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Using Sentinel-1A/B SAR data, Harvey (2021) produced an InSAR timeseries over White Island, New Zealand. The paper documents the apparent deformation through 2019, with particular focus on the mechanisms surrounding the fatal eruption on December 9 of that year. Based on the analysis, the author suggests that a sudden increase in the Line of Sight (LOS) range occurred two weeks prior to the eruption, with potential implications for hazard monitoring at White Island and globally equivalent volcanoes. More generally, a suggestion is made that dome contraction may presage eruptions. However, re-analysis of the datasets provided by the author indicates that the sudden change in LOS displacement, interpreted as a collapse of the dome, is simply an atmospheric artefact introduced by the choice of reference point on the island. Given the fatal nature of the eruption, and implications for forecasting phreatic eruptions more broadly, it is vitally important that the community carefully validate results that have forecasting implications, otherwise, spurious warnings may be communicated to the public. Based on the data presented in Harvey (2021), there is clearly no precursory deflation event in the build up to the eruption, in agreement with other datasets around this tragic event. [ABSTRACT FROM AUTHOR]

In this paper, we present our understanding of the importance of affects in people's sense-making of volcanic risk in everyday life. In doing so, we explore how local knowledge on volcanism is produced and circulated through communities' ongoing affective encounters with volcanoes. Through ethnographic fieldwork and semi-structured interviews, we draw on the heterogeneous experiences and narratives of Malalcahuello residents living next to the Lonquimay volcanic complex in the Southern Andes of Chile. Its last eruption in 1988–1990 formed a new cone on the NE flank, called Navidad (Christmas), which has allowed residents to experience active volcanism in a twofold sense: being affected by its impacts during the eruption, and responding affectively to the volcano in everyday life. The results pave the way for a typology of affect-based ways of knowing volcanism. These are constituted by multiple people's viewpoints: 1) knowing the ground, 2) knowing the territory, 3) knowing the risk, and 4) knowing the behaviour. These ways of knowing vary according to, and are in part determined by, the different rhythms of the volcano itself. Therefore, active volcanism becomes a more-than-human agent of knowledge through its rhythmic presence in people's everyday lives. Over time, the local population has become affectively attuned to both 'hazardous situations' related to volcanic eruption and 'risk and safe situations' during volcanic quiescence. These attributes of human-volcano encounters turn hazardous spaces into affect-laden spaces at different times, raising the need to rethink spatio-temporal dimensions in knowledge dialogue and disaster risk reduction. Overall, the paper underlines the importance of affect-oriented risk research in Chile and worldwide to account for the pre-existent viewpoints from which a volcano is at the heart of people's concerns. • Local communities produce forms of knowledge through their affective encounter with volcanoes. • These ways of knowing comprise the entanglement of knowledge, practices, beliefs, and emotions. • Knowledge and emotional evocations co-emerge rhythmically when interacting with volcanoes. • Volcanic affects are pivotal in the community's awareness of volcanic risk. [ABSTRACT FROM AUTHOR]

Seismicity at Mt. Vesuvius has been relatively weak in the last decades. While the occurrence of shallow volcano-tectonic (VT) events at Mt. Vesuvius is well known, the occurrence of deeper low frequency events (LF) was only recently recognized. Previous source studies only targeted VT events, which were found to have quite heterogeneous focal mechanisms. In this paper, we perform for the first time the source inversion of LF seismicity at Mt. Vesuvius, analysing 27 LF events recorded from 2012 to 2021 with the aim to investigate their source processes. Given the challenges of analysing weak LF earthquakes, we implement a specific moment tensor (MT) inversion approach that combines the fit of displacement seismograms in the time domain and amplitude spectra in the frequency domain. The inversion is simultaneously performed for the source depth and moment tensor components in the 2–7 and 2–5 Hz frequency band, assuming either a full or deviatoric MT representation. Source parameter uncertainties are estimated by using a Bayesian bootstrapping scheme. Our results confirm a larger depth of LF events compared to VTs and show a strong heterogeneity of the LF seismic sources, which present various rupture types, different orientations and heterogeneous, whilst poorly resolved, non-double-couple components. The MT variability is qualitatively confirmed by significant differences among the recorded waveforms. The heterogeneity of both VT and LF source processes is attributed to complex source processes in a highly fractured seismogenic volume submitted to a heterogeneous stress field. • The first moment tensor inversion study of LF seismic events at Mt. Vesuvius. • LF seismic events at Mt. Vesuvius occured at depths between 4 and 8 km b.s.l and have characterized by Mw < 2. • A strong heterogeneity in the fault geometry and the driving stress field characterizes LF seismicity of Mt. Vesuvius in the last 30 years. [ABSTRACT FROM AUTHOR]

Pululahua is a potentially active andesite and dacite lava dome complex. This paper presents the results of a survey focused on carbon dioxide (CO 2) diffuse degassing at Pululahua, which was conducted during the 2017 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission of the Chemistry of Volcanic Gases (CCVG) 13th Gas Workshop. Our objective was to conduct a comprehensive investigation of CO 2 diffuse degassing by employing standard methods for measuring CO 2 flux and temperature, and data processing. These methods were applied to map the spatial distribution of the measured parameters, investigate the origin of CO 2 , and quantify the volcanic CO 2 output within the surveyed area of Pululahua. We carried out a total of 350 soil CO 2 flux and 329 soil temperature measurements and collected 12 gas samples for carbon isotopic composition analysis, surrounding the three youngest domes in the complex. In addition, seventeen CO 2 flux measurements over a thermal water pool were performed. Our findings indicate that the diffuse emission at Pululahua's crater floor is fed by both biogenic and volcanic CO 2. Fluxes from each source are similar in magnitude, with approximately 90% of the measurements falling into an intermediate flux range. The occurrence of volcanic CO 2 emissions is supported by the carbon isotopic composition. Diffuse degassing distribution highlights a CO 2 anomaly surrounding the younger domes within the crater. We estimated the CO 2 diffuse emission using both statistical and geostatistical approaches over area of 3.36 km2, resulting in values of 154.2 t d−1 and 126.2 t d−1 respectively. Based on the geostatistical quantification of the total CO 2 emission from soil degassing, Pululahua's crater volcanic CO 2 contribution is estimated between 59 and 97 t d−1. Finally, the potential hazards associated with the release of cold CO 2 at Pululahua's crater are also discussed. • Pululahua emits volcanic CO 2 diffuse degassing from its crater. • Diffuse degassing structures form a circular shape around the youngest domes. • Carbon isotopic composition of CO 2 indicates both biological and volcanic sources. • Volcanic output is 59–97 t d−1, based on criteria for subtracting biological CO 2. • Probability map of fluxes above the biogenic threshold approximates a hazard map. [ABSTRACT FROM AUTHOR]

Explosive volcanism is one of the most dangerous and far-reaching natural hazards. The largest eruptions are the rarest, so studies of their temporal patterns have to rely on long archives. In this paper, we apply fractal and spectral analyses to the 6.2 Ma-long record of ash-falls at the Detroit Seamount (DS6M), > 600 km east of the Kamchatka Peninsula, NW Pacific, combined with a terrestrial record for the last 30 ka (T30ka). These datasets are the most complete for volcanism in the North Pacific, and DS6M spans all Pleistocene glaciations. In both datasets, events are grouped (Weibull parameter k < 0.84) with no characteristic scale of grouping in the time domain of thousands to millions of years. The fractal dimension of the studied data below the unity may be intrinsic to the volcanism (e.g. as a proxy of fractal composition and topography of a subducting plate) or represent uneven deposition and recovery of tephra. Only for the last 700 ka of DS6M, an increase in the correlation dimension values suggests the applicability of spectral analysis; however, no Milankovitch frequencies have been detected in this dataset. When compared to other North Pacific data for areas repeatedly glaciated in the Middle and Late Pleistocene and to a climate proxy of 18O isotopic stack LR04, the studied data suggest that variation in timing of ash-falls among the sites predominates over hemispheric-scale climatic forcing. If so, Quaternary glaciations had a limited effect on the timing of large explosive eruptions in North Pacific, still affecting the transit and deposition of erupted material. • Irregularities in long (30 ka to 6.2 Ma) records of Kamchatka volcanism have been studied. • The grouping of eruptions is more pronounced than in a Poisson process, even with assumed data loss. • Milankovitch frequencies have not been detected in the datasets. • The variation in timing of ash-falls among the North Pacific sites predominates over hemispheric-scale climatic forcing. [ABSTRACT FROM AUTHOR]

Magma migrations frequently trigger seismic swarms, resulting in seismic events that overlap in time and hinder real-time phase picking commonly used for hypocenter location. Addressing this challenge, seismic amplitude ratio analysis (SARA) allows identification of seismic migrations in real-time by simply tracking the relative seismic amplitude between a pair of seismic stations. This paper aims to identify key statistical features of the seismic network array locations that improve their ability to detect seismic migrations using SARA. We evaluated the capability to detect the most frequently oriented magma migrations in over 100 volcanoes, using a criterion previously proposed to study vertical magma migrations in Piton de la Fournaise. Additionally, we investigate the influence of vent-station proximity on magma conduit coverage and identify the distance ratio that yields improved detection. Furthermore, we estimate the seismic network efficiency by calculating the detection capability volume per station. We then use the random forest regression algorithm to identify which statistical features of the seismic network location contribute more to the efficiency disparity among different volcanoes. Notably, our findings reveal that optimizing seismic network coverage entails maximizing the standard deviation of relative pair station distances, while maintaining a prescribed minimum separation distance between station pairs. Our results reveal important criteria that can be used to optimize seismic network location design. • Optimization of seismic network locations to track magma migrations in real-time. • Calculation of the detection capability across 100+ volcanoes, using the Seismic Amplitude Ratio Analysis. • Identification of which statistical properties of the seismic network's locations impact efficiency more. • Evaluation of how the proximity between vents and stations affects the coverage of magma conduits. [ABSTRACT FROM AUTHOR]

