Session GMPV8.7

[Programme]

GMPV8.7 | Volcanic degassing

Volcanic degassing

Convener: Marco Liuzzo | Co-conveners: Nicole Bobrowski, Jonas Kuhn

Orals

| Tue, 16 Apr, 14:00–15:45 (CEST)

Room -2.33

Posters on site

| Attendance Mon, 15 Apr, 10:45–12:30 (CEST) | Display Mon, 15 Apr, 08:30–12:30

Hall X1

Magma composition, eruptive frequency, and tectonic context are highly variable features of volcanoes. Within such contexts, volcanic volatiles play a key role in magma transport, and impact on the style and timing of volcanic eruptions. Gas chemical and isotopic compositions may change over time, reflecting variations in the magmatic feeding systems of volcanoes. As the magma rises from depth, the decreasing pressure allows volatile species to partition into the gas phase. Bubbles form, grow, and coalesce, and gases start to flow through the vesciculated magma. Eventually, fluid and gases reach the surface and are released into the atmosphere through soil degassing, fumarolic vents, or bubbling through a water surface, forming large plumes or explosive eruption columns.

Volcanic emissions can also have significant impacts on the terrestrial environment, atmospheric composition, climate, and human health at various temporal and spatial scales. For instance, sulfur dioxide emissions can cause acid rain and influence aerosol formation, and if an eruption column reaches the stratosphere, it causes global dimming and a lowering of the Earth’s surface temperatures that may last for years. Similarly, halogens can dramatically affect proximal ecosystems, influence the oxidation capacity of the troposphere, and alter the stratospheric ozone layer.

Understanding the physicochemical processes underlying volcanic eruptions has improved tremendously through major advances in computational and analytical capabilities, instrumentation and monitoring networks, thereby improving the ability to reduce volcanic hazards. This session focuses on all aspects of volcanic volatile degassing in the Earth’s system through case studies and theoretical and multidisciplinary approaches. We invite contributions discussing how novel measurement techniques, field measurements, direct and remote ground and space-based observations, and modeling studies of volcanic degassing can provide new insights into volcanic and atmospheric processes at local and global scales.
Finally, but significantly, we strongly encourage critical contributions that offer alternative explanations and viewpoints, willingness to consider new ideas supported by evidence, and with the potential to improve the ability to forecast eruptions.

Orals: Tue, 16 Apr | Room -2.33

Chairpersons: Marco Liuzzo, Nicole Bobrowski, Jonas Kuhn

14:00–14:05

5-minute convener introduction

14:05–14:25

EGU24-15632

solicited

On-site presentation

Tracing Volcanic Degassing Dynamics During the 2021-2023 Eruptions on the Reykjanes Peninsula, Iceland, via OP-FTIR measurements

Samuel Scott, Melissa Pfeffer, Clive Oppenheimer, and Andri Stefánsson

The recent eruptions on the Reykjanes Peninsula presented an exceptional opportunity for in-depth analyses of volcanic gas emissions. Utilizing Open-path Fourier Transform Infrared (OP-FTIR) spectroscopy, we analyzed the abundance of major and minor gas molecular species, including H₂O, CO₂, SO₂, HCl, HF and CO, in the gas emissions on more than twenty occasions throughout the eruptions in 2021-2023. Predominantly water-rich emissions (60-95 mol % H₂O) suggest fractional degassing and substantial CO₂ loss at depth. Significant temporal variations in gas composition were observed, with lower H₂O/CO₂ and H₂O/SO₂ ratios and higher SO₂/HCl ratios measured early in the early stages of the Fagradalsfjall eruption and higher H₂O/CO₂ and H₂O/SO₂ ratios and lower SO₂/HCl ratios during later stages and subsequent eruptions. A unique set of measurements, conducted at close range and high temporal resolution during the 2021 lava fountaining phase, provided insights into the dynamics of gas segregation at shallow depths. These findings help explain the pulsatory nature of the lava fountaining, driven by pressure fluctuations in a shallow magma-filled cavity. Furthermore, the gas emission chemistry varied significantly with the degassing style, with gas emitted by surface lava flows characterized by higher H₂O/CO₂ and H₂O/SO₂ and lower SO₂/HCl and SO₂/HF ratios compared to gas emitted at actively erupting vents. This study underscores the effectives of OP-FTIR techniques for tracking the spatiotemporal evolution of basaltic magma degassing, offering valuable insights into volcanic processes.

