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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]

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]

A small phreatic eruption of Sinabung Volcano, North Sumatra on 28 August 2010, at 18:30 local time marked the first eruption in the past ~ 1200 years. The eruption took place from two small vents in the south crater area. Explosions and ash emissions from these vents generated multiple ash plumes that reached altitudes of up to 5 km during early- to mid-September. By the end of September 2010, only low level steam plumes were visible and the alert level was reduced from Level 4 (highest) to Level 3. The 2010 eruption effectively ended at this time. Beginning two days after the initial 2010 eruption, activity of the eruption has been monitored continuously by a telemetered seismic network surrounding the volcano and by remotely sensed observations. This monitoring system was supplemented with a near-field continuous GPS network, beginning in February 2011. Persistent fumarolic emissions continued for almost 3 years following the 2010 eruption, before a new eruption began on 15 September 2013. This eruption continues to the present. The ongoing eruption is divided into 5 major phases: 1) phreatomagmatic phase (July 2013–18 December 2013); 2) first dome and collapse phase with pyroclastic density currents (PDCs; block-and-ash flows and related surges) to south (18 December 2013–10 January 2014); 3) lava-flow and collapse phase (10 January 2014–mid-September 2014); 4) second lava dome and collapse phase with PDCs to south (mid-September 2014–July 2015); 5) lava dome collapse and ash explosion phase with PDCs to southeast and east (August 2015–present). The volcano erupted intermittently during the early phreatomagmatic phase with small vertical ash explosions. Then the eruption became increasingly vigorous with more repetitive and intense vertical ash explosions during late October through November. The first small pyroclastic density currents (PDCs) began on November 1. These pyroclastic flows descended the southeastern flank to a distance of 2 km. Swarms of volcano-tectonic (VT) earthquakes and volcanic tremor lasting hours occurred repeatedly during the phreatomagmatic phase and some of these VT-swarms were followed by explosions. In early December 2013, during the transition between phreatomagmatic and dome-collapse phases, swarms of hybrid earthquakes took place preceding and accompanying dome growth. The first lava dome was observed in satellite images on 18 December near the main crater rim. Partial collapses of the dome produced PDCs beginning on 30 December. Growth of this first lava dome continued into January and was accompanied by additional collapses and PDCs. By about 10 January, the lava had transitioned from a summit dome morphology into a lava flow morphology. The resulting lava flow descended the southeast flank of the volcano, producing flow-front and marginal collapses with associated PCDs. One such flow-flank collapse on 2 February 2014 resulted in a PCD that killed 16. The lava flow phase continued through mid-September 2014, when a second summit lava dome began to grow and collapse, producing PDCs initially to the south and southeast, and then beginning in July 2015 to the east and southeast. The eruption of Sinabung resulted in major impacts on the population of the resort and farming area near the volcano and in the Ginting and Karo Regencies of North Sumatra. Local residents, having not experienced eruptions in their lifetimes, were initially curious and eager to receive any information about the eruption regardless of its source. Various institutions provided information with little coordination, resulting in confusion. With time communications have improved and communities and the responsible governments have become better prepared in dealing with the persistent eruption. The Government of Indonesia has provided funding to support villagers who lived within a 5 km radius danger zone to stay in relocation camps as a permanent relocation area is being identified. Unfortunately, on 21 May 2016, 9 additional fatalities took place in the village of Gamber, within the danger zone, when a dome collapse sent a pyroclastic density current into the area. Throughout the eruption, the volcano has been monitored by the Indonesian Center for Volcanology and Geologic Hazard Mitigation (CVGHM) in partnership with the USGS-USAID Volcano Disaster Assistance Program and the Disaster Prevention Research Institute of Kyoto University. Monitoring techniques have included seismic, geodetic, gas, satellite and field observations, as well as occasional sampling of ash and lava for geochemical analyses. In this paper, we summarize key aspects of the monitoring data, their interpretations and their use in forecasting eruptive behavior and in issuance of alerts and warnings. More detailed interpretations of the monitoring data and their use are found in other papers of this special issue. • In this introductory paper to the Special Issue on the eruptions of Sinabung and Kelud volcanoes, we focus on the 2010 and 2013–present eruptions of Sinabung volcano, North Sumatra, Indonesia. • We provide information on the monitoring system used and we highlight how the monitoring data (seismic, geodetic, gas and observations) were used to forecast activity and to issue alerts and warnings. • We also describe the chronology of the 2013-present eruption and we review how the eruption has impacted the lives of residents of the region. [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]

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]

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]

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]

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 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]

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]

The Sub-Andean zone east of the Cordillera Real, Ecuador and out to the Amazon basin's western margin has been the depository of voluminous lahars related to volcanic activity in the Andean highlands. These lahars arrived to the Sub-Andean zone via gravitational transport through narrow river canyons and emplaced volumes surpassing several cubic kilometers over robust inundation zones. This paper discusses the origin, flow route, depositional zone, terrace formation and geomorphic significance of the most important lahar deposit yet mapped in this region, that of the Mera lahar, which likely formed from a late Pleistocene collapse of Huisla volcano, followed by impounding by temporary dams behind drainage-blocking debris avalanche deposits (DAD), then subsequent rupture of the blockage. The actual deposit of the Mera lahar has a thickness between 30 and 70 m, is mainly comprised of DAD breccia, is matrix-supported (c 70%), of reddish gray color and is well-consolidated. Based on geochemical and petrographic similarities, Huisla volcano's DAD is the best candidate for the lahar's source. Huisla volcano is located some 90 km up valley of the bulk of Mera lahar's mapped deposit. Clasts of Mera lahar rocks and Huisla's DAD breccias have 57–61 wt% SiO 2 , corresponding to andesites of the calc-alkaline series with mean values of 1–1.5 wt% for K 2 O. The mapped Mera lahar deposit has an actual volume estimated in 1.2 km3 compared to its original estimated volume of 5.4 km3. Cross-sectional widths of 1.5 to 4.5 km span and extend laterally beyond the actual Pastaza river channel where the lahar's deposition produced high-standing isolated surfaces that are notable local geomorphic features of the upper Sub-Andean zone. The flow modeling program LaharFlow, employing the modern landscape as the topographic base, adequately simulates the flow route and inundation zones of the Mera lahar. • Petrographic fingerprinting shows that Huisla volcano´s DAD breccias provided the bulk clastic material for the Mera lahar. • Huisla volcano had a Pleistocene collapse, possibly from shaking provoked by an active fault under its SW shoulder. Coeval eruptive activity was likely since radially fractured bombs are present in both the Huisla DAD and the Mera lahar deposit. • DAD blockage indeep canyons impounded the river system and temporary dams formed then ruptured and the ensuing mixture of water and breccia formed an enormous secondary lahar (volume ~ 5 km3) that flowed 90 km to the Sub-Andean-western Amazon area. • The lahar deposit is rich in the Huisla DAD breccias, has a high sand content, was a non-cohesive type and did not transform to a hyperconcentrated flow. • The deposit is still well preserved on the left margin of the Pastaza river, where 30-50 m high terraces now host the towns of Mera and Shell, among others. • Mapping was complex due to cover by jungle vegetation and erosion caused by avulsions of the Pastaza river. • The LaharFlow modeling program gave results that show affinity with the field mapping in certain preserved areas, ie Mera and Shell, and also showed where the deposit may have once been, but erosion has erased evidence. • A log was extracted from Mera lahar´s interior and a radio carbon date of > 43.5 ka was obtained. Overlying dated strata (17 ka - 40.5 ka) provide minimum ages for the Mera lahar. • The low profile volcano Huisla with its collapse events provoked a major lahar, whose deposits are clearly recognizable some 40 ka after the event. [ABSTRACT FROM AUTHOR]