This paper presents the first 40Ar/39Ar age data, new bulk-rock major-trace element compositions and Nd Sr isotope geochemistry, combined with detailed geological mapping of Galatia Volcanic Province (GVP) in the northwest Central Anatolia (Turkey). Here, there are voluminous extrusive rocks in a wide compositional range: a basalt, andesite and trachyte suite, and their pyroclastic equivalents. 40Ar/39Ar dating of two whole-rock samples from the GVP yielded plateau ages of 21.76 ± 0.8 Ma and 20.97 ± 0.5 Ma, constrain the volcanic activity at ca. 21 Ma (Aquitanian). The samples show by sub-parallel light rare earth element (LREE)-enrichment and relatively flat heavy rare earth element (HREE) patterns and moderate fractionation [average (La/Yb) N = 13.5]. Their initial 87/86Sr values vary between 0.704619 and 0.704998, while initial 143/144Nd values lie between 0.512673 and 0.512755. Integration of the geochemical and geochronological with geological data we propose that the volcanic rocks in the northern area of GVP with calc-alkaline affinity were produced by a lithospheric mantle magma in an extensional setting. • The volcanics erupted the earliest Miocene (Aquitanian). • The volcanism took place in an active continental arc. • FC and minor crustal contamination played role in their evolution. [ABSTRACT FROM AUTHOR]

On February 19, 2018, Sinabung Volcano erupted explosively, destroying the lava dome and producing a new crater. This eruption was the largest one since it became active again in 2010. We processed kinematic GPS observation combined with seismic data to analyze the explosion process and calculate the volume change during the deflation stage. The time series from the results of GPS data processing for 12 min shows a pattern of inflation that lasts for 180 s followed by deflation. Observation data is divided into 3 phases of activity. The first and second phases are inflation with pressure source during eruption at a depth of 2.3 km below the summit, followed by the third phase of deflation at a shallow depth. The hypocenter of explosion earthquake also in the depth of 2.3 km beneath the crater. This study provides information about the magma dynamics during and after the eruption of Sinabung Volcano. The volume change of inflation and deflation calculated approximately 3 × 106 m3 and − 2.2 × 106 m3, respectively. The ash weight produced by the February 19, 2018 eruption from seismic and ground deformation during the deflation period is approximately 5.6 million tons or 0.006 km3, equivalent with VEI 2 Sinabung eruption. • This paper determiine the volume of ash released during an explosion using kinematic GPS and seismic in nearly real-time as effective method to obtain the parameter for the ash fall modeling. • Seismic and ground deformation signals are transmitted every 1 s and the data are sent to the data center within 2 s, making it possible to determine the volume of volcanic ash release in near-real time. • GPS data with a high sampling rate processed using the kinematic method provides results that represent sudden deformation during the volcanic explosion. [ABSTRACT FROM AUTHOR]

The record of the explosive activity of Pantelleria volcano is well documented by several distal tephra collected in various areas in and around the Mediterranean, while few tephrochronological studies exist on proximal marine areas. In this paper, we investigate three selected coring sites from the northern shoulder of the Pantelleria graben, about 15–30 km from the island, in near-vent position with respect to that volcanic source. Our multiproxy analyses revealed nine tephra layers, totally composed of juvenile materials, mostly ash and pumice fragments, as well as a coarse-grained tephra deposit at the bottom of one of the cores. The major element composition of glass shards indicates a very homogeneous geochemical composition for the tephra layers, suggesting their primary origin. Using litho-stratigraphic and paleoenvironmental proxies, we associated the tephra layers to the latest (<∼13.7 ka) explosive activity of Pantelleria. The coarse-grained deposit, instead, due to its distinctive composition is considered to represent the near-vent, marine equivalent of the distal Y-6 tephra layer, related to the ∼45 ka old co-ignimbrite fallout deposit of the Green Tuff event. The geochemical characterization of such deposit, mostly rhyolitic and partly trachytic, appears to enlarge the bimodal composition recorded in other distal tephra (Y-6) reported in the literature, highlighting the potential of near-vent record in providing additional information on the eruptive history. • Marine tephra have been cored in a proximal position with respect to Pantelleria island. • They have been related to the latest (<13.7 ka) explosive activity of Pantelleria volcano. • A further, basal deposit is interpreted as the near-vent, primary marine record of the Green Tuff fallout event. • Its composition appears to enlarge the bimodal composition recorded in other distal tephra. • This might provide better proximal-distal correlations of the GT-related record and of post-GT tephra. [ABSTRACT FROM AUTHOR]

We construct 2-D numerical models of bulk heat and water transport from the mid-crust (10 km depth) to the surface in a 20 km-wide continental rift, based on observations from the Taupō Rift in the central Taupō Volcanic Zone (TVZ) of New Zealand. The model represents a simplified geological setting with two low-permeability basement-like rock-types, the first defining the margins of the rift and the second a distinct 'rifted basement'. The rift is overlain with a 2 km-thick, 20 km-wide layer of shallow volcanic infill. At the base of model there is a 10 km-deep heat source (the 'hotplate') with a specified TVZ-like heat flux of 0.77 Wm−2 and a 'target' average hotplate temperature of 700o to 900 °C, required to maintain the low melt fractions at ∼10 km depth inferred from geophysics. Parameterising the permeability of the rifted basement is a key part of the paper as it enables both the heat flux boundary condition and a temperature constraint to be satisfied at the hotplate. More generally, it allows the flexibility to control the depth of temperature contours which represent proxies for geophysical measurements. It is described as a power-law for log 10 (horizontal component of permeability, kh) with specified values of kh at two depths and a power law exponent as free parameters. Viable models which satisfy all constraints for the hydrothermal system beneath the TVZ rift have a power-law exponent less than ∼0.4, shallow (2 km deep) kh's of 10–14.0 to 10–13.0 m2, and deep (10 km) kh's <10–16.5 m2. The vertical component of the rifted basement permeability, kv, is ten times higher than kh. A generic feature of the models is that irregular, unsteady convection occurs in the upper ∼5 km of the rift. This results in temporal and spatial fluctuations in heat and fluid flow which are interpreted as high-temperature TVZ-like geothermal systems which have temperatures of ca. 300 °C at 2 km depth. Over the nominal simulation time of 3 Myr, approximately 40% of the geothermal systems are clustered within ∼2 km of the rift margins, with the remainder distributed roughly uniformly across the rift. Between the geothermal systems cool recharge from the surface occurs, with temperatures as low as 50 °C occurring at 5 km depth. The models successfully match temperature proxies for the depths of maximum seismicity (450 °C) and shallowest partial melt (> 700 °C) inferred from geophysical observations. Heat transport within the rift is dominated by convection. This is true even at 10 km depth, at the base of the geothermal systems, where kh in the rifted basement approaches 10−17 m2. In this situation, the relatively large value of vertical permeability kv, ∼ 10−16 m2, allows convection to occur. Conductive heat transport dominates in regions ∼1 km in vertical extent immediately above the hotplate and between the geothermal systems. The vigour of the hydrothermal systems is controlled by the permeability of the shallow volcanics, through which all cold surface recharge and hot outflows of fluid occur. Models with low permeability for the shallow volcanics produce longer lasting and higher temperature geothermal systems, and those with high permeability produce fewer and cooler geothermal systems. • We create a 2D source to surface models of the hydrothermal system below the TVZ. • Models with constant basement permeability cannot satisfy geophysical constraints 81. • We parameterise permeability vs depth in the basement rock 58. • The parameterisation allows models to respect temperature proxies for all constraints 85. [ABSTRACT FROM AUTHOR]

Locating sources of volcano-seismic event is very relevant to monitor and comprehend volcanic processes. Ordinary estimation of source seismic events is based on phase picking. The most accurate procedure of phase selection is the visual inspection of the records by experts, who employ local characteristics for phase detection and comparison with observed signals from other stations. This activity is highly time demanding, which in turn is a strong motivation to automatize the epicenter estimation process. However, automatic phase picking in volcano signals is highly inaccurate because of the short distances between the event epicenters and the seismograph stations. In this paper, an end-to-end based LSTM (Long-Short Term Memory) scheme is proposed to address the problem of volcano event localization without any a priori model relating phase picking with localization estimation. LSTM was chosen due to its capability to capture the dynamics of time varying signals, and to remove or add information within the memory cell state and model long-term dependencies. A brief insight into LSTM is also discussed here to justify the use of this neural network. The results presented in this paper show that the LSTM based architecture provided a success rate, i.e., an error smaller than 1.0 km, equal to 48.5%, which in turn is dramatically superior to the one delivered by automatic phase picking. Moreover, the proposed end-to-end LSTM based method gave a success rate (18%) higher than CNN (Convolutional Neural Network). The results presented suggest that the approach proposed here for automatic volcano event epicenter localization can be applied to other geophysics problems. • Locating sources of volcano-seismic event is very relevant to monitor active volcanoes and comprehend volcanic processes. • The most accurate procedure of phase selection is the inspection of the records by experts, which is highly time demanding. • Automatic phase picking in volcano signals is highly inaccurate. • In this paper, an end-to-end based LSTM scheme is proposed to address the problem of volcano event localization. [ABSTRACT FROM AUTHOR]