How to cite: Scott, S., Pfeffer, M., Oppenheimer, C., and Stefánsson, A.: Tracing Volcanic Degassing Dynamics During the 2021-2023 Eruptions on the Reykjanes Peninsula, Iceland, via OP-FTIR measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15632, https://doi.org/10.5194/egusphere-egu24-15632, 2024.

14:25–14:35

EGU24-16145

ECS

On-site presentation

Evidence of rapid conduit sealing driving explosive activity at El Reventador (Ecuador) underpinned by a permanent SO2 camera installation.

Thomas C. Wilkes, Silvana Hidalgo, Jean Battaglia, Tom D. Pering, Marco Almeida, Freddy Vásconez, Carlos Macías, and Dario García

El Reventador is a highly active stratovolcano located ≈90 km east of Quito (Ecuador). Since a paroxysmal eruption (VEI 4) in 2002, it has exhibited persistent open-vent degassing accompanied by frequent vulcanian-/strombolian-style explosions, as well as lava flows and small pyroclastic density currents. The relatively remote nature of this volcano, requiring 4-5 hours of arduous uphill hiking through thick jungle, hinders extensive research on this system. Furthermore, with changeable and often wet weather conditions in the region, reliable remote spectroscopic measurements of gas emissions can be particularly difficult to achieve. These complications highlight the importance of permanent instrument installations that can work autonomously, thus reducing the need for field campaigns and improving the chances of capturing high-quality data and/or interesting volcanic phenomena. Here, we present the first measurements from a permanent SO2 camera installation on El Reventador, focussed on a window of good measurement conditions lasting a few hours on 24th April 2022. During this period, explosions typically occurred at a sub-hourly rate, with varying sizes and repose periods. Prior to a number of the explosions we find a decrease in SO2 emissions suggestive of gas accumulating under a reduced-permeability magma seal in the upper conduit. Sealing appears to occur on the order of 10-20 minutes prior to explosions, although establishing a baseline emission rate for the freely degassing system is often precluded by the frequency of explosions. Indeed, we find periods where permeability in the upper conduit appears to begin reducing immediately after the previous explosion.

How to cite: Wilkes, T. C., Hidalgo, S., Battaglia, J., Pering, T. D., Almeida, M., Vásconez, F., Macías, C., and García, D.: Evidence of rapid conduit sealing driving explosive activity at El Reventador (Ecuador) underpinned by a permanent SO2 camera installation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16145, https://doi.org/10.5194/egusphere-egu24-16145, 2024.

14:35–14:45

EGU24-9973

ECS

On-site presentation

A novel model of volcanic plume evolution from high-temperature chemistry to reactive plume chemistry in the atmosphere

Alexander Nies, Tjarda Roberts, Guillaume Dayma, Tobias Fischer, and Jonas Kuhn

The first seconds of the interaction of volcanic gases with the atmosphere have so far often been drastically simplified, e.g., by assuming thermochemical equilibrium. In this period, hot and reduced magmatic gases mix with ambient air and undergo rapid cooling. The in-mixture of atmospheric oxygen triggers fast oxidation processes which depend on the dynamic interplay of chemical kinetics, mixing and cooling.

We present a novel chemical box model, which can capture rapid chemical kinetics alongside cooling and mixing of the early plume. The model combines a chemical combustion mechanism with atmospheric chemistry mechanisms and includes sub-mechanisms for halogens, sulfur, reactive nitrogen and mercury, respectively. It is fast and flexible to test many different emission temperatures, mixing scenarios, eruption styles, and gas compositions.

Here, we focus on the formation of reactive halogen species (e.g. bromine oxide (BrO), bromine chloride (BrCl), hypobromous acid (HOBr), and atomic bromine (Br)) during the first seconds, minute to hours of plume evolution, which significantly influence atmospheric chemistry on a regional scale. We study the impact of the high-temperature initializations on ambient-temperature plume chemistry to capture for example the catalytic destruction of ozone by bromine chemistry in the cooled plume. The simulations show that up to 40% of the emitted bromine can be converted into reactive forms within seconds. It promotes fast formation of BrO in the early evolution of the volcanic plume, at magnitudes consistent with UV-remote sensing measurements.

