Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

The eruptions of Eyjafjallajökull volcano in 2010 (including its initial effusive phase at Fimmvörðuháls and its later explosive phase from the central volcano) and Bárðarbunga volcano in 2014–2015 (at Holuhraun) were widely reported. Here, we report on complementary, interdisciplinary observations made of the eruptive gases and lavas that shed light on the processes and atmospheric impacts of the eruptions, and afford an intercomparison of contrasting eruptive styles and hazards. We find that (i) consistent with other authors, there are substantial differences in the gas composition between the eruptions; namely that the deeper stored Eyjafjallajökull magmas led to greater enrichment in Cl relative to S; (ii) lava field SO2 degassing was measured to be 5–20% of the total emissions during Holuhraun, and the lava emissions were enriched in Cl at both fissure eruptions—particularly Fimmvörðuháls; and (iii) BrO is produced in Icelandic plumes in spite of the low UV levels

Globally Significant CO2 Emissions From Katla, a Subglacial Volcano in Iceland

Volcanoes are a key natural source of CO2, but global estimates of volcanic CO2 flux are predominantly based on measurements from a fraction of world's actively degassing volcanoes. We combine high-precision airborne measurements from 2016 and 2017 with atmospheric dispersion modeling to quantify CO2 emissions from Katla, a major subglacial volcanic caldera in Iceland that last erupted 100 years ago but has been undergoing significant unrest in recent decades. Katla's sustained CO2 flux, 12–24 kt/d, is up to an order of magnitude greater than previous estimates of total CO2 release from Iceland's natural sources. Katla is one of the largest volcanic sources of CO2 on the planet, contributing up to 4% of global emissions from nonerupting volcanoes. Further measurements on subglacial volcanoes worldwide are urgently required to establish if Katla is exceptional, or if there is a significant previously unrecognized contribution to global CO2 emissions from natural sources

Understanding the environmental impacts of large fissure eruptions: Aerosol and gas emissions from the 2014-2015 Holuhraun eruption (Iceland)

The 2014-2015 Holuhraun eruption in Iceland, emitted ~11 Tg of SO2 into the troposphere over 6 months, and caused one of the most intense and widespread volcanogenic air pollution events in centuries. This study provides a number of source terms for characterisation of plumes in large fissure eruptions, in Iceland and elsewhere. We characterised the chemistry of aerosol particle matter (PM) and gas in the Holuhraun plume, and its evolution as the plume dispersed, both via measurements and modelling. The plume was sampled at the eruptive vent, and in two populated areas in Iceland. The plume caused repeated air pollution events, exceeding hourly air quality standards (350 µg/m3) for SO2 on 88 occasions in Reykjahlíð town (100 km distance), and 34 occasions in Reykjavík capital area (250 km distance). Average daily concentration of volcanogenic PM sulphate exceeded 5 µg/m3 on 30 days in Reykjavík capital area, which is the maximum concentration measured during non-eruptive background interval. There are currently no established air quality standards for sulphate. Combining the results from direct sampling and dispersion modelling, we identified two types of plume impacting the downwind populated areas. The first type was characterised by high concentrations of both SO2 and S-bearing PM, with a high Sgas/SPM mass ratio (SO2(g)/SO42-(PM) >10). The second type had a low Sgas/SPM ratio (<10). We suggest that this second type was a mature plume where sulphur had undergone significant gas-to-aerosol conversion in the atmosphere. Both types of plume were rich in fine aerosol (predominantly PM1 and PM2.5), sulphate (on average ~90% of the PM mass) and various trace species, including heavy metals. The fine size of the volcanic PM mass (75-80% in PM2.5), and the high environmental lability of its chemical components have potential adverse implications for environmental and health impacts. However, only the dispersion of volcanic SO2 was forecast in public warnings and operationally monitored during the eruption. We make a recommendation that sulphur gas-to-aerosol conversion processes, and a sufficiently large model domain to contain the transport of a tropospheric plume on the timescale of days be utilized for public health and environmental impact forecasting in future eruptions in Iceland and elsewhere in the world

Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-squarekilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, nearexponential decline of both collapse rate and the intensity of the 180-day-long eruption.</p

Volcanogenic floods at Sólheimajökull. Hazard identification, monitoring and mitigation of future events

Volcanogenic floods from underneath glaciers happen almost on a yearly basis in Iceland, mostly due to build-up of water from geothermal melting beneath glaciers or due to sub-glacial eruptions. This work examines the vulnerability of the growing tourist sector in the area of Sólheimajökull to volcanogenic floods of all sizes, but with a special focus on the most frequent minor flood events. Employees from the four largest tour operators in the area, local law enforcement and civil protection officials are interviewed to learn about their perception of risk from volcanogenic floods at Sólheimajökull and their current strategies to minimizing risk. The July 2014 minor flood of geothermal water was closely monitored and observed changes in the hydrological and seismic data from this event is applied to identify past undocumented minor events. The risk associated with these minor floods is assessed in light of their high frequency, with particular emphasis on the until-now under-monitored hazard associated with high concentrations of gas released during minor jökulhlaups. An overview of the current monitoring techniques for monitoring volcanogenic floods in the area is given, putting focus on the real-time systems. Suggestions are made for mitigating the risk associated with the ever greater number of people visiting the area of Sólheimajökull. Atmospheric gas measurements and adequate informative infrastructure are found to be needed in the area, and the tour guides could have better knowledge of the processes that take place before and during a volcanogenic flood.Jökulhlaup eru flóð sem koma undan jöklum og eru nánast árlegur viðburður hér á landi. Þau orsakast aðallega vegna uppsöfnunar vatns frá jarðhitakerfum undir jökli eða vegna eldgosa undir jökli. Þetta verkefni metur aukna hættu sem steðjar að vaxandi fjölda ferðamanna við Sólheimajökul vegna flóða af öllum stærðum er verða af völdum jarðhita eða eldvirkni, en með sérstaka áherslu á minniháttar atburði sem hingað til hafa ekki verið talnir til jökulhlaupa. Tekin eru viðtöl við örryfisfulltrúa fjögurra stærstu ferðaþjónustuaðilanna á svæðinu og viðkomandi lögregluyfirvöld til að meta skilning þeirra á áhættunni vegna jökulhlaupa undan Sólheimajökli og þær viðbragðsáætlanir sem eru til staðar. Lítið hlaup af jarðhita vatni er kom undan Sólheimajökli 2014 var vandlega vaktað vegna mikillar gaslosunar. Vatna og jarðskjálftamæligögn frá atburðinum eru notuð til að bera kennsl á fyrri óskráða atburði og áhættuna af þeim, vegna þess hve algengir þeir eru. Greint er frá þeim aðferðum sem notaðar eru í dag til vöktunar Jökulhlaupa, þar sem áhersla er lögð á rauntímakerfi. Tillögur eru gerðar til að draga úr áhættu vegna síaukins fjölda ferðamanna við Sólheimajökul. Yfirborðs- gasmælingar og fullnægjandi aðgengi að nauðsynlegum upplýsingum þarf að betrumbæta á svæðinu. Fararstjórar gætu haft betri yfirsýn yfir þá ferla sem viðhafðir eru, fyrir og meðan á Jökulhlaupi stendur

Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014-2015).

Funder: Natural Environment Research Council; doi: http://dx.doi.org/10.13039/501100000270Funder: European Research Council; doi: http://dx.doi.org/10.13039/501100000781Funder: Leverhulme Trust; doi: http://dx.doi.org/10.13039/501100000275UNLABELLED: The eruptions of Eyjafjallajökull volcano in 2010 (including its initial effusive phase at Fimmvörðuháls and its later explosive phase from the central volcano) and Bárðarbunga volcano in 2014-2015 (at Holuhraun) were widely reported. Here, we report on complementary, interdisciplinary observations made of the eruptive gases and lavas that shed light on the processes and atmospheric impacts of the eruptions, and afford an intercomparison of contrasting eruptive styles and hazards. We find that (i) consistent with other authors, there are substantial differences in the gas composition between the eruptions; namely that the deeper stored Eyjafjallajökull magmas led to greater enrichment in Cl relative to S; (ii) lava field SO2 degassing was measured to be 5-20% of the total emissions during Holuhraun, and the lava emissions were enriched in Cl at both fissure eruptions-particularly Fimmvörðuháls; and (iii) BrO is produced in Icelandic plumes in spite of the low UV levels. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11069-023-06114-7