Understanding the conditions and timescales of storage and remobilization of magma bodies in the upper crust is key to interpreting the signals of potential reawakening at active volcanoes. In this paper, we provide the first volcanological and petrochronological characterization of the Singkut caldera, a young volcanic system located in northern Sumatra (Indonesia), in close proximity to Medan, one of the country's most popoluous cities. Singkut formed at ∼44 ka during a VEI 6 explosive eruption that deposited at least ∼26 km3 of tephra (dense rock equivalent, DRE). The cataclysmic eruption was preceded by >200 ky of mostly effusive pre-caldera activity and followed by effusive to mildly explosive post-caldera activity. The lavas and pumices have high crystallinity (up to 62% crystals) with andesitic to dacitic bulk-rock composition and rhyolitic glass. Mineral textures and matrix glass compositions indicate resorption of quartz, plagioclase and zircon. Zircon crystallization ages show a complete overlap with the eruption ages in pre-caldera lavas, while a time gap in zircon crystallization (>50 ky) is identified in the caldera-forming tuff and post-caldera lavas. Ti-in-zircon thermometry shows that the Singkut magma body experienced a temperature increase starting approximately upon eruption of the pre-caldera lavas (∼254 ka). Such thermal perturbation determined progressive melting of mineral phases in the cumulate crystal mush, caused the resorption of the youngest zircon domains before the caldera-forming eruption, and hampered zircon crystallization between the caldera-forming eruption and the effusion of the post-caldera lavas (∼16 ka). Our data demonstrate how cumulate melting processes played a key role in leading the volcanic system towards a caldera-forming eruption and controlled the transitions in eruptive style between the effusive phases and the explosive climactic eruption. • Singkut caldera formed at 44 ka during a large explosive eruption (∼26 km3 DRE). • Caldera-forming eruption was preceded by >200 ky of effusive volcanic activity. • Magmas are crystal-rich with textural and geochemical evidence of cumulate melting. • Temperature increase in magma reservoir started upon eruption of pre-caldera lavas. • Cumulate mush rejuvenation was triggered by increasing mafic recharge flux. [ABSTRACT FROM AUTHOR]

The Domuyo volcanic complex (DVC) and its geothermal field in the retroarc zone of the southern Central Andes of Argentina present reduced seismicity according to different catalogs (USGS and INPRES). However, in 2015/2016, a local project was carried out in the area to describe its seismo-volcanic activity, registering a large number of volcano-tectonic (VT) events (538 VT). Considering there is scarce information on these events, this study focuses on analyzing the Domuyo Volcanic Complex (DVC) to assess its seismicity. Therefore, we installed a local seismological network in the study area and compared results with data registered by other authors. Four seismological networks were used, to obtain a more precise location of the seismic events and calculate the focal mechanisms of earthquakes with magnitudes greater than 2. For the first record of crustal seismicity detected by INPRES the September 10th, 2016 with a Ml 3.3, we calculated the focal mechanism with two possible solutions: a thrust solution with a strike component and a favored normal solution with a strike component. Additionally, we relocated the largest event in the Domuyo region on March 27th, 2019, with a magnitude of 4.4 (NEIC – USGS) and focal mechanism with a normal solution and a small strike component, obtaining a shallower depth of 3.9 km instead of 10 km. The new seismological data used in this paper, correspond to September 10th 2016, and two different time periods, the first comprising continuous data from March to April 2019, when the largest registered earthquake occurred in the Domuyo region, and the second from December 2019 to January 2021. At these periods, registered seismicity had magnitudes Ml between 1.9 and 2.8, and focal depths between 1.8 and 5.2 km. Four of these events count with focal mechanisms with extensional and limited strike-slip components that are tentatively linked to the known neotectonic structures affecting the western slope of the DVC. This seismic sequence agrees with previous proposals in which degasification from a magmatic body at shallow depths constitutes the trigger factor. • First focal mechanisms in Domuyo Volcanic Complex (DVC), with principally normal solution. • DVC from 2016 to 2020 was subject to an extensional deformation. • This deformation is associated with the degasification of a shallow magmatic body. [ABSTRACT FROM AUTHOR]

This paper presents the results from a geographic information systems (GIS) workflow, which was used to analyze the spatial distribution and temporal evolution of volcanoes in the Mio-Pleistocene monogenetic Bakony-Balaton Highland Volcanic Field (BBHVF), located in the Pannonian Basin, Hungary. Volcanism occurred during the tectonic inversion in a back-arc setting and a compressive/transpressive tectonic regime on the hottest and thinnest lithosphere of continental Europe. The main goal of this study is to clarify the effect of the pre-existing structure of the upper lithosphere in the distribution of the volcanic centers across the volcanic field using an innovative GIS methodology. Orientation of the volcanic field was compared to the orientation of the faults in the BBHVF, and in its larger vicinity, which resulted in correspondence, suggesting the dominance of the SW-NE direction. The directions of the volcanic lineaments fit well to the two main fault directions. The fault-volcano proximity analysis suggests that the fault plane of a thrust fault was an important structural feature during the lifespan of the volcanism. All results suggest that the fault plane of a regionally significant Cretaceous thrust fault (Litér Fault) might have served as a temporary pathway for the ascending magma, whereby (similarly to other, smaller faults) redirecting the magmas causing clustering of the volcanoes. This highlights the importance of major upper crustal structural heterogeneities for magma transport in a compressive tectonic system, especially in the case of active, monogenetic volcanic fields from a volcanic hazard perspective. The present GIS workflow can be effective in analyzing the spatial patterns of the volcanism and its connection with crustal structures at monogenetic volcanic fields worldwide. • Spatial and temporal patterns of monogenetic volcanism were investigated in the Bakony-Balaton Highland Volcanic Field • A wide range of GIS tools was used, such as density distribution, or orientation of volcanic lineaments. • Major inherited structures played a vital role in directing magma transport and clustering volcanic centers. • Volcanic lineaments follow fault geometries, providing further evidence of the tectonic control. [ABSTRACT FROM AUTHOR]

The paper considers the formation of native sulfur and sulfides in the bottom sediments of volcanic lakes in the Golovnin Caldera. Our observations and microstructure studies indicate the presence of sulfur melt at the bottom of Kipyaschee Lake. Drops of this melt are carried to the surface of the lake as part of a light gray foam. The significant differences of sulfur spherules in the concentration of sulfide mineralization, in its composition, as well as in the presence or absence of numerous opal inclusions are most simply explained by the capture of droplets in various parts of the sulfur melt and their subsequent movement by a gas stream passing through the melt. The effusions of sulfur melt in 1979 are direct evidence of its existence. Molecular chemical modeling shows that the stability of sulfur condensate in the bottom sediments is controlled by two thermobaric surfaces. The upper is controlled by the beginning of water condensation and a wave of acidity, the lower by the beginning of sulfur condensation. Both surfaces are a consequence of the cooling effect of lake water, and when bottom sediments accumulate, they move following changes in the surface of the lake bottom. Elemental sulfur condensate is formed between these surfaces as a result of forced cooling of endogenous gas flows. This process is most active in crater depressions at the bottom of Golovnin Caldera lakes, where sulfidization of the sulfur melt occurs simultaneously with the condensation of sulfur itself. Gravitational deposition of sulfides in the sulfur melt leads to their enrichment of the root parts of crater depressions, where pyrite ore bodies are formed in real time. [Display omitted] • Our research indicates the presence of sulfur melt at the bottom of Kipyaschee Lake. • The stability of sulfur condensate is controlled by two thermobaric surfaces. • Both surfaces are a consequence of the cooling effect of lake water. • We found no colloidal sulfur in the Golovnin caldera. [ABSTRACT FROM AUTHOR]

A detailed historic record on Volcán de Colima, Mexico, of lahar activity and related phenomena dating back to the sixteenth century has proven that debris flows have caused more human casualties in the area than any other volcanic activity including pyroclastic flows. In this paper we present a multi-approach study of a relevant lahar (a non-cohesive debris flow with the largest runout and one of the most voluminous of the volcano) at Volcán de Colima, Mexico. Observations and information relevant to the lahar deposit and event including componentry, textural, sedimentological, stratigraphic, morphometric and geochronologic analyses and oral testimonies from eyewitnesses enable us not only to confirm a relationship between the studied outcrops and the 1913 Plinian eruption of the Colima Volcano (the most intense and large in volume eruption of this volcano of the last century), but also to find a clear and direct correlation among morphometric features such as slope, ravine width, curves and kinematics, flow patterns, flow transport mechanisms, volume, shape of clasts, granulometry and sub-unit formations. In particular, we maintain the slope has a marked control on the thickness of the deposits, deposited volume, longitudinal changes, and patterns of downstream changes in particle morphology and granulometry. All this information will be useful for generating or updating hazard maps, taking these lahars as a worst-case scenario. • The January 1913 Plinian eruption of the Colima Volcano was correlated with post-eruptive volcaniclastics. • The study confirms that these lahars are among the largest events that have occurred at the Colima Volcanic Complex. • The application of quantitative texture analysis in this study proves its sensitivity and accuracy. • Our paper demonstrates the strong probable relationship between deposit texture and changes in ravine morphometry. • Our study shows an exponential relationship between lahar volumes and runouts in the Colima Volcano area. [ABSTRACT FROM AUTHOR]