The last several years have seen a very rapid increase in the development and availability of unmanned aerial vehicles/systems (UAV or UAS), more commonly called "drones." UAS are remotely-operated aerial vehicles that can be fixed-wing planes, helicopters, or aerial systems with multiple propellers. Small versions of UAS, here called "sUAS," in particular, have become so prevalent that they can be easily purchased at general retail stores. This paper seeks to review and summarize the use of sUAS in volcanic research. Given their size, low cost, and relative durability, sUAS provide a light-weight tool platform that is easy to transport to field locations; quick to set-up; and easy to launch, and control. They require very little launch and recovery space. Because of these characteristics, sUAS are useful in collecting immediate and real-time aerial data, especially in remote, inaccessible, dynamic, and/or hazardous, volcanic environments. In volcanic areas, sUAS have been used for mapping, sample collection, thermal imaging, magnetic surveys, slope stability studies, and as platforms for sensors to measure outgassing of CO 2 and SO 2. They are also becoming invaluable for real-time hazard assessment during and after an eruption. They are, however, limited by their flight time, which is greatly affected by wind speeds. Since they are predominately made of plastic, they are also impacted by the high thermal temperatures found in active volcanic areas, which can degrade their structure and performance. With continued technological improvement however, sUAS have the potential to dramatically improve our ability to collect field data. Because of additional natural, technological, and legal challenges related to their use, it is critical that users be aware of, and adhere to, all national and local laws associated with sUAS. • Small drones (sUAS) have become common in field work due to their low cost, durability, ease of use and transport, and as a safe means to access hazardous areas. • sUAS are being used in volcanic areas for a variety of purposes, such as monitoring change over time, assessing hazards, creating digital maps, and sampling gas and tephra. • Although challenges exist with using sUAS, they have become standard tools in volcanological research. • Any research done using sUAS should be done only by following national and local regulations governing their use. [ABSTRACT FROM AUTHOR]

Knowledge of Etna's eruptions has been profoundly influenced by the illustrations, though these can only provide limited information on the lava flows and their effects on the territory. Indeed, the absence of iconographic sources or again the disparity between the physical reality and the illustrations has led to many gaps and uncertainties that have lasted for centuries. This paper traces the progress of the representations of the historical eruptions of Etna volcano, from the earliest attempts in the 17th century, be they iconographic documents or pictorial illustrations, to the modern geological cartography of 21st century. It seeks to reconstruct the evolution of the history and methods of representing Etnean eruptions, highlighting the crucial steps in the progress of knowledge on the historical flank eruptions. The turning point in the long process of drawing and rendering the eruptions of Etna came with the work of Sartorius von Waltershausen, with the realization of the first geological map of the volcano at a 1:50,000 scale between 1836 and 1843. In this long history of the representations of eruptions, begun in the 17th century, Sartorius' cartography finally overcame the problem of rendering these events in space by inserting the notion of history in the map. What now remained for those engaged in mapping the volcano was to solve the issue of defining the "time" of Etna's historical lava flows. This would be tackled only at the end of the 20th century with a multidisciplinary approach comprising stratigraphy, historiographical studies and the dating of the lavas. In this frame, the present state of the knowledge of the flank eruptions occurring on Etna in the past 2500 year has evidenced that during the Greek-Roman and Medieval epochs up to the 17th century flank eruptions commonly involved the middle-lower slopes, impacting mainly the south sector of the volcano with the location of the eruptive fissure sometimes below 1000 m of altitude. This eruptive behavior of the volcano has been radically modified following the occurrence of the large 1669 eruptions since the opening of the fissures was mainly concentrated in the upper-middle slopes between 1600 m and 2500 m a.s.l. • A marked increase in the illustrations of Etna's eruptions is related to the major 1669 event • Sartorius's geological map remained the enduring benchmark on the knowledge of the eruptive history right up the 1900 • The opening of fissures at low elevation were common during the Ancient and Medieval periods • During the last 340 years, no flank eruptions have occurred below 1000 m of altitude. [ABSTRACT FROM AUTHOR]

The magmatic components of continental Large Igneous Provinces (LIPs) include flood basalts and their plumbing system of giant mafic dyke swarms (radiating, linear, and the recently discovered circumferential type), mafic sill provinces, a lower crustal magmatic underplate, mafic-ultramafic (M–UM) intrusions, associated silicic magmatism, and associated carbonatites and kimberlites. This paper proposes a new plumbing system framework for mantle plume-related continental LIPs that incorporates all of these components, and provides a context for addressing key thematic aspects such as tracking magma batches "upstream" and "downstream" and their geochemical evolution, assessing the setting of M-UM intrusions and their economic potential, interpreting deep magmatic component identified by geophysical signatures, and estimating magnitudes of extrusive and intrusive components with climate change implications. This plumbing system model, and its associated implications, needs to be tested against the rapidly improving LIP record. • New plumbing system framework for plume-related continental LIPs • Provides context for tracking magma batches "upstream" and "downstream" in the system • Identifies the setting of different types of mafic-ultramafic intrusions within this plumbing system [ABSTRACT FROM AUTHOR]

Clusters of small-volume volcanoes that individually may be defined as monogenetic, but have interlinked and interconnected plumbing systems, are used to be categorized as monogenetic volcanic fields (MVF). We argue that such volcanic clusters should be distinguished as separate type of volcanism, intermediate between monogenetic and polygenetic. The magma plumbing system structure of the MVF (its complexity and polymagmatic character) is the key argument for the potential separation of them in a classification. To avoid confusion caused by genetic meaning of the used words we suggest using a term "areal volcanism" or "areal volcanic fields" (AVF instead of MVF) as defining this special type of volcanic activity. Here we provide a review of the main characteristic features of one of the largest Holocene AVF, which is active now – the Tolbachik field of cinder cones in the southern part of Klyuchevskaya volcano group (Kamchatka), known in the literature as Tolbachinsky Dol. This paper is focused on the research of magma plumbing system. We consider structural, morphological, geological, geochemical and petrological data on the erupted basalts and their genesis. Specially planned seismic experiments made in 2010–2015 (seismic tomography and microseismic sounding) allowed modeling of the principal elements of the magma plumbing system of Tolbachik AVF. Analysis of the investigations made in this area shows that Tolbachik AVF has a complex, dynamic, variable magmatic feeding system, which can be visualized as a superposition of subvertical and sublateral magma conduits. The contrast composition of the erupted rocks is caused by their different, although genetically connected, magma sources and mixing processes. One of the long-lived eruptive centers of Tolbachik AVF is Plosky Tolbachik stratovolcano, which lost its independent activity and was captured by Tolbachik AVF in Holocene. The AVF formed rejuvenated volcanism using the feeding system of the stratovolcano like an "old anthill". The magma plumbing system characteristics of Tolbachinsky Dol strongly support the idea of separation of AVF from monogenetic volcanism type in the classification. • We combine petrological and geophysical data to study Tolbachik areal volcanic field. • We discuss features of magma supply of Tolbachik historical fissure eruptions. • We show integrated models of magma plumbing system for Tolbachik areal volcanic field. • We argue for classification of areal volcanic fields as separate type of volcanism. [ABSTRACT FROM AUTHOR]

