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Cotopaxi is a large, ice-capped stratovolcano located in the Ecuadorian Andes. After 72 years of repose, Cotopaxi erupted on August 14, 2015. The precursory activity included long-period (LP) events followed by volcano-tectonic (VT) earthquakes, very-long-period events accompanying LP signals (VLP/LP events), tremor, deformation and SO 2 emissions. VLP/LP events were first observed at Cotopaxi in 2002, and persistently occurred from 2009 to 2014 and during the 2015 eruptions. Previous studies of the VLP/LP seismicity suggested that these events originated by repetitive volume changes in a crack due to degassing of water from magma at a depth of 2–3 km beneath the NE flank. Based on this interpretation, we estimated the magma volumes related to individual VLP/LP events from 2009 to 2015, which were systematically extracted from continuous seismic records of the Cotopaxi broadband seismic network. Based on the accumulated magma volume and the VLP/LP activity, our study is divided into seven periods (phases A − G), during which the magma supply rate significantly fluctuated. In phase E (June 1–July 27, 2015), before the eruptions, the magma supply rate increased. Degassing at the VLP source generated gas flows in the conduit and pre-eruptive tremor, gradually drying out a shallow hydrothermal system. In phase F (July 28–September 15, 2015), we estimated the highest magma supply rate, leading to magma fragmentation at the VLP source and eruptions accompanied by tremor. In phase G (September 16–December 29, 2015), the magma supply rate decreased, and overall eruptive activity, VLP/LP events, and tremor gradually waned. These results indicate that the VLP/LP events were likely generated by degassing from magma supplied to the VLP source through an intruded dike before and during the eruptions. The VLP/LP activity provides critical useful information about the magma supply rates that controlled eruptive and gas emission activity at Cotopaxi during this period and may help to constrain magma volumes during future reactivations. • VLP/LP events are related to the overall seismic activity and SO 2 emissions during pre-eruptive and eruptive periods. • Seismic patterns indicating heightened activity and impending eruptions. • New methodology to quantify magma volume using a non-destructive VLP source at the volcano. • Degassing changes occur during passive and active states, and when the volcanic system's conduit becomes more open. [ABSTRACT FROM AUTHOR]

It is intuitive to think that an earthquake near a volcano could disrupt its equilibrium and potentially trigger an eruption. But this cause-and-effect link is far from obvious for active volcanoes with an unknown internal stress state and the complexity of its magma-hydrothermal processes. This phenomenon is clearer in continental-oceanic subduction zones where volcanoes generally have closed-vent systems, differentiated high-viscosity magma, and active hydrothermal systems. This phenomenon is less well known in oceanic-oceanic subduction zones, where volcanoes often have open-vent systems, low-viscosity mafic magma, and hypothetic hydrothermal systems. The Vanuatu oceanic-oceanic subduction is an ideal zone to perform such study due to a high-seismic rate and volcanoes with different characteristics. The Vanuatu volcanoes display both open- and closed-vent systems, low and relatively high viscosity magma that enhance different types of volcanic activities (such as lava lakes, strombolian eruptions, high-eruptive columns, phreatic activity), and potential active hydrothermal systems. We compiled and identified sixty-nine cases of earthquakes potentially triggering volcanic activities on Vanuatu volcanoes from 1913 to 2018. Our findings indicate that the triggered volcanic responses occur co-seismically or shortly (at most 2–3 months later) after the earthquake, that the activated volcanoes are mainly located at near-field distances of the potentially triggering earthquake, implying a strong influence of static stress changes. Using the value of the seismic density energy, we suggest that the mechanism of the Vanuatu volcanic responses is due to changes of the permeability within active hydrothermal systems at Lopevi and Ambrym volcanoes in addition to the well-established ones, at Ambae, Garet, and Yasur volcanoes. • Vanuatu's volcano eruptions triggered by large earthquakes are mostly at near-field distances. • Hydrothermal systems faciliate triggering eruptions by earthquakes. • The Vanuatu volcanic responses is due to changes of the permeability within active hydrothermal systems. [ABSTRACT FROM AUTHOR]