Monogenetic volcanoes are characterised worldwide by a single eruptive phase that is short-lived, with small eruptive volumes that produce a wide range and complexity of landforms. Investigating the evolution in eruptive styles through the active history of a volcano is key to understanding the role of phreatomagmatism in the formation of these complex monogenetic systems. The classification of the complexity of a monogenetic volcanic centre is of great significance to understanding both past volcanoes and the hazards of future volcanoes. Complexity can be defined by the number of volcanic structures created, the presence of multiple types of eruptions, and the number of conduits involved. In this paper we reconstruct the volcanic history of the Waitomokia Volcanic Complex, located in the southern lowlands of the active monogenetic Auckland Volcanic Field (AVF), New Zealand. Activity began with deposition of an initial tuff ring, followed by vent migration and establishment of a maar with a surrounding tuff ring. Four smaller tuff rings developed on the north and northeastern rim of the maar. This was followed by the noteworthy deposition of complex intercalated transitional deposits from at least two tuff rings and magmatic deposits from a scoria cone. Three scoria cones were then built within the maar, followed by minor effusion of short lava flows. Waitomokia highlights the prospect of having a complex system with ten or more landforms being created in different areas active at the same time, with associated eruptive styles and mechanisms. The possibility of a complex eruption, where several styles may occur simultaneously from distinct vents, should be considered in hazard assessment and crisis management plans. • Investigating eruptive evolution is key to understanding complex monogenetic systems. • Waitomokia Volcanic Complex is an end member in its field in terms of complexity. • Multiple tuff rings, maar, scoria cones, lava flow, intercalated deposits. • Reconstructing the volcanic history of an anthropogenically damaged volcanic centre. [ABSTRACT FROM AUTHOR]

The Okataina groundwater catchment (OGC), with the Okataina caldera complex and its large caldera structures and rhyolite domes, 11 lakes, numerous shallow, cold, groundwater systems and 15 geothermal fields, is a spectacular part of the Taupō Volcanic Zone (TVZ) and an example of the many meteoric-dominated hydrothermal systems, ancient and modern, that bound the Pacific Ocean. This paper describes Quaternary OGC evolution in four phases with 4D models of geology and groundwater-geothermal systems. The early-TVZ Proto-KWG phase had development of the KWG graben, the Proto-Tarawera River and catchment, and ended with deposition of Whakamaru Group ignimbrites, sourced south of the OGC. Then, Matahina phase volcanism resulted in the Matahina caldera with Matahina Formation ignimbrite deposited over a wide area within, and beyond, the OGC. Groundwater flowed into Lake Matahina which was the location of multiple geothermal fields. Thirdly, the Penultimate phase produced the Rotoiti caldera, Lake Haroharo, and two OGC ignimbrites, i.e., Rotoiti Formation and Earthquake Flat Formation. Lake Haroharo recieved inflow from groundwater-geothermal systems. Lastly, the Infill phase resulted in today's major OGC landforms, e.g., the Mt. Tarawera and Haroharo domes, multiple lakes, their catchments, groundwater systems and geothermal fields. Deep drilling is recommended to address key science gaps, i.e., the locations and properties of subsurface caldera-lake sediments and the processes (chemical and physical) of fluid flow from deep geothermal reservoirs to surface hydrothermal areas. • Pleistocene Okataina groundwater catchment (OGC) geology and groundwater-geothermal systems evolved in four phases • The 'proto-Kapenga–Whakatane Graben phase' preceded 'Matahina phase' Matahina caldera, ignimbrites and Lake Matahina. • 'Penultimate phase' Rotoiti caldera, ignimbrites and lakes were followed by 'Infill phase' volcanism, e.g., Mt Tarawera. • Hydrothermal systems are meteoric-dominated as rainfall recharge typically provides more than 79% of system spring flow. • Most current–day hydrothermal systems were formed in the two OGC caldera-forming phases and associated with caldera lakes. [ABSTRACT FROM AUTHOR]

Volcanic crisis exercises are usually run to test response capabilities, communication protocols, and decision-making procedures by agencies with responsibilities to cope with scenarios of volcanic unrest with inherent uncertainty, such as volcano observatories and/or civil protection authorities. During the last decades, the use of questionnaires has been increased to evaluate people's knowledge on volcanic hazards and their perception of risk, to better understand their preparedness to respond to emergency measures plans. In this paper, we present a study carried out within the European Network of Observatories and Research Infrastructures for Volcanology project (EUROVOLC) focused on extracting information on the experience gained during volcanic-crisis exercises by the project's participants and beyond. An open-ended question questionnaire was firstly distributed for a survey within the project community. Through the results obtained, we developed a user-friendly online multi-choice questionnaire that was submitted to the volcanological communities within and outside EUROVOLC. Analyzing the answers to the online questionnaire, we extracted a prototype checklist for guiding the design of such exercises in the future. Our results confirm this type of survey as a very useful tool for gathering information on participants' experience and knowledge, able to understand which data and information may be useful when designing exercises for scientists, emergency managers and decision makers. In particular, the main lessons learnt regard the need i) to increase training activities involving people exposed to volcanic hazards and media, ii) to improve external communication tools (between players and public/media), equipment and protocols and iii) to better define decision-makers' needs. • An open-ended question questionnaire collected information and personal evaluation on the experience gained during volcanic-crisis exercises • The analysis of responses led us to create a user-friendly online multi-choice questionnaire for volcanological communities • As final product, a prototype checklist was created for guiding the design of such exercises in the future [ABSTRACT FROM AUTHOR]

Seismicity offers valuable information on the internal activity of volcanoes and the interpretation of seismic signals is crucial for volcano monitoring. As the seismic signal is multi-component & non-stationary, the time-frequency analysis like Wigner-Ville distribution (WVD) has played a significant role, but the presence of cross-term limits the applicability of WVD and other bilinear time-frequency representations (TFRs). This paper introduces a successive variational mode decomposition (SVMD)-based cross-term reduction method in WVD. The proposed method is robust and accurate due to reduced sensitivity to initialization parameters, lesser computational burden, and automatic selection of the number of decomposed modes. SVMD-based WVD outperforms other related signal decomposition-based methods for removing cross-terms and reconstructing auto-terms, as demonstrated by similarity and concentration-based performance measures for synthetic multi-component and seismic signals. SVMD-based WVD is also applied for the seismo-volcanic events identification system development and evaluated on the Llaima volcano dataset to find the applicability of the proposed method in real-world field data. Novel TFR-based features are extracted based on 3-D segmentation of TFR and 2-D normalized correlation between the segments. Feature ranking and SVM classifier optimization result in an overall classification accuracy of 97.10 % , surpassing previous approaches on the same dataset. [Display omitted] • Novel SVMD-based cross-term reduction method in WVD of seismic signal is given. • Similarity & concentration-based measures assess proposed method for multiple signals. • Similarity-based measures reveal better auto-term estimation than similar TFR methods. • Extraction of 2-D correlation-based feature from 3-D segmented TFR for classification. • Seismo-volcanic events are identified with better accuracy than previous approaches. [ABSTRACT FROM AUTHOR]

Volcanic eruptions are sometimes preceded by tilt changes that are an indicator of immediate pre-eruptive processes. In this study, the tilt changes before all monitored eruptions in Japan were surveyed for the first time to address the generality and common features of these signals. An automated procedure was devised to identify tilt changes. The results showed that approximately half of the analyzed eruptions were preceded by tilt changes. Detection ratios depended on station locations, and approximately 10–20% of the total waveforms consisted of detectable tilt changes. Broadband seismic records, when integrated into displacements, showed detection ratios comparable to those of tiltmeter records. The lead times and durations of the tilt changes showed large variations. The durations correlated with amplitudes, although with considerable scatter. Both accelerating and decelerating types of tilt changes were common, and their ratios depended on the volcanoes. These are the first findings on the nature of pre-eruptive tilt changes from many volcanoes, and the waveform analysis procedure proposed in this paper is applicable to other regions. Future works involve extending this study to datasets from other regions, detecting tilt changes from continuous records, applying the proposed method to an early warning system, and detecting longer tilt changes, which require that the proposed approach be improved by subsequent studies. [Display omitted] • All pre-eruptive tilt changes in Japan were systematically surveyed. • Approximately half of the eruptions were preceded by tilt changes. • Broadband seismometers detected tilt changes at rates comparable to tiltmeters. • Durations of the tilt changes weakly correlated with amplitudes [ABSTRACT FROM AUTHOR]