During the ongoing (2013–present) eruption of Sinabung volcano, north Sumatra, we have routinely used a variety of satellite remote sensing data to observe and forecast lava dome and lava flow collapse events, to map the resulting pyroclastic deposits, and to estimate effusion rates. In this paper, we focus on the first two years of the current eruption (September 2013–December 2015), and we summarize major events in 2016. We divide the eruption into 5 major phases: 1) phreatomagmatic (July 2013–18 December 2013), 2) first dome growth and collapse (18 December 2013–10 January 2014), 3) lava-flow (10 January 2014–mid-September 2014), 4) second lava dome and collapse (mid-September 2014–July 2015), 5) lava dome collapse and ash explosion phase (August 2015–present). Throughout the eruption, remotely sensed information has been instrumental in assessing the stability of the lava dome and flow and to forecast collapse events that produce pyroclastic density currents (PDCs: block-and-ash flows, co-ignimbrite surges, and blasts). Forecasts based on remote sensing data in combination with seismic, geodetic and gas-monitoring data have also helped inform decisions related to alert levels and evacuations. Relatively unusual aspects of the Sinabung eruption include the transition from dome to flow morphology (phase 2 to phase 3 transition) and the frequent occurrence during phase 3 of collapses from the lava flow-front and flow-margins—collapses that produced extensive pyroclastic density currents. By analogy to the well-known "Merapi type" collapses and pyroclastic deposits, we propose that lava flow-front and flow-margin collapses with associated PDCs be known as "Sinabung type." Although detailed study of deposits has not been possible due to continuing hazards, our observations suggest that the transition from lava dome to lava flow and the occurrence of flow-front and flow-margin collapses reflect a particular combination of lava viscosity and steepness of slope. Our observations also show clear evidence of at least one slope-parallel high-velocity and dilute PDC (a "blast") that emanated from a lava-margin collapse site 500 m downslope from the vent. This 1 February 2014 blast downed and singed a forest out to at least 3.9 km from the collapse site and killed 16 people. We also use a combination of field and remotely sensed data to map the distribution of Sinabung deposits. We estimate eruptive volumes and extrusion rates by combining sequential measurements of lava surface and pyroclastic flow areas with thickness estimates derived from simple geometric assumptions, oblique photographs and Digital Elevation Models (DEMs) derived from remotely sensed data. Our estimates of short-term effusion rates vary widely on a daily to weekly basis, from <1 to >20 m3 s−1. In a few cases, periods of increased extrusion precede lava flow-front collapses by a few days to a week, suggesting delays in transmittance of effusion pulses as lava moves from vent to flow front. We find that, as of 1 January 2016, the total area of deposits is 107 m2, and their approximate deposit volume is about 0.3 km3, equivalent to 0.2 km3 Dense Rock Equivalent (DRE). We anticipate that our deposit maps will be valuable in the future as a framework for the study of the magmatic and textural evolution of eruptive products through time. • Satellite remote sensing was used with and ground-based monitoring was used to issue warnings and reduce risk during the eruption of Sinabung volcano. • Eruption rates and volumes and distribution of lava and pyroclastic deposits were determined with remote sensing. • Unusual lava flow front and margin collapses were deadly; eruptions with these types of collapses are deemed "Sinabung type." [ABSTRACT FROM AUTHOR]

Volcano monitoring and eruption forecasting are based on the observation and joined interpretation of several precursory phenomena. It is thus important to detect new types of precursor and to study their relationship with forthcoming eruptions. In the last years, variations of seismic velocity have been observed in some volcanoes, mainly basaltic, before eruptions. In this paper, we look for velocity variations and waveform decorrelations before the 2014 eruptive sequence of the andesitic Ubinas volcano in Peru. We compute velocity changes by using seismic ambient noise cross-correlation (between pairs of stations) and cross-components correlation (between vertical and horizontal components of single stations), as well as coda wave interferometry of seismic multiplets. With these different approaches, we show that the major explosions that occurred from 13 to 19 April were preceded by a clear velocity decrease and waveform decorrelation. The amplitude of velocity change is generally larger on single-station cross-components correlation than on two-station cross-correlation in all the frequency ranges tested (between 0.1 and 8 Hz). We highlight an apparent anisotropy of velocity change in single-station cross-components correlation, with larger amplitudes when correlating vertical and tangential components than using vertical and radial components with respect to the crater. The Mw = 8.1 Iquique earthquake on 1 April 2014 produced also a marked co-seismic velocity drop detected in a high frequency range(3–5 Hz) in both single-station cross-components correlation and cross-correlations. We locate in the horizontal plane and in depth the velocity perturbation and the structural change related with decorrelation. During the main phase of eruptive activity, the velocity decrease at low frequency (0.1–1 Hz) appears to affect the whole edifice mainly at depth of about 1 to 3 km below the surface. The structural perturbation is more concentrated on the south flank of the volcano, a zone that corresponds to an ancient collapse. We suggest that the observed velocity variations are due to the dilatation of the edifice and to microfracturation induced by magma pressurization. The structural change may be locally enhanced by a possible zone of material weakness in the southern sector. The co-seismic velocity perturbation is located mostly in the southeast flank, at depth smaller than 0.5 to 1 km, and may be related to the presence of the hydrothermal system of the volcano. • Noise correlation functions are calculated both on pairs of stations and on single stations. • Velocity decrease and waveform decorrelation are detected 3 weeks before eruption. • Velocity variations are larger when correlating tangential component than radial. • At higher frequency sharp velocity drop is induced by the M W = 8.1 Iquique earthquake. • Velocity and structural perturbations are located in the edifice at 1–3 km depth below crater. [ABSTRACT FROM AUTHOR]

On 10 October 2011, a submarine volcanic eruption began 2 km south of the island of El Hierro (Canary Islands, Spain). It was the first eruption after 40 years of quiescence in the Canarian archipelago. Since mid-July 2011, a multiparametric network has been deployed by the Instituto Geográfico Nacional (hereinafter IGN) to monitor volcanic processes. The data recorded by five stations, measuring the air and soil temperature, CO 2 and radon concentration in the air inside four galleries and one well, are the focus of the present paper. Two important anomalies were found that improve comprehension of the volcanic process. First, a clear increase in CO 2 concentration in one gallery (from 825 ± 19 to 2305 ± 35 ppm) which seems to be mainly controlled by ground deformation measured during the unrest period preceding the eruption. Second, a relationship between radon concentration in air in a well located in the northern side of the island with seismic energy release (several peaks with up to 115% increase), and ground deformation (50% growth in background level), also before the eruption onset. Lastly, changes in radon concentration during eruptive period seem to be modulated by seismic activity (increases up to 233%), which in turn is likely related to variations in magma rheology. • CO2 concentration in air in one gallery controlled by ground deformation during unrest period. • Sharp increases in radon concentration in one well related with changes in ground deformation rate before the eruption. • Variations in carbon dioxide concentration in one gallery linked with magma degassing in the eruption period • Changes in radon concentration in one well during eruptive process [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]

This paper brings a global perspective to volcanic arc geothermal assessments by evaluating trends and correlations of volcanic characteristic and surface manifestation data from world power production sites in subduction zone volcanic settings. The focus of the work was to evaluate volcanic centers individually and as a group in these arcs by correlating various geologic characteristics with known potential to host electricity grade geothermal systems at the volcanic centers. A database was developed that describes key geologic factors expected to be indicative of productive geothermal systems in a global training set, which includes all 74 subduction zone volcanic centers world-wide with current or proven power production capability. Importantly, this data set only contains data from subduction zone volcanoes and contains no negative cases, limiting the populations of any statistical groups. Regardless, this is the most robust geothermal benchmark training set for magmatic-heated systems to date that has been made public. The work reported here is part of a larger project that included data collection, evaluation, correlations and weightings, fairway and favorability modeling and mapping, prediction of blind systems, and uncertainty analysis to estimate errors associated with model predictions. This first paper describes volcano characteristics, compositions and eruption ages and trends along with surface manifestation observations and temperatures as they relate to known power producing systems. Our findings show a strong correlation between the presence and size of active flank fumarole areas and installed power production. Additionally, the majority of volcanic characteristics, including long-held anecdotal correlations related to magmatic composition or size, have limited to no correlation with power production potential. Notable exceptions are correlations between greater power yield from geothermal systems associated with older (Pleistocene) caldera systems than systems hosted by Holocene calderas or non-caldera volcanic centers. Power-hosting volcanic centers that have erupted within the last 160 years supply 50% of the global installed geothermal power in subduction zones, and nearly all of these systems are generally mafic (basaltic or andesitic) in average composition. Volcanic centers erupting between 160 and 900 years ago are dominated by felsic volcanic systems, and provide 47% of the global power from volcanic arcs. Only 3% of geothermal power produced in subduction zones are hosted by volcanic center erupting more than 900 years ago. We anticipate that these results may be able to help guide future geothermal exploration efforts. [ABSTRACT FROM AUTHOR]