We investigated the accurate locations of 443 explosion earthquakes that happened at Sinabung Volcano, North Sumatra, between October 2014 and June 2017. The explosion earthquakes were concentrated at shallow depths of approximately 1–5 km from the active crater. We used seismic tomography imaging to track the magma migration. Low Vp anomalies with low seismicity at shallow depths indicate that molten material originated from the shallow magma chamber. The presence of a shallow magma chamber of the Sinabung volcano was also revealed. The magma chamber with a volume of 2 km3 is located at a depth of 1.5–3.5 km below the summit. The magma plumbing system at shallow depths of approximately 1–5 km beneath the active crater was successfully imaged in detail. • An uppermost structure of Sinabung Volcano is derived from seismic tomography inversion analysis of explosion earthquake. • The explosion earthquakes are concentrated at a depth of approximately 1–5 km from the summit. • A shallow magma chamber characterized by low Vp and low seismicity is located at 1.5–3.5 km below the summit. [ABSTRACT FROM AUTHOR]

Understanding the detailed eruptive history and conditions during the buildup to catastrophic caldera-forming eruptions is essential for understanding the evolution of caldera volcanoes and predicting eruptive hazards. Towada Volcano is an active caldera volcano in the northern part of the Northeast Japan Arc. At least two catastrophic caldera-forming eruptions (eruptive episodes N and L) occurred during its caldera-forming stage (61–15.7 ka). A detailed geological survey identified three small vulcanian tephra layers that were erupted during the caldera-forming stage. The tephra layers are blue–gray ash fall deposits that consist mainly of fresh blocky dacite–rhyolite fragments. In ascending order, these deposits are assigned to eruptive episodes O′, N′, and M′. Each eruption had a volume of <0.11 km3, which is much smaller than that of other eruptions during the caldera-forming stage. The eruptive ages of episodes O′, N′, and M′ are estimated to be ca. 40, 23.1, and 17.2 ka, respectively, based on new 14C ages and paleosol thicknesses data. At least three cycles of a medium- to large-scale (3–20 km3) explosive eruption, preceded by a small vulcanian eruption (<0.11 km3), occurred during the latter half of the caldera-forming stage. The small vulcanian eruptions (episodes O′, N′, and M′) occurred after relatively long periods of quiescence (4000–14,000 years) and were followed by medium- to large-scale explosive eruptions (episodes N, M, and L) 1500–4000 years later. This cyclic activity probably reflects changes in overpressure in the magma reservoir. As the overpressure increased, episodes O′, N′, and M′ probably occurred when the overpressure had not increased sufficiently to trigger a medium- to large-scale explosive eruption, and episodes N, M, and L occurred at higher overpressures. These cycles characterize the fermentation phase of Towada Volcano, and terminated with the formation of the Towada Caldera during episode L at 15.7 ka. The magma composition and eruption frequency changed abruptly after episode L, and a small stratovolcano was formed through intermittent eruptions of mafic magma. This change suggests that the caldera collapse during episode L changed the entire shallow magmatic system that existed during the fermentation phase, and the system shifted to a recovery (post-caldera) phase. Based on eruptive volumes and frequencies, the present Towada Volcano has not yet reached the conditions that existed during the late caldera-forming stage and is therefore unlikely to produce a catastrophic caldera-forming eruption in the near future. • The eruptive history of Towada Volcano was updated and summarized. • Three small vulcanian eruptions were identified during the caldera-forming stage. • Eruptive cycles of large explosive eruptions preceded by small vulcanian eruptions. • Changes in the magma overpressure probably controlled these cycles. • This cyclic activity characterizes the fermentation phase of Towada Volcano. [ABSTRACT FROM AUTHOR]

