Physics of Volcanoes 2021Workshop Pov-7

PHYSICS OF VOLCANOES 2021 WORKSHOP POV-7 9-10 March, 2021 13:00 - 18:00 & 12:30 - 18:00

VIRTUAL ZOOM EVENT https://lmu-munich.zoom.us/j/99838242091 Meeting-ID: 998 3824 2091 Code: 211509

PROGRAM FOR DAY I PROGRAM FOR DAY II

Introduction and welcome - 13:00 12:30 Meeting: DGG AK Vulkanologie Presentation (block 1 – 5 talks) 13:15 13:00 Introduction and welcome Coffee break 14:30 13:05 Presentation (block 1 – 6 talks) 14:35 Coffee break

Presentation (block 2 – 5 talks) 14:45 14:45 Presentation (block 2 - 6 talks) Coffee break 16:00 16:15 Coffee break

Short pico talks (9 picos) 16:15 16:30 Short pico talks (6 picos) Summary and virtual beer 17:00 17:00 General discussion, photo competition results, planning of future PoV

PROGRAM DAY I

13:00 Walter & Introduction and welcome Küppers

BLOCK I (convener: U. Küppers)

13:15 Petri Explosive eruptions triggered by magma injection

13:30 Plank Joint multi-sensor infrared satellite and laboratory measurements for lava discharge rate estimation of 2018 Kīlauea Volcano, Hawai‘i eruption 13:45 Zorn Insights into lava dome and spine extrusion using analogue sandbox experiments 14:00 Spang A Multidisciplinary approach to constrain the dynamics of the Altiplano-Puna magmatic system 14:15 Massimetti Overview of Láscar’s recent activity as monitored by different observation platforms: multi-years thermal cyclicity as seen from space during the 2013-2020 eruptive episode

14:30 Coffee break

BLOCK II (convener: C. Helo)

14:45 Riel A new and efficient computational thermodynamics approach for magmatic systems 15:00 Eul Constraining the freezing temperature of vesicle volumes in decompressed hydrous silicate melt using an image-based analytical method 15:15 Mueller Detection and monitoring of hydrothermal alteration by Principal Component Analysis on UAV based optical data, Vulcano Island - Italy 15:30 Bobrowski Reactive chemistry in volcanic plumes – advances 2020

15:45 Surl The WRF-Chem Volcano (WCV) model and its application for atmospheric halogen chemistry processes in a degassing plume

16:00 Coffee break

PICOS (convener: N. Richter)

16:15 Küppers Drone-deployed sensors: Searching for secrets of Strombolian explosions 16:19 Schmid Realistic vent geometries in shock-tube experiments

16:22 Shevchenko Sector collapse at Mount Thorbjorn, Iceland

16:25 Rüth Ozone depletion in volcanic plumes? – Presentation of an interference-free measurement technique and assessment calculations 16:29 Schneider Transient Electromagnetic Measurements at Stromboli volcano, Italy: synthetic and field data 16:31 Warnach A global perspective on Bromine monoxide composition in volcanic plumes derived from S5-P/TROPOMI 16:35 Arens Electrical self-potential anomalies from strain-induced groundwater flow in volcanic aquifers 16:38 Hensch Update on seismic monitoring in the East Eifel

16:42 Schmincke The pre-LST Glees Diatrem, an enigmatic and unique structure, caused by powerful CO2-streaming?

17:00 Summary and virtual beer

PROGRAM DAY II

12:30 Walter Meeting: DGG AK Vulkanologie (open to all)

13:00 Plank Introduction and welcome

BLOCK I (convener: S. Plank)

13:05 De Siena Voice of Volcanoes: generating seismic signals from both volcano dynamics and geological and geomorphological records 13:20 Eckel How to use pattern recognition in volcano monitoring – on the example of Mt Etna 13:35 Eibl Bubble Trap of Strokkur Geyser Feeds its Eruptions

13:50 Schmid Identification and interpretation of seismic short-duration events inside the Kolumbo submarine volcano in the Southern Aegean 14:05 Deasy Average fast spread oceanic crustal composition and insights into its plumbing system 14:20 Walter Ebeko volcano

14:35 Coffee break

BLOCK II (convener: C. Helo)

14:45 Bartels A multi-criterial approach to predict future volcanic eruptions in Germany 15:00 Sievers SO2 Cloud over Bavaria, Germany

15:15 Berckhan Experimental constraints on the phase stability of sulfur-bearing sodalites in a wet Foidite of the East Eifel volcanic field 15:30 Ritter Monitoring a Magmatic Channel in the East Eifel Volcanic Field

15:45 Schmincke The Pulvermaar cluster system, new answers to an old question

16:00 Colombier Textural and chemical analysis of obsidian-bearing trachytic bombs at Kilian Volcano, Chaîne des Puys, France

16:15 Coffee break

PICOS (convener: U. Küppers)

16:30 Armeni Modelling magma pathways and magma storage scenarios in the Eifel volcanic area 16:34 Lehr Inferring a shallow degassing model for Villarrica Volcano from seismic explosion signals 16:38 Castillo Volcanic deformation at Sakurajima between 2019 and 2020 revealed by Sentinel-1 InSAR time series 16:42 Arts Numerically modelling routes of sequential magma pulses in the upper crust 16:46 Kaus An open source Julia package to simulate the thermal evolution of magmatic systems 16:50 Hedelt Extremely fast retrieval of volcanic SO2 layer heights from UV satellite data using inverse learning machines

17:00 General discussion (U. Küppers), photo competition (N. Richter), planning of future POVs (S. Plank)

LIST OF PARTICIPANTS

Family name First name Affiliation Arens Fee University of Bristol Armeni Valentina Deutsche GeoForschungsZentrum GFZ Arts Mara Johannes Gutenberg University Bartels Alexander BGR Berckhan Johanna Johannes Gutenberg University Mainz Blanke Aglaja GFZ Potsdam Bobrowski Nicole Institute of Environmental Physics, Heidelberg University, Germany and Max Planck Institute for Chemistry, Mainz, Germany Bonanati Christina Freelance Brachmann Caroline Geodynamics Bredemeyer Stefan GFZ-Potsdam Bussmann Lena Institute of Glass and Glass Technology, TU Bergakademie Freiberg/DPG Cáceres Francisco LMU Munich Cichy Sarah University of Potsdam Cigala Valeria LMU Munich Colombier Mathieu Ludwig Maximilian University of Munich Cueva Medina Steven LMU Munich Master Student Miguel De Siena Luca Johannes Gutenberg University Mainz Dietrich Thoralf University of Potsdam Dr. Berberich Gabriele M. Wissenschaftlich-technisches Büro Dr. Berberich Dr. Koziol Martin Landessammlung für Naturkunde Rheinland / Maarmuseum Manderscheid Eckel Felix Christian-Albrechts-Universität zu Kiel Eibl Eva University of Potsdam Esenyel Halil Sarp EGU student membership Eul Dennis Eberhard Karls University Tübingen Freundt Armin GEOMAR, Kiel Friedrichs Bjarne Heidelberg University Fuchs Christopher IUP, University of Heidelberg Geil Bastien Johannes Gutenberg-Universität Geisler Andre University of Hamburg Glink Arne Universität Hamburg Gottschämmer Ellen KIT, Geophysical Institute Grunert Katharina Universität Hamburg Gutierrez Xochilt Johannes Gutenberg Universotät Mainz Carolina Hansteen Thor H. GEOMAR Hedelt Pascal DLR Helo Christoph JGU Mainz Hensch Martin Landeserdbebendienst Baden-Württemberg Hinze Florian Universität Bayreuth Hobiger Manuel Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover Hüggenberg Constantin Tum/lmu student of Geoscience Bachelor