In this paper we present the new high-resolution magnetic anomaly map of the La Fossa Caldera system and Lipari island (Southern Italy), obtained by merging two low-altitude aeromagnetic surveys. In these islands a variegated ensemble of magnetic anomalies develops in the north-south direction. The La Fossa Caldera is characterized by very high-intensity and short-wavelength magnetic anomalies, related to mafic intrusive/effusive sources, mainly aligned along the NNW-SSE and NS faults. Instead, the Lipari island is characterized by lower intensity anomalies related to sources with more evolved chemistry, elongated in the NE-SW, NNE-SSW and EW of the subordinate faults. Both the two sets of structures belong to the Tindari-Letojanni strike slip fault-system, a regional lineament along which the southern side of the Aeolian Archipelago is emplaced. The study identifies three distinctive magnetic zones on the Lipari island: the southern, the central, and the north-western ones. The southern zone is characterized by negative magnetic monopoles in correspondence with the younger rhyolitic domes and a Curie Isotherm upwelling. The central part of the island has an average lower intensity of positive anomalies, corresponding to the less evolved products of the intermediate Lipari volcanic epochs. The north-western side is characterized by higher intensity anomalies related to older volcanic epochs. The interplay among strike-slip tectonics, chemistry of the uprising magmas, and the thermal setting has contributed to the overall anomaly pattern in this sector of the Aeolian Archipelago. This interpretation is supported by the application of digital enhancement to the total intensity magnetic anomaly field and by the spatial correlation analysis of the magnetic and volcano-tectonic features. The obtained insights are useful to better understand the relationship between arc volcanism and tectonics. Moreover, they can also outline new inferences to forecast future eruptions of the active La Fossa volcanic system. In fact, recent unrest signals were registered at La Fossa Cone, which is one of the present-day active volcanoes of the Aeolian Archipelago, along with Stromboli island. La Fossa volcanic system of Vulcano and Lipari islands high resolution aeromagnetic surveys; Strike slip tectonics magnetic anomaly signature; Spatial correlation analysis of volcano-tectonic and magnetic features. • High-resolution magnetic anomaly map of the La Fossa Caldera system of Vulcano island and Lipari island (Aeolian Archipelago, Southern Italy); • The interplay among strike-slip tectonics, magmas chemistry, thermal setting and the magnetic anomalies; • Spatial correlational analysis of magnetic and volcano-structural features [ABSTRACT FROM AUTHOR]

Kizimen Volcano (Russia, Kamchatka Peninsula) was erupting during 2010 through 2013, that was first recorded by a network of seismic stations. During this eruption many low-frequency volcanic earthquakes with quasi-periodicity were recorded, which were attributed to the drumbeats seismic regime. A similar seismic regime was recorded during the eruption of several volcanoes in the world and was recorded for the first time during a volcanic eruption of the Kamchatka Peninsula. The drumbeats usually accompanies the squeezing of extrusive domes. In this paper, we study the evolution of waveforms of volcanic earthquakes recorded during the 2011-2012 Kizimen eruption. The analysis of earthquake multiplets showed that they associated with the movement of powerful viscous lava flow along the slope of the volcano. This was probably the first time such a phenomenon had been described in the field of volcanology. • During the eruption of the Kizimen volcano in 2011–2012, quasi-periodic earthquakes were recorded - drumbeat earthquakes. • Drumbeats earthquakes were grouped into multiplets, which corresponded to the periods of lava flow movement. • The frequency of earthquakes and their amplitude correlate with the features of the lava flow movement and its parameters. [ABSTRACT FROM AUTHOR]

Whether the magma storage system is responsible for the formation of the 74 ka Youngest Toba Tuff (YTT) is still debatable. It is currently believed that the YTT super-eruption was formed either by a single voluminous chamber or by multiple magma chambers. This paper presents a detailed component analysis of eruption products, comprehensive stratigraphy, mineralogy, and geochemistry of phenocrysts and matrix glass to shed light on the issue. Based on the componentry, mineral assemblages, mineral and glass compositions, and vesicle texture, we identified four distinct pumice types: YtA–YtD. Of these, YtA is an amphibole-bearing pumice containing an average of 77.1 wt% SiO 2. This type of pumice is characterized by abundant matrix vesicles, with plagioclase showing a wide range of anorthite content (An 20 –An 90) and disequilibrium texture. The YtB and YtC types are the most evolved pumices, with 77.5 and 77.6 wt% SiO 2 , respectively. The plagioclase of these pumices commonly has an unzoned texture with low anorthite content (~An 30). The YtB pumice is biotite-bearing, distinctively characterized by abundant pheno-vesicles; while the YtC pumice includes rare pheno-vesicles, skeletal-polyhedral quartz, and no biotite. The YtD type is a quartz- and sanidine-free pumice, with a less-evolved glass composition (76.3 wt% SiO 2), and is characterized by dominant matrix-vesicles and crystal clots of plagioclase, amphibole, pyroxene, and biotite. The plagioclase of the YtD pumice shows a hollow texture and high anorthite content (~An 50). In situ trace element analysis for the matrix glass of YtA, YtB, YtC, and YtD showed very distinct geochemical signatures, which correlated with the four pumice types. Bivariate plots (Ba vs. Y, Sr vs. Y, and Ba vs. Sr) showed that YtA pumice is characterized by medium Ba (400–875 ppm) and Sr (41–67 ppm), and variable Y (20–53 ppm) content. YtB and YtC pumices are characterized by low Ba (8–136 ppm) and Sr (13–37 ppm), and highly variable Y (27–77 ppm) content. YtD pumice is characterized by high Ba (1173–1340 ppm) and Sr (95–124 ppm), but a narrow range of Y (21–31 ppm) content. The trace-element geochemical signatures, occurrence and absence of certain minerals (i.e., biotite and quartz), and vesicle type from the distinct pumice type, suggest the presence of four distinct magma bodies before the eruptions, namely YtA, YtB, YtC, and YtD. The number of distinct glass shards and pumices with the same geochemical signatures represents the volume fraction of each magma type. The approximate total volume of the magma (5300 DRE km3) and the geographical distributions of each pumice type demonstrated that the voluminous YtA (3406 km3), medium YtB (1354 km3), and smallest YtD (168.5 km3) chambers in the northern direction, and the small YtC chamber (371.5 km3) in the southern caldera, were evacuated during the 74 ka YTT eruption. Eruptions from multiple magma chambers were initiated by a high supersaturation of pheno-vesicle-rich magma (YtB magma), triggering the subsequent eruptions of the YtA, YtB, YtC, and YtD magmas. • The first detailed studies on the 74 ka Youngest Toba Tuff (YTT) eruption products for juvenile and non-juvenile materials. • The classification of pumice types by the human eye correlates with different internal structures and geochemical signatures. • There were at least four pre-eruptive magma chambers prior to the 74 ka YTT super-eruption, namely YtA, YtB, YtC, and YtD. • Eruptions from YTT multiple magma chambers were initiated by a high supersaturation of pheno-vesicle-rich magma (YtB magma). [ABSTRACT FROM AUTHOR]

This paper discusses the challenges and opportunities for cross-border eruption management between Chile and Argentina, focussing on an examination of the 2011–2012 eruption of Cordon Caulle in Chile and other crises between 2012 and 2015. We discuss the differences between Chile and Argentina in volcano monitoring, eruption impacts, eruption management and governance during this timeframe. We also discuss the issues in communication of the risks and the potential for future integration at the scientific level. The study is based on 31 interviews with scientists and local officials in 2014–15 (15 in Chile and 16 in Argentina), a questionnaire survey of 128 Argentinian residents in 2015 and a questionnaire survey of 25 disaster managers and residents of Pucón during the 2015 eruption of Villarrica volcano. We conclude that in 2011–12, there were issues with communication across the border, particularly at the political level, and that there are important ways that the scientific institutions in both countries complement each other. • We present new social data concerning the 2011–12 eruption of Puyehue Cordon Caulle. • We show that the eruption was significant in the evolution of institutions and agreements between the countries. • We show that locally, there was dissatisfaction with risk communication in Argentina (which was worse affected). • We argue that the scientific institutions complement each other well but need more resourcing from government. [ABSTRACT FROM AUTHOR]

The Valle del Bove is a profound and wide scar on the east Etna flank witnessing the Holocene main volcano-tectonic event of the volcano, frequently invaded by lava flows during the last centuries. The Valle del Bove slope failure produced the Milo debris avalanche deposit on the lower east flank that is partially covered by the Mongibello lavas and a pyroclastic succession. In this paper, we constrain for the first time the age of the Milo debris avalanche deposit and the overlying lava succession exposed at three quarries recently caved at the valley mouth through a multidisciplinary approach integrating stratigraphic and petrographic analyses, 14C, and paleomagnetic dating. In particular, 14C age determinations of the Milo debris avalanche deposit indicate that the initial stage of the catastrophic flank collapse of the Valle del Bove occurred at 7478–7134 BCE during the Mesolithic age. Conversely, the main portion of the lava succession filling the valley floor emplaced after the sub-Plinian picritic eruption occurred at 2579–2278 BCE (FS tephra layer) consistently with the increasing occurrence frequency of flank eruptions documented in the geological record of Etna during the past 4000 yrs. Paleomagnetic dating highlighted that in the study area the sub-Plinian eruption was followed by two quasi-contemporaneous flank eruptions during the Late Copper age (2600–2400 BCE), whereas other two flank eruptions occurred during Greek-Roman and Medieval ages. These results have relevant implications on the stratigraphy and evolution of Etna, particularly on the Valle del Bove initial collapse and the relative emplacement of the Chiancone detritic-alluvial sequence. • We used a multidisciplinary approach to constrain the age of the VdB flank collapse • We constrained the age of the Milo debris avalanche deposit • We reconstructed the age of the first lava flow successions after the VdB formation [ABSTRACT FROM AUTHOR]

