Volcanoes and the Environment: Lessons for Understanding Earth's Past and Future from Studies of Present-Day Volcanic Emissions

Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Contents lists available at ScienceDirect

Journal of Volcanology and Geothermal Research

journal homepage: www.elsevier.com/locate/jvolgeores

Review Volcanoes and the environment: Lessons for understanding Earth's past and future from studies of present-day volcanic emissions

Tamsin A. Mather ⁎

Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK article info abstract

Article history: Volcanism has affected the environment of our planet over a broad range of spatial (local to global) and temporal Received 22 September 2014 (b1 yr to 100s Myr) scales and will continue to do so. As well as examining the Earth's geological record and using Accepted 14 August 2015 computer modelling to understand these effects, much of our knowledge of these processes comes from studying Available online 22 August 2015 volcanism on the present-day planet. Understanding the full spectrum of possible routes and mechanisms by which volcanism can affect the environment is key to developing a realistic appreciation of possible past and po- Keywords: Volcanic environmental impacts tential future volcanic impact scenarios. This review paper seeks to give a synoptic overview of these potential Volcanic gases mechanisms, focussing on those that we can seek to understand over human timescales by studying current Tephra volcanic activity. These effects are wide ranging from well-documented planetary-scale impacts (e.g., cooling Subduction zones by stratospheric aerosol veils) to more subtle or localised processes like ash fertilisation of ocean biota and im- Halogens pacts on cloud properties, atmospheric oxidant levels and terrestrial ecosystems. There is still much to be gained Trace metals by studying present-day volcanic emissions. This review highlights the need for further work in three example areas. Firstly, to understand regional and arc-scale volcanic emissions, especially cycling of elements through subduction zones, more volatile measurements are needed to contribute to a fundamental and systematic understanding of these processes throughout geological time. Secondly, there is still uncertainty surrounding whether stratospheric ozone depletion following volcanic eruptions results solely from activation of anthropogenic halogen species. We should be poised to study future eruptions into the stratosphere with regard to their impacts and halogen load and work to improve our models and understanding of the relevant underlying processes within the Earth and the atmosphere. Thirdly, we lack a systematic understanding of trace metal volatility from magmas, which is of importance in terms of understanding their geochemical cycling and use as tracers in environmental archives and of igneous processes on Earth and more broadly on silicate planetary bodies. Measurements of volcanic rock suites and metals in volcanic plumes have an important part to play in moving towards this goal. © 2015 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Contents

1. Introduction...... 161 2. Studiesofthepresent-dayenvironmentaleffectsofvolcanism:abriefsynopticoverview...... 161 3. Understandingemissionbudgets:global,regionalandarc-scaleprocesses...... 163 3.1. Uncertainties in global volcanic ﬂuxes...... 163 3.2. Understandingregional/arc-scalebudgets...... 166 4. Thepotentialoffutureeruptionstodepletestratosphericozone...... 168 4.1. StratosphericinjectionsofvolcanicHCl?...... 168 4.2. Recentadvancesinourunderstandingofvolcanicbromineemissions...... 170 5. Thereleaseofmetalsfromvolcanoes:towardsasystematicunderstanding...... 171 6. Summary...... 173 Acknowledgements...... 175 References...... 175

⁎ Tel.: +44 01865 282125. E-mail address: [email protected].

http://dx.doi.org/10.1016/j.jvolgeores.2015.08.016 0377-0273/© 2015 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 161

1. Introduction transfer of significant quantities of different materials from the Earth's interior to its surface reservoirs, although volcanic heat has also been Volcanism is a key planetary process transferring heat and matter suggested to play a role (e.g., Mather, 2008). The actual emissions them- between the Earth's interior and its surface reservoirs. The balance selves are studied, in the case of the major volatile gas, aerosol species between these fluxes and other planetary scale processes has been im- and ash by satellite-based or ground-based remote sensing or in situ di- plicated in the development of Earth's atmosphere and in maintaining rect measurements. In the case of ash emissions such measurements are long-term stability of the surface environment and thus habitability complemented by mapping and sampling the products left behind on (e.g., Kasting and Catling, 2003). Changes in both short- and long-term the Earth's surface by volcanic activity. Melt inclusion and other petro- rates of planetary outgassing and/or its composition have been connected logical/geochemical studies of these products can also yield key insights with a range of perturbations to the global environment (e.g., Table 1). into volatile loss during volcanism. Current techniques applied to the These range from the short-lived effects of individual eruptions measurement of volcanic gas and aerosol are summarised in Table 2. (Robock, 2000), to the more prolonged proposed consequences of clus- Similarly a mixture of remote sensing, field studies and experiments ters or periods of enhanced volcanism occurring both by chance (Miller are used to study the environmental consequences of volcanism. Fig. 1 et al., 2012) and due to silicic ‘flare ups’ (de Silva and Gosnold, 2007)or and Table 3 summarise the different environmental effects of volcanism large igneous province (LIP) volcanism (Self et al., 2014a). Other mecha- suggested by present-day observations of volcanic events and continu- nisms linking volcanism to global change include more subtle feedbacks ous activity. Some of these effects, such as global cooling resulting from between the Earth's surface and rates of long-term volcanism or the stratospheric sulphate aerosol veils following large explosive eruptions mean composition of the gases emitted, for example, in response to degla- into the stratosphere, are relatively well documented. Others, such ash ciation or resulting from the subduction of carbonate-rich sediments fall to marine and terrestrial ecosystems, the effects of volcanic aerosol (Table 1). on cloud properties and levels of atmospheric oxidants, are more subtle Given the rarity or long-term nature of many of these effects, which and less well understood. On geological timescales, other mechanisms both maintain and perturb Earth's surface environment, much of our have also been suggested. These include: (i) significant and prolonged evidence for their characteristics and effects must come from proxy volcanic CO2 emissions associated with LIP volcanism leading to records. For example, much can be learnt by combining volatile emis- global warming (Chenet et al., 2008; Sobolev et al., 2011; Joachimski sions estimates gleaned from melt inclusions in rock samples scaled et al., 2012) and ocean acidification (e.g., Payne and Clapham, 2012); by deposit volume/mass (Scaillet et al., 2003) with environmental proxies (ii) long-term increased uptake of atmospheric CO2 due to increased in archives such as tree rings (e.g., Briffa et al., 1998; D'Arrigo et al., 2013), weathering resulting from fresh volcanic rock on the Earth's surface ice cores (e.g., Zielinski et al., 1994; Bay et al., 2004; Lavigne et al., 2013; following extended periods of enhanced volcanism (e.g., Schaller Sun et al., 2014) or sedimentary sections (e.g., Sanei et al., 2012; et al., 2012; Dessert et al., 2001); (iii) continental ash blankets Percival et al., 2015). Considerable advances have also been made via increasing planetary albedo (Jones et al., 2007). The primary associ- modelling studies both of individual past eruptions (e.g., Timmreck ation of these effects with very large-scale volcanism and their spa- et al., 2010; English et al., 2013) and extended events such as fissure erup- tial and temporal scales can make testing their likely extent tions (e.g., Stevenson et al., 2003; Highwood and Stevenson, 2003; Oman challenging using present-day field measurements. Nonetheless such et al., 2006; Schmidt et al., 2010) or LIPs (e.g., Caldeira and Rampino, observations have a clear role to play. Examples include efforts to im- 1990; Beerling et al., 2007; Iacono-Marziano et al., 2012; Black et al., prove our understanding of C partitioning during igneous processes 2013; summarised in Self et al. (2014a)). Comparing similar classes of (see Section 3) and studies of present-day weathering rates at active past events that have varying degrees of global environmental impacts volcanoes (Jones et al., 2011). is also a powerful approach (e.g., Ganino and Arndt, 2009; Jones et al., The limitation of our direct observation of volcanism to the scale that 2015). However if we are to develop a process understanding of planetary has occurred in recent times is important to consider when seeking to outgassing and its effects on the Earth's environment it is important to understand the broader interactions of volcanic activity with the environ- consider what we can learn from present-day measurements of volcanic ment. Several studies have shown that ‘scaling up’ from present-day vol- emissions and their impacts. It is also timely to consider how future canism to larger-scale events or episodes is not straightforward with advances in our analytical and measurement capabilities might open factors such as aerosol microphysics and oxidation agent depletion caus- the way for a broader understanding in this area. ing complications (e.g., Bekki et al., 1996; Oman et al., 2006; Schmidt et al., This review seeks to give a brief overview of what we have learnt to 2010; Timmreck et al., 2010; English et al., 2013). Feedbacks in terms of date about the potential effects of volcanism on our planet's surface en- environmental and climatic impacts via changes in the levels of atmo- vironment over its geological past by studying present-day volcanism spheric oxidants induced by volcanic emissions (e.g., Iacono-Marziano (Section 2). This section is intended to be synoptic and to act as a et al., 2012) are also hard to explore, although there were suggestions of guide towards the relevant literature to facilitate deeper study of the such effects in atmospheric records following the eruption of Pinatubo many research areas covered. I then highlight 3 example areas where in 1991 (Manning et al., 2005; Telford et al., 2010). These and other uncer- the scene is set to make substantial progress over the coming years. tainties regarding the environmental effects of volcanism have recently Section 3 covers the area of global, regional and arc-scale volatile bud- been discussed with respect to LIPs (Self et al., 2014a). gets. Section 4 discusses the impacts of volcanism on stratospheric The scientific efforts following the Pinatubo eruption in 1991 (the ozone levels and the challenges of understanding the consequences of largest eruption to the stratosphere to date in the satellite era) yielded past volcanism given the uncertainties associated with volcanic plume extensive new insights into numerous volcanic impacts on the environ- processes and present-day anthropogenically perturbed stratospheric ment. Historical records, such as those associated with the Laki fissure chemistry. Section 5 examines our understanding of the behaviour of eruptionin1783(theclosestrecentanaloguetoflood basalt volcanism) trace metals in volcanic systems and considers how we might further pose numerous further hypotheses about such impacts. With unprece- systematise this understanding in the future. dented arrays of satellite-borne and ground-based sensor networks the scientific community is now better positioned than ever to use current 2. Studies of the present-day environmental effects of volcanism: a and future large-scale volcanism to test hypotheses about the response brief synoptic overview of climate, atmospheric dynamics and chemistry and feedbacks (e.g., via the response of vegetation, ocean fertilisation or oxidant Present-day active volcanism has a range of chemical and physical levels). The recent response to the 6-month fissure eruption that took impacts on the local to regional and global surface environment and at- place at the Holuhraun lava field in Iceland between August 2014 and mosphere of our planet. These effects are largely mediated by the February 2015 is a good example (Gíslason et al., 2015; Schmidt et al., 162 Table 1 Examples of modes of volcanism postulated to have the potential to lead to prolonged global change. For further detailed discussion see Mather and Pyle (2015).

Mode Scale of volcanic input Timescale of changed volcanic input Comments

Short-lived large scale explosive eruptions

(e.g., Pinatubo 1991; Tambora 1815; 10s–1000s Tg SO2 released. Hours–weeks. • Clear evidence for global effects following these types of eruption (e.g., Robock, 2000; the Young Toba Tuff ~74 ka) Large-scale stratospheric injection. (McCormick et al., 1995; Oppenheimer, 2002) Oppenheimer, 2003; Chesner and Luhr, 2010) • Recent modelling studies suggest global temperatures recover on decadal time scales, without tipping the Earth system into a new steady state (Jones et al., 2005; Robock et al., 2009; Timmreck et al., 2010)

Temporal clustering of explosive eruptions

Clusters of relatively small-scale 4 large sulphur-rich explosive eruptions each with global Decadally-paced explosive volcanism over • Sea-ice/ocean feedbacks suggested to lead to the little ice age in ~AD 1350–1850 (Miller individual explosive eruptions sulphate loading N60 Tg within 50 years. a ~50 year period. et al., 2012)

Silicic ‘flare ups’ Large-scale silicic ‘flare-ups’, e.g., the Altiplano-Puna complex, Altiplano-Puna (10–1 Ma) • Iron fertilisation of the ocean by great volumes of silicic volcanic ash suggested as an effective central Andes: total volume of erupted silicic magma N104 km3 erupted at time-averaged rate climatic forcing mechanism that helped establish Cenozoic icehouse conditions coincident with 160 (2015) 304 Research Geothermal and Volcanology of Journal / Mather T.A. − − (Mason et al., 2004; de Silva and Gosnold, 2007) ~10 3 –10 2 km3/yr (de Silva and Gosnold, 2007). the ignimbrite flare-up of southwestern North America (Cather et al., 2009)

Large Igneous Provinces (LIPs)

Every 1 km3 of basaltic magma emplaced during a subaerial LIP Emplacement over several Ma. Detailed studies • Age correlation between at least ﬁve LIP provinces of the past 300 Ma with mass eruption releases ~3.5–6.5 Mt SO2. Estimates for entire LIP suggest most provinces have a ~1 Ma period of extinction events and other environmental changes (Wignall, 2001; Courtillot and Renne, 6 provinces of 3.5–68 × 10 Tg SO2 (Self et al., 2014a) peak activity with pulses of 10–100 years 2003; Kelley, 2007). separated by longer hiatuses (Self et al., 2014a,b) • Thought to be due to eruptive gas release from the magmas but exact mechanisms remain elusive • Recent work has highlighted that mantle volatiles might not be the only important factor, e.g., enhanced volatiles from the recycled oceanic crustal component of the mantle plume (Sobolev et al., 2011) and release of volatiles from sedimentary rocks by magmatic heating (Ganino and Arndt, 2009; Svensen et al., 2009). • Fraction of released gases injected into the stratosphere also still debated (Self et al., 2014b)

Feedbacks from the Earth's surface changing the long-term rate of volcanism1

Deglaciation Proposed 2 to 6-fold enhancement in global eruption rates after 5–6 kyr after the LGM (Huybers and Langmuir, • Proposed that associated increases in volcanic emissions may have contributed the last glacial maximum (LGM) (Huybers and Langmuir, 2009; 2009; Watt et al., 2013a) signiﬁcantly to the post-glacial increase in atmospheric CO2 (Huybers and Langmuir, Watt et al., 2013a). 2009) • Modelling studies of the oceanic carbon cycle (e.g., Roth and Joos, 2012), ﬁnd only a small role for volcanic forcing in post-glacial CO2 • A more detailed analysis of volcanic eruption records (Watt et al., 2013a)showssparser evidence for a strong post-glacial volcanic ‘pulse’ and highlights more arc data needed.

Variations in total paleosubduction Proposed that since the Triassic (250–200 Ma) the total Modelling work suggests variations on timescales • Global subduction zone length through time since Triassic quantiﬁed using seismic ≫ zone length paleosubduction-zone length reached up to approx. twice 5 Myr (variation wavelengths ~100 s Myr) but tomographic images of deep mantle relics of subduction zones. – the present-day value at times (Van Der Meer et al., 2014) poorly constrained (Van Der Meer et al., 2014) • Results show agreement with ocean production rates, Sr isotope curves and 179 reconstructed atmospheric CO2 levels. • Increased resolution in tomographic models, more detailed plate reconstructions and improved constraints on subducting slab carbon content needed to better constrain the evolution of subduction zones and their individual volcanic degassing outputs (Van Der Meer et al., 2014). Perturbations to magma volatile load and the composition of the volcanic gases emitted2

Subduction of carbonate-rich Proposed that closure of the Tethys led to up to a ~2-fold ~100 Ma during the closure of the Tethys • A poorly constrained portion of subducted C is released to mantle wedge by progressive sediments increase in global CO2 emissions due to consequent arc volcanism metamorphism during subduction. (Edmond and Huh, 2003; Kent and Muttoni, 2008; Johnston et al., • The paleogeography of the closure of the Tethys ocean suggests subduction of large 2011) volumes of marine carbonate. • The recycling of the C to the atmosphere via volcanism has been postulated as a major factor contributing to late Cretaceous to early Cenozoic elevated atmospheric CO2 concentrations (Edmond and Huh, 2003; Kent and Muttoni, 2008; Johnston et al., 2011). • Further work is needed to understand the factors controlling the efﬁciency of C recycling through subduction zones however (Section 3.1; Gorman et al., 2006).

1 Other proposed links between surface forcings such as sea level and the rates of volcanism and its feedbacks through the C cycle remain to be thoroughly tested (e.g., McGuire et al., 1997; Lund and Asimow, 2011; Burley and Katz, 2015). 2 Other links between volcanic gas composition and factors such as mantle oxidation state, volatile cycling and average degassing pressure (e.g., Holland, 2002; 2009; Gaillard et al., 2011) have been linked to the oxygenation of Earth's atmosphere. T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 163

2015). There is also much that can be learnt from studies of persistent vol- crucial component of efforts to improve these inventories. Measure- canic emissions or smaller scale eruptions. In the following sections I pick ments of volcanic SO2 in explosive eruption clouds have been increas- out 3 examples of broad-reaching scientificquestionsthatoffergoodop- ingly frequent since the 1980s but current sensors lack sufficient portunities for progress. sensitivity to reliably capture low-level tropospheric degassing. Recent studies using the Ozone Monitoring Instrument (OMI) explore the un- 3. Understanding emission budgets: global, regional and arc-scale certainties surrounding its application to low level, passive volcanic processes emissions and suggest that it measures only 20–40% of these emissions compared to ground-based methods (e.g., Carn et al., 2013; McCormick 3.1. Uncertainties in global volcanic fluxes et al., 2013). Investigations are underway to assess the capabilities of other current instruments such as IASI for such measurements also There are many challenges when determining budgets for volcanic (Walker et al., 2012). Future instruments such as the Dutch-designed emissions to the atmosphere. SO2 is generally the best quantified volcanic Tropospheric Ozone Monitoring Instrument (TROPOMI), scheduled for gas species. This is due to its low concentration in the background atmo- launch aboard ESA's Sentinel-5 Precursor in 2016 have the potential to sphere, and the availability of straightforward spectroscopic measure- offer significant new capabilities in this area. TROPOMI has been de- ment techniques that facilitate the measurement of its flux. With some signed as a replacement for OMI and SCIAMACHY and will offer both notable exceptions, where scanning DOAS networks are installed the global daily coverage of the former with the large spectral range of (e.g., Etna, Stromboli, Vulcano, Soufrière Hills Volcano, Tungurahua), the the latter. TROPOMI will measure in the UV–vis–near-infrared–short- emissions from the majority of volcanoes worldwide are not measured wavelength infrared ranges, with high spectral resolution and better on a daily basis for prolonged periods even for SO2. Instead they are mea- nadir spatial resolution than either earlier satellite. It is expected to sured sporadically during field campaigns or periods of heightened activ- show even greater sensitivity to SO2 and the focus on tropospheric mea- ity. When compiling these measurements to yield global or regional-scale surements (mainly owing to the mission focus on air quality) is poten- flux estimates the challenge is to combine data that is non-uniformly dis- tially advantageous in terms of the measurement of low-level but persed in both space and time and contains sampling biases to produce persistent volcano emissions into the lower atmosphere. the best possible assessments. Efforts have been made to compensate Although SO2 fluxes are most easily constrained, the fluxes of a for under-sampling. These have been mainly based on an assumed number of other gas species emitted by volcanoes are also of interest. power law distribution of volcanic fluxes on a global scale (proposed For example, constraining global volcanic carbon fluxes are important by Brantley and Koepenick (1995), and used in, e.g., Andres and for a number of reasons. The short- to medium-term impacts of increas-