Many volcanoes show continuous but variable deformation over timescales of years to decades. Variations in uplift rate are typically interpreted as changes in magma supply rate and/or a viscoelastic response of the host rock. Here we conduct analogue experiments in the laboratory to represent the inflation of a silicic magma body at a constant volumetric flux, and measure the chamber pressure and resulting surface displacement field. We observe that dyke intrusions radiating from the magma body cause a decrease in the peak uplift rate, but do not significantly affect the spatial pattern of deformation or spatially averaged uplift rate. We identify 4 distinct phases: 1) elastic inflation of the chamber, 2) a gradual decrease in the rate of uplift and pressurisation, associated with the formation of visible cracks 3) propagation of a dyke by mode 1 failure at the crack tip and 4) a pressure decrease within the chamber. Phase 2 can be explained by either a) crack damage, which reduces the elastic moduli of the surrounding rock or b) magma filling pre-existing cracks. Thus these experiments provide alternative mechanisms to explain observed variations in uplift rate, with important implications for the interpretation of deformation patterns at volcanoes around the world. • Analogue experiments represent an inflating magma chamber at constant volume flux • Radial dyke intrusions change the uplift rate but not the deformation pattern • Reduced uplift rate can be explained by damage zone or opening of pre-existing cracks • Key implications for the interpretation of deformation patterns at volcanoes [ABSTRACT FROM AUTHOR]

Several powerful explosive eruptions have taken place in the populated lower East Rift Zone of Kīlauea within the past ∼750 years. These have created distinctive landforms, including a tephra rim enclosing Puʻulena Crater immediately south of the Puna Geothermal Venture power station, a tuff cone at Kapoho Crater near the eastern cape of the Island of Hawaiʻi, and a set of littoral cones, the Sand Hill in Nānāwale, where the 1840 lava flow poured into the ocean. Kapoho Crater tuff cone is the largest of these recent pyroclastic features. Mineral, glass, and melt inclusion analyses of tuff cone ash and later fissure-related scoriaceous materials also found within the crater indicate slightly evolved basaltic magmas (1120–1130 °C) that are compositionally similar to parts of the effusive lower East Rift Zone eruptions in 1955 and 2018. Tuff cone magmas were stored at depths of ∼2.5–3.5 km and had pre-eruptive volatile contents (0.5–0.8 wt% H 2 O, 280–340 ppm CO 2 , 1400–1800 ppm S) similar to other Kīlauea eruptions (e.g., 1959, 1960), suggesting that internal magma properties were unlikely to account for the unusual explosiveness of this eruption. Tephra componentry, grain-size analyses, and field observations confirm that the cone grew during a phreatomagmatic eruption mostly of vitric ash, probably where a fissure opened across the coastline or shallow ocean floor nearby. Supporting this hypothesis is the identification of at least two genera of marine diatoms within tuff cone strata. Sand Hill littoral cone ash is also vitric like that of Kapoho Crater, but distinctly coarser with abundant fluidal ejecta represented. In contrast, the Puʻulena Crater eruption deposited lithic ash and related blocks with minor juvenile magmatic contribution; a phreatomagmatic eruption that was dominantly phreatic. Differences in eruption styles are related to unique mechanics that tephra analyses help us interpret. While powerful explosive eruptions in the lower East Rift Zone are rare, they present a definite future hazard for inhabitants in this part of Hawaii. • Multiple violent explosive eruptions have occurred in Kīlauea's lower East Rift Zone. • Puʽulena Crater formed in a phreatomagmatic eruption within a hydrothermal region. • Kapoho Crater tuff cone formed when a fissure erupted in shallow seawater. • These sizable explosive eruptions occurred in the past 750 years in now-populated areas. • Geology, ash textures and componentry, and geochemistry discern formation mechanisms. [ABSTRACT FROM AUTHOR]