In this paper we propose an automatic volcano event detection system based on Hidden Markov Model (HMM) with state and event duration models. Since different volcanic events have different durations, therefore the state and whole event durations learnt from the training data are enforced on the corresponding state and event duration models within the HMM. Seismic signals from the Llaima volcano are used to train the system. Two types of events are employed in this study, Long Period (LP) and Volcano-Tectonic (VT). Experiments show that the standard HMMs can detect the volcano events with high accuracy but generates false positives. The results presented in this paper show that the incorporation of duration modeling can lead to reductions in false positive rate in event detection as high as 31% with a true positive accuracy equal to 94%. Further evaluation of the false positives indicate that the false alarms generated by the system were mostly potential events based on the signal-to-noise ratio criteria recommended by a volcano expert. [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]

Abstract The Copahue volcano host one of the most attractive geothermal resources of Argentina. Several studies focused on both the volcanic activity and the related geothermal manifestations, including a feasibility report during the '90s. However, limited, unclear and usually contradictory structural interpretations are found in the literature, and the role of the main faults over the geothermal system remains thus unsolved. This paper provides the first structural characterization and role assessment of the faults over the fluid flow and the reservoir geometry. A 3D structural model has been constructed to achieve this goal, and a fault-plane striations survey has been carried out at Anfiteatro, Termas and Maquinitas hydrothermal zones. Using this dataset, a slip and dilation tendency analysis over the main structures have been performed. The 3D structural model indicates that the Copahue geothermal field is bounded by an N60°-trending fault set and constrained to the north by the Trolope fault and to the south by the Chancho-Co fault, both with WNW-ESE trend. The collected fault-plain striations data was inverted to obtain the paleostress tensor related to the formation of the Copahue village fault system (CVFS), the structure that controls the hydrothermal areas. The subvertical maximum principal stress axis obtained defines a well constrained tensional regime, with a subhorizontal NW-SE minimum principal stress, consistent in all the surveyed locations. Both the 3D model and the inverted paleostress tensor indicate that the geothermal field, and probably the entire northeastern slope of the volcano, is subjected to an extensional faulting regime. Our analysis shows that the N°60-trending fault set is critically stressed for dilation and probably behaves as an active hydrological fault system, whereas the N105° and N135° fault sets have intermediate and low dilation tendency, respectively. These tendencies might lead to a northeast-trend fluid path between the Chancho-co and the N135° faults and might define the extension of the steam cap. We propose a compartmentalized reservoir model made up by three fault segmented blocks. While a steam cap over a deeper reservoir controlled by the CVFS characterizes the central segment, a pressurized liquid-dominated reservoir could prevail to the west of Termas and the east of Maquinas hydrothermal zones. This model explains the differences between the fumaroles inside the CVFS (i.e., Termas to Maquinas fumaroles) and outside this structural system (i.e., Anfiteatro), is consistent with the steam cap identified by the exploration boreholes and is consistent with the 3D structural framework proposed. Also, the model suggests that the collapse of the eastern slope of the Chancho-co hill might constitute the initial state of the current configuration of the geothermal system. Additional studies are needed to verify the proposed reservoir model before defining deep exploration targets, including magnetotellurics, discrete fracture network analysis, and preliminary thermodynamical models. Highlights • Geothermal field subjected to extensional stress regime(NW-SE Sh min) • N60°, N105°, and N135°-trending faults have respectively high, medium and low dilation tendency • Compartmentalized reservoir explains isotopic differences between fumaroles • Steam cap is related to the Copahue village extensional fault system [ABSTRACT FROM AUTHOR]

Abstract Volcanoes are usually monitored through observations of many physical and chemical phenomena. In the most dangerous cases, as the one of the Campi Flegrei caldera (Italy), great amount of data are collected, both in discrete or continuously, and regularly stored. However, how to transform such mass of data in a deeper understanding of the volcano dynamics is still an open question. Dissimilar information are in fact always hard to compare, but just integrating all the available knowledge hazardous events could be prevented in a reliable way. Fluids, as water and gasses mobilized in the subsoil by the heat induced by deep magmatic sources, are widely recognized as the first engine of similar occurrences and the volcanic gas emissions represent, together with the seismic activity, one of the most considered precursors. At the same time, the electrical geophysical methods are the most applied in order to detect and characterize the fluid patterns in the subsoil. So, the integration of geoelectrical and geochemical observations should represent one of the most pursued approach in volcanoes monitoring. On the contrary, standard way to compare such data has been not yet codified. The ERT tomograms capability to individuate that parts of the subsoil where gasses cumulate is well understood in literature. However, we look for indications about its proficiency in associating the electrical resistivity changes relative to these zones, once compared to the geochemical time series, to deep related contributes, distinguishing them from the seasonal ones. The electrical signature of the fluid patterns, reconstructed through a time-lapse ERT approach, could be of relevance to better characterize the volcanic phenomena and their origins. In this paper a first test of ERT and geochemical time series integration was performed to enhance the understanding of the Pisciarelli fumarolic field evolution, now the most active area in the whole Campi Flegrei caldera. Highlights • Time lapse ERT surveys were performed in the Pisciarelli site. • ERT and superficial data integration was performed to study the site. • Mutual relationship between the parameters and their interdependence is analysed. • Seasonal anomalies and features linked to volcanic contributions are marked. • A conceptual model of the fumarolized area is presented. [ABSTRACT FROM AUTHOR]

The Alcantara River marks the northern border of Etna volcano, and along its NE sector, it forms a narrow NW-SE elongated valley that is carved in the Mts. Peloritani sedimentary sequences. The valley has been invaded by several lava flows during the growth of the main bulk of the stratovolcano edifice in the past 60 ky (Ellittico and Mongibello volcanoes). In this paper, we have constrained the age of the main lava flows forming the valley floor and reconstructed the length and volume of the main lava flow that impacted this area through a multidisciplinary approach integrating stratigraphic and aeromagnetic data analysis together with new paleomagnetic and 14C dating. The new age determinations showed that the evolution of the present-day geological and hydrographic setting of the valley was mainly conditioned by a few flank eruptions that occurred in the lower N flank of Etna during the activity of the Mongibello volcano. In particular, between 13.9 and 9.7 ka BP the valley floor was filled by the so-called Alcantara lava flow for its entire length up to the river mouth, reaching a maximum length of about 24 km. Later, two other flank eruptions – producing the so-called Mt. Dolce and Solicchiata lava flows – occurred at 9.1–7.2 and 7.3–7.2 ka BP (respectively), covering the eruptive fissure and the proximal portion of the Alcantara lava field and generated the most recent northward shift of the riverbed. Finally, 3D magnetic modeling allowed us to calculate the total on- and off-shore volume of the Alcantara lava flow as 1 km3, a value comparable to those of the long-lasting historical eruptions of Etna. Conversely, the 24 km length reached by this lava flow is anomalously high when compared to lava flows of the past 15 ky, likely because its emplacement occurred within the valley floor, preventing any possibility of lateral expansion. • The paleomagnetic and 14C datings allow constraining the timing of lava flow invasions of the Alcantara valley • the main lava flow that filled the entire valley was emplaced between 9.7 and 13.9 ka BP • The lava volume of 1 km3 of the Alcantara flow is comparable to the highest lava volumes of the historical Etna's eruptions • The maximum length of the lava flow is about 24 km [ABSTRACT FROM AUTHOR]