In situ measurement of the Icelandic Holuhraun/ Bárðarbunga volcanicplume in an early “young state” using a LOAC

International audienceVolcanic eruptions have huge societal and economic consequences. In Iceland, one of the best known examples isthe Laki eruption (1783-84 CE) (Thordarson and Self, 2003) which caused the death of > 20% of the Icelandicpopulations and likely increased European levels of mortality through air pollution (Witham and Oppenheimer,2004). The recent fissure eruption at Holuhraun (31 August 2014 – 27 February 2015) was a major source ofsulfur gases and aerosols and caused also both local and European-wide deteriorations to air quality (Gislason etal. 2015; Schmidt et al. 2015).The capability of atmospheric models to predict volcanic plume impacts is limited by uncertainties in thenear-source plume state. Most in-situ measurements of the elevated plume involve interception of aged plumesthat have already chemically or physically evolved. Small portable sensors airborne drone or balloon platformsoffer a new possibility to characterize volcano plumes near to source.We present the results of a balloon flight through the plume emitted by Baugur the main vent during the nightof the January 22th 2015. The balloon carrying a LOAC (Renard et al. 2015) has intercepted the plume at 8kmdistance downwind from the crater which represents a plume age of approximately 15 minutes. The plume waslocated in altitude between 2 and 3.1km above the sea level. Two layers were observed, a non-condensed lowerlayer and a condensed upper layer. The lower layer of 400m thick was characterized by a mode of fine particlescentered on 0.2m in diameter and a second mode centered on 2.3m in diameter and a total particle concentrationaround 100 particles per cubic centimeter. The upper layer of 800m thick was a cloud-like signature with dropletscentered on 20 m in diameter and a fine mode, the total particles concentrations was 10 times higher than thefirst layer. The plume top height was determined between 2.7 and 3.1 km, the plume height is in good agreementwith an estimate made by analysis of IASI satellite remote sensing data, thus demonstrating in-situ validation ofthis recent satellite algorithm (Carboni et al. 2015).This experimentation shows that under such difficult field campaign conditions (strong wind, low temperatures,only car batteries for power supply, night time and active volcano close to the launch site) it is possible to launchmeteorological balloons with novel payloads to directly sample in-situ the near-source plume, determine theplume altitude, identify dynamical phases of the plume and document the size distribution of particles inside aplume which is only a quarter of an hour old

Environmental pressure from the 2014-15 eruption of B\ue1r\uf0arbunga volcano, Iceland

The effusive six months long 2014-2015 B\ue1roarbunga eruption (31 August-27 February) was the largest in Iceland for more than 200 years, producing 1.6 + 0.3 km3of lava. The total S02emission was 11 \ub1 5 Mt, more than the amount emitted from Europe in 2011. The ground level concentration of SO2exceeded the 350 μg m-3hourly average health limit over much of Iceland for days to weeks. Anomalously high SO2concentrations were also measured at several locations in Europe in September. The lowest pH of fresh snowmelt at the eruption site was 3.3, and 3.2 in precipitation 105 km away from the source. Elevated dissolved H2SO4, HCl, HF, and metal concentrations were measured in snow and precipitation. Environmental pressures from the eruption and impacts on populated areas were reduced by its remoteness, timing, and the weather. The anticipated primary environmental pressure is on the surface waters, soils, and vegetation of Iceland

Degassing regime of Hekla volcano 2012-2013

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 Hekl