Janssen Georg --- Jentsch Anna GFZ Kaus Boris Johannes-Gutenberg University Mainz Keller Franziska ETH Zürich Klügel Andreas Universität Bremen Komeazi Abolfazl Goethe university Koushesh Mohsen Karlsruhe Institute of Technology (KIT) Krohn Katrin German Aerospace Center Berlin (DLR) Kueppers Ulrich LMU München Kuhn Jonas Institute of Environmental Physics, Heidelberg University Küppers Andreas GFZ Langmann Baerbel Institute of Geophysics Lehr Johanna Dep. of Geosciences, Kiel University Lerner Geoffrey Earth Observatory of Singapore Mantiloni Lorenzo Deutsche GeoFroschungsZentrum GFZ Massimetti Francesco University of Torino; GFZ Potsdam Meyer Romain Geological Survey of Luxembourg Müller Daniel GFZ Potsdam Nies Alexander Institut für Umweltphysik, Universität Heidelberg Nikkhoo Mehdi GFZ Potsdam Nowak Marcus University of Tübingen Petri Patricia Universität Tübingen, Geowissenschaften, Experimentelle Mineralogie Pfanz Hardy Lehrstuhl für Vulkanbiologie, Universität Duisburg-Essen Plank Simon German Aerospace Center (DLR) Platt Ulrich Institute of Environmental Physics, University of Heidelberg Pohlenz Andre Universität Potsdam Rauscher Jakob GFZ Potsdam Richter Nicole GFZ Potsdam Riel Nicolas Johannes Gutenberg University Ritter Joachim Karlsruhe Institute of Technology Rivalta Eleonora GFZ, University of Bologna Rücker Nontje University of Potsdam Rummel Lisa BGR Rüth Maja Institute of Environmental Physics, Heidelberg University, Germany Scharff Lea CEN - Uni Hamburg Scheu Betty LMU München Schmid Florian GEOMAR - Helmholtz Zentrum für Ozeanforschung Kiel Schmid Markus Ludwig Maximilians Universität München Schmidt Bernd Geological Survey of Rhineland-Paltinate Schmincke Hans-Ulrich Geomar Schneider Carolin TU Bergakademie Freiberg Scholz Alexandra --- Shevchenko Alina GFZ Sievers Klaus VC, Vereinigung Cockpit Silverii Francesca Deutsche GeoForschungsZentrum GFZ Sobolewski Linda Ruhr-University Bochum

Spallanzani Roberta University of Potsdam Spang Arne Johannes Gutenberg University, Mainz Sperl Matthias DLR Strehlow Karen GEOMAR Helmholtz Centre for Ocean Research Kiel Sturm Anne Heidelberg University Sudibyo Maria University of Potsdam Sumita Mari GEOMAR Helmholtz Centre for Ocean Research Kiel Surl Luke CNRS Troll Valentin Uppsala University Van Camp Michel Royal Observatory of Belgium van den Bogaard Christel GEOMAR Helmholtz Zentrum für Ozeanforschung Vásquez Castillo Alejandra Universität Hamburg Vassileva Magdalena GFZ Viereck Lothar Friedrich-Schiller-Universität Jena von der Lieth Jost Uni Hamburg Vossen Caron Ludwig-Maximilians-Universität München, Munich, Germany Wagner Thomas MPI for Chemistry, Mainz, Germany Walter Thomas GFZ Potsdam Warnach Simon Max-Planck-Institut für Chemie Wartho Jo-Anne GEOMAR Helmholtz Centre for Ocean Research Kiel Weller Daniel LMU Werdenbach- Philipp University of Hamburg Jarklowski Zimmer Martin GFZ Zorn Edgar GFZ

ABSTRACTS - DAY I - BLOCK I

Explosive eruptions triggered by magma injection

Petri P., Allabar A., Nowak M. (University of Tübingen, University of Göttingen)

Explosive eruptions of silicic magmas depend mainly on the amount and the degassing behavior of soluble volatile components like H2O and CO2. The injection of a hot mafic magma into a cooler volatile-rich rhyolitic magma chamber might initiate mingling and mixing processes at the interface of the two melt reservoirs (Paredes-Marino et al. 2017). An accompanying increase in temperature and a buoyant ascent of the H2O-saturated rhyolitic melt may cause a sufficiently high decrease in solubility at pressures < 300 MPa (e.g. Holtz et al. 1995) to trigger vesicle formation. Furthermore, the interface between different melt compositions might act as a site for enhanced vesicle formation. To test this hypothesis, bimodal decompression experiments were conducted. Basaltic and rhyolitic compositions similar to the Askja eruption 1875 in Iceland (Sparks et al. 1977) were used for this purpose. For the preparation of the experiments, rhyolitic and basaltic glass cylinders were molten and hydrated separately in an internally heated argon pressure vessel with H2O excess at 200 MPa and 1523 K for 96–168 h and then isobarically quenched with 16 K/s. The hydrated glass samples were cut perpendicular to the cylinder c-axis. The cylinder faces were polished to enable a perfect contact of the rhyolite cylinder with the basalt cylinder. An additional decompression experiment with two contacted hydrated rhyolite cylinders was conducted as a reference to test the experimental setup.

Joint multi-sensor infrared satellite and laboratory measurements for lava discharge rate estimation of 2018 Kīlauea Volcano, Hawai‘i eruption

Plank, S., Massimetti, F., Soldati, A., Hess, K.-U., Nolde, M., Martinis, S., Dingwell, D.B. (DLR, Uni Torino, LMU, LMU, DLR, DLR, LMU)

Kīlauea Volcano, Hawai’i, is one of the world’s most active volcanoes. From 1983 to 2018 the magmatic system was in near continuous eruptions. This eruption ended on 30 April 2018 when the deflation of Kīlauea caldera began and seismic data showed a dike intrusion from the Middle East Rift Zone of Kīlauea Volcano downrift towards the Lower East Rift Zone (LERZ). On 3 May 2018, the first of final 24 eruptive fissures opened at the LERZ. This was the beginning of the largest effusive event of the last two hundred years at the LERZ. Here, we present a joint analysis of multi-sensor infrared (IR) Visible Infrared Imaging Radiometer Suite (VIIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite Earth observation data together with laboratory viscosity measurements to estimate the Time-Averaged Discharge Rate (TADR) and lava eruption volume of this large eruption event at the LERZ. After an TADR estimation performed independently for each sensor data in order to cross-check the results against each other, a joint timeseries of the VIIRS and MODIS TADR estimates was created to obtain more frequent measurements. This joint analysis of VIIRS and MODIS data resulted in an erupted lava volume of 0.924 ± 0.462 km³. Independent measurements based on airborne LIDAR and Synthetic Aperture Radar Interferometry (InSAR) topography changes are within the range of the IR data-based estimates of the erupted lava volume. Based on major element compositions of the eruptive products, the 2018 LERZ eruption could be differentiated into four main phases, which showed according to the VIIRS and MODIS-based TADR estimation a strong increase of the Mean Output Rate (MOR) during the evolution of the eruption from early/late Phase I, over Phase II until Phase III. This strong increase of the MOR during the different phases of the 2018 LERZ eruption agrees well with the evolution of the lava from low-temperature, highly differentiated lava flows in the beginning to high-temperature mafic more fluid lava from Phase II onwards, as observed in the field by the USGS.

A Multidisciplinary approach to constrain the dynamics of the Altiplano-Puna magmatic system

Spang, A., Baumann, T.S., Kaus, B.J.P. (Johannes Gutenberg University, Mainz)

Continuous Interferometric Synthetic Aperture Radar (InSAR) monitoring (> 25 years) has revealed a concentric surface deformation pattern centered around the summit of Uturuncu volcano above the Altiplano-Puna magma body (APMB) in the central Andes. For the past decades, several numerical studies have successfully reproduced this pattern with models of varying complexity. However, the temperature- and strain rate-dependent visco- elasto-plastic rheology of rocks, the buoyancy of magma, the effects of modelling in 3D as well as the shape of the magma body have often been simplified or neglected. Here, we use a joint interpretation of seismic imaging, gravity anomalies and InSAR surface deformation data to constrain location, 3D shape and density of the magma body. With the help of the thermomechanical stokes code LaMEM, scaling law analysis, the neighborhood algorithm and bayesian inference, we estimate the uncertainties associated with the geometry of the mid-crustal magma body and identify the most important parameters that control the dynamics of the system. We find that the density contrast between the APMB and the surrounding host rock must be in the range of 90 to 130 kg/m3 (2 sigma) to satisfy both tomography and Bouguer data. Based on that and the chemistry of eruption products, we estimate the melt content of the APMB to be on the order of 15 - 22 %. We also present a 3D model that can reproduce the observed surface deformation self-consistently by buoyancy driven magma transport without the need for additional pressure sources. The flow pattern is controlled by a central rise at the top of the APMB whose geometry can be constrained with the help of the thermomechanical code while gravity anomalies help to constrain the deeper parts of the magma body. Scaling law analysis shows that the rheology of the upper crust and the magma mush as well as the density contrast between the two are the most important parameters in the system and need to be constrained for a better understanding of the subsurface processes.