Kasgnoc (1998),andHilton et al. (2002)). However a recent study ing CO2 in surface reservoirs have been much discussed over recent of volcanic emission fluxes in Japan from 1975 to 2006 demonstrated years and include global warming and ocean acidification. Understand- that the SO2 flux distribution in the cumulative frequency flux plot ing the natural C cycle is important to better understand how human does not obey a power law distribution. This suggests that correcting activities are perturbing it and informs the debate about the drivers of the global flux using the power law assumption may not represent current and future global change (Plimer, 2009; Gerlach, 2011). Under- best practice. The Japanese dataset was more complete than most standing this cycle on the present-day planet and in the recent past is and crucially included measurements from small emitters as well also the key to understanding the coupling between the deep Earth as the major sources. The cumulative log frequency-log flux plot for and the surface environment over longer geological timescales the Japanese dataset was represented not as a straight line but by a (Table 1). As mentioned above, this coupling can take the form of atmo- roll-off curve bending most significantly at ~500 t d−1 (Mori et al., spheric maintenance (e.g., Kasting and Catling, 2003) or perturbation 2013). (Section 2; Table 1). In other words it has been postulated that volcanic Despite these challenges measurements using ground-based carbon emissions have played a role in both stabilising Earth's surface techniques and satellite sensors have gone a long way over recent environment and in periods of abrupt environmental change. decades to determining the global SO2 flux. Recent estimates of total Measuring present-day C fluxes in volcanic gases (dominated by −1 annual emissions range from ~13 to 18 Tg y SO2 (Stoiber et al., 1987; CO2) is more challenging than SO2 for a number of reasons. These in- Andres and Kasgnoc, 1998; Halmer et al., 2002) and show reasonable clude the spectroscopic properties of the CO2 molecule, the high levels convergence. For Japan, Mori et al. (2013) report flux data from over 20 in the background atmosphere and the lower solubility of CO2 in volcanoes from 1975 to 2006. However, more than 94% of the total flux magmas. This lower solubility means that CO2 is exsolved deep within was contributed by 6 volcanoes for most of the period: Tokachi, Asama, volcanic systems and is often lost via diffuse degassing through the Aso, Sakurajima, Satsuma–Iwojima, and Suwanosejima. In other words, ground or interactions with hydrological systems in volcanic areas. the highest flux emitters (greater than a few hundred t d−1)dominated This diffuse degassing can be as well as or instead of through a focussed the total flux. This highlights that measurement strategies focussed on plume or fumaroles. Capturing these more spatially extensive diffuse the larger continuous or sporadic fluxes are likely to give good global or fluxes is generally more challenging than focussed emissions emanating regional scale SO2 budgets. Similarly, a few volcanoes (including Masaya, from visible vents or fumaroles. San Cristóbal, Pacaya and Fuego) dominate the SO2 flux estimates for the Vent or fumarole (sometimes termed ‘plume’)CO2 emissions are Central American Volcanic Arc for both the periods 1972–1997 (Andres often estimated by scaling the SO2 flux with measured C/S ratios. The re- and Kasgnoc, 1998) and 1997–2003 (Mather et al., 2006). These regional cent advent of MultiGas and similar systems has greatly extended the examples when extrapolated to the global scale in part explain the conver- range of systems where C/S plume measurements have been deter- gence between estimates of global SO2 fluxes. Essentially if the world's mined (Table 2). These C/S ratios are then also used to scale up to global major emitters are well constrained then reasonable agreement can be ob- plume CO2 fluxes using the global volcanic SO2 flux. Thus uncertainties tained despite the incompleteness of the data. in the global volcanic SO2 flux propagate to global CO2 flux estimates. Nonetheless the uncertainties surrounding this global volcanic However, additional uncertainties are introduced due to the choice of

SO2 flux could certainly be improved and there are major challenges representative C/S ratios (see Section 3.2)andCO2 flux emissions, in terms of getting good arc-scale and regional constraints (see such as diffuse soil degassing, that are decoupled from SO2 emissions. Section 3.1). This is especially true in poorly monitored areas Measurement of diffuse CO2 emission fluxes are usually achieved via (e.g., Indonesia) which nonetheless form important inputs to regional soil accumulation chamber measurements (e.g., Chiodini et al., 1998) and global scale models aimed to understand the impacts of volcanic although other methods such as tunable lasers are more infrequently emissions (Pfeffer et al., 2006; Schmidt et al., 2012). Pushing satellite applied (Pedone et al., 2014). Localised or grid measurements are then sensors to measure volcanic SO2 deeper in our atmosphere will be a scaled up to the total area of the volcanic structure using systematic 164 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Table 2 Examples of methods for measuring volatile gases and aerosol emissions from present-day volcanism.

Species/parameter Techniques Comments Example references measured

Gas ﬂuxes (SO2) Ground-based traversing or scanning by Due to its low background levels and spectroscopic properties the Ground-based: Reviewed in

COSPEC/DOAS spectroscopic methods for lower volcanic gas ﬂux of SO2 is most commonly measured. Permanent McGonigle and Oppenheimer altitude plumes networks can give high frequency measurements over prolonged (2003). Satellite U.V. or I.R. sensors for larger/higher periods. Galle et al. (2010) volcanic plumes Satellite: Reviewed in Carn et al. (2013) and McCormick et al. (2013). Carboni et al. (2012)

Major gas species Bulk plumes Used to scale up to fluxes of other major gas species from those of FTIR: Burton et al. (2007) ⁎ ratios with SO2 H2O/CO2: FTIR or Multi-Gas SO2. Trace gases like HBr and HI can be measured in alkali traps Multigas: Shinohara et al. (2008) HCl/HF: FTIR or alkali traps in filter packs or using more sensitive techniques like ICP-MS. Filter packs: Aiuppa et al. (2005a) other device followed by lab analysis (e.g., ion Multi-Gas or similar sensors can be ground-based or mounted on Giggenback flasks: Taran et al. chromatography). UAVs or manned aircraft. (1995)

Fumaroles New more recent innovations are discussed in Wittmer et al. Giggenbach ﬂasks for all species as well as bulk (2014). Robustness is a strong consideration when working in plume methods volcanic environments.

Diffuse soil The accumulation chamber method is most There are challenges surrounding scaling up from a discontinuous Chiodini et al. (1998)

degassing (CO2) commonly used. measurement grid to an appropriate ﬂux. Areas of degassing may also be inaccessible or too large to cover densely. Particle numbers Optical particle counters (in situ) Reviewed in Table 2 of Mather and size Sun photometers and other remote sensing methods. et al. (2003) distribution

Particle chemistry Direct sampling of volcanic plume particles onto Reviewed in Table 2 of Mather ﬁlter papers or traps including the use of et al. (2003) impactors to gain size resolved information.

⁎ If measurements of volcanic emissions are not feasible then petrological study melt inclusions or volatile-bearing minerals (e.g., apatite) in the volcanic rock products can often be used to gain insight into the melt parental volatile contents and degassing.

Fig. 1. Schematic summary of volcanic processes observed to have environmental impacts from studies of present-day volcanism. Two example volcanic scenarios are presented, namely ash-free passive degassing to the troposphere and substantial explosive volcanism with an ashy Plinian column punching into the stratosphere. In reality volcanic activity can have characteristics of both these scenarios and its nature can vary through an eruption with time. Major gas species in volcanic plumes at the point of emission are H2O, C (mainly as CO2), S (as SO2 and H2S depending on P, T and redox conditions) and halogen halides (examples of these are given in the explosive plume). The numbers in red circles refer to different volcanic processes that have environmental consequences. Their consequences are expanded upon in Table 3 with reference to these numbers. Other long-term/larger-scale effects of volcanism

(e.g., prolonged CO2 emissions, enhanced weathering of fresh volcanic material and increased albedo due to ash blankets) have also been postulated and are discussed in Section 2 of the text. T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 165

Table 3 A summary of the environmental effects of volcanism for which we have found evidence through recent studies of present-day volcanism. Other long-term effects have also been postulated (see Section 2 of the text for discussion).

Volcanic process Measured environmental effects Example references (numbers refer to those shown in Fig. 1)

Explosive volcanism

(1) Oxidation of volcanic SO2 to sulphate aerosol in • Sulphuric acid aerosol in the stratosphere interacts with Reviewed in Robock (2000). Krakauer and Randerson the stratosphere incoming solar radiation increasing planetary albedo. (2003); Trenberth and Dai (2007) • After the 1991 Pinatubo eruption average cooling of the troposphere lasted 1–3 years. • Evidence that this cooling impacts global precipitation rates. • Interaction of the aerosol with incoming and outgoing radiation warms the stratosphere leading to dynamic responses of the atmosphere such as northern hemisphere winter warming. • Associated increase of diffuse (as opposed to direct) radiation suggested to impact forest photosynthesis rates although evidence is not conclusive. • Change in stratospheric UV ﬂux, temperature and the presence of aerosol surfaces have potential to perturb stratospheric chemistry (see 2).

(2) Heterogeneous chemistry on/in particles in the • Presence of surfaces for heterogeneous reactions affects O3 Reviewed in Robock (2000); Ayris et al. (2013; 2014) stratosphere reaction cycles. • Quantifying the global scale effects of volcanic eruptions on stratospheric ozone challenging - chemical and dynamic effects occur simultaneously and effects are not much larger than natural variability. • Depletions may be dependent on the presence of anthropogenic chlorine in the stratosphere (see discussion in Section 4). • Understanding of the importance of reactions on ash surfaces especially in the high-T regime of dense explosive eruption plumes is in its infancy.

(3) Ash fall onto land • Near to eruption ash has a clear physical effect blanketing Witham et al. (2005); Horwell and Baxter (2006); Stewart ecosystems, choking drainage etc. and can effect the et al. (2006); Martin et al. (2009); Henríquez et al. (2015) respiratory health of animals following inhalation. • Ash releases various chemical species to the environment following deposition and contact with rain or surface water. • Recent results from Chile suggest explosive volcanism inﬂu- ence on structure and composition of temperate rainforests over the last 10,000 years.

(4) Ash fall into sea • Volcanic ash fall into the Earth's oceans brings with it a Reviewed in Duggen et al. (2010) and Browning et al. wide range of chemical elements that can have impacts on (2015). Hamme et al. (2010); Langmann et al. (2010); the marine environment including macro- and Hoffmann et al. (2012); Olgun et al. (2013); Achterberg micro-nutrients. et al. (2013); Browning et al. (2014); Mélançon et al. • The delivery of volcanic ash to Fe-limited waters has been (2014) hypothesized as a natural fertilisation mechanism for phytoplankton. • Increased marine productivity has been proposed to lead

to enhanced drawdown of atmospheric CO2.

(5) Aerosol settling from the stratosphere • Evidence for the possible effect of stratospheric volcanic Reviewed in Robock (2000). Sassen et al., (1995); Luo et al. aerosols on seeding cirrus cloud formation exists for (2002); Campbell et al. (2012) individual cases following tropopause folds. • Initial studies of the global signiﬁcance of such effects following Pinatubo suggest not a signiﬁcant climate feedback on the global scale.

(6) Volcanic lightning and particle charging • Electrostatic charging likely exerts control on fall out Reviewed in Mather and Harrison (2006). Rose et al., patterns of ash. (2006); Martin and Ilyinskaya (2011)

• Plume lightning will produce reactive species such as NOx that may then take part in further reactions.

Passive degassing

(7) Oxidation of volcanic SO2 to sulphate aerosol in • Sulphate aerosol is present in volcanic plumes from the Reviewed in Mather et al. (2003; 2004). Sutton and Elias the troposphere point of emission and further sulphate is generated during (1993); Schmidt et al. (2011) advection of the plume downwind following the entrainment of atmospheric oxidants. • This aerosol can have detrimental effects on vegetation and human/animal health if it fumigates surface environments, provides surfaces for heterogeneous chemistry (see (9)) and interactssolarradiationdirectlyaswellaseffectingcloudcover and properties (see (11)).

(continued on next page) 166 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Table 3 (continued) Volcanic process Measured environmental effects Example references (numbers refer to those shown in Fig. 1)

(8) Plume gas fumigation and particle settling to • Leaf damage observed downwind of passively degassing Reviewed in Delmelle (2003). Quayle et al. (2010); Martin ground-level volcanoes due to fumigation by acid gases. et al. (2012). • Chemical and magnetic evidence for particle and gas uptake by leaves.

(9) Heterogeneous chemistry on/in particles in the • Particular recent progress understanding Reviewed in von Glasow et al. (2009) and von Glasow troposphere halogen-mediated destruction of ozone and formation of (2010) BrO. • Involves heterogenous reactions in/on particles (acid aerosol), the entrainment of atmospheric oxidants into the plume and photochemistry. • Thought to be initiated by trace reactive chemical species from high-T reactions in the volcanic vent or during lightning ﬂashes in more explosive eruptions.

(10) Rain through the plume • Rain falling through volcanic plumes strips out soluble gas Delmelle (2003); Calabrese et al. (2011); Mather et al. species, aerosol and any ash present. (2012) • Leads to acid rain (with similar detrimental environmental effects to anthropogenic acid rain) and the release of other chemical species such as trace metals to the environment.

(11) Mixing with the background atmosphere • Many possible reactions as a volcanic plume mixes with Gassó (2008); Yuan et al. (2011); Schmidt et al. (2012); the background atmosphere or anthropogenic pollution. Ebmeier et al. (2014) • Recent evidence of modification of cloud occurrence and properties by volcanic aerosol with important implications for planetary radiative budget. assumptions about how fluxes vary spatially (e.g., variations with volca- volcanic impact detailed in Table 1 we require fluxes on more specifictec- nic activity, fault locations, observed ground alteration; Chiodini et al., tonic or geographical scales. For example, the balance between the fluxes 1998; Parks et al., 2013; Hutchison et al., 2015). The balance between from arc volcanoes compared to those in other tectonic regimes is impor- diffuse and plume emissions appears to vary depending on the eruptive tant to quantify given evidence of different responses to deglaciation be- state of the volcano. Hernández et al. (2015) showed that volcanoes tween tectonic settings (Huybers and Langmuir, 2009; Watt et al., 2013a). with a recurrent eruptive period shorter than 10 years generally show Similarly, a key issue in the understanding of the cycling of volatiles be- a diffuse/plume ratio in the range 0.1–1, whereas those with a longer re- tween the surface and the mantle is volatile processing through subduc- current eruptive period (~100 years) show an exponential increase of tion zones (Luth, 2014; Schmidt and Poli, 2014). One method employed this ratio. The state-of-the-art regarding present-day volcanic C fluxes to understand the processes involved in this cycling and its efficiency is was recently reviewed by Burton et al. (2013). They compiled previous by comparing estimated input volatile fluxes associated with the estimates of global volcanic subaerial CO2 flux as between 66 and subducted slab with estimated output degassing fluxes (e.g., Hilton 300 Mt/yr and revised this flux upwards to 540 Mt/yr by including et al., 2002; Fischer, 2008; Johnston et al., 2011). diffuse flank emissions (117 Mt/yr), emissions from volcanic lakes (94 As discussed above because of the relative ease of its measurement

Mt/yr) and emissions from tectonic, hydrothermal and inactive volcanic SO2 fluxes are generally the best constrained for global volcanoes. This areas (66 Mt/yr) in addition to the more usually quantified plume emis- is also true on smaller geographical scales. Several studies have compiled sions (271 Mt/yr). More recent estimates have suggested that the SO2 fluxes from different arcs and then used these fluxes and X/SO2 ratios plume emission estimate for volcanic CO2 in Burton et al. (2013) may (where X is another element or compound present in volcanic emissions) be too high as it depends on what method you use to correct for unmea- to scale up to the arc-scale fluxes of other chemical species such as CO2 sured fluxes (Pedone et al., 2014). This highlights the need for further (e.g., Hilton et al., 2002; Mather et al., 2006; Fischer, 2008; Taran, 2009; measurements of both plume and diffuse fluxes (see also Section 3.2) Johnston et al., 2011). Complementary techniques use melt inclusions and improved understanding regarding how best to scale up spatially and petrological modelling of the geochemistry of the eruptive products dispersed fluxes such as diffuse volcanic CO2 emissions. Satellite measure- of arc magmatism to calculate output fluxes (e.g., Wallace, 2005; ments might one day also play a role for volcanic CO2 measurements al- Freundt et al., 2014). Both approaches have their issues but in general though there are extensive challenges to overcome first (e.g., Heymann agree that higher fractions of the volcanic arc outputs of H2O and Cl are et al., 2015). Large, high-altitude explosive plumes will likely offer the contributed by the downgoing subducting slab than for CO2 (Straub and most promising initial targets rather than lower flux, surface level diffuse Layne, 2003; Wallace, 2005; Mather et al., 2006; Taran, 2009; Freundt degassing. et al., 2014). Similar estimates for S are less common, in part, as generally Recent reviews also exist regarding the fluxes of volcanic halogens the input flux on the downgoing slab is not as well constrained. The wide (e.g., Pyle and Mather, 2009), which are of interest in terms environ- spread in the subduction zone recycling efficiency estimates for S (i.e., the mental impacts such as acid rain and ozone depletion (Fig. 1). In all ratio of inputs to outputs) reflects sensitivity to this poorly constrained cases data from more volcanic systems as well as systematising our un- input (Taran, 2009; Freundt et al., 2014). derstanding of the degassing process is crucial in terms of improving Hilton et al. (2002) made one of the first attempts to compile these estimates (see also Section 4). degassing data on an arc-by-arc basis to probe the comparative volatile recycling efficiencies through the different global arcs. Johnston et al.

3.2. Understanding regional/arc-scale budgets (2011) then used these data to explore the relationship of CO2 recycling efﬁciency to the thermal structure of the subduction zones in question,

While there is some convergence, at least for SO2, in the global volca- and argued that their results supported the proposal that changes in Ce- nic ﬂux estimates, to further our understanding of several of the modes of nozoic climate could be related to the closure and subduction of the T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 167

Tethys Ocean (Edmond and Huh, 2003; Kent and Muttoni, 2008). In light volcanoes. Satellite measurements offer an attractive solution to these of these studies it is useful to review the current state-of-the-art in terms problems given their global coverage. As discussed in Section 3.1 there of the global arc-scale degassing budgets made from present-day mea- are still limitations to the application of satellite volcanic SO2 in the surements. This will allow us to assess the validity of this approach and lower atmosphere but better understanding of the associated uncer- what work we need to prioritise in order to promote progress in the tainties and future sensors like TROPOMI provide exciting new opportu- future. nities in this area. More extensive continuous volcanic SO2 monitoring I will discuss arc-scale SO2 fluxes first. Hilton et al. (2002) extrapo- at more volcanoes, better compilation and archiving of data and im- lated SO2 fluxes by filtering the degassing fluxes compiled in Andres proved methods for dealing with under-sampling will also allow us to and Kasgnoc (1998) for each arc. They then used a power law correction make meaningful progress in terms of constraining arc-scale SO2 fluxes proposed by Brantley and Koepenick (1995) to account for unmeasured over the coming decades.