The master joints bounding the columns that make up the basal colonnade of large lava flows of the Columbia Plateau are, in places, flanked by sub-horizontal mini-columns that have grown normal to the master joints. The secondary mini-columns grow into the main columns and are clearly younger than them. They are small adjacent to the master joint, but merge together and thicken away from the fracture toward the master column interior. Commonly the mini-columns are one-half meter in length and 2–12 cm in diameter. Where the horizontal mini-columns grow longer they intersect toward the middle of the master joints. This plexus of joints changes the aspect of the original master columns making them almost unrecognizable producing ghost columns. The basalt flow may acquire an entablature-like appearance where the ghost column outlines disappear due to extensive secondary fracturing. At the time that the hot flow center had cooled sufficiently below the brittle-plastic transformation, the primary vertical basal colonnade joints growing up from the bottom connected with those in the upper colonnade growing down. This allowed steam trapped beneath the flow to be released to the surface and ushered in a change from a conduction-cooling regime to a convection-cooling regime. The steam beneath the flow was formed and sustained by heat from the lava that boiled the groundwater in the underlying substrate. Large volumes of the rising steam was on average much cooler than the hot fractures in the flow interior through which it passed, causing contraction of the master column walls to produce the secondary horizontal mini-columns. The presence of mini-columns indicates emplacement of lava over moist ground and are absent where the lavas advanced across arid areas or flowed over recently-erupted lava. The extreme shattering that forms ghost columns by late stage convective cooling can produce a flow layer of considerable thickness, a layer that can later serve as an aquifer with high porosity and permeability. • This paper describes newly recognized types of columnar joints from the Miocene Columbia River Basalt Group in Washington and Oregon. • Horizontal mini-columns form as the walls of previously formed master basal columns are cooled by the escape of steam trapped beneath the lava flow. • Where numerous mini-columns intersect one another the original master column is almost unrecognizable as ghost columns are produced. • Recognition of these column types opens the door for new interpretations and models of columnar joint formation. [ABSTRACT FROM AUTHOR]

Abstract Textural evidence from occurrences of mingled magmas in lava flows often yields insights into chemical and thermal disequilibrium between multiple magma batches at depth. An understanding of these interactions is key as they can occur on short timescales and may act as eruption triggers, particularly important in very active volcanic settings. This paper focuses on the Pietre Cotte lava flow (Vulcano, Aeolian Islands, Italy), a short (<1 km in length), texturally-heterogeneous rhyolitic extrusion on the northern slope of the active Fossa Cone. The occurrence of (i) multiple magma compositions, (ii) distinct magmatic cumulates (as glomerocrysts) and (iii) mineral resorption textures within glomerocrysts and isolated feldspar phenocrysts in the Pietre Cotte lava flow highlight a complex pre-eruptive magmatic history, including crystal mush remobilisation. Petrographic observations and mineral, bulk rock and glass geochemistry suggest that multiple mingling events occurred during the evolution of the Pietre Cotte magmatic system, evidenced by the recognition of the following components: (1) a remobilised predominantly mafic crystal mush, evident as macrocrysts (crystals >500 μm), which form glomerocrysts within enclaves, (2) a microlitic (<100 μm) trachytic enclave groundmass with microcrysts (100–500 μm), and (3) a rhyolitic glass, which hosts both the enclaves and the glomerocrysts. The macrocrystic mafic assemblage includes clinopyroxene (En 38-47 Wo 45–50 ; Mg# 0.72–0.89), olivine (Fo 49–66) and magnetite (Usp 7–26), with plagioclase (An 40–63 Ab 5–50) and rare alkali feldspar (Or 41–57) also present. Enclaves are comprised of a groundmass of plagioclase (An 43–47) and alkali feldspar (Or 33–57) microlites, with clinopyroxene microcrysts (En 39-42 Wo 47–51 ; Mg# 0.75–0.81) and trachyte groundmass glass. The rhyolitic host is characterised by glass, spherulites, microlites and enclave-derived macrocrysts. Compositionally and texturally distinct magmas are attributed to storage and interactions of distinct magma batches and their cumulates at various temperatures and depths beneath the Fossa Cone. Compositions vary from basaltic-shoshonitic, through latitic-trachytic and rhyolitic magmas. The macrocrystic glomerocryst assemblage shows resorbed, chemically-zoned and cumulate textures; the glomerocrysts are attributed to a shoshonitic parent and remobilisation from a crystal mush. Macrocrysts formed at a pressure of 825 ± 80 MPa and temperatures of 789–1117 °C at around the Moho (~23–28 km). Pressure and temperature calculations of the shoshonitic mineral assemblage give average crystallisation conditions of 710 ± 80 MPa (above the Moho) and 1128 ± 25 °C, respectively. The trachytic magma crystallised at ~640 ± 75 MPa and 1000–1130 °C. The average liquidus of the rhyolitic magma has been calculated at 970 ± 7 °C, at depths of <5 km (<60 MPa). New textural observations and intensive variable calculations permit the development of a new pressure and temperature-constrained model of the magmatic evolution of the Pietre Cotte system prior to eruption, with useful insights into the interactions of different magmatic components prior to and during the rapid onset of eruptions linked to magma mingling/mixing. Highlights • Disequilibrium textures in the Pietre Cotte lava flow signify a complex evolution. • Petrography and geochemistry highlight several magmatic mingling events. • Crystal mush, trachyte and rhyolite magmas interacted at various crustal depths. • Shallow magmatic interactions may trigger eruptions following migration from depth. [ABSTRACT FROM AUTHOR]

Abstract The aim of the paper is to provide quantitative elements on the mechanisms that controlled the slope instabilities occurred after two major recent eruptions at Stromboli volcano (i.e. 2002–2003 and 2007). After a brief description of the geological setting and of the largest well documented instability phenomena on volcano flanks, the main objective is pursued using three-dimensional stress-strain analyses for modelling the effects of the magma intrusion on the stability of the volcano flank. Modelling is based on the results of an extensive geotechnical characterization of the volcaniclastic and lava materials. The numerical analyses investigate the influence of different paths and geometry of magma intrusion as well as the spatial variation of mechanical properties. As a result, favourable conditions for specific failure modes are identified. The stress-strain analyses show that magma intrusion can cause both a local failure of a wedge immediately downslope from the dyke or deep-seated movement involving large part of the slope; these two mechanisms were consistent with the deformative patterns observed during the 2007 and 2002–2003 eruptions, respectively. The magma thrust induces shear strains up to levels associated to appreciable grain crushing even below the sea level, where flow liquefaction can be invoked to explain the occurrence of past submarine slides. The submarine landslide is analysed by a combined finite element – limit equilibrium approach that demonstrates that instability conditions can develop if the loading exerted by the upper portion of the slope is sufficiently fast to produce undrained conditions. The analyses also support the hypothesis that at the 2002 subaerial failure occurred, due to combined effects of a magma mild thrust and the removal of the toe support caused by the preceding submarine slide. Highlights • Volcanological evidences were useful for modelling the slope movements of Stromboli. • Subvertical dyke intrusion affects only local stability of the dry subaerial slope. • Larger instabilities can be triggered only by dyke intrusion with relevant horizontal component. • Static liquefaction due to grain crushing can explain the submarine slide. • Submarine sliding can propagate backwards and influence the subaerial sector. [ABSTRACT FROM AUTHOR]