Overview of Láscar’s recent activity as monitored by different observation platforms: multi-years thermal cyclicity as seen from space during the 2013-2020 eruptive episode

Massimetti, F. (University of Torino, GFZ Potsdam), Bredemeyer, S. (GFZ Potsdam, GEOMAR Kiel), Bravo, C.G. (SERNAGEOMIN OVDAS), Franco, L.M.(SERNAGEOMIN OVDAS), Coppola, D. (University of Torino), Laiolo, M. (University of Torino), Walter, T. (GFZ Potsdam)

Láscar is the most active volcano in Northern Chile and known for its frequent small-to-moderate explosive eruptions, which since a phreatic explosion in April 2013 occurred quite regularly about every 3 years (in October 2015 and November 2018). Here we present the results of more than half a decade of continuous observations (2013-2020) obtained from multiple satellite-based thermal sensors (MODIS, SENTINEL-2 and LANDSAT-8), and a permanent ground-based network consisting of seismometers, cameras operating in the visible range of the electromagnetic spectrum, and a weather station. We observe pronounced cyclic long-term variations in heat- flux and dimension/intensity of the thermal anomaly located in Láscar’s active crater, which follow a common pattern. Each of the thermal cycles seems to be initiated by one of above-mentioned explosions leading to an abrupt onset of intense heat-flux accompanied by instantaneous growth of the hotspots dimension, which is followed by an extended waning phase spanning ca. 2.5-3 years. To elucidate the enigmatic nature of these thermal cycles, we compare our thermal dataset to seismic events (LP, VT and Tornillo signals), camera observations (crater glowing and column height) and precipitation records. Our preliminary results suggest a complex and variable interplay between shallow and deeper processes. Most likely, a destabilization of the hydrothermal surficial system occurs, related to a pre-eruptive paths fluid sealing mechanism, and followed by the mobilization of a small volume of magmatic gas towards superficial levels and/or by resuming of shallow activity triggered by an increasing local overpressure. Post-explosive thermal emissions could be enhanced by the exposure of hot magmatic portions previously sealed in the crater. Such findings could have major implications for contemporary monitoring efforts and hazard assessment.

ABSTRACTS - DAY I - BLOCK II

A new and efficient computational thermodynamics approach for magmatic systems

Nicolas Riel, Boris Kaus, Eleanor Green, Nicolas Berlie and Lisa Rummel

During the last decade, the development of numerical geodynamic tools helped the geosciences community to unravel complex thermo-mechanical processes at play during plate tectonics. Yet, the high computational cost of thermodynamic calculations, which simulates phase change, hampers our ability to integrate complex chemistry in such problems. This is particularly important for simulating magmatic processes, where the chemistry of differentiating melts can vary significantly from the mantle to the upper crust. The typical approach, currently used, is to precompute one or many phase diagrams and use them as look-up tables. For many geodynamic processes this is adequate but when the melt chemistry varies drastically it would be better to be able to do thermodynamic calculations on the fly, along with the geodynamic models. For that, the thermodynamic computational approach must be sufficiently fast, should work fully automatically and be tuned for melting models of magmatic systems, for example by utilizing the recently developed thermodynamic melting model of Holland et al. (2018). Existing approaches do not fulfill all criteria, which is why we have developed a new computational library for this purpose. Our code is written in C, runs on massively parallel machines (MPI) and uses an adaptive mesh refinement strategy to compute phase diagrams. At the moment we have focused on the 'igneous set' of the Holland & Powell dataset (as defined in the THERMOCALC software) to calculate stable phase equilibria in the system K2O–Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2– Fe2O3–Cr2O3 (KNCFMASHTOCr). The code uses pressure, temperature and bulk-rock composition as input and returns relevant petrological and geodynamic information such as (but not restricted to) stable assemblage, phase fractions and phase densities. Different than many of the existing approaches, our method can efficiently utilize initial guesses which naturally occur in geodynamic simulations where the changes in chemistry between timesteps are usually minor. The methodology performs a Gibbs free energy minimization and involves two main steps. First, we use a combination of levelling methods (iterative change of base) to reduce the number of potential (pure and solution) phases and to bring the G-hyperplane close to solution. Second, we use a partitioning of Gibbs energy approach coupled with local minimization to satisfy the Gibbs-Duhem rule and to retrieve the final set of stable solution phases. To illustrate the efficiency of the library up to supra-solidus conditions we present a set of dry phase diagrams, ranging from peridoditic to granitic composition, and compare results of our computations with THERMOCALC calculations. Ongoing development includes the treatment of solvus to extend its applicability to complex wet systems involving solution phase such as amphibole.

Constraining the freezing temperature of vesicle volumes in decompressed hydrous silicate melt using an image-based analytical method

Eul, D., Allabar, A., Nowak, M. (Eberhard Karls University Tübingen, Georg-August University Göttingen, Eberhard Karls University Tübingen)

Experimentally vesiculated and vitrified samples are used to investigate the degassing behavior of hydrous silicate melt. The melts are decompressed to a certain pressure P and subsequently quenched from high temperature Texp to glass. Vesicles formed during decompression may shrink during quench due to the resorption of H2O back into the melt (McIntosh et al., 2014) and due to the decreasing molar volume of H2O in the vesicles (Marxer et al., 2015). Due to this shrinkage, the porosity in the vitrified samples does not represent the state of melt vesiculation at Texp but rather at a lower “freezing” temperature Tf. To constrain Tf, McIntosh et al. (2015) developed a computed tomography (CT) based technique estimating Tf from the volume fraction of liquid H2O (fill grade) in the vesicles, which contain a gas and a liquid H2O phase. We developed a 2D transmitted light microscopy (TLM) based approach to analyze the fill grade of vesicles and thus Tf of samples based on the considerations of these authors. To derive estimates on volume fractions from our 2D data, we applied two different approaches: 1) We approximated the vesicle and phase boundaries with

11 polynomial functions, calculating the fill grade from the solid of revolution volumes of these functions. 2) Considering the vesicles to be perfectly symmetrical spheroids and calculating volumes and thus fill grade based on simple ellipsoid axes measurements. The application of our method to hydrous haplogranitic samples yielded mean Tf’s ~ 250 to ~300 K lower than Texp, in good agreement to values calculated with an independent glass porosity equation (Gardner et al., 1999). The range of Tf’s of individual vesicles in a single sample mimics the scatter observed in phonolitic samples of Allabar et al. (2020) analyzed using the CT method. Hence, we propose this scatter to be independent of applied analytical technique and rather induced by small-scale fluctuations of physicochemical properties of the melt during quench. No spatial trend of individual Tf’s and vesicle position in the experimental capsule is observed. The optical resolution limit of observable phase boundaries constrains this method for our equipment to fill grades above ~10% liquid volume fraction. The results of our image-based Tf determination further highlight the importance to consider vesicle shrinkage before the interpretation of vitrified, vesiculated samples. It provides a relatively easy and fast analytical tool to constrain the temperature conditions represented by vitrified samples which improves the quality of derived interpretations and inter-sample comparability.