Volcanic plumes are rich in fine juvenile ash, representing magma fragments expelled from the crater during explosive eruptions. The composition of fine ash is of primary importance for volcano monitoring and hazard assessment, but not much effort has been put until now to build portable instrumentation allowing real-time measurements. In this paper, a laboratory experiment is carried out to build and test an apparatus based on Calibration-Free Laser Induced Breakdown Spectroscopy (CF-LIBS). This methodology is extremely promising because it does not require any standard calibration strategies and the elemental composition is directly obtained by the laser-induced breakdown optical emission. In the experiment, volcanic ash samples are suspended in the air by a laser-induced shockwave in a dedicated chamber, as to mimic the conditions of a volcanic plume, and contemporaneously the laser-induced plasma (LIP) spectrum is analyzed. After spectrum acquisition, the quantitative analysis is performed using the so-called Calibration-Free (CF) analytical method, which is based on the assumption of plasma local thermodynamic equilibrium (LTE). Results show that by such methodology it is possible to measure ash composition in real-time, during its dispersion, with good precision. Based on the result of this experiment, the construction of a portable instrument to be used in the field for the monitoring of active volcanoes could be possible in the future. [Display omitted] • We present a new approach for the measurement of flying volcanic ashes based on LIBS. • The method proposed does not require calibration standards and is flexible for real application in-situ. • Volcan ash samples: deposits of the Agnano Monte-Spina Plinian eruption of Campi Flegrei and the Pompeii eruption of Vesuvius • General discussion for in-situ application of CF-LIBS on flying ash is reported for the first time. [ABSTRACT FROM AUTHOR]

The Asian-Pacific - continental margins have been the object of intensive geochemical research in recent years, as areas within this zone have been found to contain large hydrocarbon deposits in a variety of forms including: oil, natural gas, gas condensate, and gas hydrates. One such area is Sakhalin Island, located in Russia's Far Eastern Federal District. Genetically, the territory of Sakhalin Island is a part of the shelf of the Hokkaido-Sakhalin fold area, therefore, the nature of the sub-vertical gas migration is controlled by deep faults, along which the concentrations of natural gases change, and is also influenced by high seismotectonic activity of the Okhotsk region. This paper presents data regarding the distribution of helium, hydrogen, carbon dioxide and methane from mud volcanoes, thermal springs, mineral waters and other seep types on Sakhalin island and the surrounding marine margins, along with an interpretation of the geological and tectonic factors that have likely led to the present distribution of these gases. In general, the results of geothermometry equations based on the concentration and stable isotopic composition of carbon dioxide indicate much higher temperatures than equations involving the saturation concentrations of hydrogen gas. We interpret this to indicate that deeply-sourced carbon dioxide does not reequilibrate at near-surface conditions, whereas the equilibration time for hydrogen gas is relatively rapid. Areas on the island which are observed to have active degassing, coupled with high apparent reservoir temperatures also provide indicators of geodynamics along the regional tectonic structures. Mud volcanoes to the south of the island are predominantly situated at the juncture between NW-SE trending faults which extend the entire length of Sakhalin and continue as far south as Hokkaido Island, and more recently developed NE-SW trending faults. Despite the relatively low water temperatures of these mud volcanoes, the high reservoir temperatures indicated by gas chemistry suggest a source of fluids and gas at several km from the surface. • Distribution of helium, hydrogen, carbon dioxide and methane on Sakhalin Island and the surrounding marine margins. • Geological and tectonic factors leading to helium, hydrogen, carbon dioxide and methane distribution on Sakhalin Island. • Areas of active degassing present high apparent reservoir temperatures as a consequence of regional tectonic structures. • The high reservoir temperatures in Sakhalin mud volcanoes suggest a source several km from the surface. [ABSTRACT FROM AUTHOR]

Between 1993 and 1998, the Hengill volcanic region in southwest Iceland was subject to a significant volcano-tectonic event which caused a total of 8 cm uplift and induced >90 thousand earthquakes, most of magnitude smaller than 2 M L and a small intrusion has been proposed as its cause. In this paper, we study fault activation around the uplift center to analyze whether the Coulomb stress change induced by such an intrusion would cause the observed crustal response. The locations of a subset of 12,000 micro-earthquakes are significantly improved by a double-difference relocation algorithm and the use of cross-correlation of waveforms to refine phase arrival times. The vast majority of seismic activity is scattered, but twenty-five (25) rectangular prisms, consisting of 11 to 363 earthquakes and 200 to 3000 m long, were identified and are interpreted as faults. Most of these faults are sub-vertical (within 5° from vertical) and only two faults dip at angles of 62° and 65°, respectively. Focal mechanism analysis of individual events was applied to estimate slip direction on these faults. Simulation of the Coulomb stress changes reveals that the stress changes would have been able to induce the observed fault movement on 22 of 25 faults. Discrepancies on the remaining faults are likely caused by uncertainties in the rake directions. Our results emphasize that the seismicity caused by a volume change in the crust is controlled by the interplay between the local stress field and the induced stresses. • Relative relocations of earhtquakes in Hengill, SW-Iceland • Joint interpretation of locations and focal mechanisms to map faults • Twenty-three of twenty-five faults are near-vertical strike-slip faults • Modeled Coulomb stress changes account for movement on faults [ABSTRACT FROM AUTHOR]

The 1886 eruption of Mt. Tarawera, in the Taupo Volcanic Zone of New Zealand, caused significant changes in the hydrothermal system in the vicinity of the pre-eruption Lake Rotomahana. In particular, the world-renowned Pink and White silica terraces disappeared from view. Our aim in this paper is to understand the general features of the pre-eruption Rotomahana hydrothermal system, and how they changed as a result of the eruption to give rise to the manifestations of geothermal activity seen in the area today. We present a numerical model of the heat and water flow in the pre-eruption hydrothermal system surrounding and beneath 'old' (pre-1886) Lake Rotomahana. The model uses a simplified geological structure combining an upper ~2 km of volcaniclastic cover and ~ 1 km of underlying basement material into a single geological unit, in addition to a second unit representing the morphological boundary of the Okataina Volcanic Centre (OVC). Results from the model suggest that at least part of the present-day geothermal heat source, as inferred from recent MT and seismic imaging, was active prior to the eruption in 1886. Only models where this heat source is confined to the area to the north-west of the lineation that extends from Mt. Tarawera to Waimangu valley can satisfactorily reproduce the main features of the Pink and White Terraces hydrothermal systems. The morphological boundary of the OVC appears to be a major geological control on fluid circulation within the pre-1886 Rotomahana hydrothermal system. If the permeability of this boundary is reduced with respect to that of the surrounding material, separate geothermal upflows occur on each side of it which broadly match the locations and separation of the Pink and White Terraces and their respective hydrothermal systems. The simulations further suggest that the Terraces may have been only 3‐4,000 years old at the time of the eruption of Mt. Tarawera. • Mount Tarawera in New Zealand erupted in 1886. • The Pink and White silica Terraces at Lake Rotomahana were lost in the eruption. • A computer model describes the geothermal systems at Lake Rotomahana before 1886. • The Pink and White Terraces were separated by a low permeability caldera boundary. • The Terraces were at most 3–4000 years old when the eruption occurred. [ABSTRACT FROM AUTHOR]

• Turrialba volcano slowly transitioned from a closed- (2010) to an open-vent system (2017). • Seismic tremor decreases precede eruptive phases at Turrialba volcano. • Pre-eruptive tremor abatement is accompanied with SO 2 flux decrease. • Chromatic signals are common seismic precursors (e.g. tornillos, harmonic tremor). • Magnitude 5.5 earthquake correlates with the transition to an open-vent system. Turrialba is a stratovolcano located at the easternmost part of the Costa Rican volcanic front. After remaining quiescent for more than a century, in 1996 it started to show signs of unrest, until a first phreatomagmatic explosion occurred on January, 2010. Since then, the activity evolved from phreatic to magmatic, in a series of distinct eruptive phases. In this paper, we investigate the seismic records that span the whole eruptive process (2010-present), in order to identify precursory signals and characterize the volcanic evolution. A long-term analysis was carried out based on the continuous records, as well as seismic catalogs (volcano-tectonic seismicity, harmonic tremor, etc.). In addition, the gradual character of the evolution of this eruption allowed for the analysis of independent precursory stages. Thus, we inspected in detail the most important of those periods, particularly, prior to the first 2010 phreatomagmatic eruption, and prior to the 2016 transition to an open vent system. Temporary tremor amplitude decreases were found to precede most of the eruptive phases. In total, 9 pre-eruptive tremor abatement periods were identified spanning several days (5–44), which often concurred with a decrease in the SO 2 flux. The analysis of the volcano-tectonic seismicity highlights the migration of magma from a deep (6–10 km) reservoir beneath the neighboring Irazú volcano towards Turrialba volcano, especially between the years 2015 and 2016. This activity peaked on December 2016 when a Mw 5.5 earthquake took place between both volcanoes. Harmonic tremor episodes thrived in the later phase when the system finally opened (2017–2018). In the short-term, compounded tonal seismic signals were identified as precursor events, such as long-period events followed by harmonic tremor or by a multichromatic coda similar to tornillo-type events. The co-occurrence of tremor amplitude decreases and tonal seismic signals is interpreted to be caused by a sealing of the hydrothermal system, which blocked the circulation of fluids and permitted the resonances in the inner cavities. This process leaded to pressure accumulation and the consequent eruptions. Thus, trough a series of cycles of sealing and rupture the system of conduits gradually opened. The seismic characterization of this eruption constitutes insightful knowledge useful for monitoring and risk assessment purposes. [ABSTRACT FROM AUTHOR]