We further assess the presence of reduced species (e.g. molecular hydrogen (H₂) and carbon monoxide (CO)) in the cooled plume and potential implications for the interpretation of observations of redox pairs in the plume. Our kinetic model contrasts to previous thermochemical equilibrium assumptions of near-complete oxidation of H₂ and CO. We identify emission temperatures and plume cooling conditions that allow these reduced species to persist whilst reactive bromine is formed, as well as conditions where the reduced species become oxidized.

The combustion-atmospheric model is a unique tool for analyzing volcanic plume composition measurements as it provides the link to the original composition of the magmatic gas by a kinetic treatment of the magma-atmosphere interface. Future applications include the study of aerosol formation by SO₂-sulfate transformation, mercury and NO_x-nitrate chemistry.

How to cite: Nies, A., Roberts, T., Dayma, G., Fischer, T., and Kuhn, J.: A novel model of volcanic plume evolution from high-temperature chemistry to reactive plume chemistry in the atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9973, https://doi.org/10.5194/egusphere-egu24-9973, 2024.

14:45–14:55

EGU24-5990

On-site presentation

Exceptional eruptive CO2 emissions from intra-plate alkaline magmatism in the Canary volcanic archipelago

Mike Burton and the Tajogaite 2021 Gas Team

Alkaline mafic magmas forming intra-plate oceanic islands are believed to be strongly enriched in CO₂ due to low-degree partial melting of enriched mantle sources. However, until now, such CO₂ enhancement has not been verified by measuring CO₂ degassing during a subaerial eruption. Here, we provide evidence of highly CO₂-rich gas emissions during the 86-day 2021 Tajogaite eruption of Cumbre Vieja volcano on La Palma Island, in the Canary archipelago. Our results reveal sustained high plume CO₂/SO₂ ratios, which, when combined with SO₂ fluxes, melt inclusion volatile contents and magma production rates at explosive and effusive vents, imply a magmatic CO₂ content of 4.5 ± 1.5 wt%. The amount of CO₂ released during the 2021 eruptive activity was 28 ± 14 Mt CO₂. Extrapolating to the volume of alkaline mafic magmas forming La Palma alone (estimated as 4000 km³ erupted over 10 Ma), we infer a maximum CO₂ emission into the ocean and atmosphere of 10¹⁶ moles of CO₂, equivalent to 20% of the eruptive CO₂ emissions from a large igneous province eruption, suggesting that the formation of the Canary volcanic archipelago produced a CO₂ emission of similar magnitude as a large igneous province.

How to cite: Burton, M. and the Tajogaite 2021 Gas Team: Exceptional eruptive CO2 emissions from intra-plate alkaline magmatism in the Canary volcanic archipelago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5990, https://doi.org/10.5194/egusphere-egu24-5990, 2024.

14:55–15:05

EGU24-9892

On-site presentation

The P-T-X dependent water and carbon dioxide saturation in silicate melts of virtually any composition

Paolo Papale

Volatile components, especially water and carbon dioxide, play a controlling role on practically any process and any property related to magmas and their dynamics, influencing to a first order volcanic eruptions and their related hazards. Consequently, knowing the partitioning of water and carbon dioxide among silicate melts and coexisting gas phases is one major objective in a variety of disciplines such as petrology, rock and fluid geochemistry, and magma and volcano physics and dynamics. Here I present the most updated, most comprehensive model of water and carbon dioxide solubility and saturation in silicate melts of virtually any composition spanning from two-component metal slags to natural magmas from the most iron and magnesium –rich, silica under-saturated, to the most chemically evolved ones found on Earth, the Moon, or Mars. The model rests on rigorous thermodynamic modelling, and on a robust calibration involving nearly 2000 individual saturation data – the entire set of appropriate existing data to my knowledge. Pressure and temperature of calibration also span wide ranges from one bar to several GPa, and from just above liquidus to above 2000 °C, respectively. I show here the capability of the model to properly account for virtually any aspect previously described from the experiments and related to the compositional-dependent water and carbon dioxide saturation surface in silicate melts; its capability to extend further that knowledge by revealing additional aspects not yet experimentally highlighted; and some examples of the use of the model to explore the characteristics of real magmatic systems and simulate their dynamics.

How to cite: Papale, P.: The P-T-X dependent water and carbon dioxide saturation in silicate melts of virtually any composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9892, https://doi.org/10.5194/egusphere-egu24-9892, 2024.