Allabar, A. et al. (2020), Contrib. Mineral. Petrol, 175, 21, 1-19 Gardner, J.E., Hilton, M. and Carroll, M.R. (1999), Earth Planet. Sci. Lett, 168, 201-218 Marxer, H., Bellucci, P. and Nowak, M. (2015), J. Volcanol. Geotherm. Res, 297, 109-124 McIntosh, I.M. et al. (2014), Earth Planet. Sci. Lett, 401, 1-11 McIntosh I.M. et al. (2015): Abstract, 10th Silicate melt workshop. La Petite Pierre, France

Detection and monitoring of hydrothermal alteration by Principal Component Analysis on UAV based optical data, Vulcano Island – Italy

D. Mueller, S. Bredemeyer, E. Zorn, E. De Paolo, T. Walter

Modern UAS (unmanned aircraft system), light weight sensor systems and new processing routines allow us to gather optical data of volcanoes at a high resolution. However, due to the typically poor colorization, our ability to investigate and interpret such data is limited. Further, the information stored in the red, green and blue channel (RGB) is correlated. This makes any analysis a 3 dimensional task. Principal Component Analysis (PCA) helps us to overcome these problems by decorrelating the original band information and generating a variance representation of the original data. Therefore PCA is a suitable tool to detect optical anomalies, as might be caused by volcanic degassing and associated processes. Applied in a case study at La Fossa Cone (Vulcano Island - Italy), the PCA showed a high efficiency for the detection and pixel based extraction of areas subject to hydrothermal alteration and sulfur deposition. We observed a broad alteration zone surrounding the active fumarole field, but also heterogeneities within, indicating a segmentation. Systematic variations in color and density distribution of sulfur deposits have implications for structural controls on the degassing system. Combining the efficiency of PCA with the high resolution of UAS derived data, this methodology has a high potential to be employed in the spatio-temporal monitoring of volcanic hydrothermal systems and processes at surface.

Reactive chemistry in volcanic plumes – advances 2020

Nicole Bobrowski1,2, Jonas Kuhn1,2, Christopher Fuchs1, Alexander Nies1, Maja Rueth1, Xochilt Guiterrez3, Thorsten Hoffmann3, Ulrich Platt1,2

1Institute of Environmental Physics, Heidelberg University, Germany, 2Max Planck Institute for Chemistry, Mainz, Germany, 3Department of Chemistry, Johannes Gutenberg-University, Mainz, Germany

From the moment volcanic gases are exsolved from the magma and leave the volcanic interior to be emitted into the atmosphere, reactions with the gases in the atmosphere - especially oxidation processes – start immediately. The dynamics of mixing and the particular composition of the volcanic and atmospheric gas mixture leads to a

12 very special chemical evolution that is still poorly understood. However, this chemistry can have significant impact on the atmosphere and can be important for the interpretation of volcanic gas measurements in the context of volcanology. For instance, the conversion of the emitted hydrogen halides might also, in the case of bromine, influence atmospheric and volcanic mercury conversion and its deposition or, in the case of chlorine, affect the abundance of methane. Reactive halogen species catalyse O3 destruction, interfere with NOx-reactions and enhance the atmospheric OH/HO2 ratio. It is long known that halogen-sulfur ratios also depend on the volcanic activity. However, it is only with a deeper understanding of the chemistry that the gas ratio changes can be clearly attributed to either chemical transformation processes or a change in volcanic activity. In this presentation we will give an overview on the measurements carried out by the authors in 2020, introducing new measurements techniques and concepts applied and reporting on their progress as well as showing first results and putting them in the context of the above named motivation. At Nyamulagira and Nyiragongo, DR Congo, we measured right above active lava surfaces of both volcanoes in February 2020. In particular we used a novel high spectral resolution spectrograph, the design of which is based on a high finesse Fabry-Perot interferometer (FPI) aiming to determine the amount of OH in the volcano- atmospheric air mixture. The very compact and robust prototype used artificial light from UV-LEDs being reflected from a retro-reflector set up on the other side of the active lava surface. In October 2020 new imaging instruments also based on FPI technique were used to study transport and mixing processes as well as chemical transformation within the plume of Mt Etna. FPI-camera systems for SO2 and BrO were applied on the flanks of the volcano. In parallel, a mobile and compact chemiluminescence ozone monitor was tested at the summit area of Mt Etna. Right afterwards some studies employing a quarto-copter were undertaken at Vulcano Island to study bromine speciation at various fumarole emission points and further downwind using a denuder based sampling approach.

The WRF-Chem Volcano (WCV) model and its application for atmospheric halogen chemistry processes in a degassing plume

Surl, L [1,2]; Roberts, T [1]; Bekki, S [2] :: 1 = CNRS, Laboratoire de Physique et de Chimie de l’Environnement et de l’Espace, Université d’Orléans, Orléans, France; 2 = LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, Paris, France

Volcanoes emit halogens into the atmosphere that undergo chemical cycling in plumes and cause the destruction of ozone. The impacts of volcanic halogens are inherently difficult to measure at volcanoes, and the complexity of the chemistry, coupled with the mixing and dispersion of the plume, makes the system challenging to model numerically. We present a new numerical 3D model “WRF-Chem Volcano” (WCV), a version of WRF-Chem we have modified to incorporate volcanic emissions (including HBr and HCl) and multi-phase halogen chemistry. The model preprocessor allows the user to easily adjust the emissions of the volcano. We have applied this model for Mount Etna during a period where several measurements were made, which we use to evaluate the model's performance. Through use of nested grids we model at 1 km resolution close to the volcano nested grids close to the volcano. The model reproduces the so-called ‘bromine explosion’: the daytime bromine activation process by which HBr in the plume is converted to a continuously cycling set of other forms that includes ozone-destroying radicals. Quantitatively, the model shows good skill when compared to the observed ozone losses, and also yields quantities of \ce{BrO} --- a species of bromine often observed in volcanic plumes --- at a similar ratio to \ce{SO2} as was observed in this plume. We exploit the level of detail with which we can interrogate the model results and evaluate the bromine-cycling processes that cause these phenomena. We investigate the influence of variations in emissions, wind speed, and time of day in the magnitude of potentially measurable volcanic atmospheric impacts. We confirm the importance of high temperature near-vent products, notably bromine radicals, in initiating the ambient temperature plume halogen cycling. Model diagnostics show how volcanic halogen plume chemistry impacts HOx, NOx, methane, sulfur, and mercury chemistry. Halogens deplete HOx within the plume, which has the effect of increasing the lifetime of SO2 and hence slowing sulfate aerosol formation. They also promotes the conversion of NOx into HNO3. The model results

13 demonstrate that halogen chemistry has to be considered for a complete understanding of many chemical systems within volcanic plumes. We intend to show the utility of the WCV system to addressing the chemistry of volcanic plumes. We welcome feedback from the community on how it can be utilised and/or developed further.