The Waimangu Geothermal Valley (WGV) is the youngest geothermal area in New Zealand. It was formed as a result of the 1886 Tarawera Rift eruption and contains the world's largest hot pool (Frying Pan Lake), numerous hot springs, fumaroles and areas of steam heated ground. Assessments of surface heat loss from geothermal systems can provide information and insight into the size and character of the underlying geothermal resource, and, provides a monitoring tool to help assess increases or decreases in activity in the geothermal system. Historically, many different methods have been used to measure heat loss that can result in a wide range of estimates. Surface heat loss of the WGV is estimated in this paper using aerial thermal infrared imagery (TIR), and, several terrestrial based surveys, including calorimetry, chloride-flux assessments, and shallow temperature-depth profiles. The terrestrial heat loss survey consisted of 22 calorimeter and temperature-depth profile measurements in varying groundcover. The measured heat fluxes of these sites are scaled-up using a new groundcover map to determine a total surface heat loss of the valley. This surface heat loss estimate is combined with a calculated evaporative heat flow from the surfaces of the two heated lakes, Frying Pan Lake and Inferno Crater. Similarly, ground-surface and water-surface temperatures were inferred from aerial TIR data. A heat flux per pixel is calculated using one of two methods, depending on whether the pixel of interest represents a water surface or a ground surface. A total heat loss for the valley is estimated by adding the heat flux per pixel for the total area. Total heat loss for the WGV is estimated to be 300 MW th using terrestrial methods, and 330 MW th using the aerial TIR data. These total surface heat loss estimates are in close agreement with each other, and with historic estimates for the area. • Aerial Thermal Infrared and Terrestrial-base heat flux measurements at Waimangu Geothermal Valley are collected. • A total heat loss of approximately 300–330 MW for the Waimangu Valley is derived. • Remote sensing and terrestrial-based measurement techniques provide similar total heat loss values. [ABSTRACT FROM AUTHOR]

Monogenetic volcanoes are small-volume landforms (< 1 km3) which can develop complex eruption histories. Their genesis may include variations in their primary magma sources and petrogenetic evolution, eruption styles transitions, changes in their emplacement conditions. The Central Andes (Northern Chile) contains >900 small-volume volcanoes, most of which lack a detailed knowledge of their eruption histories due to the limited volcanological studies available. In this paper, we present a detailed volcanostratigraphic, morphometric and petrologic study are used to reconstruct the geology and eruptive history of Cerro Negro volcano. It is a Pleistocene pyroclastic cone which stands out from all monogenetic volcanoes of this region due to its larger size (~1 km3) and location along the axis of the orogen. The activity of Cerro Negro began with a phreatomagmatic phase that produced breccias and a lithic-rich tuff, followed by magmatic activity with lava fountaining and Strombolian styles. This latter magmatic phase produced short lava flows, but mostly spatter agglutination and tephra fallout layers. The composition of erupted materials spans from calk-alkaline basaltic andesite to dacite. The least evolved magmas of Cerro Negro are derived from mantle wedge's partial melts without significant crustal assimilation. However, changes in the composition through the eruption suggest crystal fractionation and shallow magma storage, followed by mixing and crustal contamination during the late stage of the eruption. The absence of significant repose period between the deposition of the distinct products and their total volume together with the observed compositional variations imply that Cerro Negro represents a large volume polycyclic monogenetic volcano. These results are important to understand the mafic magma evolution in thickened crusts and the eruptive styles of long-lasting monogenetic eruptions. • Cerro Negro (CNV) is a c. 1 km3 (bulk volume) Pleistocene pyroclastic cone; it classifies as a large monogenetic volcano • CNV erupted in successive phreatomagmatic, lava fountaining and Strombolian phases; the eruption may have lasted years • CNV magmas were calk-alkaline (55.1 to 66.5 wt% SiO 2) and became more silicic as the eruption progressed • Magmas sourced from metasomatized spinel peridotite; polymagmatism involving fractionation, crustal assimilation and mixing [ABSTRACT FROM AUTHOR]

This paper presents results from a magnetotelluric survey at Ceboruco Volcano in Mexico. The observed data require an anisotropic 3-D electrical resistivity model which links a near-surface geothermal reservoir to the magmatic system and finally to the local tectonic setting. Ceboruco is an active stratovolcano, which is located in the Tepic-Zacoalco Rift and is part of the Trans-Mexican Volcanic Belt. Together with Chapala and Colima, the Tepic-Zacoalco Rift forms a triple rift system, which developed as a consequence of the subduction of the Rivera and Cocos oceanic plates beneath the North American continental crust. Ceboruco is the largest and most active volcano in the region. Broadband magnetotelluric data were collected at 25 sites distributed on and around Ceboruco Volcano during a two-week campaign. The survey focused on the electrical resistivity distribution to characterize the geothermal potential and the deep structure beneath the volcano. The data quality is very high in a wide period range between 10−4 and 102 s and there is a consistent data pattern at all sites. For sites located on the volcano, topographical effects dominate the shortest periods. At all sites a highly conductive layer is implied for periods below 1 s , and a spatially constant phase split and coincident small induction vectors are observed to the long period end. The 3-D isotropic inversion of the data yields an excellent data fit for short and intermediate periods and reveals a shallow magma storage and an extensive hydrothermal reservoir between 1 km a.s.l. and approximately 2 km b.s.l. At greater depth, the inversion algorithm generates large-scale high resistivity contrasts, reaching far outside the area of investigation. The resulting structures are inconsistent with the known geological setting and are considered to be artifacts of the isotropic inversion. We present an alternative model, which includes two anisotropic layers below 10 km depth. The conductive principal axes of the anisotropy are consistent with the local rifting direction in the Tepic-Zacoalco Rift and relate to a ductile deformation of the host rock and a large mush zone at mid- to lower-crustal depths. • MT powerful technique for volcano sub-structure. • 3D electrical anisotropy modelling approach is novel and gives additional insights. • Evidence that magmatic system is controlled by local tectonics. [ABSTRACT FROM AUTHOR]

A maar-diatreme forms in response to the phreatomagmatic eruption caused by violent interaction between magma and externally derived water. Experimental work on phreatomagmatic eruptions has yielded considerable knowledge on maar-diatremes. However, the mechanism and process at natural scale remain poorly understood, especially when surface deposits are present. This paper presents a magnetotelluric and magnetic study of the Late-Pleistocene maar-diatreme volcanoes in the Lei-Hu-Ling area of northern Hainan Island, China. The regional 3D electrical structures show shallow high resistivities below craters and a low resistivity layer overlying the deep high-resistivity basement. The local magnetic structure of maar Luo-Jing-Pan reveals a cylinder-like diatreme with high susceptibility. The shallow low-resistivity zone, which coincides with the Fushan depression controlled by the Changliu-Xiangou Fault, is associated with the accumulation of high-salinity fluids with high porosity. The considerable volume of water stored in the Fushan depression and the sedimentary basement ridges beneath maars could have enabled a high level of magma-water interaction. This indicates a fault-controlled type for the phreatomagmatic eruption in the Lei-Hu-Ling volcanic area. The explosion depth is at least 600 m for Ru-Huang-Ling and Luo-Jing-Pan maar-diatreme volcanoes, indicating deep phreatomagmatic eruptions with less contribution to surface deposits. In addition, the explosion energy of the Ru-Huang-Ling maar with a diameter of 1900 m is about 7–8 times that of Luo-Jing-Pan maar with a diameter of 900 m. • Late-Pleistocene maar-diatremes of northern Hainan Island, China are delineated by a magnetotelluric and magnetic imaging. • Fushan depression provides a considerable volume of water for phreatomagmatic eruption. • The phreatomagmatic eruptions are of the fault-controlled type with explosion depth of at least 600 m. [ABSTRACT FROM AUTHOR]

