite: Asensio-Ramos, M., Keeley, N., Reichrath, O., Riddell, A., Martín-Lorenzo, A., Rodríguez, F., Melián, G. V., Di Nardo, D., Padilla, G. D., Padrón, E., Pérez, N. M., Hernández, P. A., and D'Auria, L.: Diffuse CO2 and H2S degassing monitoring at the summit crater of Teide volcano, Tenerife, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19718, https://doi.org/10.5194/egusphere-egu24-19718, 2024.

Tenerife (2,034 km²), the largest and one of the most active islands of the Canarian volcanic archipelago, has registered six volcanic eruptions in the last 500 years. One of the main volcano-structural and geomorphological features of Tenerife is the triple junction-shaped rift system, as a result of inflation produced by the concentration of emission vents and dykes at 120º one to another. The oriented North South Rift Zone (NSRZ; 325 km²) is one of the three active volcanic rift-zones of the island and is characterized mainly by effusive activity of basaltic lavas forming spatter and cinder cones and comprising 139 monogenetic cones representing the most common eruptive activity occurred on the island during the last 1My. The main structural characteristic of the NSRZ is the apparent absence of a distinct ridge and a fan shaped distribution of these monogenetic cones. Since no visible degassing at Tenerife NSRZ surface occurs, a geochemical monitoring program at Tenerife NSRZ was established mainly consisting on performing diffuse CO₂ emission surveys to evaluate the temporal and spatial variations of soil CO₂ efflux values and the diffuse CO₂ emission rate. Ten diffuse CO₂ degassing surveys have been carried out at NSRZ of Tenerife since 2002, the last one in the summer period of 2023. Measurements of soil CO₂ efflux were performed in situ by means of a portable non-dispersive infrared sensor following the accumulation chamber method at about selected 600 sampling sites to obtain a homogeneous distribution after taking into consideration the local geology, structure and accessibility. During the 2023 survey, soil CO₂ efflux values ranged from non-detectable up to 55.5 g m⁻² d⁻¹. Statistical-graphical analysis of the 2023 data show three different geochemical populations; background (B), intermediate (I) and peak (P) represented by 93.9%, 5.4% and 0.7% of the total data, respectively. The geometric means of the B, I and P populations are 1.6, 11.4 and 36.6 g m⁻² d⁻¹, respectively. Most of the area showed B values while the P values were observed as multiple isolated anomalies in the study area. 100 equiprobable sequential Gaussian simulations were performed to construct the spatial interpolation map and to estimate the diffuse CO2 emission in tons per day released from Tenerife NSRZ in the 2023 survey. The diffuse CO₂ output released to atmosphere by the NSRZ of Tenerife estimated in the 2023 survey was 884 ± 27 t d^-1. This value overcomes the estimated background range (201 - 760 t d^-1), and confirms the clear relationship  between the temporal evolution of the CO₂ output released by the NSRZ and the 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. Monitoring the diffuse CO₂ emission contributes to detect early warning signals in the activity of the Tenerife North-South Rift-Zone volcanic system.

How to cite: de los Ríos, H., Ostorero, L., Melián, G. V., Rodríguez, F., Asensio-Ramos, M., Pérez, N. M., Hernández, P. A., Padrón, E., and Padilla, G. D.: Diffuse CO2 degassing monitoring of the Tenerife North-South Rift Zone (NSRZ) volcano, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13196, https://doi.org/10.5194/egusphere-egu24-13196, 2024.

Tenerife (2,034 km²), the largest island of the Canarian archipelago, is characterized by three volcanic rifts oriented NW-SE, NE-SW and N-S with a central volcanic complex, Las Cañadas Caldera, hosting Teide-Pico Viejo volcanoes. The North West volcanic Rift Zone (NWRZ, 72 km²) of Tenerife is one of the youngest and most active volcanic systems of the island, where four historical eruptions have occurred: the volcanic eruption witnessed by Christopher Columbus in 1492, Boca Cangrejo in 16^th Century, Arenas Negras in 1706 and Chinyero in 1909. In order to monitor the volcanic activity of NWRZ, since the year 2000, 56 soil CO₂ efflux surveys have been performed at NWRZ (with more than 300 observation sites each one) to evaluate the temporal an spatial variations of CO₂ efflux and their relationships with the volcanic-seismic activity. Soil CO₂ efflux measurements were performed in accordance with the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO₂ emission from the studied area, 100 simulations for each survey have been performed. We report herein the results of the last diffuse CO₂ efflux survey at the NWRZ undertaken in summer 2023 to constrain the total CO₂ output from the studied area. During this survey, soil CO₂ efflux values ranged from non-detectable up to 34 g m^-2 d^-1. The total diffuse CO₂ output released to atmosphere were estimated in 311 ± 11 t d^-1, value higher than the background CO₂ emission estimated on 151 t d^-1. Since the 2000s, total CO₂ output ranged between 52 and 867 t d^-1. Long-term variations in the total CO₂ output suggest the occurrence of subsurface magma degassing and magmatic fluid injection, perhaps due to strain-stress changes beneath the NWR zone (Hernández et al., 2017). Regular surveys of soil CO₂ efflux seem to be an effective geochemical surveillance tool at the NWRZ, able to detect changes in the CO₂ emission rate that might presage future episodes of volcanic unrest.

Hernández et al., (2017). Bull. Volcanol. 79:30.

How to cite: Leal Moreno, V. J., Atton, L., Rodríguez, F., Asensio-Ramos, M., Melián, G. V., Hernández, P. A., Padilla, G., Pérez, N. M., and Padsrón, E.: Twenty three years of monitoring diffuse CO2 emission from the Tenerife North-West Rift Zone (NWRZ) volcano, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17401, https://doi.org/10.5194/egusphere-egu24-17401, 2024.