Abstract The Kilauea volcano on the Hawaii island started erupting on 3rd May 2018 after an earthquake of magnitude 5.0. The initial volcano eruption and the subsequent earthquakes resulted in the opening of new volcanic fissures, continuous lava flow at the lower east rift zone and the collapse of the summit caldera floor. All these activities continued until the 1st week of August 2018. The Small Baseline Subset (SBAS) technique is an advanced form of Differential Interferometry (DInSAR) which is capable of monitoring surface deformations with millimetre level accuracy. SBAS technique was utilised here for estimating the surface deformation on Hawaii island due to the volcanic episode. InSAR coherence technique was also utilised in this study for localised analysis at the summit and at the lower east rift zone to detect the time series deformation information and lava flow patterns. 14 interferometric datasets acquired by the ESA's Sentinel-1 C-band satellite from April 2018 to September 2018 were used in this study. The data acquired by the seismometers installed at Kilauea by Hawaii Volcano Observatory, the SWIR band of Sentinel-2 and the thermal band of Landsat-8 were used to correlate and verify the results obtained through the SBAS and InSAR coherence analysis. The combined interpretation of results obtained from all the sources gave insights about the underground magma conduit system, surface deformations, lava flow channels and the correlation between the magmatic and seismic activity happened there which are discussed in detail in this paper. Highlights • Detected subsidence at the Kilauea summit and Puu Oo crater due to magma withdrawal • Increased seismic activity at summit due to Caldera floor collapse • Open channel lava flow from fissures at Leilani Estates • Lava delta formation due to ocean entry of lava flowing through open channel • Sub-terrain magma conduit from summit reservoir to Leilani Estates [ABSTRACT FROM AUTHOR]

Abstract The summit region of steep volcanoes hosting lava domes often displays rapid geomorphologic and structural changes, which are important for monitoring the source region of hazards. Explosive crater excavation is often followed by new lava-dome growth, which is one of the most dynamic morphometric changes that may occur at volcanoes. However, details of these crater formations, and the ensuing new dome growth remain poorly studied. A common problem is the lack of observational data due to hazardous field access and the limited resolution of satellite remote sensing techniques. This paper describes the destructive-constructive crater activity at Volcán de Colima, Mexico, which occurred between January and March 2013. The crater geometry and early dome formation were observed through a combination of high-resolution TerraSAR-X spotmode satellite radar images and permanently installed monitoring cameras. This combined time-lapse imagery was used to identify ring-shaped gas emissions prior to the explosion and to distinguish between the sequential explosion and crater excavation stages, which were followed by dome growth. By means of particle image velocimetry, the digital flow field is computed from consecutive camera images, showing that vertical dome growth is dominant at the beginning. The upward growth is found to grade into spreading and a lateral growth domain. After approximately two months of gradually filling the excavated craters with new magma, the dome overflows the western margin of the crater and develops into a flow that produces block and ash flow hazards. We discuss and compare the observations to discrete element models, allowing us to mimic the vertical and lateral growth history of the dome and to estimate the maximum strength of the bulk rock mass. Moreover, our results allow a discussion on the controls of a critical dome height that may be reached prior to its gravitational spreading. Graphical abstract Unlabelled Image Highlights • Crater formation and lava-dome growth monitored at Volcán de Colima, Mexico • Spotlight satellite radar and time-lapse camera data show morphologic changes at high resolution • Ring-shaped gas emissions prior to Vulcanian explosions, and crater formation at the volcano summit • Data suggests that dome growth is first mainly vertical, reaching a critical dome height followed by lateral spreading of the dome • Numerical models allow to simulate the growing dome and to estimate the maximum strength of the rock mass [ABSTRACT FROM AUTHOR]

Abstract Mt. Etna (Italy) with 55 effusive events in the last six years is one of the most active volcanoes in the world, with a million people living on its flank and thousands of tourists who visit it every summer. For this reason, the lava flow monitoring for risk mitigation and Civil Protection purposes is one of the fundamental tasks of the Cartographic Laboratory of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo. This activity was traditionally performed using data collected from the field (with terrestrial GPS surveys) and from helicopter taking visible and thermal images. During the 27 February–02 March 2017 eruption the FlyEye Team, applied Unmanned Aerial Vehicles to monitor the active lava flow. Two high-resolution UAV surveys were performed on the lava flow field on the south flank of Mt. Etna, between 3050 and 2600 m a.s.l., obtaining almost 1170 images. Structure-from-Motion techniques were applied to create orthophotos and Digital Elevation Models (DEM) of the lava flow field and surroundings. The obtained DEM has a resolution of 14.2, and 20.7 cm/px for the main lava flow and the west branch, respectively. On the wall, the 96% of the lava flow field was mapped using aerial images by UAV covering an area of 0.3 × 106 m2. Lava flow volume was calculated with the topographic approach: difference between post- and pre-eruption surface, DEM 2017 and DEM 2014, respectively. The impossibility of spreading the GCPs homogenously distorted the resulting DEM; for this reason, it was necessary to align the lava flow point clouds, obtained from the photogrammetry software, to the basal 2014 DEM. Subtracting the two DEMs a lava flow thickness grid resulted leading to a total volume of 1.4 × 106 m3 and an error estimation of about 20%. Finally, dividing the total volume for the effusion duration (63 h) a mean output rate of 6.2 m3/s resulted. The calculated volcanological parameters have the same order of magnitude of the previous activity of Mt. Etna, between 2011 and 2016. This research demonstrates that UAV photogrammetry was successfully exploited during an eruptive crisis, allowing a first fast processing, to obtain an orthophoto of the lava flow field, useful for "decision makers" and a further slower processing for the realization of a high-resolution DEM. The latter makes it possible to update the topography, another important argument for Civil Protection purpose. This paper describes a methodology that could be applied during other natural events in extreme environmental conditions. Highlights • UAV as a support in volcanological monitoring: maps and volume estimation. • Unconventional solutions in UAV survey during an eruptive crisis. • The usage of a Natural Neighbor interpolated basal surface when a pre-eruption surface and/or GCPs lack. • A point cloud manipulation software is necessary for clouds alignment. • Etna 27 February - 2 March 2017 eruption volume calculated with topographic approach is 1.4 × 106 m3. [ABSTRACT FROM AUTHOR]

Abstract The seismic to geodetic moment ratio (M o /M G) related to seven magma intrusion episodes, occurring at Mt. Etna volcano between 1981 and 2008, are considered. The lateral eruptions show a moment ratio of 0.04–0.06; meaning that only about 5% of the stress energy accumulated with ground deformation was released by earthquakes. Significantly higher values instead characterized vertical (0.25–0.50) and non-eruptive (0.17) dike intrusions. This paper proposes a simple relationship, in order to estimate, during the early phases of an eruption, the intruding magma volumes by the cumulative seismic moment (of the ongoing seismicity) and elapsed time. Highlights • We focused on seven magma intrusion episodes, occurred at Mt. Etna between 1981 and 2008 • We calculated the cumulative seismic moment (Mo) released during the dike emplacements. • We obtained the geodetic moment (MG) from ground deformation data source models referred to in current literature. • We discussed the seismic to geodetic moment ratio (Mo/MG) related to the different intrusive processes. • We proposed a relationship that estimates the intruding magma volumes by the cumulative seismic moment and elapsed time. [ABSTRACT FROM AUTHOR]