The pre-LST Glees Diatrem, an enigmatic and unique structure, caused by powerful CO2- streaming? (Young diatremes at Glees)

C. Park1), H-U. Schmincke1), M. Sumita1) 1) GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel

At least 3 enigmatic tuff pipes (diatremes) – rare structures in the Eifel volcanic fields – were exposed during the past 10 years in a pumice/lava pit at the northern slope of Glees valley near the area of recent tectonic unrest and seismic events, remnants under study by us still visible in 2020. The largest diatreme is c. 20 m in diameter. Stratigraphy above the Devonian basement: lower pumiceous phonolite tephra (Wehr or Rieden), basanitic bedded fallout tephra, 4 m thick Veitskopf (?) lava flow and upper phonolitic pumiceous tephra (Glees). All lithologies are represented in the diatreme fill. An unusually high percentage of wood fragments (e.g. a tree trunk up to 30 cm in diameter and several meters long) intermixed within the diatreme fills (up to > 20 m below the pre-eruptive surface) indicate that: 1) the area was densely forested; 2) the diatremes erupted during an interglacial; 3) the exposed upper part of the diatreme fill consists either of fallback, or the upper part of the pipes was originally open, but was subsequently filled by the ejecta of a neighboring pipe erupting after a minor hiatus, 4. the prominent vertical alignment of lithoclasts within the diatreme fill (especially close to the diatreme walls) reflects late vertical gas-streaming. This and the massive blow-out of fine matrix leaving back extensive voids and open-framework lithoclast concentrations - especially below large basalt blocks that impeded free upward movement of the gas stream - indicate that major CO2-degassing persisted following the main paroxysmal eruptive event. The diatreme filling was superficially eroded and weathered indicating a break before it was overlain by a greenish tuff breccia up to 40 cm thick associated with numerous (mostly basanitic) blocks. This tuff was erupted either by a younger Glees tuff pipe or by a minor eruption in the northern Laacher See basin. Cementation of the green tuff breccia indicates a temporal hiatus to LSE. Numerous molds of larger roots within the green tuff breccia indicate that the area was densely vegetated, soil and vegetation becoming completely eroded by LSE. The LST sequence starts with a green fine-grained, non- cemented tuff layer and is overlain by large-scale primary crossbedding (MLST). Apparently, the Glees area was subject to young diatreme eruptions powered by major CO2-degassing - potentially during one of the late Weichselian interglacial (preceding the final interglacial during which LSE took place) when the evolving Laacher See magma reservoir already existed. The diatreme eruptions may thus be related to dynamic processes within the nascent LS reservoir. More detailed analyses are in progress.

ABSTRACTS - DAY I & II – PICOS

Sector collapse at Mount Thorbjorn, Iceland

Shevchenko, A.V. (GFZ, Institute of Volcanology and Seismology FEB RAS), Dvigalo, V.N. (Institute of

Volcanology and Seismology FEB RAS), Walter T.R. (GFZ) We performed an unoccupied aircraft systems (UAS) survey of Mount Thorbjorn for a better understanding of the structural evolvement of this volcano in SW Iceland. As a result of the UAS data processing, we obtained a 20 cm resolution DEM that allowed us to analyze its morphology in detail. We speculate about a collapse of the WNW flank of the volcano that appears to be controlled by intense faulting.

Ozone depletion in volcanic plumes? – Presentation of an interference-free measurement technique and assessment calculations

Maja Rüth(1), Ulrich Platt(1,2), Christopher Fuchs(1), Jonas Kuhn(1,2), Nicole Bobrowski(1,2), Stefan Schmitt(1,3)

1 Institute of Environmental Physics, Heidelberg University, Germany 2 Max Planck Institute for Chemistry, Mainz, Germany 3 Airyx GmbH, Eppelheim/Heidelberg, Germany

Volcanic plumes are known to contain reactive halogen species, especially bromine oxide. Therefore, halogen- catalysed ozone (O3) destruction should lead to local O3 depletion (OD) inside volcanic plumes. This OD has been measured in several field studies of volcanic plumes and is also found in several modelling studies. Recently, O3 mixing ratios in volcanic plumes have been mainly measured by ultraviolet (UV) absorption monitors, since these devices have become the standard technique for ambient O3 monitoring. However, these instruments show a large positive interference with sulphur dioxide (SO2) as they are only about 100 times more sensitive to O3 than to SO2. This poses a significant problem for volcanic plume measurements where SO2 mixing ratios can exceed O3 mixing ratios by factors of 1000 or more. Thus, laborious SO2 filtering introducing further problems, as e.g., humidity dependence, needed to be employed. This interference problem can be solved by using the ‘antiquated’ technique of chemiluminescence (CL) ozone monitors, which we recently showed in comprehensive laboratory experiments to be completely free of SO2 interferences. In this work, simultaneous O3 measurements were conducted with a compact and mobile (backpack-size, ~10kg) CL ozone monitor and a conventional UV absorption monitor inside a fumarole at the summit of Mt Etna volcano, Italy. In parallel, SO2 and CO2 measurements were carried out with a MultiGAS- instrument. In this first field study, we observed no significant interference with the high volcanic SO2 concentrations for the CL monitor. Under field conditions the CL monitor’s detection limit was determined to be ~1 ppb (1σ) at an integration time of 1 second. This is sufficient to resolve expected O3 losses inside volcanic plumes containing larger amounts of reactive halogens, which were not accessible within this field study. Additionally, a rough calculation to estimate the expected OD in volcanic plumes was made. Contrary to popular belief, our calculations suggest that for typical bromine oxide concentrations no significant (i.e., <1%) reactive halogen catalysed O3-loss should be expected in young (i.e. < 10km downwind) volcanic plumes.

Transient Electromagnetic Measurements at Stromboli volcano, Italy: synthetic and field data

Schneider, C., Spitzer, K., Hort, M. (TU Bergakademie Freiberg, TU Bergakademie Freiberg, Universität Hamburg)

The transient electromagnetic method (TEM) is capable of imaging conductive structures. In investigating volcanic systems its targets are, e.g., hydrothermal systems and magmatic pathways. Using TEM, we aim to investigate the medium depth resistivity structure of Stromboli volcano, Italy. Therefore, we conduct so-called virtual experiments, i.e., three-dimensional simulations on a digital elevation model, and evaluate data recorded during our field measurement at Stromboli volcano, Italy, in June 2019.

A global perspective on Bromine monoxide composition in volcanic plumes derived from S5- P/TROPOMI

S. Warnach, H. Sihler, C. Borger, N. Bobrowski, S. Schmitt, M. Schöne, S. Beirle, U. Platt, and T. Wagner (Max- Planck-Institut für Chemie, Institut für Umweltphysik Universität Heidelberg)

Bromine monoxide (BrO) is a halogen radical capable of influencing atmospheric chemical processes, in particular the abundance of ozone, e. g. in the troposphere of polar regions, the stratosphere as well as in volcanic plumes. Furthermore, the molar bromine to sulphur ratio in volcanic gas emissions is a proxy for the magmatic composition of a volcano and potentially an eruption forecast parameter. The high spatial resolution of the S5-P/TROPOMI instrument (up to 3.5x5.5km²) and its daily global coverage offer the potential to detect BrO even during minor eruptions and also to determine BrO/SO2 ratios during continuous passive degassing. Here, we present a global overview of BrO/SO2 molar ratios in volcanic plumes derived from a systematic long- term investigation of three years of TROPOMI data. We retrieved column densities of BrO and SO2 using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrO/SO2 molar ratios for each volcano. As expected, the calculated BrO/SO2 molar ratios differ strongly between different volcanoes ranging from several 10-5 up to several 10-4. In our study of three years of S5P/TROPOMI data we successfully recorded elevated BrO column densities for more than 100 volcanic events and were able to derive meaningful (coefficient of determination, R² exceeding 0.5) BrO/SO2 ratios for multiple volcanoes.

Electrical self-potential anomalies from strain-induced groundwater flow in volcanic aquifers

Arens, F. (University of Bristol, UK), Gottsmann, J. (University of Bristol, UK), Strehlow, K. (GEOMAR, Germany), Hickey, J. (University of Exeter, UK), Kilgour, G. (GNS Science, New Zealand)

Pre-eruptive electrical signals at active volcanoes are generally interpreted in terms of electrokinetic processes in the subsurface. Spatio-temporal self-potential (SP) signals can be caused by strain-induced fluid flow in volcanic aquifers, however, previous studies lack the quantitative assessments of these phenomena and the underpinning poroelastic responses. Here, we use Finite-Element Analysis to study poroelastic responses and emerging SP signals induced by subsurface stressing from sill and dike sources by jointly solving for resultant ground displacements, aquifer pressure changes and SP signals. We evaluate the influence of pressure source orientation on the SP response in two different volcanic aquifers (pyroclastic and lava flow) and provide insights on the sensitivity of SP signals to governing model parameters. Strain-induced SP amplitudes deduced from a reference parameter set vary in both aquifer models and are of negative polarity (-0.35 mV and -22.6 mV) for a pressurized dike and of positive polarity (+4 mV and +20 mV) for a pressurized sill. Overall, we find that SP amplitudes are most sensitive to elastic and electrical properties of the subsurface and source orientation with uniquely different SP and ground displacement patterns from either sill or dike intrusions. We observe SP amplitudes of up to -947 mV in the parametric study for a dike-generated poroelastic response, indicating that predicted SP signals are broadly representative of records from volcanic areas (mV to few V). Our study demonstrates that electrokinetic processes can reflect subsurface straining and highlights the potential of joint geodetic and SP studies for volcano monitoring to gain new insights on the causes of volcanic unrest.