15:05–15:15

EGU24-7723

ECS

On-site presentation

Decoding the H2O phase separation mechanism as the trigger for the explosive eruption of the Lower Laacher See phonolite

Patricia Louisa Marks and Marcus Nowak

The Laacher See volcano is one of the youngest volcanoes in Germany with its last eruption 13,006 ±9 years BP⁽¹⁾. About 6.3 km³ of hydrous phonolitic magma was explosively erupted by phreatomagmatic and plinian eruptions in less than 10 days⁽²⁾. The eruption behavior of such volcanic systems is determined by the phase separation mechanism of H₂O fluid from the supersaturated hydrous silicate melt during ascent. The number of fluid vesicles per unit volume of silicate melt (VND in mm^-3) is a standard parameter used to quantify the efficiency of fluid-melt separation and thus the acceleration of magma ascent. According to the nucleation theory, the VND increases strongly with decompression rate⁽³⁾ and is thus a suitable parameter for quantifying magma ascent velocity. Recently and specifically for phonolitic melts, the process of spinodal decomposition has been proposed, which manifests in the independence of VND from the decompression rate⁽⁴⁾.

To characterize the degassing behavior of the lower Laacher See phonolite, systematic decompression experiments were conducted in the internally heated pressure vessel. The melts were hydrated with 5.7 or 5.0 wt% H₂O at 200 MPa and 1523 K for 96 h and then continuously decompressed at 1323 K with 0.064 – 1.7 MPa/s to final pressures between 110 MPa and 30 MPa. By reaching the final pressure, the samples were rapidly quenched to room temperature to preserve the vesicle textures and the residual H₂O contents in the melts and to minimize vesicle shrinkage during cooling. The VNDs and the spatial distribution of the vesicles, as well as the H₂O contents in the decompressed melts were analyzed with quantitative image analysis, transmission light microscopy, and FTIR-spectroscopy.

Upon reaching sufficient supersaturation pressure of >80 MPa, all samples exhibit homogeneously dispersed and micrometer-sized vesicles in the sample center (Fig. 1). The results consistently show that the initial VND is independent of the decompression rate, with high logVNDs of 4.1 to 5.6 causing very fast near equilibrium adjustment of H₂O concentration of the melt by degassing. Further decompression of the vesiculated melts leads to vesicle coalescence, resulting in a significant reduction of VND by orders of magnitude.

These observations are consistent with that of Allabar and Nowak (2018), who determined a decompression rate independent logVND of ~5.2 ±0.5 for hydrous phonolitic melt of the AD79 Vesuvius white pumice composition. From this, a trend emerges that at least for hydrated phonolitic melts, spinodal decomposition plays a crucial role in the H₂O degassing behavior of the melt and thus in the explosive eruption behavior of the volcanic systems.

⁽¹⁾Allabar A., Nowak M. (2018) Message in a bottle: Spontaneous phase separation of hydrous Vesuvius melt even at low decompression rates. EPSL, 501, 192-201.

⁽²⁾Reinig F., et al. (2021) Precise date for the Laacher See eruption synchronizes the Younger Dryas. Nature, 595, 66-69.

⁽³⁾Toramaru A. (2006) BND (bubble number density) decompression rate meter for explosive volcanic eruptions. J. Volcanol. Geotherm. Res., 154, 303-316.

⁽⁴⁾Wörner G., Schmincke H.-U. (1984) Petrogenesis of the Zoned Laacher See Tephra. J. Petrol., 25, 805-835.

How to cite: Marks, P. L. and Nowak, M.: Decoding the H2O phase separation mechanism as the trigger for the explosive eruption of the Lower Laacher See phonolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7723, https://doi.org/10.5194/egusphere-egu24-7723, 2024.

15:15–15:25

EGU24-9803

On-site presentation

Inverting thermal imagery of fumarole plumes to reveal gas fluxes

David Jessop and Amelie Klein

The mass and heat fluxes emitted by fumarole vents form a large portion of the total degassing budgets at volcanoes undergoing unrest, particularly at hydrothermal volcanoes. For example, the fumarole fluxes at la Soufrière represent around 78% of the total heat budget (Jessop et al., 2021). Pitot-tube instruments provide perhaps the most reliable data for fumarole fluxes but require the user to directly contact the hot, acidic, and toxic gases. Flux estimations from MultiGAS traverses still require the user to be in contact with fumarole gases but at a distance from the vent where the plume is much cooler. The errors associated with this method are substantial (c. 40%).