SO2 fluxes. Hilton et al. (2002) used the continuously erupting fluxes As discussed above fluxes of other chemical components of volcanic listed in Andres and Kasgnoc (1998) augmented in some cases by degassing are often scaled to those of SO2. Therefore, as for global esti- other sporadic fluxes. The challenges associated with combining fluctu- mates, uncertainties in arc-scale SO2 fluxes (i.e., a minimum of a factor ating continuous fluxes with large sporadic short-lived fluxes to achieve of 2 even in well studied arcs) propagate to such flux estimates for meaningful volcano SO2 flux estimates on various temporal and spatial other plume components. Again, when scaling up to arc-scale emissions scales are discussed above in the global context. In terms of arc-scale of other plume components a further complication comes into play, measurements lessons can again be learnt from the well-monitored namely choosing appropriate X/SO2 ratios. Measurements of these areas of the world. As mentioned above, Mori et al. (2013) recently ratios again tend to be temporally and spatial sparse and focussed on compiled all available SO2 flux data from 32 years (1975–2006) of mon- well-monitored systems. Taking C/S ratios for example, studies at itoring at Japanese (Japan, Nankai, Izu-Bonin and Ryukyu) volcanoes well-monitored volcanoes show that carbon and sulphur degassing (93 volcanoes corresponding to about 10% of the world's arc volcanoes is poorly correlated in many cases, e.g., due to deep exsolution and by number). The activity of these volcanoes was well recorded over this diffuse rather than plume emission of CO2 (discussed in Section 3.1). period. Using these data they were able to evaluate the temporal varia- At Etna, one of the best monitored volcanoes worldwide and a major tion of the flux of each volcano in some detail. This analysis unveiled the volcanic CO2 source, the C/S ratio of the gases varies over short time- magnitude of variability from year to year possible over this length of scales (~months) by a factor of N2 and over longer timescales by a factor arc (3950 km or ~9% of total global trench length). Their maximum es- of N~30 (Aiuppa et al., 2007; Shinohara et al., 2008). At Mt St Helens timated annual arc-scale flux was 9.2 Tg yr−1 in 2001, with a minimum during the 1980s a ~10-fold variation in the C/S was noted (Harris of 0.8 Tg yr−1 in 1981. This variability of over an order of magnitude was and Rose, 1996). As well as fractional degassing, processes such as vari- largely due to the intense degassing of Miyakejima volcano after 2000. able scrubbing of SO2 by hydrothermal systems and sulphide breakdown The average annual flux for the period is 2.2 Tg yr−1 with Miyakejima in magmas are sources of variability in C/S ratios (e.g., Edmonds et al., included and 1.4 Tg yr−1 with Miyakejima emissions omitted. Thus a 2013). Understanding the degassing processes in operation at each indi- single high emitter is capable of significantly skewing regional time- vidual system is important for the interpretation of C/S ratios. averaged degassing totals. Hilton et al. (2002) used different C/S molar ratios for the different Fig. 2 compares the different estimates for arc-scale fluxes for Japan arcs based on measurements made at each, largely at fumaroles. These and globally. In order to aid inter-arc comparisons the total fluxes are nor- values ranged from 1.7 for Kamchatka–Kuriles to 6.5 for Japan and 8.5 malised to arc length although this does introduce a further uncertainty in for Italy (higher measured values for New Zealand and the Philippines terms of the appropriate arc length to choose. Arc lengths were taken of 28.7 and 104.5 were not used but were replaced by a ratio of 5). from those compiled in Hilton et al. (2002). They were similar to Johnston et al. (2011) used a slightly different range of arc ratios based those used in Johnston et al. (2011) other than (i) for Japan where the on the compilation of fumarole measurements in Fischer (2008).These Nankai, Izu-Bonin and Ryukyu arc lengths were all included here and varied from 0.32 and 0.92 for Alaska–Aleutians and Kamchatka–Kuriles (ii) Indonesia where Java, Sumatra and E. Sunda were summed for our estimates. The length for the Andes only includes Colombia and Peru (2550 km). A more realistic value (N7000 km) includes Chile, and reduces the fluxes per km by about a third. Fig. 2 shows that based on current measurements, we can constrain the time-averaged SO2 fluxes from well-studied arcs (e.g., Japan) to within a factor of ~2. However, for less well-studied arcs this is not the case. Hilton et al. (2002) used the Andres and Kasgnoc (1998) compilation of data from only 3 volcanoes to estimate a flux of 0.1 Tg a−1 from the 1900 km long Kamchatka–Kurile arc. A more recent and complete survey (Taran, 2009)withdatafromN20 volcanoes suggests that the arc-scale flux is N1.1 Tg a−1, more than an order of magnitude higher. Estimates are also very sensitive to the mode of degassing included in compilations. For the Indonesian arc, which hosts N70 active volcanoes, Halmer et al. (2002) estimated an −1 average annual SO2 flux for Indonesia of 2.1–2.6 Tg yr including both explosive and quiescent activity. This is again over an order of magnitude Fig. 2. Different estimates of the SO2 flux from different global subduction zones. Subduc- −1 greater than arc fluxes based solely on passive emissions (0.1 Tg yr : tion zones are distinguished according to their thermal parameter (Syracuse et al., 2010). Hilton et al., 2002). A similar situation is observed for Alaska (Fig. 2). Where this parameter varied along the arc a mean value was taken. Arc lengths are taken Quiescent and continuous emissions from both these arcs are also from those compiled in Hilton et al. (2002) other than the exceptions described in the text. The filled red diamonds are the estimates used in Hilton et al. (2002) and Johnston et al. under-sampled due to inaccessibility (e.g., Bani et al., 2015). (2011) from Andres and Kasgnoc (1998). The open black squares are the median of the es- Thus, while on the global scale there is some convergence in our un- timates compiled in Halmer et al. (2002) with the error bars representing the ranges. fi derstanding of time-averaged volcanic SO2 emissions, caution is needed These estimates include explosive and passive emissions. The lled blue square represents when interpreting arc-scale emissions budgets. Not only is more work the mean estimate for the CAVA from Mather et al. (2006) with error bars indicating the range. Filled blue circles represent the estimates for Japan from Mori et al. (2013) with needed to understand how best to include short-lived periods of high the higher value including the period of intense degassing by Miyakejima and the lower fl fl ux in time-averaged arc-scale uxes, but we are also dealing with value not. The filled blue triangle is that value for Kamchatka–Kuriles estimated by data that is sparse in time and space and biased towards accessible Taran (2009). All values are without correction for unmeasured fluxes. 168 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 respectively, to 6.60 and 17.87 for the Andes and Italy respectively. Fig. 3 and prolonged volcanic episodes. However, even for explosive plumes compares the Fischer (2008) C/S measurements with those made with al- that are known to reach the stratosphere, much remains to be understood ternative methodologies from main ‘plumes’ rather than individual fuma- about the fate of chlorine and other volcanic halogens and hence their po- roles. The ratios span a great range of values for individual volcanic tential effects on stratospheric ozone. Here again there is much to learn systems, within arcs and globally. While there may well be real variation from studying present-day volcanism. in the C/S ratios between arcs, current data coverage (Fig. 3)isnotsuffi- cient to distinguish this. For example, the range of fumarole C/S ratios 4.1. Stratospheric injections of volcanic HCl? measured in Japan (Fig. 3) is almost as great as the global range. In addition, although the fumarole measurements for the Andes (from Stratospheric ozone depletion was attributed to the Pinatubo erup- Galeras) suggest a higher C/S ratio than some other arcs might be tion in 1991. Estimates of column depletions ranged from about 2% in appropriate for the Andes, this is not borne out by the ‘plume’ measure- the tropics to about 7% in the mid latitudes and reached about 20% in ments (from Villarrica, Lascar and Lastarria). In both ‘plume’ and ‘fuma- the aerosol cloud itself. This depletion has been attributed to anthropo- role’ datasets in Fig. 3 there is some suggestion that Italian C/S fluxes are genic chlorine in the stratosphere being activated via heterogeneous at the higher end of global compilations. This may be attributed to base- chemistry involving volcanic aerosols (summarised in Robock (2000)). ment rock decarbonation at in the Mediterranean region (e.g., Parks No substantial HCl (in general the most abundant halogen in volcanic et al., 2013; Tassi et al., 2013). While interesting in itself, this is distinct emissions) increase was detected in the stratosphere following this from control on C/S ratios by deeper subduction driven processes. Similar eruption (Mankin et al., 1992; Wallace and Livingston, 1992), despite processes have been suggested to explain the C degassing systematics at petrological estimates of HCl emissions of ~4.5 Mt HCl (Westrich and Popocatépetl (Goff et al., 2001) that also plots with a high C/S ratio in Gerlach, 1992). This indicates efficient removal of HCl in the Pinatubo Fig. 3. eruption column before it could enter the stratosphere (likely by

Compiling the arc-by-arc uncertainties in SO2 ﬂux and C/S ratios it scavenging of soluble gas into hydrometeors) and suggests that in the becomes apparent that, while broad-brush global estimation of volcanic pre-anthropogenic era volcanic eruptions would not have caused

CO2 flux is improving, the degassing data on an arc-by-arc scale must stratospheric ozone depletion. However, measurements from El still be treated with caution. These data are not yet fit for purpose Chichón and smaller eruptions since Pinatubo present a more complex when trying to understand the factors affecting the efficiency of C picture (Table 4). Mid latitude and tropical eruptions show evidence recycling by comparing arc to arc CO2 gas emission and much work re- for significant HCl injection into the stratosphere (up to 0.04 Tg for El mains to be done before we can claim to have a quantitative under- Chichón) despite estimated scavenging rates of 80–99.8% during standing of present-day let alone past subduction recycling scenarios. plume transit through the lower atmosphere (Table 4). Measurements Large uncertainties are therefore associated with estimates of individual from the high latitude eruption of Hekla in 2000 show little evidence arc CO2 recycling efficiencies obtained from gas measurements to date for HCl removal in the lower atmosphere (although the composition (Johnston et al., 2011). Future work should aim to use current and of the source gases is poorly constrained). Localised areas of complete new technologies to improve arc-scale degassing measurements of all ozone destruction were observed within the plume during aircraft en- gas species (e.g., MultiGas/gas sensor boxes, Aiuppa et al., 2014; counters with the Hekla 2000 plume in the stratosphere (Rose et al., Tamburello et al., 2014). Understanding subduction zone volatile pro- 2006). In all cases in Table 4 where HCl mixing ratios are reported, cessing will require the combination of more extensive gas data with holistic budget and process understanding from multiple approaches including experimental techniques, petrological methods, exhumed subduction zone studies and innovative new modelling (e.g., Connolly, 2005; Gorman et al., 2006; Dasgupta and Hirschmann, 2010; Marín-Cerón et al., 2010; Watt et al., 2013b; Shinohara, 2013; Ague and Nicolescu, 2014; Kelemen and Manning, 2015). Although given the complexity of the processes thermodynamic and geodynamic modelling of the behaviour of C through subduction zones is in its infancy, initial modelling studies do suggest that both arc-thermal structure and sediment thickness, are indeed important, with sheer input amount of C into the subduction zone also a key player (Gorman et al., 2006; Fig. 4).

4. The potential of future eruptions to deplete stratospheric ozone

fi ‘ ’ Fig. 3. The mean and range of molar ratios of C/S in volcanic plumes from different arcs. The widespread identi cation of mutated forms of fossil spores and The arc fumarole measurements (filled squares) are taken from the compilation in Fischer pollen in end-Permian rocks has led to recent claims that the Siberian (2008) made using the Giggenbach flask method. The arc ‘plume’ measurements (filled Trap volcanism, coincident with the Permo-Triassic mass extinction circles) include some plumes that originate from fumaroles (e.g., Vulcano, Soufrière Hills (251 Ma), led to a worldwide depletion of stratospheric ozone Volcano) but many are from open vents or lava lakes. ‘Plume’ measurements for non-arc volcanoes (open circle) are also illustrated. ‘Plume’ measurements are based on FTIR mea- (Beerling et al., 2007). Modelling studies to explore the possibility of surements or Multigas measurements. The numbers below the x-axis indicate the number such large-scale ozone depletion suggest the delivery of magmatic of volcanoes where measurements were taken and that the mean and range ratio is based halogens to the stratosphere from Siberian Trap volcanism is an impor- on. References: CAVA (Masaya: compiled in Martin et al., 2010, Telica and Turrialba: tant atmospheric input to consider (Beerling et al., 2007; Black et al., Conde et al., 2014), Andes (Villarrica: Shinohara and Witter, 2005; Sawyer et al., 2011, 2013). LIP volcanism presents particular challenges when considering Lascar: Tamburello et al., 2014, Lastarria: Tamburello et al., 2014), Italy (Stromboli: Burton et al., 2007,Vulcano:Aiuppa et al., 2005b; McGonigle et al., 2008), Japan (Aso: Mori and the stratospheric effects of associated halogen emissions. The explosivity Notsu, 1997,Mikakejima:Shinohara et al., 2003), Kamchatka (Gorely: Aiuppa et al., of trap volcanism like that in Siberian is uncertain and thus estimates of 2012), Antilles (Soufrière Hills Volcano: Edmonds et al., 2010), Mexico (Popocatépetl: the fraction of LIP emissions that would have reached the stratosphere Goff et al., 2001), Vanuatu (Yasur: Métrichetal.,2011), non-arc volcanoes (Erebus: are not reliable (Self et al., 2014b). Further, in addition to the issues of Oppenheimer and Kyle, 2008, Erte 'Ale: Sawyer et al., 2008a, Nyiragongo: Sawyer et al., 2008b, Etna: Aiuppa et al., 2006; 2008,Kīlauea: Gerlach et al., 1998 and Edmonds et al., obtaining good estimates of magmatic halogen degassing, the importance 2013 and references therein). Measurements from explosive eruptions in Alaska of emissions of organohalogens due to magmatic interactions with coun- suggested mean mass CO2/SO2 values of 0.8–1.3 with higher values attributed to hydro- try rock and other indirect sources is poorly constrained for these intense thermal scrubbing of SO2 (McGee et al., 2010 and references therein). T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 169 maximum in-plume levels (2.5–70 ppbv) were well above natural back- The strength of volcanic HCl stratospheric injection is critical to in- ground levels and comparable to the anthropogenically perturbed form our understanding and modelling of the environmental impacts stratosphere. of past, current and future volcanism. For example, Beerling et al. Modelling studies also show some variation in terms of the predict- (2007) allowed 75% of the HCl emitted by the Siberian Traps to reach ed stratospheric HCl injection from explosive volcanic eruptions. the stratosphere in their model. They argued that this was appropriate Modelling by Tabazadeh and Turco (1993) suggested that HCl partitions due to the high latitude of this volcanic activity making it more analo- almost completely into supercooled drops, leading to a reduction in the gous to the Hekla 2000 scenario (Rose et al., 2006) than the modelling gas phase concentration of up to four orders of magnitude. However, all studies of Tabazadeh and Turco (1993) and Textor et al. (2003).Theirre- the hydrometeors in the Tabazadeh and Turco (1993) model were sults would have likely been different if they had used the 0–25% strato- liquid, and incorporation of gases in ice particles was not included. spheric injection rates suggested by these modelling studies and the Textor et al. (2003) used a different plume model and suggested that other observations summarised in Table 4. However without a process- the ice phase was in fact dominant. This reduced liquid scavenging of based understanding for the likely stratospheric injection rate under dif- HCl in the model and suggested that scavenging by ice particles was a ferent conditions it is hard to identify a most likely scenario. Progress in significant process. Many of these particles reach the stratosphere and this area will rely on improved understanding in several inter-related they concluded that, despite scavenging, more than 25% of the HCl areas of research. Firstly, we must better understand the initial abundance reaches the stratosphere. The results of both these modelling studies and release of Cl from magmatic systems and any associated shallow con- are consistent with observations to date of mid latitude and tropical tributions involved in different volcanic scenarios (e.g., Pyle and Mather, eruptions (Table 4) but not with the high latitude Hekla case. The 2009; Svensen et al., 2009). New analytical techniques, opening up the Textor et al. (2003) model runs used subtropical atmospheric condition use of mineral phases such as apatite, offer exciting new potential in addi- values, so it is perhaps not surprising that there is a better fittolower tion to improved melt inclusion methodologies (e.g., Stock et al., 2015). latitude data. Despite progress in the modelling of HCl behaviour in vol- Secondly, further work is needed to understand the processing of chlorine canic plumes, there are still important processes that have yet to be fully within the plume once it is emitted. This will involve further exploration understood, parameterised and included in the models. For example re- of the sensitivity of stratospheric injection to different environmental cent experimental studies highlight the complex role of HCl uptake onto (e.g., ambient atmosphere water content, tropopause height, atmo- volcanic ash as a possible mode of HCl transport to the stratosphere as spheric dynamics) and volcanological factors (e.g., explosivity) using well as a mode of removal and deposition (Ayris et al., 2014). current models (e.g., Textor et al., 2003; Glaze et al., 2015). It will also

Fig. 4. (a) and (b) Recycling efficiency (%) at different subduction zone calculated based on the modelling results presented in Gorman et al. (2006) plotted against (a) thermal parameter (Syracuse et al., 2010) – note the log scale – and (b) sediment thickness (Plank and Langmuir, 1998) on the downgoing slab. (c) Subducting C flux in downgoing slabs (Jarrard, 2003). (d) Recycling efficiency (%) at different subduction zone calculated from Gorman et al. (2006) plotted against total C input per km of trench (Jarrard, 2003). There is a general trend towards decreasing C recycling efficiency for colder (i.e., higher thermal parameter) slabs. Thick sediment (e.g. S. Antilles) and high input of C held in sediment (e.g. CAVA, Colombia) tend to reduce recycling efficiency at a given thermal parameter. Conversely in some arcs C is recycled more efficiently than their thermal parameters would suggest. At Tonga this can be explained by low sediment thickness and a relatively high C input to the subduction zone held in the oceanic crust rather than sediments. A broad trend of reducing C recycling efficiency with total input per km into the subduction zone is also seen with thick C-poor sediments pulling Andaman and S. Antilles off this trend. No immediate reasons for the deviation of Kermadec from the broad trend is discernible from these plots. Gorman et al. (2006) predicted a global slab-derived C flux of 0.35–3.12·1012 mol/yr (15–140 Mt/yr) from convergent margins which agrees well with the lower end of the estimate range for total global subaerial volcanic CO2 fluxes (see text and Burton et al. (2013)). 170 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

require further field measurements and laboratory experiments to un- (~30% of all volcanoes which emitted SO2 plumes detectable by the sen- derstand poorly parameterised plume processes and facilitate their sor during this period). These included several examples (Dalaffilla, eventual inclusion in the models (e.g., gas uptake by hydrometeors Kizimen, Kliuchevskoi, Nabro and Sarychev) where BrO was detected and ash and their fate: Ayris et al., 2014 and Martin et al., 2012 and ref- for the first time. erences therein). Measurements of HCl and other halogen species in the stratosphere following future major eruptions are also to be encouraged (b) Gas-phase HBr (believed to be the major gas species emitted by (see Table 4 and Section 4.2 for discussion of Br measurements). magma) As an aside, we can use the measurements presented in Table 4 to estimate the time-averaged HCl flux to the stratosphere. If we assume an This has been quantified in the tropospheric plumes from the arc average stratospheric volcanic SO2 flux of 1–4TgSO2/yr (Pyle et al., volcanoes Masaya, Telica and Villarrica (Witt et al., 2008; Sawyer 1996) and a mass ratio into the stratosphere of HCl/SO2 of between et al., 2011) and the non-arc volcanoes Etna, Kīlauea and Nyiragongo 0.006 and 0.06 (Table 4), this yields a time-averaged HCl flux to the (Aiuppa et al., 2005a; Mather et al., 2012; Bobrowski et al., 2015) via stratosphere of 0.006–0.24 Tg/yr. collection on filter packs and analysis using ICP-MS.