Update on seismic monitoring in the East Eifel

Hensch, M. (Landeserdbebendienst Baden-Württemberg), Schmidt, B. (Landeserdbebendienst Rheinland-Pfalz)

The local seismic monitoring network in the East Eifel has been significantly improved in recent years, especially since the first detection of recurring deep low-frequency (DLF) earthquakes and subsequent shallow microearthquake swarms around Laacher See volcano.

This short presentation will give an overview on recent seismic activity and improvements of the permanent seismic network in the region, as well as a quick outlook on future plans and possibilities for seismic monitoring.

Modelling magma pathways and magma storage scenarios in the Eifel volcanic area

Armeni, V., Silverii, F., Mantiloni, L., Rivalta, E. (Deutsche GeoForschungsZentrum GFZ, Deutsche GeoForschungsZentrum GFZ, Deutsche GeoForschungsZentrum GFZ, Deutsche GeoForschungsZentrum GFZ & Alma Mater Studiorum-Università di Bologna)

The Eifel Volcanic Field (EVF) is an area of distributed volcanism located in the western central Rhenish Shield between the Upper and Lower Rhine Graben. Volcanic activity began in the Tertiary both within and outside the graben and, since then, eruptions have clustered in the West and East Eifel, displaying spatial-temporal migration and orientation changes in the volcanism. The last known eruptions are the Laacher See ( ̴12,800 yr) and the Ulmener Maar ( ̴10,900 yr), and, in light of the recent geophysical and geodetic evidence, volcanic activity cannot be considered over yet. Recently, a coherent prolonged uplift anomaly reaching a maximum of ~1 mm/yr has been observed over a large area around the EVF, coupled with extensional strain, as highlighted by Kreemer et al. (2020). Moreover, reprocessing of data collected during previous seismic surveys (Dahm et al., 2020) has shown evidence for a low- velocity layer at 30–36 km depth underlying the EVF Quaternary volcanic fields, compatible with the presence of partial melt. It is desirable to understand the geometry of both the source of such uplift and of the magma pathways linking any magma storage zone to the Earth’s surface. Here we test the hypotheses that the current uplift is due to magma injection in a lower crustal sill or zone of partial melt, and that magma pathways have been controlled throughout the tectonic history of the area by evolving crustal stresses. To test these two hypotheses, we first perform numerical Boundary Element models (BEs) to simulate magma pathways controlled by tectonic stress and gravitational loading evolve over time, and compare it to the observed vent locations. Then, we test two end-members source models on surface deformation data reprocessed by Kreemer et al. (2020): a pressurized sill embedded in an elastic medium and a permeable rock layer deformed by the injection of hot and pressurized magmatic fluids, in the form of disk-shaped Thermo-Poro-Elastic (TPE) inclusions (Mantiloni et al., 2020). Preliminary results show, on one side, that the interplay between tensile tectonic and gravitational stresses can effectively lead to focusing of volcanism inside or outside the graben, consistent with migration patterns of vent distribution. On the other side, the observed uplift pattern with higher values in correspondence of the Quaternary volcanic field can be reproduced by a sill with spatially distributed opening or a distribution of TPEs with different intensities. Higher values of opening/TPE intensity correspond to the region where most of recent seismicity occurred.

Inferring a shallow degassing model for Villarrica Volcano from seismic explosion signals

Lehr, J. (Kiel University), Stefan Bredemeyer (GFZ), Wolfgang Rabbel (Kiel University)

Villarrica is a basaltic volcano with an active lava lake in South Central Chile. The lava lake displays a variety of degassing styles from gentle seething to more violent Strombolian explosions. This activity is accompanied by sequences of transient seismic waveforms suggesting the presence of discrete gas bubbles in the upper magma column. Gas bubbles flow through liquid-filled pipes according to distinct patterns depending on viscosity of the liquid and volumetric gas flow rate. Laboratory experiments indicate that these regimes are characterized by distinct frequency distributions of bubble sizes and spacings. By assuming that these parameters are reflected by the magnitude of the transients and the time between them, we compared their statistical distributions to infer a flow regime for the shallow conduit of Villarrica. The approximately log-normal distributions indicate a sustained slug flow regime in which the gas ascends in trains of conduit-wide gas slugs.

Volcanic deformation at Sakurajima between 2019 and 2020 revealed by Sentinel-1 InSAR time series

Vásquez Castillo, A., Hort, M. (University of Hamburg)

Surface displacements recorded in volcanically active regions are often driven by magmatic, hydrothermal or tectonic processes. Measuring the deformation experienced by the ground as a result of these processes allows to constrain the changing volcanic conditions and to infer quantitative estimates of the subsurface magmatic storage, thus increasing the knowledge of volcanic hazards for the closest local population. Interferometric synthetic aperture radar (InSAR) has proven to be an useful tool to observe ground deformation in volcanically active areas like the Sakurajima volcano, southern Japan, one of the most active volcanoes worldwide. Its current activity is characterized by degassing and almost daily explosive eruptions. We performed an InSAR time series analysis to identify and characterize time-dependent ground deformation using Sentinel-1 data between 2019 and 2020. During this period several large explosions with plume heights of up to 5 km occurred. We found evidence of ground deformation associated with precursory inflation connected to major explosions.

An open source Julia package to simulate the thermal evolution of magmatic systems

Kaus, B. (Johannes Gutenberg University Mainz)

Much of our understanding of the development and evolution of magmatic systems comes from thermal models in which dikes or sills are periodically intruded into the crust and the subsequent thermal evolution and melt content is tracked. Here, I present an open source package with which such experiments can be done in 2D, 2D axisymmetric and 3D geometries, using very short scripts (~100 lines). The package takes thermal diffusion, variable thermal properties and the effects of latent heat into account. Dike/sill intrusion is modelled with analytical solutions for penny- shaped fluid-filled cracks in elastic host rocks, while phase diagrams or parameterised melting models are used to compute the melt fraction of the system. Tracers are inserted into the dikes to track the thermal evolution and deformation of the intruded magmas, which allows predicting zircon age distributions. The package, MagmaThermoKinematics.jl is available on GitHub and fully written in Julia, a relative new and very efficient computer language, which merges the benefits of MATLAB (short and readable codes) with the speed of more traditional languages like C/Fortran, while being fully parallel. It comes with a build-in testing framework that compares the various routines with available analytical solutions, such as diffusion and advection. All this allows doing 2D simulations at very large resolutions on a laptop or 3D simulations on normal sized work stations. Examples are provided to show how to use it. As it is a fully open and extendable code, it is easy to adapt the scripts to your own field area. Moreover, MagmaThermoKinematics can be readily incorporated into other codes, for example to compute geophysical observables such as gravity anomalies from the models, or to simulate wave propagation through the system.

ABSTRACTS - DAY II – BLOCK I

Voice of Volcanoes: generating seismic signals from both volcano dynamics and geological and geomorphological records

L. De Siena

Volcanoes speak with many voices - seismic signals that continuously shake their surface. Magma breaks the underlying crust, hazardous fluids flow through volcanic arteries, while the natural environment and humans either enhance or dampen deep signals of volcanic unrest. Our certainties when modelling seismic signals produced and crossing a volcano are few and sparse. Even when interpreting or inverting seismic with alternative geophysical signals, we set this interpretation into the present. Including the deep geological and shallow geomorphological record of a volcano to link today's voices with those of tomorrow is an unexplored path. Can we produce seismic signals from any hypothesis of how a magmatic source acts or volcanic structures look? Even if this hypothesis is based only on fracture observations at the surface or morphologies reconstructed by satellites? And can we model how these signals will evolve with the volcano?