Physically, fumarole plumes are similar to volcanic plumes produced by explosive activity in the absence of particles and hence similar models can be used (e.g. Woitischek et al., 2021). In this work, we propose using a wind-bent plume model (e.g. Woodhouse et al., 2013; Aubry et al., 2017) to match thermal images of the fumarole plume. Fumarole plumes typically are not opaque (see image) and so we develop a radiative model to account for this (cf. Cerminara et al., 2015). Our model requires the mass and heat flow rates to be specified at the vent. These parameters are retried by inverting our model with data extracted from thermal images acquired between 2017–2023 using a ground-based camera at the level of the vent. We find a slow but steady increase in vent flux over the period of study which is in keeping with data from MultiGAS and Pitot-tube measurements during the same period. The errors associated with our method are much lower than those of the MultiGAS traverse method and will allow for finer analyses of fumarole degassing data and its implications for understanding volcanic unrest.

Aubry, T. J. et al. (2017). “Turbulent entrainment into volcanic plumes: new constraints from laboratory experiments on buoyant jets rising in a stratified crossflow”. Geophys. Res. Lett. 44.20, pp. 10198–10207. DOI: 10.1002/2017GL075069.

Jessop, D. E. et al. (2021). “A multi-decadal view of the heat and mass budget of a volcano in unrest: La Soufrière de Guadeloupe (French West Indies)”. Bull. Volcanol. 3, p. 16. DOI: 10.1007/s00445-021-01439-2.

Cerminara, M. et al. (2015). “Volcanic plume vent conditions retrieved from infrared images: a forward and inverse modeling approach”. J. Volcanol. Geoth. Res. 300, pp. 129–147. DOI: 10.1016/j.jvolgeores.2014.12.015.

Woitischek, J. et al. (2021). “On the use of plume models to estimate the flux in volcanic gas plumes”. Nat. Commun. 12.1, p. 2719. DOI: 10.1038/s41467-021-22159-3.

Woodhouse, M. J. et al. (2013). “Interaction between volcanic plumes and wind during the 2010 Eyjafjallajokülleruption, Iceland”. J. Geophys. Res.-Solid Earth 118.1, pp. 92–109. DOI: 10.1029/2012JB009592.

How to cite: Jessop, D. and Klein, A.: Inverting thermal imagery of fumarole plumes to reveal gas fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9803, https://doi.org/10.5194/egusphere-egu24-9803, 2024.

15:25–15:35

EGU24-15866

ECS

On-site presentation

Monitoring of rainwater chemistry during the recent volcanic unrest at Vulcano Island (Italy)

Francesco Tripodi, Filippo Brugnone, Walter D'Alessandro, Sergio Bellomo, Lorenzo Brusca, Antonio Paonita, and Sergio Calabrese

Volcanoes are an important source of gas and particles into the atmosphere, during the eruptive periods or even during passive degassing activity. The study of volcanic gases is a robust geochemical tool to understand, monitor and predict the behaviour of volcano activity, but it is also important to evaluate the effects of volcanic emission on a local and regional scale. The study of the chemistry of atmospheric deposition can provide important information in this regard. Vulcano Island is a stratovolcano located in the southernmost sector of the Aeolian archipelago (Sicily). Since the last eruption occurred in 1888-1890, volcanic emissions are characterized by intense fumarolic activity localized on the northeastern rim of La Fossa crater. Several episodes of volcanic unrest have occurred over the past 130 years, and the most recent period of crisis was between 2021 and 2022. It was characterised by the increasing fumarole temperatures and gas fluxes, shallow long-period seismicity, and diffuse soil degassing around the main crater. This study reports on the chemical composition of rainwater samples collected from November 2021 to January 2023, during the last unrest period of Vulcano Island. Fifteen rainwater samples were collected through a network of three bulk collectors; two of them were placed inside the fumarolic field, and the last one was located near Vulcano Porto. Rainwater samples were analysed for major and trace element contents, and physicochemical parameters were also measured. The pH of rainwater collected near the summit area reaches very low pH values (min 1.63), with a mean value of 2.29, which is significantly lower respect to the mean value at Vulcano Porto (5.7). The concentrations of dissolved solutes in rainfall (expressed as Total Dissolved Solids) are inversely proportional to pH and reach extremely high values in the most acidic samples (up to 1133 mg/L). The most influenced samples by the volcanic emissions are strongly enriched in sulphate, chlorine and fluorine as a direct result of the dissolution of acid gases in rainwater. In addition to the major species, high concentrations of potentially toxic trace elements (Al, As, B, Cd, Fe, Pb, Sb, Te, Ti, Tl, and REE) were found. At the most distal site (Vulcano Porto) the impact of volcanic emissions on rainfall is much less pronounced and the dominant source is mainly related to marine aerosol. These preliminary results on trace element concentrations in rainfall at Vulcano highlight the importance of these studies to fully evaluate the potential impact of volcanic emissions on rainwater and consequently on other environmental matrices (e.g. soils and plants), especially during a period of intense outgassing.