4.2. Recent advances in our understanding of volcanic bromine emissions (c) In situ glass concentrations of Br

Chlorine is not the only halogen released by volcanoes with the po- The first measurements of Br in melt inclusions and matrix glass by tential to deplete ozone. Bromine is thought to be at least an order of synchrotron–X-ray fluorescence were recently presented from 14 large magnitude more effective in terms of destroying stratospheric ozone explosive eruptions over the last 70 ka from Nicaragua (Kutterolf et al., than chlorine (Daniel et al., 1999). The behaviour of volcanic bromine in 2013). A further study presenting measurements across the broader magmas, during degassing and once in the atmosphere is more poorly un- Central American volcanic arc seeks to explore the arc-scale origins of derstood than chlorine. This is due in part to the greater analytical chal- volcanic Br (Kutterolf et al., 2015). lenges associated with its measurement. These are largely associated with its lower concentrations in both rocks and volcanic gases (Bureau There have been many key lessons from these initial studies. They et al., 2000; Bureau and Métrich, 2003; Pyle and Mather, 2009). Recent suggest that Br is about 3 orders of magnitude less abundant in volcanic analytical advances allow for optimism that the next decades will see a gases than Cl (Pyle and Mather, 2009; Mather et al., 2012; Kutterolf step change in our understanding of volcanic Br emissions. Recent inno- et al., 2013) and that our current best estimate of the average flux to vative measurements of volcanic bromine include: the atmosphere of HBr is 5–15 Gg/a (Pyle and Mather, 2009). The gas- phase and melt inclusion measurements of Br suggest that it is likely (a) Gas phase BrO (a product of ozone destruction by Br) enriched in subduction-related emissions due to the contribution of the downgoing slab (Mather et al., 2012; Pyle and Mather, 2009; Kutterolf BrO has been measured in both ‘passive’ or mildly explosive tro- et al., 2015), although recent measurements from the non-arc volcano pospheric plumes (Stromboli, Etna, Villarrica, Tungurahua, Masaya, Nyiragongo suggest further complexity here (Bobrowski et al., 2015). Soufrière Hills Volcano, Nyiragongo, Sakurajima and Ambrym) by The melt inclusion data suggest that large individual eruptions can poten- ground-based remote sensing (Bobrowski et al., 2003; von Glasow tially emit at least up to 1100 kt Br (Kutterolf et al., 2015) and the satellite et al., 2009 and references therein) and in more ash-rich plumes from based measurements show that volcanic Br can be transported to the explosive eruptions (Kasatochi, Eyjafjallajökull and Puyehue) via air- upper troposphere/lower stratosphere region by even relatively small ex- borne or satellite platforms (plume heights 8–14 km in the upper tropo- plosive eruptions (e.g., Theys et al., 2009; Heue et al., 2011; Theys et al., sphere/lower stratosphere region: Theys et al., 2009; Heue et al., 2011; 2014). The measurements of BrO suggest that Br is involved in heteroge- Theys et al., 2014). Hörmann et al. (2013) used the satellite-based neous chemistry within the plume following emission with associated GOME-2 instrument to systematically look for BrO during moderate to impacts on atmospheric ozone levels (von Glasow et al., 2009). major eruptions and very strong degassing events. Plumes from 10 to The scene is set but there is much still to be done. As discussed above 12 different volcanoes were found to contain BrO of volcanic origin our understanding of Br behaviour in volcanic systems is in its infancy

Table 4 Summary of explosive volcanic plume HCl measurements around the tropopause or in the stratosphere since 2003.

Volcano Measurementsa Altitude Lat./Long. Comments (km)

b El Chichón HCl: 0.04 Tg N11.9 km 22°N to • Using arc mean HCl/SO2 mass ratio of 0.3 suggests scavenging

March/April 1982 SO2:7Tg 35°N efﬁciency of ~98%. (Mankin and Coffey, 1984; Gives a mass ratio = 6 × 10−3 • Aircraft FTIR measurements using the sun as a source through the Bluth et al., 1997) upper atmosphere

Hekla SO2 ~ 1ppmv 10.4 km a.s.l 76.4–75.7°N • Little evidence of HCl scavenging (HCl/SO2 mass ratios tend to be Feb 2000 HCl ~70ppbv (lower 9.0–4.4°W lower for non-arc volcanoes)b (Rose et al., 2006) Mean mass ratio = 0.068 (from paper) stratosphere) • In-situ HCl measurements made by CIMS on board an aircraft

b Soufrière Hills Volcano 0.003–0.01 Tg HCl Stratosphere Tropics • Based on Soufrière Hills Volcano HCl/SO2 ratio of 0.34–6.80 gives

May 2006 0.2 ± 0.02 Tg SO2 scavenging efﬁciencies of 84–99.8% (Prata et al., 2007) Gives mass ratio = 0.014–0.056 • HCl measurements made by satellite microwave limb sounder (MLS)

b Puyehue-Cordón Caulle HCl up to 2.5 ppbv 12–14 km a.s.l. 40.59°S • Using arc mean HCl/SO2 mass ratio of 0.3 suggests scavenging

June 2011 Molar HCl/SO2 = 0.03–0.11 based on (around 72.12°W efﬁciency of 80–93% (Theys et al., 2014) mixing ratios reported. tropopause) • HCl measurements made by satellite microwave limb sounder (MLS) Mass ratio = 0.02–0.06

a Note for comparison that the natural background level of Cl in the stratosphere is about 0.6 ppbv and levels peaking at ~3.7 ppbv around 1997 (Nassar et al., 2006). b Pyle and Mather (2009) compiled direct plume measurements from high-temperature emissions of HCl/SO2.Arcgasesweremassratio0.1–0.3 with geometric/flux-weighted mean of ~0.3. Erebus was higher (phonolite) but other volcanoes from non-arc settings tended to be lower. This compilation did not include measurements of opaque explosive plumes. T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 171 compared to Cl. Future studies focussing on the content and degassing the importance of diffusion as well as partitioning and melt composition behaviour of Br in melts (Bureau et al., 2000; Bureau and Métrich, as a control on the trace metal composition of the emitted gases. 2003) and building up our database of Br emissions data (especially The lower concentrations of metals in volcanic plumes continue to the major species HBr) are to be encouraged. Modelling or laboratory be an analytical challenge and blank levels can be an issue in some studies to understand the fate of Br once in the atmosphere would be cases. This has led to many previous studies of metals in volcanic of great value (Cadoux et al., 2015). Key issues in terms of understand- gases focussing on condensates and sublimates collected a volcanic fu- ing the potential of volcanism to impact stratospheric ozone surround maroles and thermodynamic modelling (reviewed in Pokrovski et al. how much volcanic Br might reach the upper atmosphere for different (2013)). While valuable, in many cases these fumarolic studies are a emissions scenarios and under different atmospheric conditions. step removed from the actual volatilisation of the metals from the magma. Between emission from the magma and measurement at the fumarole, processes such as cooling of the gas stream, gas-wallrock and hy- 5. The release of metals from volcanoes: towards a systematic drothermal interactions etc. might have occurred. Over the past few understanding decades more data has been amassing on metal emissions measured direct from magma–air interfaces such as lava lakes, vents and flows. There Volcanic emissions are an important source of trace metals to the have also been technological developments with techniques such as ICP- environment (e.g., Hinkley et al., 1994; Pyle and Mather, 2003). For MS now being routinely available and we have learnt much about the re- some metals such as Hg and Cd they may account for up to 50% of natu- leased of trace metals from magmas via such measurements at active rally occurring emissions (Nriagu, 1989). Understanding the release of volcanoes. With some notable exceptions (e.g., Hg, Pyle and Mather, these often toxic trace metals from volcanoes followed by their transport 2003) the majority of trace metals in volcanic plumes are present by in volcanic plumes is important. Many of them impact human health and the time of measurement in the particle phase (Hinkley, 1991). Metals the environment (e.g., Fig. 1, Martin et al., 2009) and are important signals measured in volcanic plumes will be from 2 main sources: (i) release/ in archives of volcanic activity and environmental impacts such as ice volatilisation of metals from the magma followed by gas-particle phase cores (e.g., Hinkley and Matsumoto, 2007; Kellerhals et al., 2010). For ex- conversion and (ii) a silicate phase. The silicate phase will include com- ample, recent work on Hg has shown that volcanogenic trace metals have ponents from fragmentation of the magma during explosions or bubbles great potential in global chemostratigraphy, and might thereby help un- bursting at its surface and erosive dust from the conduit walls (reviewed ravel in even finer detail the links between past episodes of large-scale in Mather et al., 2003). These 2 pathways from magma in the vent to volcanism and their global environmental consequences (e.g., Sanei metals measured on the particle filter have different implications in et al., 2012; Percival et al., 2015). An understanding of metal volatility terms of the propensity of a metal to be volatilised and emitted into and release from magmas is also important due to its role in the for- the environment independent of ash or lava. mation of some ore deposits (although this is thought to be generally To disentangle the contributions from ash/silicate versus volatilisation limited without hydrothermal processes e.g., Pokrovski et al., 2013,and and thus assess the volatility of trace metals from magmas several meth- references therein Williams-Jones and Heinrich, 2005). On a larger scale, odologies have been used including: (i) emanation coefficients (εx), trace metal volatility from silicate melts is key to understanding their (ii) enrichment factors (EFs) and (iii) weight ash fraction (WAF). These use as tracers of igneous/magmatic processes and wider processes asso- different methods are summarised in Table 5. Each of them has their ad- ciated with the composition, evolution and differentiation of silicate vantages and disadvantages. While emanation coefficients should be eas- planets (e.g., Wood et al., 2006; Edmonds, 2015). ily comparable between different systems, their nature means that they However, the processes by which trace metals are released from can only be directly measured under rare circumstances (e.g., Rubin, magmas and the factors controlling their release are poorly understood. 1997; Norman et al., 2004). Even then it is hard to know how to be sure

Once a gas phase is present other minor elements such as trace metals that the final concentration, Cf, has truly been measured. Further, can diffuse through the liquid and partition into the vapour. This although the orders of element volatilities can be compared, it is not partitioning behaviour is likely dependent on temperature, pressure, clear how useful emanation coefficients are in terms of comparing with magmatic composition and gas composition (which in the case of experimental results. Johnson and Canil (2011), for example found little surface degassing may include an atmospheric component). Thus, the correlation between their results and emanation coefficients (maybe as degree to which trace metals migrate and partition into the gas phase they were measuring diffusion coefficients). Enrichment factors (EFs) is a function of their diffusion rate in the liquid, affinity for the vapour are more regularly possible to estimate but can vary considerably even phase and equilibrium solubility. A systematic understanding of metal at the same volcano on the same day due to factors such as variable volatility is desirable. This section addresses how studies of present- ash/silicate content of plumes. This, and the different choices of reference day volcanism might further contribute to this overall aim. element between studies, are challenges in terms of comparing the vola- While there has been recent progress in terms of experimental stud- tility of different metallic elements from different volcanic systems. This ies on the behaviour of volatile trace metals during degassing from makes developing a systematic framework to explain differences in magmas, much remains to be done. Mackenzie and Canil (2008) exper- their behaviour (e.g., as a function of magma composition) challenging. imentally measured diffusivities for Te, Tl, Re, Cd, Pb and Sb in a simple Comparison of the order of element EFs between different systems should Fe-free ‘haplobasalt’ melt composition. They proposed that trace metals yield useful if qualitative information however. Another method that has with different diffusivity and partition behaviour will fractionate during been used to estimate the ash contribution to trace metals on particle bubble growth and degassing and that metal ratios such as Cd/Re could filtersistheweightashfraction(WAF,Table 5)defined in Aiuppa et al. be used as a precursory signal of volcanic eruptions. Johnson and Canil (2003). This has many advantages, although it relies on good quality (2011) investigated the degassing of volatile heavy metals (Bi, Pb, Tl, measurements of the rare Earth elements (REEs) in both the magma Au, Re, Sb, Sn, Cd, Mo, As, Cu) from doped natural basalt and and plume phases and the (likely relatively safe) assumption that the dacite and synthetic rhyolite melts over a range of temperatures REEs are not volatilised. In the absence of reliable REE data, the concen- (1200–1430 °C) exposed to air at 0.1 MPa. They showed that the addi- trations of other non-volatile elements like Mg or Al could be used in the tion of Cl and S increased by two-to five-fold the volatilities of all metals, calculation instead. It is also by definition an estimate of the fraction of with S having a more profound effect. Limited spectroscopic plume mea- ash in the sample and is not a measure of metal volatility that can be surements (CuCl(g): Murata, 1960), laboratory experiments (Amman compared between systems. As well as improving the number and qual- et al., 1993) and thermodynamic modelling (e.g., Symonds et al., 1992) ity of measurements of metals in high-temperature volcanic plumes, have previously suggested that metals are generally volatilised from considering how best to compare these results quantitatively to develop the magma as chloride species. JohnsonandCanil(2011)also highlight aunified framework of metal volatility is also a key ongoing challenge 172 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Table 5 Summary of some of the main methods used in the literature to assess metal volatility in volcanic eruptions.

Method Deﬁnition Comments

− Emanation ε ¼ Ci C f • Defined by Gill et al. (1985) and Lambert et al. (1985/86) in order to study x C coefficients i the degassing of radionuclides such as 222Rn, 210Po, 210Bi and 210Pb where Ci is the initial concentration of element x in the magma and (εx) • Challenging to quantify εx values for elements that have intermediate Cf is the final concentration of element x in post-eruptive lava. properties. By considering disequilibrium with a radioactive decay series Lambert et al. (1985/86) determined values for Bi and Pb and Pennisi et al. 1 (1988) used these to calculate other εx values • This makes the determination of all other emanation coefficients reliant on

how well the value of εPb is determined and care should be taken about when to make an ash/spatter correction in the calculation • Rubin (1997) used this approach to calculate and compile global average emanation coefﬁcients for a number of elements

ð = Þ Enrichment ¼ Xplume Yplume • As noted by numerous other authors (e.g., Crowe et al., 1987; Aiuppa et al., EF ðX =Y Þ factors magma magma 2003), these values will vary even at the same volcano on the same day where X is the element of interest and Y is a reference element (E.F.) • One of the main factors leading to this variation is the variable ash/silicate content of volcanic plumes even over short timescales2

ðREE Þ ðX=REE Þ Weight ash ¼ Xer ¼ t a t r • Deﬁned by Aiuppa et al. (2003) this allows the subtraction of the ‘noise’ of WAF X X fraction t t ash contribution from total element content in order to gain insight into trace where Xer is the erosive contribution to Xt the total amount of element X in the (WAF) metal degassing mechanisms aerosol, (REEt)a is the total rare earth elements measured on the particle ﬁlter • Other non-volatile elements could be used in place of the REE and (X/REEt)r is the average ratio of element X to the total rare earth elements in the parent rocks

1 By considering disequilibrium with a radioactive decay series Lambert et al. (1985/86) determined values for Bi and Pb. Pennisi et al. (1988) then used the values for values for Bi and ðX=PbÞ ε =ε ε gas ¼ x pb Pb (Lambert et al., 1985/86) and the following relationship to calculate other x values: ð = Þ ð −ε Þ=ð −ε Þ. X Pb lava 1 x 1 pb 2 If we assume, for an open vent system, that the elements in the plume derive from 2 routes: (i) volatilisation from the magma and (ii) emission of ash or other silicate material from the magma surface then Xplume = Xvol + Xsil, where Xvol is the component of X contributed by the volatile route and Xsil is the component contributed from the silicate phase and similarly Yplume ððX þX Þ=ðY þY ÞÞ = Y + Y . Thus the equation for E.F. becomes:EF ¼ vol sil vol sil .IfY is very much less volatile than X (e.g., when Mg or Al are taken as reference elements, Mather et al., 2012) then vol sil ðXmagma =Ymagma Þ increasing the amount of ash collected on the filter will decrease the EF as the increasing silicate component will have a proportionally greater effect on (Yvol + Ysil)than(Xvol + Xsil) all else being equal. Conversely if Y is very much more volatile than X (e.g., when Br is taken as the reference element, Crowe et al., 1987) EF will increase if the amount of ash collected on the filter increases. for scientists working in this area. It is this challenge and possible future in the sample divided by the concentration of gaseous S ideally mea- ways to resolve it that I focus upon for the rest of this section. sured on alkali impregnated filters within the same filter stack) multi- Most geochemical processes, including degassing are modelled by plied by the concentration of S (in g g−1) in the gas mixture at the use of partition coefficients. Most of the experimental data on metal point of emission can be used. This requires knowledge of the gas com- melt-fluid/vapour partitioning is for geological systems at moderate position for that particular volcano at least in terms of the major gases pressures and high temperatures (P = 0.1 to 2 kbar; T = ~1000 °C; H2O, CO2 and SO2 and any other significant contributions. Typical gas see e.g., Pokrovski et al. (2013), and references therein) with little compositions can be used if suitable simultaneous measurements are data existing for low-pressure scenarios relevant in terms of magmatic unavailable. In Table 6 I apply this methodology (aerosol measurements degassing. However, the broadly used concept of partition coefficients corrected using WAF and dilution before comparison with rock mea- was recently applied to field observations of high-temperature volcanic surements) to estimate ‘volatility coefficients’ (i.e., approximate degassing of trace metals. Zelenski et al. (2014) estimated partition degassing partition coefficients) for metals in the gas and rock from 2 coefficients from the effusive basaltic eruption of Tolbachik volcano, example volcanic systems where suitable published data exist: Etna vol- Kamchatka by taking the ratio of the metal concentrations in the high cano, Italy (Aiuppa et al., 2003) and Masaya volcano, Nicaragua (Moune concentration gas stream (corrected for dilution by air) with elemental et al., 2010). Table 7 summarises the results of these calculations and concentrations measured in the rock. They made similar estimates for compares them to those in Zelenski et al. (2014). The normalisation to Erta Ale and Kudryavy for comparison citing uncertain contributions rock composition would ideally be based on a sample from the lava from the erosive/ash component to the aerosol and reference lava flow/lake or shallow reservoir at a similar time to the gas sampling values as among possible factors accounting for differences. This but, as with EF calculations in the past, this is hard to achieve due to seems like a promising approach to compare metal volatilities mea- practical constraints. sured at different volcanic systems and with experimental data. In an These estimates are by no means without uncertainties. For example, extension of Zelenski et al. (2014)'s approach, I suggest correcting for it requires good quality geochemical measurements of a range of volcanic the variable contribution from the silicate fraction in the sample using products and, as with EF and WAF above, it is sensitive to the rock compo- the WAF in order to consider only the volatile-derived component in sition chosen. This rock composition itself can vary with processes such as the aerosol: magma source, thermal/crystallisation and degassing history of the magma. Nonetheless this preliminary exploration shows promise as a Conc. element X in volatile derived aerosol = (1-WAF) × Total conc. unifying framework and there are interesting similarities and differ- element X in aerosol. ences between the results from Etna, Masaya, Tolbackik, Erta Ale and Kudryavy (Table 7). If we define volatile elements as those with volatil- In order to estimate a ‘partition coefficient’ for degassing for X by ity coefficient N1, moderately volatile with 0.1–1 and non-volatile those normalising each element in the gas phase to its concentration in the with b0.1, we see broad agreement between the elements falling into magma, these concentrations have to be corrected for dilution prior to these categories between the different volcanoes. This is especially the measurement. Zelenski et al. (2014) used a dilution factor derived case if we consider volatile and moderately volatile as one group from the ratio of total pumped air to condensate to correct back to mag- (Table 7). As, Bi, Cd, Hg, Re, Se, Tl and In all have volatilities N0.1 in matic gas concentration upon emission from the magma. Alternatively each case where they are measured. Al, Ba, Ca, Co, Cr, Fe, Ga, Ge, Hf, K, the measured mass ratio X/S (i.e., the volatile component of element X Li, Mg, Mn, Na, Nb, Ni, Rb, Sc, Si, Sn, Sr, Th, Ti, U, Y, Zn and Zr are non- T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 173

