Ilyinskaya, Evgenia

Recent Icelandic rifting events have illuminated the roles of centralized crustal magma reservoirs and lateral magma transport1-4, important characteristics of mid-ocean ridge magmatism1,5. A consequence of such shallow crustal processing of magmas4,5 is the overprinting of signatures that trace the origin, evolution and transport of melts in the uppermost mantle and lowermost crust6,7. Here we present unique insights into processes occurring in this zone from integrated petrologic and geochemical studies of the 2021 Fagradalsfjall eruption on the Reykjanes Peninsula in Iceland. Geochemical analyses of basalts erupted during the first 50 days of the eruption, combined with associated gas emissions, reveal direct sourcing from a near-Moho magma storage zone. Geochemical proxies, which signify different mantle compositions and melting conditions, changed at a rate unparalleled for individual basaltic eruptions globally. Initially, the erupted lava was dominated by melts sourced from the shallowest mantle but over the following three weeks became increasingly dominated by magmas generated at a greater depth. This exceptionally rapid trend in erupted compositions provides an unprecedented temporal record of magma mixing that filters the mantle signal, consistent with processing in near-Moho melt lenses containing 107-108 m3 of basaltic magma. Exposing previously inaccessible parts of this key magma processing zone to near-real-time investigations provides new insights into the timescales and operational mode of basaltic magma systems.

One of the aims of EUROVOLC is to raise awareness and share data by exploiting existing tools for hazard and risk. Here we present the ongoing effort within EUROVOLC WP12 to create an online tool to collect information from people witnessing volcanic events at European or other volcanoes. In the recent past, building on the experience from earthquakes, and from the trans-national effects of Eyjafallajökull eruption, European research groups have built tools (e.g. questionnaires or apps) for facilitating the collection of data by citizens. These efforts are presently fragmented and sparse across Europe (and across the world). As the first step we have conducted a reconnaissance survey of existing citizen science tools in volcanology (from operational and research projects), available for download through EUROVOLC website One of the aims of EUROVOLC is to raise awareness and share data by exploiting existing tools for hazard and risk. Here we present the ongoing effort within EUROVOLC WP12 to create an online tool to collect information from people witnessing volcanic events at European or other volcanoes. In the recent past, building on the experience from earthquakes, and from the trans-national effects of Eyjafallajökull eruption, European research groups have built tools (e.g. questionnaires or apps) for facilitating the collection of data by citizens. These efforts are presently fragmented and sparse across Europe (and across the world). As the first step we have conducted a reconnaissance survey of existing citizen science tools in volcanology (from operational and research projects), available for download through EUROVOLC website. The new EUROVOLC tool will: - access and collate data collected by several pre-existing tools. These tools currently include ‘myVolcano’ by British Geological Survey; sulphur dioxide and ash recording tools by Iceland Met Office; Osservatorio Vesuviano web questionnaire & Tefranet by INGV-Catania. These tools were selected based on whether their data can be ‘pulled’ in real-time; - allow additional tools to be incorporated as they become available; - allow recording of new data by the users; - allow visualizing on a map the data in which the users are interested in, that can be selected by region/country, by recording time, or by observed phenomenon; - allow downloading the data in which the users are interested in In this way, the users of EUROVOLC tool will have access to observations collected by the multiple tools available across EUROPE through a single access point. The EUROVOLC tool will become available in July 2020.

The 2014–2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO2, with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios of SO2/HCl = 30–110 and SO2/HF = 30–130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3–5.5 km agl were measured with ground- and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting

Hekla is a frequently active volcano with an infamously short pre-eruptive warning period. Our project contributes to the ongoing work on improving Hekla’s monitoring and early warning systems. In 2012 we began monitoring gas release at Hekla. The dataset comprises semi-permanent near-real time measurements with a MultiGAS system, quantification of diffuse gas flux, and direct samples analysed for composition and isotopes (δ13C, δD and δ18O). In addition, we used reaction path modelling to derive information on the origin and reaction pathways of the gas emissions. Hekla’s quiescent gas composition was CO2-dominated (0.8 mol fraction) and the δ13C signature was consistent with published values for Icelandic magmas. The gas is poor in H2O and S compared to hydrothermal manifestations and syn-eruptive emissions from other active volcanic systems in Iceland. The total CO2 flux from Hekla central volcano (diffuse soil emissions) is at least 44 T d−1, thereof 14 T d−1 are sourced from a small area at the volcano’s summit. There was no detectable gas flux at other craters, even though some of them had higher ground temperatures and had erupted more recently. Our measurements are consistent with a magma reservoir at depth coupled with a shallow dike beneath the summit. In the current quiescent state, the composition of the exsolved gas is substantially modified along its pathway to the surface through cooling and interaction with wall-rock and groundwater. The modification involves both significant H2O condensation and scrubbing of S-bearing species, leading to a CO2-dominated gas emitted at the summit. We conclude that a compositional shift towards more S- and H2O-rich gas compositions if measured in the future by the permanent MultiGAS station should be viewed as sign of imminent volcanic unrest on Hekla.