Volcanism at Mt. Etna (Italy) started with an early tholeiitic stage dating back to 542 ka during which subaqueous to subaerial magmas were emitted chiefly through fissure-type eruptions on widespread areas located on the southern flank of the modern volcano edifice. Volcanic products belonging to the earlier Aci Trezza Synthem (542–496 ka) and those of the later Adrano Synthem (332–320 ka) are basalts within a narrow range of variation. Despite the rather homogeneous geochemical characteristics, zoning patterns and Fe Mg diffusion chronometry on olivine crystals from lavas of both the Synthemic Units have evidenced different dynamics and kinetics of storage and transfer before eruptions. Specifically, one dominant, normally-zoned, Fo 83 – 86 olivine population makes peculiar lavas of the Aci Trezza Synthem, whose patterns can be interpreted as due to simple upward migration from deep storage reservoirs directly to the surface with timescales of 109–200 days. Volcanic rocks of the Adrano Synthem have at least three additional olivine populations (i.e., Fo 78 - 81 , Fo 73 - 74 , Fo 64 - 70) bearing more complex normal and reverse zoning patterns, features revealing that magmas ascended from the deeper storage zones and then intruded and stalled in shallower reservoirs before being erupted. Transfers throughout these magma reservoirs record both short (<46 days) and long timescales (>106 days), suggesting that tectonics could have accelerated or inhibited magma supply during this later stage of volcanic activity. This new dataset points out that the embryonic plumbing system of Mt. Etna developed a more complex architecture throughout the first ~200 ka of volcanism as a consequence of a declining effect of transtensional tectonics over time. [Display omitted] • The early Etnean volcanic rocks are subaqueous and subaerial tholeiites. • Tholeiites covering 200 ka of activity have distinct petrography and chemistry. • Olivine zoning and diffusion timescales are used to track magma dynamics. • Modes and kinetics of storage and transport changed over the first 200 ka. • Regional tectonics control the evolution of the plumbing system configuration. [ABSTRACT FROM AUTHOR]

The coexistence of monogenetic and polygenetic volcanoes is a common phenomenon in volcanic areas. However, the genetic relationship between monogenetic and polygenetic systems and the factors controlling their distinct eruptive styles are not well understood. In active volcanic areas, analysing the clustering and vent alignment of monogenetic volcanoes, as well as examining the geomorphology and relative ages of scoria cones, offers quantitative insights into magma supply rates, volcano type distribution, and volcanic development trends. Our study presents geomorphological and spatio-temporal analyses of the co -existing monogenetic volcanoes in the Longgang Volcanic Field (LVF) and those associated with a polygenetic volcano (Tianchi) in the Changbaishan Volcanic Area, China. The distance between the two volcanic areas is around 150 km. Monogenetic vents in the LVF exhibit greater density compared to the dispersed system associated with Tianchi. The LVF vents also show better alignment, particularly in the direction of pre-existing basement faults (NE-SW, NW-SE and EW). By using scoria cone morphometric parameters and features, we estimated the relative ages and erupted volumes of monogenetic volcanoes in the LVF and the Tianchi area. We classified the cones of the two volcanic systems into five eruptive periods and found that, despite similar magma sources and output rates over approximately 870 kyr, differing numbers of scoria cones across age classes suggest that Tianchi's magma system influences its associated monogenetic volcanic plumbing. Furthermore, the continuous rise in output rates of monogenetic volcanoes in the Tianchi area highlights the increasing magma supply sustaining Tianchi volcano. Together, these interpretations are consistent with the two systems being controlled by different factors: the Tianchi monogenetic volcanic system is more controlled by magmatism, whereas the LVF is more strongly controlled by local tectonic structures, alongside an increasing magma supply causing the formation of progressively larger individual volcanoes. In volcanic areas, analysing monogenetic volcanoes' spatial-temporal distribution, volumes and recurrence rate provides a framework to evaluate magma supply rates and tectonic associations, which are key to the development of different volcano types. • In the CVA, changes in scoria cones' crater morphological parameters are sensitive to their relative age. • LVF volcanism is more controlled by tectonism, whereas Tianchi's distributed vents are more controlled by magmatism. • Analysing spatial-temporal data of monogenetic volcanoes can assess transitions between volcanic types within an area. • The increasing rate of magma output in the LVF indicates the potential for future, larger volcanic events. [ABSTRACT FROM AUTHOR]