Table 6 This might reflect uncertainties in the data. Alternatively these may be Volatility coefficients (estimate of concentration in gas/concentration in rock at point of real differences due to magmatic or fluid phase compositions, redox emission) for Etna and Masaya calculated from published data (Etna: Aiuppa et al., conditions and temperature for example, and the complexity of the pro- 2003;Masaya:Moune et al., 2010). cesses of metal degassing from magmas and fluid transport Element Volatility coefficient (e.g., Johnson and Canil, 2011; Vlastélic et al., 2013; Johnson et al., ⁎ $ Etna Masaya 2013; Henley and Berger, 2013; Edmonds, 2015). Mean (s.d.)+ Mean (s.d.) It is interesting to compare the data presented in Table 7 to other Ag 3.5 × 10−2 (8.1 × 10−2) systems for quantifying elemental volatility. If we group the emanation −2 −2 −2 Al 1.1 × 10 (1.5 × 10 ) coefficients detailed in Rubin (1997) into 3 classes with (i) εx N 10 , − − As 3.3 × 10 1 (2.8 × 10 1) −4 −2 −4 (ii) εx 10 –10 and (iii) εx b 10 , the elements break down into Au 3.0 × 10−2 (5.1 × 10−2) the categories as follows: Ba 0§ 0 Be 3.7 × 10−2 (7.5 × 10−3) Bi 3.8 (1.8) 23 (4.2) (i) B, Bi, Se, Cd, Re, Hg, Au, Ag, Pb Ca 1.1 × 10−3 (1.6 × 10−3) (ii) Cu, Ir, As, Te, Zn, Tl, In, Mo, Sn, W, Sb, Cs, K, Ni, Li, Na −1 −2 Cd 1.6 × 10 (7.7 × 10 ) 10.4 (2.1) (iii) Hf, Cr, Co, Rb, Sr, V, Ce, Fe, Yb, Mn, Ba, Sc, Th, Eu, Ca, La, Sm, Al, Mg. Co 1.9 × 10−2 (2.3 × 10−2)§ 0 Cr 7.2 × 10−3 (6.4 × 10−3)§ Cs 9.0 × 10−2 (1.7 × 10−1)§ 2.0 × 10−1 (3.8 × 10−2) Cu 1.5 × 10−1 (1.7 × 10−1) 1.2 × 10−1 (2.2 × 10−2) There is broad agreement with Table 7, although also some interest- Fe 0 ing exceptions. For example, the εx of B suggests that it is more volatile Ga 9.5 × 10−3 (1.3 × 10−2) − − than the volatility coefficients suggest and the ε of Tl suggests that it is Ge 1.0 × 10 3 (9.7 × 10 4) x § fi Hf 0 0 less volatile. For both these elements the Kudryavy volatility coef cients # Hg 19 are more consistent with the εx than those for the other systems. The In 3.0 × 10−1 (1.8 × 10−1) − − relatively high volatility of B suggested at Kudryavy and in Rubin K 1.6 × 10 2 (2.8 × 10 2) fi −3 −2 § (1997) is also in contrast to the ndings from a recent melt inclusion Li 9.7 × 10 (2.5 × 10 ) ī Mg 6.4 × 10−4 (9.0× 10−4) study at K lauea (Edmonds, 2015). Fig. 5a also highlights that Te and Mn 3.4 × 10−3 (2.9 × 10−3) Sb show greater volatility in terms of their volatility coefficients com- −3 −3 Mo 9.8 × 10 (5.7 × 10 ) pared to εx. Based on EFs, Moune et al. (2010) grouped elements in to −3 −2 Na 7.4 × 10 (1.5 × 10 ) highly volatile (Cd, Tl, Bi and Te) and moderately volatile (Be, U, Zn, Nb 0§ − − Rb, Cu, Sb, Cs and Pb). Again there is general consistency, but in our vol- Ni 6.8 × 10 4 (9.4 × 10 4)§ − − − − fi fi Pb 1.3 × 10 1 (1.4 × 10 1)§ 5.9 × 10 1 (1.6 × 10 1) atility coef cient analysis U, Zn and Rb are de ned as non-volatile and Pt 3.8 × 10−1 (4.1 × 10−1) Sb belongs in the most volatile group for Etna. On a broader planetary Rb 3.1 × 10−2 (5.6 × 10−2)§ 7.0 × 10−2 (1.5 × 10−2) scale, the condensation temperatures (Tc, at which 50% of an element's Re 7.3 (4.9) atoms in a protoplanetary gas disc would have condensed) calculated Sb 17 (30) 1.6 × 10−1 (4.5 × 10−2) Sc 1.5 × 10−3 (1.4 × 10−3)§ by Lodders (2003) are often used to probe the role of volatility in the Se 9.2 (8.4) chemical evolution of the Earth and silicate planets. Comparing these Si 0 with our estimate of metal volatilities based on measurements at −3 −3 Sn 1.3 × 10 (1.8 × 10 ) degassing volcanoes suggests, for example, that Ge, Rb, Sn and Zn are Sr 0§ 0 − − less volatile under these circumstances than their T values suggest, Te 1.5 × 10 2 (1.2 × 10 2) 26 (7.3) c Th 8.5 × 10−6 (1.5 × 10−5)§ 1.4 × 10−3 (8.9 × 10−4) while Pt, Sb and Re are more volatile (Fig. 5b). These differences likely Ti 1.1 × 10−3 (1.4 × 10−3)§ stem from the very different conditions considered in the Lodders Tl 9.8 (13) 20 (3.3) (2003) calculations which were for condensation from gas in the −3 −3 § −2 −2 U 4.6 × 10 (6.2 × 10 ) 4.7 × 10 (1.3 × 10 ) low pressure, reduced conditions in the planetary disc rather than V 4.6 × 10−4 (6.8 × 10−4)§ W 3.2 × 10−3 (6.8 × 10−3) volatilisation from present-day magmas into an oxygenated atmosphere. Y0 0 These differences between volcanoes and volatility classification Zn 1.4 × 10−2 (1.2 × 10−2) 4.4 × 10−2 (1.2 × 10−2) systems highlight the importance of a systematic understanding of § Zr 0 0 metal volatility under different conditions when considering their be- ⁎ 2− X/SO2 ratios were calculated assuming SO4 /SO2 ~0.01 by mass. Etna gas data was taken haviour in the Earth system in the past, present and future. This also from Aiuppa et al. (2008). Etna is an alkali-basaltic volcano formed on tensional lithospheric highlights the importance of developing a unified framework to under- – faults cutting the eastern margin of the Apennine Magrehebide chain in the Ionian Sea. stand their partitioning during volatilisation/condensation processes. + In some cases one or more filters of the set were not estimated to have any volatile component on them or yielded WAF N 1. These were assigned volatility coefficients of 0. There is much further work to be done in this area. More measurements # −6 Taking bulk plume Hg/SO2 ~8.7 × 10 by mass from Bagnato et al. (2007) as Hg is are needed of metals in both rock and aerosol in conjunction with gas predominantly in the gas rather than particle phase at the point of emission. 4.2 × 10−1 measurements at diverse volcanoes to allow us to build up a more was calculated for the aerosol alone. complete picture of metal volatility from silicate melts. Melt inclusion § To test the sensitivity of the results to the rock data used I repeated the analaysis using studies, where possible, are also of great value (e.g., Edmonds, 2015). the trace element composition data for ash erupted from Etna's North East Crater May– December 1995 (Schiavi et al., 2006) for all the elements indicated. Pb was the only element Further experiments to determine elemental volatilities from melts of that would change categories in Table 7 based on this re-analysis with a new volatility coef- varying composition will also undoubtedly play a role as well as ther- − ficient of 9.9 × 10 2. This is still within the standard deviation of the results from the different modynamic calculations and modelling (review of previous work in filters. This comparison is unlikely to capture the effects of using an undegassed magma. $ Pokrovski et al., 2013). X/SO2 ratios were calculated from gas filter data in the Moune et al. (2010) paper. Masaya gas data was taken from Martin et al. (2010). Masaya is a basaltic shield volcano, forming part of the Central American Volcanic Arc associated with the subduction of the 6. Summary Cocos plate beneath the Caribbean plate. We have learnt much about the impacts of volcanism on our planet volatile in all cases measured. For the elements Ag, Au, B, Cs, Cu, Mo, Pb, by studying present-day activity. Studies during the satellite era have Pt, Sb, Te and W there is some disagreement in their volatility between shown us how large explosive eruptions can have clear impacts on plan- systems, although some like Pb are only borderline non-volatile in a sin- etary albedo, global atmospheric circulation patterns and stratospheric gle case and Mo is only borderline moderately volatile in a single case. chemistry. Numerous more subtle and more poorly understood effects 174 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Table 7 Summary of volatile, moderately volatile and non-volatile elements as deﬁned by the measurements at Etna and Masaya (Table 6) compared to literature values for Tolbackik, Erte Ale and Kudryavy.

Etna1 Masaya1 Tolbackik2 Erte Ale3 Kudryavy3,4

Volatile (volatility Bi, Hg, Re, Sb, Se, Tl Bi, Cd, Te, Tl As, Bi, Cd, Re, Se, Te, Tl Bi, Cd, Re, Se, Te, Tl 5B, Bi, Re, Se, Te coefficient N1) Moderately volatile As, Cd, Cu, In, Pb, Pt Cs, Cu, Pb, Sb Au, In, Pb, Pt Ag, As, Au, In, Pb, Pt, Sn As, Au, Cd, Mo, Sb, Tl, (volatility W coefficient 0.1–1) Non-volatile Ag, Al, Au, Ba, Ca, Co, Cr, Cs, Fe, Ga, Ge, Hf, K, 5Li, Ba, Be, Co, Hf, Ag, 5B, Ba, Cs, Co, Cu, Fe, K, 5B, Ba, Co, Cs, Cu, Fe, K, Ba, Co, Cs, Cu, Fe, K, 5Li, (volatility Mg, Mn, Mo, Na, Nb, Ni, Rb, Sc, Si, Sn, Sr, Te, Th, Ti, Rb, Sr, Th, U, Y, 5Li, Mn, Mo, Na, Rb, Sb, Si, 5Li, Mn, Mo, Na, Rb, Sb, Mn, Na, Pb, Pt, Rb, Si, coefficient b0.1) U, W, Y, Zn, Zr Zn, Zr Sn, W, Zn Si, Zn, W Sn, Zn

1 See Table 6. 2 Estimated in Zelenski et al. (2014) who were sampling high-concentration volcanic gases from lava tube windows ~300 m away from the lava lake. 3 Read off Fig. 11inZelenski et al. (2014) from data from Zelenski et al. (2013) for the basaltic Erta Ale volcano (collected in January 2011 from high-temperature (1084 °C) fumarolic gases emitted from a spatter cone in the middle of the north pit crater of the Erta Ale volcano) and Taran et al. (1995) for the basaltic andesite Kudryavy (fumarole condensates 585–940 °C collected during quiescent outgassing). 4 The vapour/melt partitioning coefficients calculated from fumarole condensates and associated lavas/rocks from Kudryavy by Pokrovski et al. (2013) from data presented in Taran et al. (1995) give Cl, Re, Se, B, S, Au, Ag, and Pt in the volatile category (N1), As, Mo and Sn in the moderately volatile category (0.1–1) and Pb, Sb, Zn, Zr, K, Cu, Na, Si and Fe in the non- volatile category (b0.1). 5 The results for B and Li are broadly consistent with the findings of Edmonds (2015) based on Kīlauea melt inclusions (vapour-melt partition coefficient for Li 0.02–0.24 and for B 0.014–0.5) other than in the case of B at Kudryavy. These data Kīlauea suggest that partitioning is inhibited at higher temperatures and depends also on the other melt volatile phases. The co-depletion of Cl and H2O in the M.I.s and the Fo contents of the host olivines supports low-pressure, high-temperature (N1100 °C) degassing. on the troposphere, such as modification of cloud properties, levels of on ozone. Measurement-based estimates suggest a wide range of frac- atmospheric oxidants, local sulphuric acid haze and marine or terrestrial tions of HCl reach the stratosphere, from ~100% for the high latitude erup- ecosystems, have also been suggested following these large eruptions as tion of Hekla to maybe b1% during the 2006 eruption from Soufrière Hills well as smaller explosive eruptions and passive degassing (summarised Volcano in the tropics (Table 4). Estimates from and input to modelling in Fig. 1 and Table 3). studies cover a similar range. Further measurements and modelling are There are many areas where further measurements of present-day needed in order to understand the scavenging processes operating in vol- volcanic emissions have great potential to further our understanding canic plumes and how they vary with different plume and atmospheric of volcanism's impacts on the environment. Here I highlight 3 examples. conditions. Current measurements allow us to make a ‘best guess’ time- Firstly, while there is some convergence in published estimates for averaged HCl flux to the stratosphere of 0.006–0.24 Tg/yr. Recent studies the global SO2 flux from volcanoes (likely due at least in part to the of volcanic Br emissions suggest that they could significantly impact dominant contribution from the highest flux volcanoes), more mea- stratospheric ozone levels following large eruptions. However, more measurements are needed to better constrain the fluxes of other key volca- surements of halogens, especially Br, are also needed to develop a full un- nic gases such as CO2 and halogens. On the scale of individual arcs even derstanding of the potential past and future effects of volcanism on SO2 fluxes are not well constrained over time (with a minimum uncer- stratospheric ozone without the influence of anthropogenic halogen tainty of a factor of 2 even for well studied arcs) and much more work is species. needed to determine whether or how key gas ratios (e.g., C/S) vary be- Thirdly, the partitioning of trace metals between silicate melts and tween and along individual arcs. Even for high-temperature plume the gas phase at the relatively low pressures characteristic of volcanic measurements C/S ratios vary by over 2 orders of magnitude globally degassing is poorly constrained. More comparison is needed of volatil- with significant variations within individual arcs and at individual vol- ities measured at different volcanic systems. I build on recent work to canoes. These uncertainties are among current barriers to advancing estimate the gas/melt partition coefficients using literature data from our understanding of volatile recycling through subduction zones. Etna and Masaya and compare these with limited literature values Variations in this recycling have been postulated to cause global change from Tolbackik, Erte Ale and Kudryavy. This allows elements to be during periods of the Earth's past. grouped into volatile/moderately volatile (As, Bi, Cd, Hg, Re, Se, Tl and Secondly, we still lack a systematic understanding of volcanic halogen In) and non-volatile (Al, Ba, Ca, Co, Cr, Fe, Ga, Ge, Hf, K, Li, Mg, Mn, Na, inputs to the stratosphere during explosive eruptions and their impacts Nb, Ni, Rb, Sc, Si, Sn, Sr, Th, Ti, U, Y, Zn and Zr). For some elements (Ag,

Fig. 5. (a) A plot of mean volatility coefficient based on the Etna and Masaya data presented in Table 6 against the emanation coefficients (defined in Table 5)fromRubin (1997).(b)Aplot of mean volatility coefficient based on the Etna and Masaya data presented in Table 6 against the condensation temperatures (at which 50% of an element's atoms in a protoplanetary gas disc would have condensed) calculated by Lodders (2003). T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 175