Abstract Correlation of individual tephra layers over large areas permits the assessment of eruption magnitude and synchronization of disparate sedimentary archives. The middle Pleistocene Pauzhetka caldera with a diameter of ~30 km is one of the largest in Kamchatka. Distal tephra from the caldera-forming eruption has, however, never been found, hampering precise estimates of the eruption volume and magnitude. In this paper, we report first geochemical identification of distal tephra from the Pauzhetka caldera in the Northwest (NW) Pacific and Okhotsk Sea sediments recovered by ODP 145 cores 881B, 882A and 884B, and IMAGES cores MD01-2415 and MD01-2416. Distal tephras are rhyolites of narrow compositional range allowing their reliable identification among the studied marine cores using major and trace element data. Geochemical correlation of the distal tephra to the proximal strongly welded and altered ignimbrite was performed based on immobile trace elements determined in situ by laser ablation ICP-MS. Based on this case study, we propose that a number of trace elements (U, Th, Nb, Ta, Zr, Hf, Ti, REE, Y and Sc) are immobile during on-shore alteration of welded tuffs and can be used for correlation of pristine glass and altered rock groundmass allowing direct identification of volcanic source of distal tephra. Our new data on the spatial dispersal of the airborne Pauzhetka tephra in the NW Pacific sediments defines its minimum dense rock equivalent (DRE) volume of ~46 km3. Together with the exposed volcanic material around the caldera, the total DRE volume is estimated at 150–170 km3 (3.8–4.4 × 105 Mt) corresponding to the eruption magnitude of 7.60–7.65. Stratigraphic position of the Pauzhetka tephra in the studied cores at transition between marine isotope stage 12 and 11c (Termination V) yields a precise astrochronologic age of 421.2 ± 6.6 ka (weighted mean ± 2σ), which is 27 ka younger than the published average 39Ar/40Ar dates on plagioclase from the proximal ignimbrite. Due to the characteristic composition and precise age, the Pauzhetka tephra may serve as a regional marker for Termination V in the NW Pacific and Okhotsk Sea sediments. A multidisciplinary approach adopted in this study is useful for identification and precise dating of the past explosive eruptions in Kamchatka and other volcanic arcs. Highlights • First identification of distal tephra from the Pauzhetka caldera offshore Kamchatka. • Geochemical correlation of Pauzhetka proximal altered ignimbrite to distal tephra. • Pauzhetka caldera-forming eruption has an astrochronologic age of 421.2 ± 6.6 ka. • The eruption had DRE volume of 150–170 km3 and magnitude of 7.60–7.65. • Pauzhetka tephra marks Termination V in the NW Pacific and Okhotsk Sea sediments. [ABSTRACT FROM AUTHOR]

Abstract The Kos-Nisyros-Yali volcanic region is one of the centers in the South Aegean Volcanic Arc to exhibit Holocene volcanic activity, with poorly dated thin tephra layers on Yali associated with Neolithic artifacts. This paper helps to resolve the age and character of early to mid - Holocene volcanism in the South Aegean Sea. It presents the lithostratigraphic record of seven newly recovered cores from this region at the SE termination of the South Aegean Volcanic Arc. The cores were scanned for magnetic susceptibility, split, logged and sampled at one centimeter resolution for carbonate content. Selected intervals were analyzed for grain size, organic carbon content, and feldspar content by XRD, in order to identify lithostratigraphic levels with enhanced volcanic minerals. Subsequently, textural and electron microprobe analyses of volcanic glass shards and pumice fragments were carried out on 20 samples. Chronology was inferred from the upper and lower limits of the S1 sapropel and from five AMS 14C dates on foraminifera. In several cores in the S1 interval, mixed volcanic glass types that compositionally correlate with the Nisyros Lower and Upper Pumice, Yali pumices and KPT suggest that the volcanic glass is reworked from previous deposits and transported by turbidity currents. Cores from deep water northeast and northwest of Yali have a single population of tephra at two or more horizons within S1 that geochemically resembles Holocene Yali–4 pumice on land. These beds likely represent air-fall ash that was dispersed at least 10 km from Yali, with ages of 8 and 10 ka. Moreover we report two or more tephra layers within S1 from the Kalymnos Basin that are not reworked and geochemically resemble Santorini tephra. This study thus confirms the occurrence of small early Holocene eruptions at Yali and provides possible evidence for early Holocene eruptions at Santorini. Highlights • A lithostratigraphic record of seven cores from Kos–Nisyros–Yali volcanic center • S1 sapropel constitutes a chronostratigraphic marker for the volcanic deposits. • Reworked volcanic glass shards of Nisyros, Yali and KPT origin traced within S1 • Cryptotephra of minor Santorini eruptions traced within S1 in Kalymnos Basin • Minor early Holocene eruptions on Yali island confirmed [ABSTRACT FROM AUTHOR]

Abstract We investigate the transient behavior of bubble deformation in magma. Previous studies have used the relationships between capillary number and equilibrium shape for a single bubble under either steady simple shear or steady pure shear to estimate strain rates in pyroclasts and to calculate bubble shapes in a conduit flow. We developed a deformation model for a bubble by adjusting the empirical functions used in an existing model for a droplet to fit experimental data for bubble deformation. The modified model was used to calculate transient large deformations of a single bubble in arbitrary shear flows. In this paper, we demonstrate the significance of the modified model through two different applications. Firstly, using this model, we are able to simulate the entire history of the evolution of bubble shapes in a time dependent flow using the computational code, Conflow. In this simulation, we further include the effect of gas expansion on the bubble shape. From this simulation, we show that bubble deformation in conduit flow is controlled by the history of both capillary number and strain. Secondly, by using this model to analyze bubble shapes observed in natural magma samples, we are able to better estimate the strain rates and deformation durations. We apply this model to certain transient features in the relationship between bubble shape and radius in the published data of obsidian clasts from Newberry Volcano and estimate a deformation duration of 2.7–4.0 min. Highlights • A deformation model for a bubble is developed. • Bubble deformation in conduit flow is controlled by the history of capillary number and strain. • Deformation duration of bubbles was estimated from the relationship between bubble shape and radius. [ABSTRACT FROM AUTHOR]

Abstract Surficial mass movements, such as debris avalanches, rock falls, lahars, pyroclastic flows, and outburst floods, are a dominant hazard at many volcanoes worldwide. Understanding these processes, cataloging their spatio-temporal occurrence, and detecting, tracking, and characterizing these events would advance the science of volcano monitoring and help mitigate hazards. Seismic and acoustic methods show promise for achieving these objectives: many surficial mass movements generate observable seismic and acoustic signals, and many volcanoes are already monitored. Significant progress has been made toward understanding, modeling, and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements. However, much work remains. In this paper, we review the state of the art of the topic, covering a range of scales and event types from individual rock falls to sector collapses. We consider a full variety of volcanic settings, from submarine to subaerial, shield volcano to stratovolcano. Finally, we discuss future directions toward operational seismo-acoustic monitoring of surficial mass movements at volcanoes. Highlights • Surficial mass movements are common in volcanic areas and generate signals that are recorded by seismic and acoustic arrays. • Our understanding of the relation of these signals to characteristics of the mass movement is limited but improving. • We review the literature on the study of mass movements at volcanoes using seismic and acoustic monitoring. • We discuss future research directions and steps toward operational monitoring. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to summarize all of the published data on the Tolbachik volcanic massif in order to provide a clear framework for the geochronologic, petrologic, geochemical and to a lesser extent the geophysical and tectonic characteristics of the Tolbachik system established prior to the 2012–2013 eruption. The Tolbachik massif forms the southwestern part of the voluminous Klyuchevskoy volcanic group in Kamchatka. The massif includes two large stratovolcanoes, Ostry (“Sharp”) Tolbachik and Plosky (“Flat”) Tolbachik, and a 70 km long zone of the basaltic monogenetic cones that form an arcuate rift-like structure running across the Plosky Tolbachik summit. The Tolbachik massif gained international attention after the 1975–1976 Great Tolbachik Fissure Eruption (GTFE), which was one of the largest eruptions of the 20th century and one of the six largest basaltic fissure eruptions in historical time. By the end of the GTFE, 2.2 km 3 of volcanic products of variable basaltic compositions with MORB-like isotopic characteristics covered an area of > 1000 km 2 . During the following three decades more than 700 papers on various aspects of this eruption have been published both in national and international journals. Although the recent 2012–2013 eruption, which is the main topic of this volume, was not as long as the GTFE in duration or as large in area and volume of the erupted deposits, it brought to the surface a unique volcanic material never found before. In order to understand the data from new eruptions and make significant progress towards a better understanding of the Tolbachik magmatic system it is important to be able to put the new results into the historic context of previous research. [ABSTRACT FROM AUTHOR]