Here, I will discuss recent computational advances that allow to tackle propagation of seismic waves in volcanic media effectively, starting from geological hypotheses and interpretations of volcano dynamics. The availability of these signals is one of the stepping stones necessary to produce Synthetic Volcanoes, where we aim at creating geophysical and geochemical signals which increasingly represent reality.

How to use pattern recognition in volcano monitoring – on the example of Mt Etna

Eckel, F., Langer, H., Sciotto, M. (Christian-Albrechts-Universität zu Kiel - Institut für Geowissenschaften, Istituto Nazionale di Geofisica e Vulcanologia - Osservatorio Etneo)

Active volcanoes in populated areas like Mount Etna on Sicily require constant monitoring. In this process huge amounts of data are acquired that most often need expert knowledge for interpretation. Infrasound recording for example play a vital role in volcano monitoring and can be used to identify (upcoming) volcanic activity. But these data streams are also influenced by noise sources. To the untrained human eye the patterns can look similar although they share no common source mechanism. Pattern recognition techniques can help to classify signals into regimes. Infrasound signals can for example be classified into regimes describing volcanic activity (like degassing processes or Strombolian activity) or noise dominated periods (that is mainly induced by wind). Unsupervised training methods like Self-Organizing maps (SOMs) exploit so-called “features” derived from the raw data streams to identify similar patterns. SOMs can detect patterns with common source mechanisms and provide a very intuitive color coding of the results that makes it easy also for non-experts to assign meaningful source mechanisms to the signals in the infrasound waveform.

Bubble Trap of Strokkur Geyser Feeds its Eruptions

Eibl, E. P. S., Müller, D., Walter, T. R., Allahbakhshi, M., Jousset, P., Hersir, G. P., Dahm, T. (University of Potsdam, GFZ, GFZ, GFZ, GFZ, ISOR, GFZ)

Strokkur geyser in Iceland erupts in single to sextuple eruptions. In a multidisciplinary study using seismometers, a tiltmeter, video cameras and pressure sensors we studied the typical eruptive cycle. We find 4 phases in which the geyser erupts, the conduit fills with water, the bubble trap fills with gas and bubble explosions at depth heat the water in the conduit. We located the bubble trap offset to the vent at a depth of 23.7+-4.4m depth generating single to sextuple eruptions.

Identification and interpretation of seismic short-duration events inside the Kolumbo submarine volcano in the Southern Aegean

Schmid, F., Karstens J. (GEOMAR - Helmholtz Zentrum für Ozeanforschung Kiel, Deutschland), Nomikou, P. (National and Kapodistrian University of Athens, Greece)

Kolumbo represents one of the most hazardous, currently active, volcanoes in the eastern Mediterranean. Its last eruption in 1650 AD was associated with a vast explosion, causing a tsunami of regionally devastating impact. The eruption was also associated with the voluminous and rapid release of toxic gases asphyxiating humans and animals on the nearby Islands. Earthquake records from the recent decades document on-going unrest beneath the volcano. Remotely operated vehicle dives revealed several hydrothermal vent sites and bacterial mats at the crater floor, which are concentrated near the northern crater wall. The vents emit mainly CO2, leading to the accumulation of acidic waters in the crater. Accordingly, one of the main volcanic hazards associated with Kolumbo is that rapid overturning of waters in the crater may release harmful amounts of toxic gases. Monitoring the hydrothermal processes inside the Kolumbo crater will provide an important contribution to the understanding and evaluation of this and other volcanic hazards. In October 2019, we deployed an ocean bottom seismometer and hydrophone (OBS/H) inside the Kolumbo crater. During the four days of passive recording we identified about 100 so-called short duration seismic events, which were only present on the seismometer channels, but absent on the hydrophone channels. The events have durations of less than one second with dominant frequencies between 5 to 30 Hz. Most of the events represent well-polarized seismic phases, which enables us to determine their azimuth angle (with a 180-degree bias) and angle of incidence at the OBS/H. We cross-correlated all polarized seismic waveforms and subsequently used the cross-correlation coefficients for a hierarchical cluster analysis to elaborate whether the events have a random origin or stem from a common origin. Our analysis revealed that the majority of events is associated with two clusters. The azimuth angles of all events in the largest cluster coincide with the azimuth angle between the station and the field of hydrothermal vents and bacterial mats inside the crater. This coincidence suggests that the origin of the short duration events is associated with the sub-seafloor migration of fluids or the fluid discharge process at the crater floor. In fact, short-duration events of similar characteristics, recorded by OBS/H, were previously attributed to sub-seafloor fluid migration and the discharge of fluids at the seafloor. Our analyses indicate that seismic monitoring of submarine volcanoes should include the detection and analysis of short duration events, which may act as a novel tool in the characterization of volcanic unrests and volcanogenic geohazard monitoring.

Average fast spread oceanic crustal composition and insights into its plumbing system

Deasy, R., Meyer, R., Wintsch, W. (U.S. Geological Survey & Indiana University, Geological Survey of Luxembourg, Indiana University & Wesleyan University)

Oceanic crust formed at fast-spreading mid-ocean ridges (MOR) is composed predominantly of plutonic rocks, but are inherently difficult to sample. Petrological and geochemical studies of these rocks offer the opportunity to study ongoing processes within the plumbing system of fast spreading MOR, the most active volcanoes on Earth. Cores recovered by IODP Expedition 345 (Hess Deep Rift) include lower crustal cumulates from the East Pacific Rise (EPR) — the first-ever drilled layered gabbroic MOR section — and primitive basalts from the Cocos- Nazca Rift (CNR). However, the collection of representative bulk samples from drill cores are historically difficult to obtain representative geochemical studies due to the heterogeneous distribution of the rocks and the mineral/chemical compositions therein, in addition to biases in the selection of core samples for analysis. We have developed a new “in situ” sampling strategy that avoids these difficulties and facilitates measurement of representative chemical and mineralogical compositions. As a result, this study presents first “in-situ” major and trace element compositions of the lower oceanic crust and a calculated average bulk composition of fast- spreading oceanic crust, produced at the equatorial EPR. The REE geochemistry of the lower crustal rocks, with high Eu/Eu* anomalies (1.37-5.22) and strong correlations among major elements, indicate that the petrogenesis is controlled by accumulation and segregation of plagioclase and olivine. However, constant Mg-numbers (82.22 ±0.66) through a ~50 m interval suggest that this cumulus rock sequence was host to percolating, replenishing melt(s). Modeling suggests the investigated cumulate lithologies to be in equilibrium with melts having Mg-

20 numbers of 58-61, which overlaps with the mean value (57.7 ±6.2) for EPR MORB lavas, and suggests (1) that melt-buffering in a permeable crystal mush is a common and important process in controlling MORB compositions at fast-spreading MOR, and; (2) that the drilled and sampled lithologies are representative of the EPR lower crust. Geochemical analysis of these primitive lower crustal plutonic rocks — in combination with published geochemical data for shallow-level plutonic rocks, sheeted dykes and lavas — provides the best constrained estimate of the bulk composition of fast-spreading oceanic crust currently available [1]. This modelled average oceanic crust is fascinatingly similar to the composition of the sampled primitive CNR basalts, which have nearly identical modeled fractional crystallization histories.

[1] Deasy, R., Wintsch., R., Meyer, R., Bulk composition of fast-spreading oceanic crust: insights from the lower cumulates of the East Pacific Rise and from Cocos-Nazca Rift basalts, Hess Deep (in press.), Journal of Petrology x, x-x.