Au, B, Cs, Cu, Mo, Pb, Pt, Sb, Te and W) there is some disagreement in Bagnato, E., Aiuppa, A., Parello, F., Calabrese, S., D'Alessandro, W., Mather, T.A., McGonigle, fl A.J.S., Pyle, D.M., Wängberg, I., 2007. Degassing of gaseous (elemental and reactive) their volatility between volcanic systems, which could re ect real differ- and particulate mercury from Mount Etna volcano (Southern Italy). Atmos. Environ. ences in the conditions at the different volcanoes or uncertainties in the 41, 7377–7388. http://dx.doi.org/10.1016/j.atmosenv.2007.05.060. data. Comparison of these results with other systems to classify metal Bani, P., Normierc, A., Bacric, C., Allard, P., Gunawan, H., Hendrasto, M., Surono, Tsanev, V., 2015. First measurement of the volcanic gas output from Anak Krakatau, Indonesia. volatility highlight broad consistency but also some potentially impor- J. Volcanol. Geotherm. Res. 302, 237–241. tant differences. More measurements in volcanic plumes and rock suites Bay, R.C., Bramall, N., Price, P.B., 2004. Bipolar correlation of volcanism with millennial combined with experimental studies and thermodynamic calculations climate change. Proc. Natl. Acad. Sci. U. S. A. 101, 6341–6345. have the potential to further our systematic understanding of trace Beerling, D.J., Harfoot, M., Lomax, B., Pyle, J.A., 2007. The stability of the stratospheric ozone layer during the end-Permian eruption of the Siberian Traps. Phil. Trans. R. metal volatility. Better understanding in this area has implications in Soc. A 365, 1843–1866. http://dx.doi.org/10.1098/rsta.2007.2046. terms of metal release to the environment during volcanic activity as Bekki, S., Pyle, J.A., Zhong, W., Toumi, R., Haigh, J.D., Pyle, D.M., 1996. Theroleofmicrophys- well as their partitioning during other processes such as those involved ical and chemical processes in prolonging the climate forcing of the Toba eruption. Geophys. Res. Lett. 23, 2669–2672. with the evolution of magma geochemistry, ore formation and plane- Black, B.A., Lamarque, J.-F., Shields, C.A., Elkins-Tanton, L., Kiehl, J.T., 2013. Acid rain and tary evolution. ozone depletion from pulsed Siberian Traps magmatism. Geology 42, 67–70. http:// dx.doi.org/10.1130/G34875.1. Bluth, G.J.S., Rose, W.I., Sprod, I.E., Krueger, A.J., 1997. Stratospheric loading of sulfur from Acknowledgements explosive volcanic eruptions. J. Geol. 105, 671–683. Bobrowski, N., Hönninger, G., Galle, B., Platt, U., 2003. Detection of bromine monoxide in a – I have benefited from many useful and stimulating discussions that volcanic plume. Nature 423, 273 276. Bobrowski, N., von Glasow, R., Giuffrida, G.B., Tedesco, D., Aiuppa, A., Yalire, M., Arellano, have contributed in different ways to the writing of this review includ- S., Johansson, M., Galle, B., 2015. Gas emission strength and evolution of the molar ing those with Sandro Aiuppa, Lindy Elkins-Tanton, Frances Jenner, ratio of BrO/SO2 in the plume of Nyiragongo in comparison to Etna. J. Geophys. Res. – Charlie Langmuir, Rob Martin, Lawrence Percival, Fred Prata, David 120, 277 291. http://dx.doi.org/10.1002/2013JD021069. Brantley, S.L., Koepenick, K.W., 1995. Measured carbon dioxide emissions from Pyle, Anja Schmidt, Steve Self, Seb Watt, Jon Wade and Bernie Wood. I Oldoinyo Lengai and the skewed distribution of passive volcanic fluxes. Geology 23, would like to thank the NERC (including grant reference NE/ 933–936. M000427/1) and the Leverhulme Trust for funding. I would also like Briffa, K.R., Jones, P.D., Schweingruber, F.H., Osborn, T.J., 1998. Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years. Nature to thank the staff of St Anne's nursery for all their help and support 393, 450–455. over the last 7 years. Morgan Jones, an anonymous reviewer and the ed- Browning, T.J., Bouman, H.A., Henderson, G.M., Mather, T.A., Pyle, D.M., Schlosser, C., itor Lionel Wilson are thanked for their insightful comments on an ear- Woodward, E.M.S., Moore, C.M., 2014. Strong responses of Southern Ocean phytoplankton communities to volcanic ash. Geophys. Res. Lett. 41, 2851–2857. http://dx. lier version of the manuscript. This review is dedicated to the memory doi.org/10.1002/2014GL059364. of Roland von Glasow and his legacy in terms of advancing our under- Browning, T.J., Stone, K., Bouman, H., Mather, T.A., Pyle, D.M., Moore, C.M., Martinez- standing of the atmospheric chemistry occurring in volcanic plumes. Vicente, V., 2015. Volcanic ash supply to the surface ocean — remote sensing of bio- logical responses and their wider biogeochemical significance. Front. Mar. Sci. Mar. Biogeochem. 2, 14. http://dx.doi.org/10.3389/fmars.2015.0001. References Bureau, H., Métrich, N., 2003. An experimental study of bromine behaviour in water saturated silicic melts. Geochim. Cosmochim. Acta 67, 1689–1697. Achterberg, E.P., Moore, C.M., Henson, S.A., Steigenberger, S., Stohl, A., Eckhardt, S., Bureau, H., Keppler, H., Métrich, N., 2000. Volcanic degassing of bromine and iodine: ex- Avendano, L.C., Cassidy, M., Hembury, D., Klar, J.K., Lucas, M.I., Macey, A.I., Marsay, perimental fluid/melt partitioning data and applications to stratospheric chemistry. C.M., Ryan-Keogh, T.J., 2013. Natural iron fertilization by the Eyjafjallajökull volcanic Earth Planet. Sci. Lett. 183, 51–60. – eruption. Geophys. Res. Lett. 40, 921 926. http://dx.doi.org/10.1002/grl.50221. Burley, J.M.A., Katz, R.F., 2015. Variations in mid-ocean ridge CO2 emissions driven by Ague, J.J., Nicolescu, S., 2014. Carbon dioxide released from subduction zones by fluid- glacial cycles. Earth Planet. Sci. Lett. 426, 246–258. mediated reactions. Nat. Geosci. 7, 355–360. Burton, M.R., Allard, P., Murè, F., La Spina, A., 2007. Magmatic gas composition reveals Aiuppa, A., Dongarrà, G., Valenza, M., Federico, C., Pecoraino, G., 2003. Degassing of trace the source depth of slug-driven Strombolian explosive activity. Science 317, volatile metals during the 2001 eruption of Etna. In: Robock, A., Oppenheimer, C. 227–230. (Eds.), Volcanism and the Earth's AtmosphereGeophysical Monograph 139. Burton, M.R., Sawyer, G.M., Granieri, D., 2013. Deep carbon emissions from volcanoes. American Geophysical Union, Washington, D.C., pp. 41–54. Rev. Mineral. Geochem. 75, 323–354. http://dx.doi.org/10.2138/rmg.2013.75.11. Aiuppa, A., Federico, C., Franco, A., Giudice, G., Gurrieri, S., Inguaggiato, S., Liuzzo, M., Cadoux, A., Scaillet, B., Bekki, A., Oppenheimer, C., Druitt, T.H., 2015. Stratospheric ozone McGonigle, A.J.S., Valenza, M., 2005a. Emission of bromine and iodine from Mount destruction by the Bronze-Age Minoan eruption (Santorini Volcano, Greece). Sci. Report. Etna volcano. Geochem. Geophys. Geosyst. 6, Q08008. 5, 12243. Aiuppa, A., Federico, C., Giudice, G., Gurrieri, S., 2005b. Chemical mapping of a fumarolic Calabrese, S., Aiuppa, A., Allard, P., Bagnato, E., Bellomo, S., Brusca, L., D'Alessandro, W., field: La Fossa Crater, Vulcano Island (Aeolian Islands, Italy). Geophys. Res. Lett. 32, Parello, F., 2011. Atmospheric sources and sinks of volcanogenic elements in a basaltic L13309. volcano (Etna, Italy). Geochim. Cosmochim. Acta 75, 7401–7425. Aiuppa, A., Federico, C., Giudice, G., Gurrieri, S., Liuzzo, M., Shinohara, H., Favara, R., Caldeira, K., Rampino, M.R., 1990. Carbon dioxide emissions from Deccan volcanism and a Valenza, M., 2006. Rates of carbon dioxide plume degassing from Mount Etna volcano. K/T boundary greenhouse effect. Geophys. Res. Lett. 17, 1299–1302. http://dx.doi.org/ J. Geophys. Res. 111, B09207. http://dx.doi.org/10.1029/2006JB004307. 10.1029/GL017i009p01299. Aiuppa, A., Moretti, R., Federico, C., Giudice, G., Gurrieri, S., Liuzzo, M., Papale, P., Campbell, J.R., Welton, E.J., Krotkov, N.A., Yang, K., Stewart, S.A., Fromm, M.D., 2012. Likely Shinohara, H., Valenza, M., 2007. Forecasting Etna eruptions by real-time observation seeding of cirrus clouds by stratospheric Kasatochi volcanic aerosol particles near a of volcanic gas composition. Geology 35, 1115–1118. mid-latitude tropopause fold. Atmos. Environ. 46, 441–448. Aiuppa, A., Giudice, G., Gurrieri, S., Liuzzo, M., Burton, M., Caltabiano, T., McGonigle, A.J.S., Carboni, E., Grainger, R., Walker, J., Dudhia, A., Siddans, R., 2012. A new scheme for sul- Salerno, G., Shinohara, H., Valenza, M., 2008. Total volatile flux from Mount Etna. phur dioxide retrieval from IASI measurements: application to the Eyjafjallajökull Geophys. Res. Lett. 35, L24302. http://dx.doi.org/10.1029/2008GL035871. eruption of April and May 2010. Atmos. Chem. Phys. 12, 11417–11434. http://dx. Aiuppa, A., Giudice, G., Liuzzo, M., Tamburello, G., Allard, P., Calabrese, S., Chaplygin, I., doi.org/10.5194/acp-12-11417-2012. McGonigle, A.J.S., Taran, Y., 2012. First volatile inventory for Gorely volcano, Kamchatka. Carn, S.A., Krotkov, N.A., Yang, K., Krueger, A.J., 2013. Measuring global volcanic Geophys. Res. Lett. 39, L06307. degassing with the Ozone Monitoring Instrument (OMI). In: Pyle, D.M., Mather, Aiuppa, A., Robidoux, P., Tamburello, G., Conde, V., Galle, B., Avard, G., Bagnato, E., De T.A., Biggs, J. (Eds.), Remote-sensing of volcanoes and volcanic processes: inte- Moor, J.M., Martínez, M., Muñóz, A., 2014. Gas measurements from the Costa Rica– grating observation and modelling. Geological Society Special Publication 380, Nicaragua volcanic segment suggest possible along-arc variations in volcanic gas pp. 229–257. chemistry, Earth and Planetary Science Letters, Volume 407(1). December 2014, Cather, S.M., Dunbar, N.W., McDowell, F.W., McIntosh, W.C., Scholle, P.A., 2009. Climate 134–147. forcing by iron fertilization from repeated ignimbrite eruptions: the icehouse-silicic Andres, R.J., Kasgnoc, A.D., 1998. A time-averaged inventory of subaerial volcanic sulfur large igneous province (SLIP) hypothesis. Geosphere 5, 315–324. emissions. J. Geophys. Res. 103, 25,251–25,261. Chenet, A.L., Fluteau, F., Courtillot, V., Gerard, M., Subbarao, K.V., 2008. Determination of Ammann, M., Hauert, R., Burtscher, H., Siegmann, H.C., 1993. Photoelectric charging of ul- rapid Deccan eruptions across the Cretaceous–Tertiary boundary using paleomagnetic trafine volcanic aerosols: detection of Cu(I) as a tracer of chlorides in magmatic gases. secular variation: results from a 1200-m-thick section in the Mahabaleshwar escarp- J. Geophys. Res. 98, 551–556. ment. J. Geophys. Res. 113, B04101. http://dx.doi.org/10.1029/2006JB004635. Ayris, P., Lee, A., Wilson, K., Kueppers, U., Dingwell, D.B., Delmelle, P., 2013. SO2 sequestra- Chesner, C.A., Luhr, J.F., 2010. A melt inclusion study of the Toba Tuffs, Sumatra, Indonesia. tion in large volcanic eruptions: high-temperature scavenging by tephra. Geochim. J. Volcanol. Geotherm. Res. 197, 259–278. – Cosmochim. Acta 110, 58 69. Chiodini, G., Cioni, R., Guidi, M., Raco, B., 1998. Soil CO2 flux measurements in volcanic and Ayris, P.M., Delmelle, P., Cimarelli, C., Maters, E.C., Suzuki, Y.J., Dingwell, D.B., 2014. HCl geothermal areas. Appl. Geochem. 13, 543–552. uptake by volcanic ash in the high temperature eruption plume: mechanistic insights. Conde, V., Robidoux, P., Avard, G., Galle, B., Aiuppa, A., Muñoz, A., Giudice, G., 2014. Mea- – Geochim. Cosmochim. Acta 144, 188 201. surements of volcanic SO2 and CO2 fluxes by combined DOAS, Multi-GAS and FTIR 176 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

observations: a case study from Turrialba and Telica volcanoes. Int. J. Earth Sci. http:// Halmer, M.M., Schmincke, H.U., Graf, H.F., 2002. The annual volcanic gas input into the at- dx.doi.org/10.1007/s00531-014-1040-7. mosphere, in particular into the stratosphere: a global data set for the past 100 years. Connolly, J.A.D., 2005. Computation of phase equilibria by linear programming: a tool for J. Volcanol. Geotherm. Res. 115, 511–528. geodynamic modeling and its application to subduction zone decarbonation. Earth Hamme, R.C., Webley, P.W., Crawford, W.R., Whitney, F.A., DeGrandpre, M.D., Emerson, Planet. Sci. Lett. 236, 524–541. S.R., Eriksen, C.C., Giesbrecht, K.E., Gower, J.F.R., Kavanaugh, M.T., Peña, M.A., Sabine, Courtillot, V.E., Renne, P.R., 2003. On the ages of ﬂood basalt events. Compt. Rendus C.L., Batten, S.D., Coogan, L.A., Grundle, D.S., Lockwood, D., 2010. Volcanic ash fuels Geosci. 335, 113–140. anomalous plankton bloom in subarctic northeast Paciﬁc. Geophys. Res. Lett. 37, Crowe, B.M., Finnegan, D.L., Zöller, W.H., Boynton, W.V., 1987. Trace element geochemistry L19604. http://dx.doi.org/10.1029/2010GL044629. of volcanic gases and particles from 1983–1984 eruption episodes of Kilauea volcano. Harris, P.M., Rose, W.I., 1996. Dynamics of carbon dioxide emissions, crystallization, and J. Geophys. Res. 92, 13,708–13,714. magma ascent: hypotheses, theory, and applications to volcano monitoring at Daniel, J.S., Solomon, S., Portmann, R.W., Garcia, R.R., 1999. Stratospheric ozone destruc- Mount St. Helens. Bull. Volcanol. 58, 163–174. tion: the importance of bromine relative to chlorine. J. Geophys. Res. 104, Hernández, P.A., Melián, G., Giammanco, S., Sortino, F., Barrancos, J., Pérez, N.M., Padrón,

23871–23880. E., López, M., Donovan, A., Mori, T., Notsu, K., 2015. Contribution of CO2 and H2Semitted D'Arrigo, R., Wilson, R., Anchukaitis, K.J., 2013. Volcanic cooling signal in tree ring temper- to the atmosphere by plume and diffuse degassing from volcanoes: the Etna volcano case ature records for the past millennium. J. Geophys. Res. 118, 9000–9010. study. Surv. Geophys. 36, 327–349. Dasgupta, R., Hirshmann, M.M., 2010. The deep carbon cycle and melting in Earth's inte- Henley, R.W., Berger, B.R., 2013. Nature's refineries — metals and metalloids in arc volcanoes. rior. Earth Planet. Sci. Lett. 298, 1–13. Earth Sci. Rev. 125, 146–170. de Silva, S.L., Gosnold, W.D., 2007. Episodic construction of batholiths: insights from the Henríquez, W.I., Moreno, P.I., Alloway, B.V., Villarosa, G., 2015. Vegetation and climate spatiotemporal development of an ignimbrite flare-up. J. Volcanol. Geotherm. Res. change, fire-regime shifts and volcanic disturbance in Chiloé Continental (43°S) during 167, 320–335. the last 10,000 years. Quat. Sci. Rev. 123, 158–167. Delmelle, P., 2003. Environmental impacts of tropospheric volcanic gas plumes. In: Heue, K.-P., Brenninkmeijer, C.A.M., Baker, A.K., Rauthe-Schöch, A., Walter, D., Wagner, T., Oppenheimer, C., Pyle, D.M., Barclay, J. (Eds.), Volcanic Degassing. Geological Society, Hörmann, C., Sihler, H., Dix, B., Frieß, U., Platt, U., Martinsson, B.G., van Velthoven,

London, Special Publications 213, pp. 381–399. P.F.J., Zahn, A., Ebinghaus, R., 2011. SO2 and BrO observation in the plume of the Dessert, C., Dupre, B., Francois, L.M., Schott, J., Gaillardet, J., Chakrapani, G., Bajpai, S., 2001. Eyjafjallajokull volcano 2010: CARIBIC and GOME-2 retrievals. Atmos. Chem. Phys. Erosion of Deccan Traps determined by river geochemistry: impact on the global cli- 11, 2973–2989. mate and the Sr-87/Sr-86 ratio of seawater. Earth Planet. Sci. Lett. 188, 459–474. Heymann, J., Reuter, M., Hilker, M., Buchwitz, M., Schneising, O., Bovensmann, H., http://dx.doi.org/10.1016/S0012-821X(01)00317-X. Burrows, J.P., Kuze, A., Suto, H., Deutscher, N.M., Dubey, M.K., Grifﬁth, D.W.T., Hase, Duggen, S., Olgun, N., Croot, P., Hoffmann, L., Dietze, H., Delmelle, P., Teschner, C., 2010. F., Kawakami, S., Kivi, R., Morino, I., Petri, C., Roehl, C., Schneider, M., Sherlock, V., The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a Sussmann, R., Velazco, V.A., Warneke, T., Wunch, D., 2015. Consistent satellite XCO2 review. Biogeosciences 7, 827–844. retrievals from SCIAMACHY and GOSAT using the BESD algorithm. Atmos. Meas. Ebmeier, S.K., Sayer, A.M., Grainger, R.G., Mather, T.A., Carboni, E., 2014. Systematic satel- Tech. 8, 2961–2980. lite observations of the impact of aerosols from passive volcanic degassing on local Highwood, E.J., Stevenson, D.S., 2003. Atmospheric impact of the 1783–1784 Laki Eruption: cloud properties. Atmos. Chem. Phys. 14, 10601–10618. Part II. Climatic effect of sulphate aerosol. Atmos. Chem. Phys. 3, 1177–1189. http://dx. Edmond, J.M., Huh, Y., 2003. Non-steady state carbonate recycling and implications for doi.org/10.5194/acp-3-1177-2003.

the evolution of atmospheric P-CO2. Earth Planet. Sci. Lett. 216, 125–139. Hilton, D.R., Fischer, T.P., Marty, B., 2002. Noble gases and volatile recycling at subduction Edmonds, M., 2015. Partitioning of light lithophile elements during basalt eruptions zones. Rev. Mineral. Geochem. 47, 319–370. onEarth and application to Martian shergottites. Earth Planet. Sci. Lett. 411, Hinkley, T.K., 1991. Distribution of metals between particulate and gaseous forms in a 142–150. volcanic plume. Bull. Volcanol. 53, 395–400. Edmonds, M., Aiuppa, A., Humphreys, M., Moretti, R., Giudice, G., Martin, R.S., Herd, R.A., Hinkley, T., Matsumoto, A., 2007. Mid-Holocene change in types of degassing volcanoes, Christopher, T., 2010. Excess volatiles supplied by mingling of maﬁc magma at an an- using indium in Antarctic ice as a tracer of volcanic source type. Geophys. Res. Lett. desite arc volcano. Geochem. Geophys. Geosyst. 11, Q04005. 34, L17710. Edmonds, M., Sides, I.R., Swanson, D., Werner, C., Martin, R.S., Mather, T.A., Herd, R.A., Hinkley, T.K., Le Cloarec, M.-F., Lambert, G., 1994. Fractionation of families of major, Jones, R.L., Mead, M.I., Sawyer, G., Roberts, T.J., Sutton, A.J., Elias, T., 2013. Magma storage, minor, and trace metals across the melt-vapor interface in volcanic exhalations. transport and degassing during the 2008–10 summit eruption at Kīlauea Volcano, Geochim. Cosmochim. Acta 58, 3255–3263. Hawai'i. Geochim. Cosmochim. Acta 123, 284–301. Hoffmann, L.J., Breitbarth, E., Ardelan, M.V., Duggen, S., Olgun, N., Hassellöv, M., English, J.M., Toon, O.B., Mills, M.J., 2013. Microphysical simulations of large volcanic erup- Wängberg, S.Å., 2012. Inﬂuence of trace metal release from volcanic ash on growth tions: Pinatubo and Toba. J. Geophys. Res. 118, 1880–1895. of Thalassiosira pseudonana and Emiliania huxleyi. Mar. Chem. 132, 28–33.

Fischer, T.P., 2008. Fluxes of volatiles (H2O, CO2,N2, Cl, F) from arc volcanoes. Geochem. J. Holland, H.D., 2002. Volcanic gases, black smokers, and the Great Oxidation Event. 42, 21–38. Geochim. Cosmochim. Acta 66, 3811–3826. Freundt,A.,Grevemeyer,I.,Rabbel,W.,Hansteen,T.H.,Hensen,C.,Wehremann,H.,Kutterolf, Holland, H.D., 2009. Why the atmosphere became oxygenated: a proposal. Geochim.

S., Halama, R., Frische, M., 2014. Volatile (H2O, CO2, Cl, S) budget of the Central American Cosmochim. Acta 73, 5241–5255. subductionzone.Int.J.EarthSci.http://dx.doi.org/10.1007/s00531-014-1001-1. Hörmann, C., Sihler, H., Bobrowski, N., Beirle, S., Penning de Vries, M., Platt, U., Wagner, T., Gaillard, F., Scaillet, B., Arndt, N.T., 2011. Atmospheric oxygenation caused by a change in 2013. Systematic investigation of bromine monoxide in volcanic plumes from space volcanic degassing pressure. Nature 478, 229–232. by using the GOME-2 instrument. Atmos. Chem. Phys. 13, 4749–4781. http://dx.doi. Galle, B., Johansson, M., Rivera, C., Zhang, Y., Kihlman, M., Kern, C., Lehmann, T., Platt, U., org/10.5194/acp-13-4749-2013. Arellano, S., Hidalgo, S., 2010. Network for Observation of Volcanic and Atmospheric Horwell, C.J., Baxter, P.J., 2006. The respiratory health hazards of volcanic ash: a review for Change (NOVAC)—a global network for volcanic gas monitoring: network layout and volcanic risk mitigation. Bull. Volcanol. 69, 1–24. instrument description. J. Geophys. Res. 115, D05304. http://dx.doi.org/10.1029/ Hutchison, W., Mather, T.A., Pyle, D.M., Biggs, J., Yirgu, G., 2015. Structural controls on 2009JD011823. ﬂuid pathways in an active rift system: a case study of the Aluto volcanic complex. Ganino, C., Arndt, N.T., 2009. Climate changes caused by degassing of sediments during Geosphere 11, 542–562. http://dx.doi.org/10.1130/GES01119.1. the emplacement of large igneous provinces. Geology 37, 323–326. Huybers, P., Langmuir, C., 2009. Feedback between deglaciation, volcanism, and atmo-

Gassó, S., 2008. Satellite observations of the impact of weak volcanic activity on marine spheric CO2. Earth Planet. Sci. Lett. 286, 479–491. clouds.J.Geophys.Res.113,D14S19. Iacono-Marziano, G., Marecal, V., Pirre, M., Gaillard, F., Arteta, J., Scaillet, B., Arndt,

Gerlach, T.M., McGee, K.A., Sutton, A.J., Elias, T., 1998. Rates of volcanic CO2 degassing from N.T., 2012. Gas emissions due to magma–sediment interactions during flood airborne determinations of SO2, emission rates and plume CO2/SO2: test study at Pu'u magmatism at the Siberian Traps: gas dispersion and environmental conse- 'O'o cone, Kilauea volcano, Hawaii. Geophys. Res. Lett. 25, 2675–2678. quences. Earth Planet. Sci. Lett. 357–358, 308–318. http://dx.doi.org/10.1016/j.epsl. Gerlach, T.M., 2011. Volcanic versus anthropogenic carbon dioxide. EOS, Trans. A.G.U. 92, 2012.09.051. 201–202. Jarrard, R.D., 2003. Subduction fluxes of water, carbon dioxide, chlorine and potassium. Gill, J., Williams, R., Bruland, K., 1985. Eruption of basalt and andesite lava degasses 222Rn Geochemistry Geophysics Geosystems 4, 8905. http://dx.doi.org/10.1029/ and 210Po. Geophys. Res. Lett. 12, 17–20. 2002GC000392. Gíslason, S.R., Stefánsdóttir, G., Pfeffer, M.A., Barsotti, S., Jóhannsson, Th., Galeczka, I., Bali, Joachimski, M.M., Lai, X., Shen, S., Jiang, H., Luo, G., Chen, B., Chen, J., Sun, Y., 2012. Climate E., Sigmarsson, O., Stefánsson, A., Keller, N.S., Sigurdsson, Á., Bergsson, B., Galle, B., warming in the latest Permian and the Permian–Triassic mass extinction. Geology 40, Jacobo, V.C., Arellano, S., Aiuppa, A., Jónasdóttir, E.B., Eiríksdóttir, E.S., Jakobsson, S., 195–198. http://dx.doi.org/10.1130/G32707.1. Guðfinnsson, G.H., Halldórsson, S.A., Gunnarsson, H., Haddadi, B., Jónsdóttir, I., Johnson, A., Canil, D., 2011. The degassing behavior of Au, Tl, As, Pb, Re, Cd and Bi from Thordarson, Th., Riishuus, M., Högnadóttir, Th., Dürig, T., Pedersen, G.B.M., silicate liquids: experiments and applications. Geochim. Cosmochim. Acta 75, Höskuldsson, Á., Gudmundsson, M.T., 2015. Environmental pressure from the 1773–1784. 2014–15 eruption of Bárðarbunga volcano, Iceland. Geochem. Perspect. Lett. 1, Johnson, E.R., Kamenetsky, V.S., McPhie, J., 2013. The behavior of metals (Pb, Zn, As, Mo, Cu) 84–93. http://dx.doi.org/10.7185/geochemlet.1509. during crystallization and degassing of rhyolites from the Okataina Volcanic Center, Glaze, L.S., Self, S., Schmidt, A., Hunter, S.J., 2015. Assessing eruption column height in an- Taupo Volcanic Zone, New Zealand. J. Petrol. 54, 1641–1659. cient flood basalt eruptions. Earth Planet. Sci. Lett. http://dx.doi.org/10.1016/j.epsl. Johnston, F.K.B., Turchyn, A.V., Edmonds, M., 2011. Decarbonation efficiency in subduction 2014.07.043 (in press). zones: implications for warm Cretaceous climates. Earth Planet. Sci. Lett. 303, Goff, F., Love, S.P., Warren, R.G., Counce, D., Obenholzner, J., Siebe, C., Schmidt, S.C., 2001. 143–152.