The Late Pleistocene-Holocene Laoguipo volcano in the Tengchong Volcanic Field (TVF), southwestern China, displays significant geochemical and geophysical anomalies characteristics. Here we present petrographic observations, mineral chemistry, bulk rock geochemistry, thermobarometry, and thermodynamic simulation to evaluate the crystallization conditions and pre-eruptive magmatic processes occurring within the magma plumbing system. This study reveals the existence of two magma reservoirs beneath the Laoguipo volcano. The deep magma reservoir is composed of basaltic trachyandesite (SiO 2 = 54–57 wt%), which is located at 15–19 km depths with 1087–1160 °C, 1.5–2 wt% H 2 O content, oxygen fugacity of ΔNNO+1 (Ni-NiO buffer), melt viscosity of 101.7–102.6 Pa·s, and density of 2.5–2.6 g/cm3. The formation of the deep magma reservoir is attributed to the 31% mass fractional crystallization of primitive basalt in the TVF. The shallow magma reservoir is composed of trachyte (SiO 2 = 63–64 wt%), which is located at 6–11 km depths with 780–825 °C, 5.9–6.5 wt% H 2 O content, oxygen fugacity of ΔNNO+1 (Ni–NiO buffer), melt viscosity of 103.9–104.8 Pa·s, and density of 2.2–2.3 g/cm3. The shallow magma reservoir formed after the basaltic trachyandesite had assimilated 19% mass of the upper crustal material and fractionated 41% mass of the crystals. This study suggests that the shallow trachyte magma reservoir is being heated by the ascending deep basaltic trachyandesite magma, resulting in crystal dissolution, remobilization of crystal mush, and magma convection, which may be the main factors responsible for the geochemical and geophysical anomalies characteristics. The Laoguipo volcano is forming a mature magma plumbing system, which is of significance for forecasting future volcanic eruptions. • There are two distinct magma reservoirs beneath the Laoguipo volcano in Tengchong Volcanic Field. • Shallow magma reservoir is formed through the assimilation fractional crystallization process from the deep magma reservoir. • A mature magma plumbing system is forming beneath the Laoguipo volcano, making the Laoguipo volcano highly dangerous. [ABSTRACT FROM AUTHOR]

As magma temperature and composition drift and change, respectively, throughout an eruption, so does its rheology. These changes may span orders of magnitude in magma viscosity and result in orders of magnitude flow velocity changes, as well as transitions in eruptive style. In this study, we present a systematic high precision quantification of the rheological variations that occurred during the 2021 Fagradalsfjall Fires. In the field, we collected a suite of 22 representative samples emplaced between day 2 and 183 of the 2021 eruption. In the laboratory, we measured the melt viscosity of each sample in a concentric cylinder viscometer. Temperatures were initially raised to 1392 °C, and then lowered stepwise to eruptive temperatures as determined through syn -eruptive radiometric measurements. The resulting dataset is analyzed as a time series. An overall trend of viscosity decrease emerges. As the eruption progressed, melt viscosity decreased by 25%, from 40 Pa s to 30 Pa s at a constant temperature of 1200 °C. However, this trend is not monotonous. At least 3 positive spikes in viscosity can be identified, at day 80, 120, and 138 of the eruption. This trend tracks with geochemical variations. • We quantified the rheological variations of the 2021 Fagradalsfjall Fires. • We measured the melt viscosity of 22 samples emplaced over 181 eruption days. • As the eruption progressed melt viscosity decreased by 25% at 1200 °C. • The viscosity decrease trend is not monotonous. • Positive spikes in viscosity track with geochemical variations. [ABSTRACT FROM AUTHOR]