Quantifying the CO2 flux sustained by lowtemperature fumarolic fields in hydrothermal/volcanic environments has remained a challenge, to date. Here, we explored the potential of a commercial infrared tunable laser unit for quantifying such fumarolic volcanic/hydrothermal CO2 fluxes. Our field tests were conducted between April 2013 and March 2014 at Nea Kameni (Santorini, Greece), Hekla and Krýsuvík (Iceland) and Vulcano (Aeolian Islands, Italy). At these sites, the tunable laser was used to measure the path-integrated CO2 mixing ratios along cross sections of the fumaroles’ atmospheric plumes. By using a tomographic post-processing routine, we then obtained, for each manifestation, the contour maps of CO2 mixing ratios in the plumes and, from their integration, the CO2 fluxes. The calculated CO2 fluxes range from low (5.7 +/- 0.9 t d-1; Krýsuvík) to moderate (524 +/-108 t d-1; La Fossa crater, Vulcano). Overall, we suggest that the cumulative CO2 contribution from weakly degassing volcanoes in the hydrothermal stage of activity may be significant at the global scale.

Volcanic plume samples taken in 2008 and 2009 from the Halemàumàu eruption at Kīlauea provide new insights into Kīlauea's degassing behaviour. The Cl, F and S gas systematics are consistent with syn-eruptive East Rift Zone measurements suggesting that the new Halemàumàu activity is fed by a convecting magma reservoir shallower than the main summit storage area. Comparison with degassing models suggests that plume halogen and S composition is controlled by very shallow (<3m depth) decompression degassing and progressive loss of volatiles at the surface. Compared to most other global volcanoes, Kīlauea's gases are depleted in Cl with respect to S. Similarly, our Br/S and I/S ratio measurements in Halemàumàu's plume are lower than those measured at arc volcanoes, consistent with contributions from the subducting slab accounting for a significant proportion of the heavier halogens in arc emissions. Analyses of Hg in Halemàumàu's plume were inconclusive but suggest a flux of at least 0.6kgday -1 from this new vent, predominantly (>77%) as gaseous elemental mercury at the point of emission. Sulphate is an important aerosol component (modal particle diameter ∼0.44μm). Aerosol halide ion concentrations are low compared to other systems, consistent with the lower proportion of gaseous hydrogen halides. Plume concentrations of many metallic elements (Rb, Cs, Be, B, Cr, Ni, Cu, Mo, Cd, W, Re, Ge, As, In, Sn, Sb, Te, Tl, Pb, Mg, Sr, Sc, Ti, V, Mn, Fe, Co, Y, Zr, Hf, Ta, Al, P, Ga, Th, U, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm) are elevated above background air. There is considerable variability in metal to SO 2 ratios but our ratios (generally at the lower end of the range previously measured at Kīlauea) support assertions that Kīlauea's emissions are metal-poor compared to other volcanic settings. Our aerosol Re and Cd measurements are complementary to degassing trends observed in Hawaiian rock suites although measured aerosol metal/S ratios are about an order of magnitude lower than those calculated from degassing trends determined from glass chemistry. Plume enrichment factors with respect to Hawaiian lavas are in broad agreement with those from previous studies allowing similar element classification schemes to be followed (i.e., lithophile elements having lower volatility and chalcophile elements having higher volatility). The proportion of metal associated with the largest particle size mode collected (>2.5μm) and that bound to silicate is significantly higher for lithophiles than chalcophiles. Many metals show higher solubility in pH 7 buffer solution than deionised water suggesting that acidity is not the sole driver in terms of solubility. Nonetheless, many metals are largely water soluble when compared with the other sequential leachates suggesting that they are delivered to the environment in a bioavailable form. Preliminary analyses of environmental samples show that concentrations of metals are elevated in rainwater affected by the volcanic plume and even more so in fog. However, metal levels in grass samples showed no clear enrichment downwind of the active vents. © 2011 Elsevier Ltd.

We report results from a multidisciplinary campaign carried out at Poás crater-lake (Costa Rica) on 17-18 March 2009. Thermal imagery of fumaroles on the north side of the dome and the lake surface revealed mean apparent temperatures of 25-40°C (maximum of 80°C), and 30-35°C (maximum of 48°C), respectively. Mean radiative heat output of the lake, uncorrected for downwelling flux, was estimated as ~230 MW. The mean SO2 flux emitted by the crater measured by walking-traverses was 76 tonnes day-1, with approximately equal contributions from both the dome and the lake and fumarole plumes. Gas measurements by active open-path FTIR spectroscopy indicated molar ratios of H2O/SO2 = 151 and CO2/SO2 = 1.56. HCl and HF were not detected in measured spectra but based on the detection limits of these species, we calculate SO2/HCl > 40, and SO2/HF > 200. Particles were sampled from the plume by air filtration. The filters were analysed using ion chromatography, which revealed an abundance of K+ and SO42-, with smaller amounts of Ca2+, Mg2+ and Cl-. We discuss here the implications of the results for degassing pathways through the shallow magmatic-hydrothermal system.