Passive infrared remote sensing evidence for large, intermittent CO2 emissions at Jones, G.S., Gregory, J.M., Stott, P.A., Tett, S.F.B., Thorpe, R.B., 2005. An AOGCM simulation Popocatepetl volcano, Mexico. Chem. Geol. 177, 133–156. of the climate response to a volcanic super-eruption. Clim. Dyn. 25, 725–738. Gorman, P.J., Kerrick, D.M., Connolly, J.A.D., 2006. Modeling open system metamorphic Jones, M.T., Sparks, R.S.J., Valdes, P.J., 2007. The climatic impact of supervolcanic ash blankets. decarbonation of subducting slabs. Geochem. Geophys. Geosyst. 7, Q04007. Clim. Dyn. 29, 553–564. T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 177

Jones, M.T., Hembury, D.J., Palmer, M.R., Tonge, B., Darling, W.G., Loughlin, S.C., 2011. The Mather, T.A., Pyle, D.M., Oppenheimer, C., 2003. Tropospheric Volcanic Aerosol. In: weathering and element fluxes from active volcanoes to the oceans: a Montserrat Robock, A., Oppenheimer, C. (Eds.), Volcanism and the Earth's Atmosphere. Geophysical case study. Bull. Volcanol. 73, 207–222. Monograph 139. American Geophysical Union, Washington, D.C., pp. 189–212. Jones, M.T., Jerram, D.A., Svensen, H.H., Grove, C., 2015. The effects of large igneous prov- Mather, T.A., Tsanev, V.I., Pyle, D.M., McGonigle, A.J.S., Oppenheimer, C., Allen, A.G., 2004. inces on the global carbon and sulphur cycles. Palaeogeogr. Palaeoclimatol. Characterization and evolution of tropospheric plumes from Lascar and Villarrica vol- Palaeoecol. http://dx.doi.org/10.1016/j.palaeo.2015.06.042 (in press). canoes, Chile. J. Geophys. Res. 109, D21303. Kasting, J.F., Catling, D., 2003. Evolution of a habitable planet. Annu. Rev. Astron. Mather, T.A., Pyle, D.M., Tsanev, V.I., McGonigle, A.J.S., Oppenheimer, C., Allen, A.G., 2006. Astrophys. 41, 429–463. A reassessment of current volcanic emissions from the Central American arc with Kelemen, P.B., Manning, C.E., 2015. Reevaluating carbon fluxes in subduction zones, what specific examples from Nicaragua. J. Volcanol. Geotherm. Res. 149, 297–311. goes down, mostly comes up. Proc. Natl. Acad. Sci. U. S. A. 112, E3997–E4006. http:// Mather, T.A., Witt, M.L.I., Pyle, D.M., Quayle, B.M., Aiuppa, A., Bagnato, E., Martin, R.S., Sims, dx.doi.org/10.1073/pnas.1507889112. K.W.W., Edmonds, M., Sutton, A.J., Ilyinskaya, E., 2012. Halogens and trace metal Kellerhals, T., Tobler, L.H., Brütsch, S., Sigl, M., Wacker, L., Gäggeler, H.W., Schwikowski, M., emissions from the ongoing 2008 summit eruption of Kīlauea volcano, Hawai'i. 2010. Thallium as a tracer for preindustrial volcanic eruptions in an ice core record Geochim. Cosmochim. Acta 83, 292–323. from Illimani, Bolivia. Environ. Sci. Technol. 44, 888–893. McCormick, B.T., Edmonds, M., Mather, T.A., Campion, R., Hayer, C.S.L., Thomas, H.E., Carn, Kelley, S.P., 2007. The geochronology of large igneous provinces, terrestrial impact craters, S.A., 2013. Volcano monitoring applications of the Ozone Monitoring Instrument and their relationship to mass extinctions on Earth. J. Geol. Soc. 164, 923–936. (OMI). In: Pyle, D.M., Mather, T.A., Biggs, J. (Eds.), Remote-sensing of volcanoes and Kent, D.V., Muttoni, G., 2008. Equatorial convergence of India and early Cenozoic climate volcanic processes: integrating observation and modelling. Geological Society Special trends. Proc. Natl. Acad. Sci. 105, 16065–16070. Publication 380, pp. 259–291. Krakauer, N.Y., Randerson, J.T., 2003. Do volcanic eruptions enhance or diminish net primary McCormick, M.P., Thomason, L.W., Trepte, C.R., 1995. Atmospheric effects of the Mt. production? Evidence from tree rings. Glob. Biogeochem. Cycles 17, 1118. http://dx.doi. Pinatubo eruption. Nature 373, 399–404.

org/10.1029/2003GB002076. McGee, K.A., Doukas, M.P., McGimsey, R.G., Neal, C.A., Wessels, R.L., 2010. Emission of SO2, Kutterolf, S., Hansteen, T., Appel, K., Freundt, A., Krüger, K., Pérez, W., Wehrmann, H., CO2,andH2S from Augustine Volcano, 2002–2008. In: Power, J.A., Coombs, M.L., 2013. Combined bromine and chlorine release from large explosive volcanic erup- Freymueller, J.T. (Eds.), The 2006 Eruption of Augustine Volcano. USGS Professional tions: a threat to stratospheric ozone? Geology 41, 707–710. http://dx.doi.org/10. Paper 1769, Alaska, pp. 609–627. 1130/G34044.1. McGonigle, A.J.S., Oppenheimer, C., 2003. Optical sensing of volcanic gas and aerosol Kutterolf, S., Hansteen, T.H., Freundt, A., Wehrmann, H., Appel, K., Krüger, K., Pérez, W., emissions. In: Oppenheimer, C., Pyle, D.M., Barclay, J. (Eds.), Volcanic degassing. Geo- 2015. Bromine and chlorine emissions from Plinian eruptions along the Central logical Society Special Publications 213, pp. 149–168. American Volcanic Arc: from source to atmosphere. Earth Planet. Sci. Lett. 429 (1), McGonigle, A.J.S., Aiuppa, A., Giudice, G., Tamburello, G., Gurrieri, S., Hodson, A.J., 2008. 234–246. http://dx.doi.org/10.1016/j.epsl.2015.07.064. Unmanned aerial vehicle measurements of volcanic carbon dioxide fluxes. Geophys. Lambert, G., Le Cloarec, M.-F., Ardouin, B., Le Roulley, J.C., 1985/1986. Volcanic emission of Res. Lett. 35, L06303. radionuclides and magma dynamics. Earth Planet. Sci. Lett. 76, 185–192. McGuire, W.J., Howarth, R.J., Firth, C.R., Solow, A.R., Pullen, A.D., Saunders, S.J., Stewart, I.S., Langmann, B., Zakšek, K., Hort, M., Duggen, S., 2010. Volcanic ash as fertiliser for the sur- Vita-Finzi, C., 1997. Correlation between rate of sea-level change and frequency of face ocean. Atmos. Chem. Phys. 10, 3891–3899. explosive volcanism in the Mediterranean. Nature 389, 473–476. Lavigne, F., Degeai, J.P., Komorowski, J.C., Guillet, S., Robert, V., Lahitte, P., Oppenheimer, C., Mélançon, J., Levasseur, M., Lizotte, M., Delmelle, P., Cullen, J., Hamme, R.C., Peña, A., Stoffel, M., Vidal, C.M., Surono, Pratomo, I., Wassmer, P., Hajdas, I., Hadmoko, D.S., De Simpson,K.G.,Scarratt,M.,Tremblay,J.-É.,Zhou,J.,Johnson,K.,Sutherland,N., Belizal, E., 2013. Source of the great A.D. 1257 mystery eruption unveiled, Samalas volca- Arychuk,M.,Nemcek,N.,Robert,M.,2014.Early response of the northeast sub- no, Rinjani Volcanic Complex, Indonesia. Proc. Natl. Acad. Sci. U. S. A. 110, 16742–16747. arctic Pacific plankton assemblage to volcanic ash fertilization. Limnol. Oceanogr. 59, Lodders, K., 2003. Solar system abundances and condensation temperatures of the ele- 55–67. ments. Astrophys. J. 591, 1220–1247. Métrich, N., Allard, P., Aiuppa, A., Bani, P., Bertagnini, A., Shinohara, H., Parello, F., Di Muro, Lund, D.C., Asimow, P.D., 2011. Does sea level influence mid-ocean ridge magmatism on A., Garaebiti, E., Belhadj, O., Massare, D., 2011. Magma and volatile supply to post- Milankovitch timescales? Geochem. Geophys. Geosyst. 12, Q12009. collapse volcanism and block resurgence in Siwi Caldera (Tanna Island, Vanuatu Luo, Z.Z., Rossow, W.B., Inoue, T., Stubenrauch, C.J., 2002. Did the eruption of the Mt. Arc). J. Petrol. 52, 1077–1105. Pinatubo Volcano affect cirrus properties? J. Clim. 15, 2806–2820. Miller, G.H., Geirsdóttir, Á., Zhong, Y., Larsen, D.J., Otto-Bliesner, B.L., Holland, M.M., Bailey, Luth, R.W., 2014. Volatiles in Earth's Mantle. Treatise on Geochemistry Second edition. D.A., Refsnider, K.A., Lehman, S.J., Southon, J.R., Anderson, C., Björnsson, H., 3 pp. 355–391. Thordarson, T., 2012. Abrupt onset of the Little Ice Age triggered by volcanism and MacKenzie, J.M., Canil, D., 2008. Volatile heavy metal mobility in silicate liquids: implica- sustained by sea-ice/ocean feedbacks. Geophys. Res. Lett. 39, L02708. tions for volcanic degassing and eruption prediction. Earth Planet. Sci. Lett. 269, Mori, T., Shinohara, H., Kazahaya, K., Hirabayashi, J.-I., Matsushima, T., Mori, T., Ohwada,

487–495. M., Odai, M., Iino, H., Miyashita, M., 2013. Time-averaged SO2 ﬂuxes of subduction- Mankin, W.G., Coffey, M.T., Goldman, A., 1992. Airborne observations of SO2,HCl,andO3 zone volcanoes: example of a 32-year exhaustive survey for Japanese volcanoes. in the stratospheric plume of the Pinatubo Volcano in July 1991. Geophys. Res. Lett. J. Geophys. Res. 118, 8662–8674. http://dx.doi.org/10.1002/jgrd.50591.

19, 179–182. Mori, T., Notsu, K., 1997. Remote CO, COS, CO2,SO2, HCl detection and temperature esti- Mankin, W.G., Coffey, M.T., 1984. Increased stratospheric hydrogen-chloride in the mation of volcanic gas. Geophys. Res. Lett. 24, 2047–2050. El-Chichon cloud. Science 226, 170–172. Moune, S., Gauthier, P.-J., Delmelle, P., 2010. Trace elements in the particulate phase of the Manning, M.R., Lowe, D.C., Moss, R.C., Bodeker, G.E., Allan, W., 2005. Short-term variations plume of Masaya Volcano, Nicaragua. J. Volcanol. Geotherm. Res. 193, 232–244. in the oxidizing power of the atmosphere. Nature 436, 1001–1004. Murata, K., 1960. Occurrence of CuCl emission in volcanic ﬂames. Am. J. Sci. 258, 769–782. Marín-Cerón, M.I., Moriguti, T., Makishima, A., Nakamura, E., 2010. Slab decarbonation Nassar, R., Bernath, P.F., Boone, C.D., Clerbaux, C.D., Coheur, P.F., Dufour, G., Froidevaux, L.,

and CO2 recycling in the Southwestern Colombian volcanic arc. Geochim. Mahieu, E., McConnell, J.C., McLeod, S.D., Murtagh, D.P., Rinsland, C.P., Semeniuk, K., Cosmochim. Acta 74, 1104–1121. Skelton, R., Walker, K.A., Zander, R., 2006. A global inventory of stratospheric chlorine Martin, R.S., Watt, S.F.L., Pyle, D.M., Mather, T.A., Matthews, N.E., Georg, B., Day, J.A., in 2004. J. Geophys. Res. 111, D22312. Fairhead, T., Witt, M.L.I., Quayle, B.M., 2009. Environmental effects of ashfall in Norman, M.D., Garcia, M.O., Bennett, V.C., 2004. Rhenium and chalcophile elements in ba- Argentina from the 2008 Chaitén volcanic eruption. J. Volcanol. Geotherm. Res. 184, saltic glasses from Ko'olau and Moloka'i volcanoes: magmatic outgassing and compo- 462–472. http://dx.doi.org/10.1016/j.jvolgeores.2009.04.010. sition of the Hawaiian plume. Geochim. Cosmochim. Acta 68, 3761–3777. Martin, R.S., Witt, M.L.I., Sawyer, G.M., Thomas,H.E.,Watt,S.F.L.,Bagnato,E., Nriagu, J.O., 1989. A global assessment of natural sources of atmospheric trace metals. Calabrese, S., Aiuppa, A., Delmelle, P., Pyle, D.M., Mather, T.A., 2012a. Nature 338, 47–49. Bioindication of volcanic mercury (Hg) deposition around Mt Etna (Sicily). Olgun, N., Duggen, S., Andronico, D., Kutterolf, S., Croot, P., Giammanco, S., Censi, P., Chem. Geol. 310–311, 12–22. Randazzo, L., 2013. Possible impacts of volcanic ash emissions of Mount Etna on the Martin, R.S., Wheeler, J.C., Ilyinskaya, E., Braban, C.F., Oppenheimer, C., 2012b. The uptake primary productivity in the oligotrophic Mediterranean Sea: results from nutrient-

of halogen (HF, HCl, HBr and HI) and nitric (HNO3) acids into acidic sulphate particles release experiments in seawater. Mar. Chem. 152, 32–42. in quiescent volcanic plumes. Chem. Geol. 296–297, 19–25. Oman,L.,Robock,A.,Stenchikov,G.L.,Thordarson,T.,Koch,D.,Shindell,D.T.,Gao,C., Martin, R.S., Ilyinskaya, E., 2011. Volcanic lightning as a source of reactive radical species 2006. Modeling the distribution of the volcanic aerosol cloud from the in eruption plumes. Geochem. Geophys. Geosyst. 12, Q03002. 1783–1784 Laki eruption. J. Geophys. Res. 111, D12209. http://dx.doi.org/10. Martin, R.S., Sawyer, G.M., Spampinato, L., Salerno, G.G., Ramírez, C., Ilyinskaya, E., Witt, 1029/2005JD006899. M.L.I., Mather, T.A., Watson, I.M., Phillips, J.C., Oppenheimer, C., 2010. A total volatile Oppenheimer, C., Kyle, P.R., 2008. Probing the magma plumbing of Erebus volcano, inventory for Masaya volcano, Nicaragua. J. Geophys. Res. 115, B09215. http://dx.doi. Antarctica, by open-path FTIR spectroscopy of gas emissions. J. Volcanol. Geotherm. org/10.1029/2010JB007480. Res. 177, 743–754. Mason, B.G., Pyle, D.M., Oppenheimer, C., 2004. The size and frequency of the largest erup- Oppenheimer, C., 2002. Limited global change due to the largest known Quaternary eruptions on Earth. Bull. Volcanol. 66, 735–748. tion, Toba ~74 kyr BP? Quat. Sci. Rev. 21, 1593–1609. Mather, T.A., 2008. Volcanoes and the atmosphere: the potential role of the atmosphere in Oppenheimer, C., 2003. Climatic, environmental and human consequences of the largest unlocking the reactivity of volcanic emissions. Philosophical Transactions A 366, known historic eruption: Tambora volcano (Indonesia) 1815. Prog. Phys. Geogr. 27, 4581–4595. http://dx.doi.org/10.1098/rsta.2008.0152. 230–259. Mather, T.A., Harrison, R.G., 2006. Electriﬁcation of volcanic plumes. Surv. Geophys. 27, Parks,M.M.,Caliro,S.,Chiodini,G.,Pyle,D.M.,Mather,T.A.,Berlo,K.,Edmonds,M., 387–432. http://dx.doi.org/10.1007/s10712-006-9007-2. Biggs, J., Nomikou, P., Raptakis, C., 2013. Distinguishing contributions to diffuse

Mather, T.A., Pyle, D.M., 2015. Volcanic emissions: short-term perturbations, long-term CO2 emissions in volcanic areas from magmatic degassing and thermal decar- consequences and global environmental change. In: Elkins-Tanton, L.T., Schmidt, A., bonation using soil gas 222Rn-δ13C systematics: application to Santorini volcano, Fristad, K. (Eds.), Volcanism and Global Environmental Change. Cambridge University Greece. Earth Planet. Sci. Lett. 377–378, 180–190. http://dx.doi.org/10.1016/j. Press, pp. 208–227. epsl.2013.06.046. 178 T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179

Payne, J.L., Clapham, M.E., 2012. End-Permian mass extinction in the oceans: an ancient Schmidt, A., Leadbetter, S., Theys, N., Carboni, E., Witham, C.S., Stevenson, J.A., Birch, C.E., analog for the twenty-ﬁrst century? Annu. Rev. Earth Planet. Sci. 40, 89–111. http:// Thordarson, Th., Turnock, S., Barsotti, S., Delaney, L., Feng, W., Grainger, R.G., Hort, dx.doi.org/10.1146/annurev-earth-042711-105329. M.C., Höskuldsson, Á., Ialongo, I., Ilyinskaya, E., Jóhannsson, T., Kenny, P., Mather, Pedone, M., Aiuppa, A., Giudice, G., Grassa, F., Francofonte, V., Bergsson, B., Ilyinskaya, E., T.A., Richards, N.A.D., Shepherd, J., 2015. Satellite detection, long-range transport

2014. Tunable diode laser measurements of hydrothermal/volcanic CO2, and implica- and air quality impacts of volcanic sulfur dioxide from the 2014–2015 flood lava tions for the global CO2 budget. Solid Earth 5, 1209–1221. http://dx.doi.org/10.5194/ eruption at Bárðarbunga (Iceland). J. Geophys. Res. - Atmos. 120. http://dx.doi.org/ se-5-1209-2014. 10.1002/2015JD023638 (in press). Pennisi, M., Le Cloarec, M.-F., Lambert, G., Le Roulley, J.C., 1988. Fractionation of metals in Schmidt, M.W., Poli, S., 2014. Devolatilization During Subduction. Treatise on Geochemistry volcanic emissions. Earth Planet. Sci. Lett. 88, 284–288. Second Edition. 4 pp. 669–701. Percival, L.M.E., Witt, M.L.I., Mather, T.A., Hermoso, M., Jenkyns, H.C., Hesselbo, S.P., Al- Self, S., Schmidt, A., Mather, T.A., 2014a. Emplacement characteristics, time scales, and Suwaidi, A.H., Storm, M.S., Xu, W., Ruhl, M., 2015. Globally enhanced mercury depo- volatile release rates of continental flood basalt eruptions on Earth. In: Keller, G., sition during the end-Pliensbachian extinction and Toarcian OAE: a link to the Karoo- Kerr, A. (Eds.), Volcanism, Impacts and Mass Extinctions: Causes and Effects. Geolog- Ferrar Large Igneous Province. Earth Planet. Sci. Lett. 428, 267–280. http://dx.doi.org/ ical Society of America Special Paper 505. http://dx.doi.org/10.1130/2014.2505(16). 10.1016/j.epsl.2015.06.064. Self, S., Glaze, L.S., Schmidt, A., Mather, T.A., 2014b. Volatile release from flood basalt erup- Pfeffer, M.A., Langmann, B., Graf, H.F., 2006. Atmospheric transport and deposition of tions: understanding the potential environmental effects. In: Elkins-Tanton, L.T., Indonesian volcanic emissions. Atmos. Chem. Phys. 6, 2525–2537. Schmidt, A., Fristad, K. (Eds.), Volcanism and Global Environmental Change. Cambridge Plank, T., Langmuir, C.H., 1998. The chemical composition of subducting sediment and its University Press. consequences for the crust and mantle. Chemical Geology 145, 325–394. Shinohara, H., 2013. Volatile flux from subduction zone volcanoes: insights from a de- Plimer, I., 2009. Heaven and Earth: Global Warming — The Missing Science. Taylor Trade tailed evaluation of the fluxes from volcanoes in Japan. J. Volcanol. Geotherm. Res. Publishing, Lanham, Md pp. 504. 268, 46–63. Prata, A.J., Carn, S.A., Stohl, A., Kerkmann, J., 2007. Long range transport and fate of a Shinohara, H., Witter, J.B., 2005. Volcanic gases emitted during mild strombolian activity stratospheric volcanic cloud from Soufrière Hills volcano, Montserrat. Atmos. Chem. of Villarrica volcano, Chile. Geophys. Res. Lett. 32, L20308. http://dx.doi.org/10. Phys. 7, 5093–5103. 1029/2005GL024131. Pokrovski, G.S., Borisova, A.Y., Bychkov, A.Y., 2013. Speciation and transport ofmetals and Shinohara, H., Fukui, K., Kazahaya, K., Saito, G., 2003. Degassing process of Miyakejima metalloids in geological vapors. Rev. Mineral. Geochem. 76, 165–218. http://dx.doi. volcano: implications of gas emission rate and melt inclusion data. In: De Vivo, B., org/10.2138/rmg.2013.76.6 http://dx.doi.org/. Bodnar, B. (Eds.), Melt Inclusions in Volcanic Systems, pp. 147–161.