ABSTRACTS - DAY II – BLOCK II

A multi-criterial approach to predict future volcanic eruptions in Germany

Bartels, A., Rummel, L. (BGR), May, F. (BGR)

When looking for a repository for highly radioactive waste in Germany, areas in which quaternary volcanism occurred or future volcanic activity is expected within the next 1 Ma must be excluded. To forecast possible eruptions, several indicators can be used that provide information about past and potentially recent or future processes connected to magmatic activities. The information can be taken from quaternary or tertiary volcanic fields as well as from processes of different time and length scales to better understand the crustal and lithospheric configurations and their properties that may control the final ascent of magma. Here, we would like to present and discuss our research project “Magmatism” that was initiated by the BGR (Federal Institute for Geosciences and Natural Resources) to develop an applicable method that will allow to estimate the probability of future volcanic eruptions in Germany. We use a multi-criterial approach including a variety of indicators from seismic observations, over mantle fluids and petrological aspects to plate reconstructions and geodynamic simulations. In total 30 indicators were defined which can be quantified by multiple parameters. Each of them may describe an individual process. However, depending on the chosen parameter, dynamic or static conditions are described with different accuracy and resolution, and the deduced processes behind may vary significantly. Thereby, the chosen threshold value for a parameter defines the spatial dimension of possible areas with a higher potential for future volcanic activity. Further challenges are due to uncertainties and the lack of data that may exist in some regions of Germany as well as the central question of how to combine different parameters and how to weight each individual one regarding its importance for the forecast of future volcanic activity.

SO2 Cloud over Bavaria, Germany

VC, Vereinigung Cockpit (German Airline Pilots’ Association)

The e-mail notifications from SACS ( https://sacs.aeronomie.be/ ) indicated the presence of an SO2 cloud over Germany. The presentation shows the origin and route of the cloud, and details circumstances of a probable sighting.

Experimental constraints on the phase stability of sulfur-bearing sodalites in a wet Foidite of the East Eifel volcanic field

Berckhan, J., Helo, C. (Johannes Gutenberg University Mainz)

The behaviour of sulfur in volcanic systems is assumed to depend on temperature, pressure, fO2 and chemical composition. It can be incorporated into sulfur-bearing foides in alkaline, silica-poor magmas, most commonly into the sodalite-group minerals nosean (Na8[Al6Si6O24]SO4·H2O) and hauyne (Na6Ca2[Al6Si6O24]SO4). These minerals contain up to 9.4 wt.-% SO3.This study gives first insights into the phase stability field through high temperature experiments in a cold seal pressure vessel with natural samples of the quaternary foiditic, hauyne- bearing Perler Kopf lava. The samples are foiditic with low SiO2 (47 wt.-%) and high Na2O + K2O (7.3 and 5.8 wt.- %) contents. SO3 contents are up to 0.84 wt.-%. 7 experiments were done with fO2 = NNO, under water-saturated conditions with 7 wt.-% H2O. Temperatures of 850, 1000, 1050 and 1100 °C were conducted at 1kbar, 1050 and 1100 °C at 0.5 kbar. Sodalite group minerals are stable at high temperatures (1000-1050 °C) at any pressure. The results suggest the phase being sensitive to temperature and insensitive to pressure under water-saturated conditions at high oxygen fugacity. These experiments lay a promising foundation for following studies contributing to the knowledge of the stability field of sulfur-bearing minerals in foiditic volcanic systems.

Monitoring a Magmatic Channel in the East Eifel Volcanic Field

Joachim Ritter (1), Mohsen Koushesh (1), Bernd Schmidt (2), Andreas Rietbrock (1) (1) Karlsruhe Institute of Technology (KIT), Geophysical Institute, Karlsruhe, Germany ([email protected]) (2) Geological Survey of Rhineland-Palatinate (LGB-RLP), Mainz, Germany

The East Eifel Volcanic Field, in western Germany, is an active magmatic region where monitoring is important for hazard assessment and scientific analyses. Following two unusual deep low-frequency (DLF) micro-earthquakes in September 2013 (about 40 km depth) recorded at about 10 seismic stations, we installed an improved seismic network DEEP-TEE (Ritter et al., EGU2019-13615) to significantly improve the earthquake detection and location capabilities in the region. A first analysis by Hensch et al. (Geophys. J. Int., 2019) revealed that DLF events occur just southeast of the Laacher See Volcano with a maximum magnitude ML of ~1.8. The events are located inside a steeply dipping channel which reaches about 40 km depth. During the last years, we continuously updated the DEEP-TEE seismic network which currently consists of 11 permanent (earthquake services) and 15 semi-permanent (KIT-GPI) broadband and short-period stations. The dense station network and a new detector algorithm allow us to identify DLF events and other seismic signals to better describe the seismic activity in the region. The results confirm the magmatic channel hypothesis and help to delineate its geometry.

We thank the GFZ-GIPP (2014-2016) and the KIT-KABBA (2014-) for providing instruments and the state earthquake surveys (LGB-RLP and GD-NRW) for recordings. Part of the data is stored at GFZ (Ritter et al., 2014, doi:10.14470/6C709520).

The CO2-generated Pulvermaar diatreme and the probability of future volcanic activities in the very young SE-WEVF field

Schmincke, H-U1), Sumita, M1), Hansteen, T1), Chakraborty, S2) 1) GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel 2) Institut für Geologie, Mineralogie und Geophysik, Ruhr Universität Bochum

We postulate that the ca. 20 ka old CO2-rich melilite nephelinitic Pulvermaar (PM) magma intersected and fractured an incompletely crystallized mafic alkalic intrusive body stagnated at the boundary lower-upper crust. The depth is inferred from pressures from CO2-dominated fluid inclusions in cpx and the presence of lower crustal mm xenoliths. Cm-dm-sized nodules (3-35 cm, up to 8 kg) of the cumulates (amph, phl, cpx, ol) became efficiently rounded in a powerful fluidized CO2-rich system propelled to the surface. The xenolith cargo - including the mm country rocks - became coated en route with one or more mm-layers of the new melilite nephelinite magma. The smaller sized (< 3 cm) subspherical pellets (lacking cumulate cores) making up as much as 70 vol.% of the deposits in 15m high PM tephra pit may have formed late as some contain Devonian fragments. The nodule-pellet cargo of the CO2-fluidized systems was probably modified by near-surface phreatomagmatic explosive processes. The highly evolved composition of interstitial glass in many cumulate nodules provides an example of generation of evolved melts in the upper lower crust. The magmas of the ca. 5 overlapping melilite nephelinite maars of the PM cluster in the SE-WEVF and the more evolved nephelinitic Ulmen Maar (ca. 11 ka) to the E appear to have been derived from an enriched lithosphere mantle source. In contrast, the large basanitic Wartgesberg eruptive system (ca. 30 ka) just 2 km south of the Pulvermaar-Römerberg center and the more distant Bad Bertrich volcano groups suggest derivation from an asthenospheric mantle source. The age difference of 5-10 ky between the 5 young major eruptive sites in the SE subfield indicates a high probability for future eruptions in this area.

Textural and chemical analysis of obsidian-bearing trachytic bombs at Kilian Volcano, Chaîne des Puys, France

Mathieu Colombier (Ludwig Maximilian University, Munich), Francisco Cáceres (Ludwig Maximilian University, Munich), Didier Miallier (Université Clermont Auvergne, CNRS–IN2P3, LPC, F-63000 Clermont-Ferrand, France), Kai-Uwe Hess (Ludwig Maximilian University, Munich), Donald B. Dingwell (Ludwig Maximilian University, Munich)

Proximal deposits at Kilian Volcano revealed the presence of obsidian-bearing trachytic bombs that bear no similarity with samples of Vulcanian-Subplinian activity previously known for this volcano. Here, we study the textural and chemical properties of these bombs via scanning electron microprobe, electron microprobe ananlysis and Raman spectroscopy in order to unravel the eruptive style that caused the formation of this deposit. We combine this approach to vesiculation experiments and thermal analysis on the obsidian fragments to provide estimates of the glass transition temperature, magmatic water content and vesiculation kinetics. Finally, we compare these obsidian-bearing bombs to trachytes from the 9.4 ka Vulcanian-Subplinian eruption at Kilian Volcano.