Laguna del Maule Volcanic Field (LdMVF, 36° 10′ S), located in the Southern Andean Volcanic Zone, concentrates an extraordinary postglacial (<25 ka) rhyolitic volcanism and records one of the highest world rates of surface uplift (>20 cm/yr since 2007). Different papers have been published concerning magmatism and geophysical survey but no research has been performed concerning the associated hydrothermal system present in the area. In this work, we analyze both past and present-day hydrothermal manifestations present in the LdMVF. Seven hydrothermal fossil alteration zones were described, with different mineral assemblages suggesting paleo-fluids temperatures ranging between 150 °C - 250 °C for hydrothermal alteration. Additionally, five active fluid discharge zones were also recognized. Based on their spatial distribution, and new data on surficial water/gas geochemistry including stable isotopic composition (δ18O-δD-H 2 O and δ13C-CO 2), the Laguna del Maule Hydrothermal System is here defined. A conceptual two-layer model is proposed, which consists in a deep reservoir with estimated temperature of 178 °C -195 °C and over this a shallow aquifer system with temperature of 116 °C -143 °C. Water composition from outflow zones revealed fluid-rock interaction, due to carbonates and sulphates dissolution of Mesozoic sedimentary units. The upflow fluid discharges, which are spatially coincident with the ongoing surface uplift, provides geochemical evidence of deep origin, and consequently the arrival of fluids capable of increasing pressure in the upper crust. The spatial distribution of both past and present hydrothermal manifestations suggests a strong structural control promoting fluid circulation due to enhanced permeability, throughout the entire lifetime of the volcanic field. • Thermal springs, gas discharges, and ancient surficial alteration zones were mapped and studied for the first time. • Laguna del Maule Hydrothermal System is here defined as a two-layer reservoir with a minor contribution of magmatic fluids. • A geothermal reservoir of 178 to 195°C is located ~1.5 km depth below the centre of inflation of Laguna del Maule. • The pressure exerted by hydrothermal fluids causes the surface uplift and seismicity reported in Laguna del Maule. • Past and present-day hydrothermal manifestations suggest a structural control on permeability, promoting fluid circulation. [ABSTRACT FROM AUTHOR]

The western slope of Cerro Domuyo in northern Patagonia is characterized by thermal springs with boiling waters, Quaternary silicic domes, and pyroclastic deposits that suggest the existence of a geothermal reservoir. According to geochemical studies, the reservoir may have a temperature of 220 °C and one of the largest advective heat fluxes reported for a continental volcanic center. In this paper, we propose a more refined conceptual model for the Domuyo geothermal area, based on a geological survey supported by U Pb, U Th, and Ar Ar geochronology and by magnetotelluric and gravity surveys. Our study indicates that the Domuyo Volcanic Complex (DVC) is a Middle Pleistocene dome complex overlying middle Miocene to Pliocene volcanic sequences, which in turn cover: 1) the Jurassic-Early Cretaceous Neuquén marine sedimentary succession, 2) silicic ignimbrites dated at ~186.7 Ma, and 3) the Paleozoic metamorphic basement intruded by ~288 Ma granite bodies. The volcanic cycle in the DVC is distinctly bimodal, characterized by the emplacement of massive silicic domes and less voluminous olivine basalts on its southern slope. A major collapse of the central dome at ~600 ka produced a voluminous (19.4 km3 and 133 km2) block-and-ash flow, and associated pyroclastic flows, that filled a valley to the southwest at distances up to ~30 km from Cerro Domuyo summit. This was followed by a period of intense effusive activity that formed the Cerro Guitarra, Cerro Las Pampas, Cerro Domo, and Cerro Covunco silicic domes. The last two domes are the youngest and largest edifices, dated at 0.50 Ma (Ar Ar age) and 0.25 Ma (U Th age). Pre-Cenozoic successions were affected by N-S reverse and thrust faults that were later displaced by an ENE-WSW-trending transtensional belt. The basement rocks at the northern termination of the Cordillera del Viento anticlinorium were also displaced towards the east-northeast by this belt, which is observed NNW of Cerro Domuyo. The DVC was emplaced within this zone of crustal weakness. The integration of geologic observations with magnetotelluric and gravity data, allowed us to develop an updated conceptual model of the geothermal system. The geothermal reservoir is inferred at a depth of less than 2 km within pre-Pliocene fractured rocks, bounded by ~WSW-ENE trending faults and sealed by the pyroclastic deposits and rhyolitic lavas of the DVC. The location of most thermal springs is not directly controlled by faults. Instead, flows emerge at the contact between the fractured and faulted basement and the caprock. • The Domuyo Volcanic Complex (DVC) is a silicic dome complex formed in the Pleistocene. • The central dome collapsed at ~600 ka producing a voluminous (19.4 km3) pyroclastic deposit. • The youngest domes were emplaced at ~500 ka and 250 ka. • The DVC was emplaced within a ENE-WSW trending transtensional zone of crustal weakness. • The geothermal reservoir is hosted in pre-Pliocene rocks sealed by the DVC pyroclastics and lavas. [ABSTRACT FROM AUTHOR]

The correlation between onshore and offshore of the volcanic features in a complex volcanic field area is a difficult task, however, it is a fundamental step in order to better understand the geological evolution of such a complex area and for an assessment of geologic hazards. Ischia is a well exposed and densely populated volcanic field located in the Campania volcanic province of Italy. In order to improve our understanding of the recent volcanic history of Ischia Island, high-resolution seismic reflection profiles were used to identify volcanic and sedimentary features in the northern offshore. The volcano stratigraphy interpretation permitted us to recognize seismic units with a reflection-free/chaotic facies. These latter units have been associated with volcanic deposits and correlated to the main volcanic units outcropping on the northern coast of Ischia Island. They are limited in extent and interlayered with eight seismic units with continuous reflectors corresponding to clastic sedimentary units that were deposited during inter-eruptive phases. The main result of this work is the documentation of volcanic activity during the Holocene in the area offshore between Castello d'Ischia, Ischia Porto (mainly effusive products) and Punta della Scrofa (mainly shallow lava domes and dykes). The key volcanic units were mapped and 3D geological models were reconstructed. The reconstruction of the stratigraphic framework offshore a volcanic coast provides a pathway to the investigation of the stratigraphic relationships between inter-eruptive sedimentary deposits and volcanic units, and permits the assessment of a wide and continuous chronostratigraphic framework in a complex area. Furthermore, the onshore-offshore correlation of the main Holocene volcanic units allows us to better estimate their areal distribution, a critical factor in the hazard evaluation of a coastal volcanic area. The application of seismic volcano stratigraphy illustrates the remarkable possibilities that the study of submarine volcanic fields offers. • The goal of the paper is the stratigraphic analysis of an offshore volcanic field using seismic reflection profiles • The stratigraphic relationships between eruptive and inter-eruptive deposits have been reconstructed • We built 3D geologic surfaces of the main Holocene volcanoes offshore Ischia (Italy) • The onshore-offshore correlation of the volcanic unit permits to establish a geologic continuity across the coast • The application of seismic volcano stratigraphy proves the remarkable capabilities for the study of submarine volcanoes [ABSTRACT FROM AUTHOR]

Despite decadal–millennial repose periods, volcanoes of the Canary Islands pose significant, though poorly understood hazards to local communities and infrastructure. At least 13 volcanic eruptions forming monogenetic cones and lava flows have occurred in the archipelago since 1500 CE: six on the island of La Palma (in 1585, 1646, 1677–1678, 1712, 1949 and 1971), four on Tenerife (1704–1705, 1706, 1798 and 1909), two on Lanzarote (1730–1736 and 1824) and one on the submarine flank of El Hierro (2011–2012). In this paper, we synthesize available data on these historical eruptions, focusing on their physical characteristics and chronological development, and provide new estimates of eruption parameters, such as lava flow runout, area and volume, to inform volcanic hazard assessment in the archipelago. While incomplete and imprecise, historical records indicate that precursory seismicity began days to years prior to eruption onset, consistent with the three months of well-documented unrest for the 2011–2012 eruption. Excluding the atypical 1730–1736 event, eruptions lasted from ten days to a little under five months. Initial eruptive phases usually involved the opening of multiple vents along dike-fed fissures, with Strombolian explosive activity forming monogenetic cones. Lava flow emission generally quickly followed, and later eruptive phases were typically dominated by effusive behavior. Some eruptions (1704–1705, 1824 and 1949), however, had a complex evolution punctuated by the sequential opening of distinct vents several kilometers apart. Total lengths of vent-defined fissures range from 0.2 to 14.0 km, and maximum lava flow runout is 2.7–9.4 km, extending to the coastline in 75% of eruptions. Proximal eruptive deposits cover 1.8–7.8 km2. Published estimates of subaerial eruptive volumes average between 11 and 66 × 106 m3. In comparison, a new empirical relationship based on well-constrained lava flow area and volume data at other basaltic volcanoes yields volumes of 10–76 × 106 m3 for Canary Island eruptions. The 1730–1736 Timanfaya eruption on Lanzarote represents an outlier in the context of historical Canary Island volcanism, with a duration of 2055 days, a total fissure length ≥ 14.4 km defined by at least ten main emission centers, a maximum lava flow length of 21.7 km, a lava flow field area of 146 km2 and volume of at least 2.2–3.7 km3. Historical eruptive rates are low, at 1.0–2.1 × 106 m3/year or 7.3–11.0 × 106 m3/year including the 1730–1736 eruption, in agreement with long-term volcano growth rates based on geologic data. We find no evidence for time-predictable or volume-predictable behavior of the historical eruptive sequence, which has a mean recurrence interval of 39 ± 24 years. Our analysis outlines a useful framework for forecasting the onset, development and style of future eruptions in the archipelago. Further work, particularly detailed field-based studies of eruption deposits and petrologic reconstructions of eruption run-up processes, will help refine our understanding of historical volcanism and associated hazards in the Canary Islands. • 13 historical Canary Island eruptions formed monogenetic cinder cones and lava flows. • Precursory activity may begin days to years prior to eruption, but is poorly constrained. • Eruptions, 10–80 × 106 m3 in volume, commonly show a complex, multi-vent evolution. • An empirical relationship allows estimating volume of basaltic lava flows from their areal extent. • Historical data provide a framework for forecasting future eruption scenarios. [ABSTRACT FROM AUTHOR]