Pyle, D.M., Mather, T.A., 2003. The importance of volcanic emissions in the global atmo- Shinohara, H., Aiuppa, A., Giudice, G., Gurrieri, S., Liuzzo, M., 2008. Variation of H2O/CO2 spheric mercury cycle. Atmos. Environ. 37, 5115–5124. and CO2/SO2 ratios of volcanic gases discharged by continuous degassing of Mount Pyle, D.M., Mather, T.A., 2009. Halogens in igneous processes and their ﬂuxes to the atmo- Etna volcano, Italy. J. Geophys. Res. 113, B09203. sphere and oceans from volcanic activity: a review. Chem. Geol. 263, 110–121. http:// Sobolev, S.V., Sobolev, A.V., Kuzmin, D.V., Krivolutskaya, N.A., Petrunin, A.G., Arndt, N.T., dx.doi.org/10.1016/j.chemgeo.2008.11.013. Radko, V.A., Vasiliev, Y.R., 2011. Linking mantle plumes, large igneous provinces Pyle, D.M., Beattie, P.D., Bluth, G.J.S., 1996. Sulphur emissions to the stratosphere from ex- and environmental catastrophes. Nature 477, 312–316. http://dx.doi.org/10.1038/ plosive volcanic eruptions. Bull. Volcanol. 57, 663–671. nature10385. Quayle, B.M., Mather, T.A., Witt, M.L.I., Maher, B.A., Mitchell, R., Martin, R.S., Calabrese, S., Stevenson, D.S., Johnson, C.E., Highwood, E.J., Gauci, V., Collins, W.J., Derwent, R.G., 2003. 2010. Application and evaluation of biomagnetic and biochemical monitoring of the Atmospheric impact of the 1783–1784 Laki eruption: Part I. Chemistry modelling. dispersion and deposition of volcanically-derived particles at Mt. Etna, Italy. Atmos. Chem. Phys. 3, 487–507. http://dx.doi.org/10.5194/acp-3-487-2003. J. Volcanol. Geotherm. Res. 191, 107–116. Stewart, C., Johnston, D.M., Leonard, G., Horwell, C.J., Thordarsson, T., Cronin, S., 2006. Robock, A., 2000. Volcanic eruptions and climate. Rev. Geophys. 38, 191–219. Contamination of water supplies by volcanic ashfall: a literature review and simple Robock, A., Ammann, C.M., Oman, L., Shindell, D., Levis, S., Stenchikov, G., 2009. Did the impact modelling. J. Volcanol. Geotherm. Res. 158, 296–306. Toba volcanic eruption of similar to 74 ka BP produce widespread glaciation? Stock,M.J.,Humphreys,M.C.S.,Smith,V.C.,Johnson,R.D.,Pyle,D.M.,2015.Apatite as mag- J. Geophys. Res. 114, D10107. matic volatile probe: quantifying the mechanisms and rates of EPMA-induced halogen Rose, W.I., Millard, G.A., Mather, T.A., Hunton, D.E., Anderson, B., Oppenheimer, C., migration. Am. Mineral. 100, 281–293. Thornton, B.F., Gerlach, T.M., Viggiano, A.A., Kondo, Y., Miller, T.M., Ballenthin, J.O., Stoiber, R.E., Williams, S.N., Huebert, B., 1987. Annual contribution of sulfur dioxide to the 2006. The atmospheric chemistry of a 33–34 hour old volcanic cloud from Hekla atmosphere by volcanoes. J. Volcanol. Geotherm. Res. 33, 1–8. Volcano (Iceland): insights from direct sampling and the application of chemical box Straub, S.M., Layne, G.D., 2003. The systematics of chlorine, ﬂuorine and water in Izu arc modelling. J. Geophys. Res. 111, D20206. http://dx.doi.org/10.1029/2005JD006872. front volcanic rocks: implications for volatile recycling in subduction zones. Geochim. Roth, R., Joos, F., 2012. Model limits on the role of volcanic carbon emissions in regulating Cosmochim. Acta 67, 4179–4203.

glacial–interglacial CO2 variations. Earth Planet. Sci. Lett. 329, 141–149. Sun, C.Q., Plunkett, G., Liu, J.Q., Zhao, H.L., Sigl, M., McConnell, J.R., Pilcher, J.R., Vinther, B., Rubin, K., 1997. Degassing of metals and metalloids from erupting seamount and mid- Steffensen, J.P., Hall, V., 2014. Ash from Changbaishan Millennium eruption recorded ocean ridge volcanoes: observations and predictions. Geochim. Cosmochim. Acta in Greenland ice: implications for determining the eruption's timing and impact. 61, 3525–3542. Geophys. Res. Lett. 41, 694–701. Sanei, H., Grasby, S.E., Beauchamp, B., 2012. Latest Permian mercury anomalies. Geology Sutton, A.J., Elias, T., 1993. Volcanic gases create air pollution on the Island of Hawai'i. U.S. 40, 63–66. http://dx.doi.org/10.1130/G32596.1. Geol. Surv. Earthquakes Volcanoes 24, 178–196. Sassen, K., Starr, D.O., Mace, G.G., Poellot, M.R., Melfi, S.H., Eberhard, W.L., Spinhirne, J.D., Svensen, H., Planke, S., Polozov, A.G., Schmidbauer, N., Corfu, F., Podladchikov, Y.Y., Eloranta, E.W., Hagen, D.E., Hallett, J., 1995. The 5–6 December 1991 FIRE IFO II jet Jamtveit, B., 2009. Siberian gas venting and the end-Permian environmental crisis. stream cirrus case study: possible influences of volcanic aerosols. J. Atmos. Sci. 52, Earth Planet. Sci. Lett. 277, 490–500. 97–123. Symonds, R.B., Reed, M.H., Rose, W.I., 1992. Origin, speciation, and fluxes of trace-element Sawyer, G.M., Oppenheimer, C., Tsanev, V.I., Yirgu, G., 2008a. Magmatic degassing at Erta gases at Augustine volcano, Alaska: insights into magma degassing and fumarolic 'Ale volcano, Ethiopia. J. Volcanol. Geotherm. Res. 178, 837–846. processes. Geochim. Cosmochim. Acta 56, 633–657. Sawyer, G.M., Carn, S.A., Tsanev, V.I., Oppenheimer, C., Burton, M., 2008b. Investigation Syracuse, E.M., van Keken, P.E., Abers, G.A., Suetsugu, D., Bina, C., Inoue, T., Wiens, D., into magma degassing at Nyiragongo volcano, Democratic Republic of the Congo. Jellinek, M., 2010. The global range of subduction zone thermal models. Phys. Earth Geochem. Geophys. Geosyst. 9, Q02017. Planet. Inter. 183, 73–90. Sawyer, G.M., Salerno, G.G., Le Blond, J.S., Martin, R.S., Spampinato, L., Roberts, T.J., Mather, Tabazadeh, A., Turco, R.P., 1993. Stratospheric chlorine injection by volcanic eruptions: T.A., Witt, M.L.I., Tsanev, V.I., Oppenheimer, C., 2011. Gas and aerosol emissions from HCl scavenging and implications for ozone. Science 260, 1082–1086. Villarrica volcano, Chile. J. Volcanol. Geotherm. Res. 203, 62–75. http://dx.doi.org/10. Tamburello, G., Hansteen, T.H., Bredemeyer, S., Aiuppa, A., Tassi, F., 2014. Gas emissions 1016/j.jvolgeores.2011.04.003. from five volcanoes in northern Chile and the implications for the volatile budget Scaillet, B., Luhr, J., Carroll, M.R., 2003. Petrological and Volcanological Constraints on of the Central Volcanic Zone. Geophys. Res. Lett. 41. http://dx.doi.org/10.1002/ Volcanic Sulfur Emissions to the Atmosphere. In: Robock, A., Oppenheimer, C. 2014GL060653. (Eds.), Volcanism and the Earth's Atmosphere. Geophysical Monograph 139. Taran, Y.A., 2009. Geochemistry of volcanic and hydrothermal fluids and volatile American Geophysical Union, Washington, D.C., pp. 11–40. budget of the Kamchatka–Kuril subduction zone. Geochim. Cosmochim. Acta 73, Schaller, M.F., Wright, J.D., Kent, D.V., Olsen, P.E., 2012. Rapid emplacement of the Central 1067–1094.

Atlantic Magmatic Province as a net sink for CO2. Earth Planet. Sci. Lett. 323, 27–39. Taran, Y.A., Hedenquist, J.W., Korzhinskii, M., Tkachenko, S.I., Shmulovich, K.I., 1995. Geo- Schiavi, F., Tiepolo, M., Pompilio, M., Vannucci, R., 2006. Tracking magma dynamics by chemistry of magmatic gases from Kudryavy volcano, Iturup, Kuril Islands. Geochim. laser ablation (LA)-ICPMS trace element analysis of glass in volcanic ash: the Cosmochim. Acta 59, 1749–1761. 1995 activity of Mt. Etna. Geophys. Res. Lett. 33, L05304. http://dx.doi.org/10.1029/ Tassi, F., Vaselli, O., Papzachos, C.B., Giannini, L., Chiodini, G., Vougioukalakis, G.E., 2005GL024789. Karagianni, E., Vamvakaris, D., Panagiotopoulos, D., 2013. Geochemical and isotopic Schmidt, A., Carslaw, K.S., Mann, G.W., Wilson, M., Breider, T.J., Pickering, S.J., Thordarson, changes in the fumarolic and submerged gas discharges during the 2011–2012 un- T., 2010. The impact of the 1783–1784 AD Laki eruption on global aerosol formation rest at Santorini caldera (Greece). Bull. Volcanol. 75, 711. http://dx.doi.org/10.1007/ processes and cloud condensation nuclei. Atmos. Chem. Phys. 10, 6025–6041. http:// s00445-013-0711-8. dx.doi.org/10.5194/acp-10-6025-2010. Telford, P.J., Lathière, J., Abraham, N.L., Archibald, A.T., Braesicke, P., Johnson, C.E., Schmidt, A., Ostro, B., Carslaw, K.S., Wilson, M., Thordarson, T., Mann, G.W., Simmons, A.J., Morgenstern, O., O'Connor, F.M., Pike, R.C., Wild, O., Young, P.J., Beerling, D.J., 2011. Excess mortality in Europe following a future Laki-style Icelandic eruption. Hewitt, C.N., Pyle, J., 2010. Effects of climate-induced changes in isoprene emissions Proc. Natl. Acad. Sci. U. S. A. 108, 15710–15715. after the eruption of Mount Pinatubo. Atmos. Chem. Phys. 10, 7117–7125. Schmidt, A., Carslaw, K.S., Mann, G.W., Rap, A., Pringle, K.J., Spracklen, D.V., Wilson, M., Textor, C., Graf, H.-F., Herzog, M., Oberhuber, J.M., 2003. Injection of gases into the strato- Forster, P.M., 2012. Importance of tropospheric volcanic aerosol for indirect radiative sphere by explosive volcanic eruptions. J. Geophys. Res. 108, 4606. http://dx.doi.org/ forcing of climate. Atmos. Chem. Phys. 12, 7321–7339. 10.1029/2002JD002987. T.A. Mather / Journal of Volcanology and Geothermal Research 304 (2015) 160–179 179

Timmreck, C., Graf, H.-F., Lorenz, S.J., Niemeier, U., Zanchettin, D., Matei, D., Jungclaus, J.H., Watt, S.F.L., Pyle, D.M., Mather, T.A., Naranjo, J.A., 2013b. Arc magma compositions con- Crowley, T.J., 2010. Aerosol size conﬁnes climate response to volcanic super- trolled by linked thermal and chemical gradients above the subducting slab. Geophys. eruptions. Geophys. Res. Lett. 37, L24705. http://dx.doi.org/10.1029/2010GL045464. Res. Lett. 40, 2550–2556. http://dx.doi.org/10.1002/grl.50513.

Theys, N., Van Roozendael, M., Dils, B., Hendrick, F., Hao, N., De Mazière, M., 2009. First Westrich, H.R., Gerlach, T.M., 1992. Magmatic gas source for the stratospheric SO2 cloud satellite detection of volcanic bromine monoxide emission after the Kasatochi erup- from the June 15, 1991, eruption of Mount Pinatubo. Geology 20, 867–870. tion Geophysical Research Letters. 36 p. L03809. Wignall, P.B., 2001. Large igneous provinces and mass extinctions. Earth Sci. Rev. 53, 1–33. Theys, N., De Smedt, I., Van Roozendael, M., Froidevaux, L., Clarisse, L., Hendrick, F., 2014. Williams-Jones, A.E., Heinrich, C.A., 2005. Vapor transport of metals and the formation of First satellite detection of volcanic OClO after the eruption of Puyehue Cordón Caulle. magmatic hydrothermal ore deposits. Econ. Geol. 100, 1287–1312. Geophys. Res. Lett. 41, 667–672. Witham, C.S., Oppenheimer, C., Horwell, C.J., 2005. Volcanic ash leachates: a review and Trenberth, K.E., Dai, A., 2007. Effects of Mount Pinatubo volcanic eruption on the hydro- recommendations for analysis methods. J. Volcanol. Geotherm. Res. 141, 299–326. logical cycle as an analog of geoengineering. Geophys. Res. Lett. 34, L15702. Witt, M.L.I., Mather, T.A., Pyle, D.M., Aiuppa, A., Bagnato, E., Tsanev, V.I., 2008. Mercury and Van Der Meer, D.G., Zeebe, R.E., Van Hinsbergen, D.J.J., Sluijs, A., Spakman, W., Torsvik, halogen emissions from Masaya and Telica volcanoes, Nicaragua. J. Geophys. Res. 113,

T.H., 2014. Plate tectonic controls on atmospheric CO2 levels since the Triassic. Proc. B06203. Natl. Acad. Sci. U. S. A. 111, 4380–4385. Wittmer, J., Bobrowski, N., Liotta, M., Giuffrida, G., Calabrese, S., Platt, U., 2014. Active al- von Glasow, R., 2010. Atmospheric chemistry in volcanic plumes. Proc. Natl. Acad. Sci. U. S. A. kaline traps to determine acidic-gas ratios in volcanic plumes: sampling techniques 107, 6594–6599. and analytical methods. Geochem. Geophys. Geosyst. 15, 2797–2820. von Glasow, R., Bobrowski, N., Kern, C., 2009. The effects of volcanic eruptions on atmo- Wood, B.J., Walter, M.J., Wade, J., 2006. Accretion of the Earth and segregation of its core. spheric chemistry. Chem. Geol. 263, 131–142. Nature 441, 825–833. http://dx.doi.org/10.1038/nature04763. Vlastélic, I., Menard, G., Gannoun, A., Piro, J.-L., Staudacher, T., Famin, V., 2013. Magma Yuan, T., Remer, L.A., Yu, H., 2011. Microphysical, macrophysical and radiative signatures degassing during the April 2007 collapse of Piton de la Fournaise: the record of of volcanic aerosols in trade wind cumulus observed by the A-Train. Atmos. Chem. semi-volatile trace elements (Li, B, Cu, In, Sn, Cd, Re, Tl, Bi). J. Volcanol. Geotherm. Phys. 11, 7119–7132. Res. 254, 97–107. Zielinski, G.A., Mayewski, P.A., Meeker, L.D., Whitlow, S., Twickler, M.S., Morrison, M., Walker, J.C., Carboni, E., Dudhia, A., Grainger, R.G., 2012. Improved detection of sulphur di- Meese, D.A., Gow, A.J., Alley, R.B., 1994. Record of volcanism since 7000-BC from the oxide in volcanic plumes using satellite-based hyperspectral infra-red measure- GISP2 Greenland ice core and implications for the volcano-climate system. Science ments: application to the Eyjafjallajökull 2010 eruption. J. Geophys. Res. 117, 264, 948–952. D00U16. http://dx.doi.org/10.1029/2011JD016810. Zelenski, M., Fischer, T.P., de Moor, J.M., Marty, B., Zimmermann, L., Ayalew, D., Nekrasov, Wallace, P.J., 2005. Volatiles in subduction zone magmas: concentrations and fluxes A.N., Karandashev, V.K., 2013. Trace elements in the gas emissions from the Erta Ale based on melt inclusion and volcanic gas data. J. Volcanol. Geotherm. Res. 140, volcano, Afar, Ethiopia. Chem. Geol. 357, 95–116. 217–240. Zelenski, M., Malik, N., Taran, Y., 2014. Emissions of trace elements during the 2012–2013 Wallace, L., Livingston, W., 1992. The effect of the Pinatubo cloud on hydrogen chloride effusive eruption of Tolbachik volcano, Kamchatka: enrichment factors, partition co- and hydrogen fluoride. Geophys. Res. Lett. 19, 1209. efficients and aerosol contribution. J. Volcanol. Geotherm. Res. 285, 136–149. Watt, S.F.L., Pyle, D.M., Mather, T.A., 2013a. The volcanic response to deglaciation: evidence from glaciated arcs and a reassessment of global eruption records. Earth Sci. Rev. 122, 77–102.