In this paper, we present new data from 226 Ra– 230 Th dating and archaeomagnetism with the aim of improving the knowledge of the flank eruptions that occurred at Mt Etna during the Greek–Roman and Early Medieval periods, as defined in the new geological map of the volcano. The combination of the two dating techniques demonstrates that three major flank eruptions occurred on the lower north and west flanks during Greek–Roman epochs, producing large scoria cones and extensive lava flows. In particular, the Mt Ruvolo and Mt Minardo events highly impacted the territory of the west flank, notably by damming the Simeto River. The new data of the Millicucco and Due Monti lava flows, on the lower north–east flank, indicate a younger age than their stratigraphic ages quoted in the 2011 geological map, since they occurred around 700 and 500 AD, respectively. None of the large flank eruptions occurring on the lower slopes of Etna during the Early Medieval age are reported in the historical sources. Overall, our paper shows that a comprehensive assessment of eruptions at Mount Etna in the last three millennia can only be achieved through a multidisciplinary approach. [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 proposes a computer-based classifier to automatically identify four seismic event classes of the Llaima volcano, one of the most active volcanoes in the Southern Andes, situated in the Araucanía Region of Chile. A combination of features that provided good recognition performance in our previous papers concerning the Llaima and Villarica (located 100 km south of Llaima) volcanoes is utilized in order to train the classifiers. These features are extracted from the amplitude, frequency and phase of the seismic signals. Unlike the previous works where fixed length windows were used to obtain the seismic signals, this paper employs signals of variable lengths that span the entire seismic event. The classifiers are implemented using support vector machines. A confidence analysis is also included to improve reliability of the classification. Results indicate that the features used for recognition of the events of Villarica volcano also provide good recognition results for the Llaima volcano, yielding classification exactitude of over 80%. [ABSTRACT FROM AUTHOR]

Feature extraction and selection are very relevant processes in the design of automatic classifiers. In the context of volcanic seismic signal classification, most of the features presented in the literature have been extracted separately from a single domain, such as time or frequency. However, spectrograms, which combine time and frequency information, are widely used by experts during the classification of manual seismic events. This paper proposes to evaluate the performance of classifiers trained with features extracted from the spectro-temporal domain, individually or combined with other conventional features. The parameters were extracted from the spectrogram, based on a curve which combines the high energy components and the frequency bandwidth information through the duration of the event. The tests were performed at the Llaima volcano and seismic events were classified into four classes: long-period, tremor, volcano-tectonic and tectonic, using a database of signals recorded between the years 2009 and 2017. The main achievements of this study were the reduction of more than 70% of the error and false positive rates and also a reduction of approximately 30% of the number of features, compared with a baseline established in previous studies. Thus, the inclusion of spectro-temporal information was considered relevant to complement the conventional features and to support classification. [ABSTRACT FROM AUTHOR]

In this paper we: provide a brief account of the 1580 and 1808 eruptions on São Jorge in the Azores, which produced Pyroclastic Density Currents (PDCs); discuss the first recorded use of the term nuées ardentes to describe these PDCs; trace how this term was introduced into the scientific literature and discuss its adoption by Alfred Lacroix (1863–1948) to describe the ‘glowing clouds’ produced by Mt. Pelée (Martinique) in 1902. The 1580 and 1808 eruptions on São Jorge are important because they provide early descriptions of PDCs. Documentary evidence of the eruptions and their impacts suggest that the 1580 PDC was a hotter flow, whereas the 1808 PDCs were cooler and more moist. Contemporary accounts describe the 1580 PDC as a ‘globe of fire’, mixed with ‘caustic smoke’ and moving at speed towards the bottom of the slope. In contrast, the 1808 PDCs comprised humid ash, were not incandescent and it is likely that the flows were cooler than that produced in 1580. Since the eruption of Mt. Pelée in 1902, it has been widely accepted that the term nuées ardentes was introduced by Lacroix (1904), being based on his description of the pyroclastic flows that he witnessed. Lacroix acknowledges that the Portuguese expression, nuvem ardente was first used in contemporary accounts of the São Jorge PDCs. This was first translated as nuée ardente and introduced into the scientific by the French geologist Ferdinand Fouqué (1828–1904), who was also Lacroix's father-in-law. Indeed, Lacroix provides an account of the 1580 and 1808 eruptions of São Jorge in his 1904 work La Montagne Pelée et ses Éruptions . The seminal work of Frank Alvord Perret (1867–1943) on the 1929–32 eruptions of Mt. Pelée and his description of nuées ardentes probably helped reinforce the association between the term and Mt. Pelée. [ABSTRACT FROM AUTHOR]

Methana peninsula shows the longest recorded volcanic history at the western end of the South Aegean Active Volcanic Arc, including volcanic products from the Upper Pliocene to recent times. The volcanic rocks comprise widespread dacite domes and andesite lava flows from several small volcanic centers and are only imprecisely dated. In this paper, the integrated analysis of swath bathymetry, side scan sonar data, and high resolution seismic reflection profiles correlated with core samples, has allowed detailed mapping, characterization and precise chronological identification of the Pausanias submarine volcanic field activity offshore northern Methana. Six volcanic cones or domes are recognized, typically 1–3 km in diameter, some elongated NE–SW and some with a small central crater. On their flanks, the acoustically reflective volcanic rocks pass laterally into incoherent transparent seismic facies interpreted as volcaniclastic deposits, possibly including hyaloclastites, that interfinger with the regional basin sediments. A sea-bottom hummocky field, is interpreted as volcanic avalanche and appears to be the submarine continuation of the volcaniclastic apron of northern Methana peninsula. A robust chronostratigraphic framework has been established, based on the recognition of shoreline progradational units and their connection with Quaternary eustatic sea level cycles. Relative dating of the different phases of submarine volcanic activity during the Upper Quaternary has been achieved by correlating the imaged volcaniclastic flows, interlayered within the chronostratigraphically dated sediments. Dating by stratigraphic position, relative to 2D imaged eustatic sea level clinoform wedges appears to be more precise than radiometric methods on land. Three main submarine Volcanic Events (VE) are recognized: VE3 at ~450 ka, a less precisely dated interval at 200–130 ka (VE2), and VE1 at ~14 ka. Based on chronostratigraphic constraints, subsidence rates of 0.16 (±0.008) m/ka in-between Marine Isotopic Stages 6 and 12 and 0.19 (±0.009) m/ka in-between Marine Isotopic Stages 12 and 16 were estimated for the marine basin north of Methana. The morphological similarity to the onshore volcanoes of Methana Peninsula implies that magmatic constructive processes were dominant, regardless of whether in air or in water. The Upper Quaternary submarine volcanic rocks of Methana differ from those known from stratovolcanoes elsewhere in the Mediterranean, (e.g. Kos-Nisyros, Stromboli) and in other volcanic arcs (e.g., Montserrat, St Vincent), in the submarine development of domes or small cones, the paucity of volcano flank failure deposits and the lack of explosive events. Pausanias volcanic products date the onset of NE–SW faulting as well as the following tectonic phase of E-W striking faults, possibly related to basin inversion, caused by a major rifting phase that also affected most of the South Aegean Arc and the adjacent Gulfs of Corinth and Argolikos. [ABSTRACT FROM AUTHOR]

Volcanoes of Strombolian type are able to maintain their semi-permanent eruptive states through the constant convective recycling of magma within the conduit leading from the magma chamber. In this paper we study the form of this convection using an analytic model of degassing two-phase flow in a vertical channel. We provide solutions for the flow at small Grashof and large Prandtl numbers, and we suggest that permanent steady-state counter-current convection is only possible if an initial bubbly counter-current flow undergoes a régime transition to a churn-turbulent flow. We also suggest that the magma in the chamber must be under-pressured in order for the flow to be maintained, and that this compromises the assumed form of the flow. [ABSTRACT FROM AUTHOR]