How to cite: Tripodi, F., Brugnone, F., D'Alessandro, W., Bellomo, S., Brusca, L., Paonita, A., and Calabrese, S.: Monitoring of rainwater chemistry during the recent volcanic unrest at Vulcano Island (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15866, https://doi.org/10.5194/egusphere-egu24-15866, 2024.

15:35–15:45

EGU24-7544

ECS

Virtual presentation

Post-eruptive emission of metals and metalloids from basaltic lavas

Nicolas Levillayer, Olgeir Sigmarsson, and Céline Mandon

During basaltic eruptions, degassing occurs both syn- and post-eruptively. The atmospheric loading resulting from the latter, taking place as the lava cools down and solidifies, is poorly characterised and its environmental impacts are largely unknown. Characterising post-eruptive degassing can be attempted either by direct sampling of the gas emitted at solidifying lava flow or by analysing the degassing structure (segregation veins and vesicles) from already crystallised lava bodies. The 2021-2023 eruptions at Fagradalsfjall on the Reykjanes Peninsula, Iceland, allowed sampling of both the syn- and post-eruptive gas phases. Segregation veins from prehistorical olivine tholeiite lavas of similar composition to that of Fagradalsfjall have been collected, together with their host lava. Major and trace volatile element concentrations, particularly those of the toxic volatile metals and metalloids (VMM), were analysed in the gas and rock phases. The gas analyses reveal distinct VMM composition of the gas emitted syn- and post-eruptively, with a clear tendency for Zn, Mo and Sb to degas after the eruption, whereas Te, Cd and Bi are predominantly released syn-eruptively. Among the segregation veins sampled, several showed anomalous enrichment in numerous VMM, indicative of the post-eruptive gas phase composition. Molybdenum is largely enriched in these veins whereas Cd enrichment is low, reflecting gas phase rich in the former but poor in the latter. Taken together, both approaches indicate substantial atmospheric loading of As, Pb, Sb and Mo post-eruptively resulting in potential hazard around newly erupted lava bodies.

How to cite: Levillayer, N., Sigmarsson, O., and Mandon, C.: Post-eruptive emission of metals and metalloids from basaltic lavas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7544, https://doi.org/10.5194/egusphere-egu24-7544, 2024.

Posters on site: Mon, 15 Apr, 10:45–12:30 | Hall X1

Display time: Mon, 15 Apr, 08:30–Mon, 15 Apr, 12:30

Chairpersons: Marco Liuzzo, Nicole Bobrowski, Jonas Kuhn

X1.63

EGU24-16322

ECS

Reliable Ozone Measurements in Volcanic Plumes: A Way to Resolve the Volcanic Ozone Enigma

Maja Rüth, Niklas Karbach, Nicole Bobrowski, Ulrich Platt, Bastien Geil, Thorsten Hoffmann, Ellen Bräutigam, and Jonas Kuhn

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 O₃instrument (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.

X1.64

EGU24-7479

Nyiragongo eruption 2021 and its environmental impact: volcanic ash fallout and high levels of trace metals in drinking water

Sergio Calabrese, Patrick Habakaramo Macumu, Sergio Bellomo, Nicole Bobrowski, Guillaume Boudoire, Filippo Brugnone, Giavanni Bruno Giuffrida, Lorenzo Brusca, Walter D'Alessandro, Mathieu Gouhier, Simone Lentini, Lorenza Li Vigni, Luciana Randazzo, and Dario Tedesco

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.

X1.65

EGU24-17761

ECS

Boron and strontium isotopic signature in rainwaters from Mt. Etna, Italy

Filippo Brugnone, Matteo Salvadori, Maddalena Pennisi, Walter D'Alessandro, Lorenzo Brusca, Francesco Parello, and Sergio Calabrese

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.

X1.66

EGU24-15859

Impact of the hydrothermal activity on the seawater chemistry above the Kolumbo volcano (southern Aegean Sea - Greece)

Manfredi Longo, Walter D'Alessandro, Fausto Grassa, Lars Eric Heimbürger-Boavida, Gianluca Lazzaro, Sergio Simone Scirè Scappuzzo, Paraskevi Nomikou, Paraskevi Polymenakou, and Andrea Luca Rizzo

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.

X1.67

EGU24-16170

Volatile degassing at Stromboli Volcano: Continuous soil CO2 fluxes monitoring network and soils discrete measurements. Volcanic implications

Fabio Vita, Claudio Inguaggiato, Agnes Mazot, Marco Corrao, Marianna Cangemi, and Salvatore Inguaggiato

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.

X1.68

EGU24-18957

Decadal monitoring of the soil CO2 outgassing activity of Vulcano Island, Aeolian Archipelago, Italy.

Salvatore Inguaggiato, Fabio Vita, Claudio Inguaggiato, Agnes Mazot, 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, 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.

X1.69

EGU24-19466

ECS

Combining scanning-DOAS and SO2 camera observations leads to more robust volcanic SO2 flux records.

Giovanni Lo Bue Trisciuzzi, Alessandro Aiuppa, Giuseppe Salerno, Dario Delle Donne, Marcello Bitetto, Luciano Curcio, Angelo Vitale, Joao Pedro Nogueira Lages, Francesco Maria Lo Forte, Filippo Murè, Roberto Maugeri, and Paolo Principato

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 SO₂flux 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.

X1.70

EGU24-20368

Evidence of pre-eruptive volatile-saturated magmas before the eruption of Agnano-Monte Spina (Phlegrean Fields, Southern Italy)

Rosario Esposito, Federico Pingitore, and Maria-Luce Frezzoti

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.

X1.71

EGU24-18297

ECS

Dissolved Helium Estimation in the Casaglia Geothermal Reservoir: a Geological Active Area

Silvia Balzan, Antonio Caracausi, Dario Buttitta, and Massimo Coltorti

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.

X1.72

EGU24-20543

Do gas fluxes from numerical modeling and from field data match ?

Marielle Collombet, Alain Burgisser, Didier Bresch, and Gladys Narbona Reina

X1.73

EGU24-16089

ECS

H2O-vesicle formation in the hybrid region of a bimodal melt system. An experimental progress.

Laura Luenenschloss, Patricia Louisa Marks, and Marcus Nowak

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.

X1.74

EGU24-19758

ECS

Preparatory experiments to investigate the vesicle formation of hydrous lower Laacher See phonolite at near liquidus conditions

Frederic Hummel, Patricia Louisa Marks, and Marcus Nowak

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.

X1.75

EGU24-19718

Diffuse CO2 and H2S degassing monitoring at the summit crater of Teide volcano, Tenerife, Canary Islands

María Asensio-Ramos, Natasha Keeley, Oranna Reichrath, Alexander Riddell, Alba Martín-Lorenzo, Fátima Rodríguez, Gladys V. Melián, Daniel Di Nardo, Germán D. Padilla, Eleazar Padrón, Nemesio M. Pérez, Pedro A. Hernández, and Luca D'Auria

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.

X1.76

EGU24-13196

Diffuse CO2 degassing monitoring of the Tenerife North-South Rift Zone (NSRZ) volcano, Canary Islands

Héctor de los Ríos, Léa Ostorero, Gladys V. Melián, Fátima Rodríguez, María Asensio-Ramos, Nemesio M. Pérez, Pedro A. Hernández, Eleazar Padrón, and Germán D. Padilla

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.

X1.77

EGU24-17401

Twenty three years of monitoring diffuse CO2 emission from the Tenerife North-West Rift Zone (NWRZ) volcano, Canary Islands

Victoria Josefina Leal Moreno, Lottie Atton, Fátima Rodríguez, María Asensio-Ramos, Gladys V. Melián, Pedro A. Hernández, Germán Padilla, Nemesio M. Pérez, and Eleazar Padsrón

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.