We use new geochemical, petrological, and rheological data to constrain the formation and emplacement of the highly compositionally unusual(andesitic basalt) Kīlauea 2018 Fissure 17 (F17) eruptive products. Despite the restricted spatial and temporal distribution, F17 samples are texturally and geochemically diverse. The western samples are enriched in SiO 2 by up to 10 wt%, relative to their eastern equivalents; additionally, the western samples contain microcrystalline enclaves, absent from the homogenous eastern samples. The compositions erupted along F17 suggest interaction between the basaltic 2018 juvenile magma and a crystal mush at depth, likely a left-over from the nearby 1955 eruption. Magma mingling caused heating and local melting of remnant mush, leading to melt hybridization and volatile exsolution. Rapid water exsolution likely caused overpressurization of the reservoir underneath the western side of F17, leading to Strombolian explosions of viscous magma, in contrast to sustained Hawaiian fountaining on the eastern side. Remelting of remnant crystal mush and melt hybridization in open-conduit systems may hence be an effective mechanism in inducing volatile saturation. • F17 samples are very texturally and geochemically diverse. • We constrain the formation and emplacement of Fissure 17 eruptive products. • F17 products suggest interaction between 2018 juvenile magma and 1955 crystal mush. • Melt hybridization in open-conduit systems may induce volatile saturation. [ABSTRACT FROM AUTHOR]

The 2018 LERZ eruption of Kilauea featured a wide range of eruptive styles. In particular, Fissure 17 (F17) displayed activity ranging from Hawaiian fountaining in the eastern part of the fissure to Strombolian explosions in the western part. Lava erupted from F17-West was highly viscous and contained magmatic enclaves. Magmatic enclaves have previously been observed in many other volcanic systems (e.g. Vulcano Island, IT and Sete Cidades Volcano, PT), where they have been attributed to injection of mafic magma into an evolved magma chamber, resulting in viscous fingering, quenching, and break-off into fragments. The F17 enclaves differ from previous studies in that the chemical compositions of the enclave and host magmas are very similar, and that the enclaves have a limited spatial distribution and lack signs of viscous behavior and quenching, pointing to a different formation mechanism than inferred for other volcanic systems. In order to test a different formation hypothesis, we conducted fractal analysis of the size distribution of 84 individual enclaves from F17-West lavas. Our results, including a fractal dimension of fragmentation D f of 2.59, indicate that the F17 enclaves likely formed by brittle fragmentation. Since the enclave and host magmas were at temperatures far above the glass transition during the magma hybridization, high strain rates have to be invoked to explain the brittle fragmentation. This may have caused the enclave magma to transition into solid-state behavior, allowing it to break off into fragments that were subsequently picked up by the host magma and carried to the free surface. The enclaves from F17-West therefore offer a unique insight into the diversity of processes that characterizes the shallow parts of volcanic systems, as well as the importance of strain rates in modulating the rheological behavior of magmas. • The Fissure 17 lava of the 2018 Kilauea LERZ eruption carried magmatic enclaves. • Fractal analysis indicates that the enclaves were formed by brittle fragmentation. • The brittle fragmentation was likely caused by high strain rates. • This formation mechanism differ from that of enclaves in other volcanic systems. [ABSTRACT FROM AUTHOR]

Sinabung volcano in Indonesia reactivated, with a series of phreatic eruptions, in August and September 2010. These eruptions were followed by various types of magmatic eruption at the summit, including lava dome growth, pyroclastic density currents, lava flow, and vulcanian eruptions, starting in December 2013. Prior to the magmatic eruptions, Sinabung exhibited two sequences of phreatic eruption and an increase in the seismicity of volcanic earthquakes. This study clarifies the progress of magma intrusion during the pre-magmatic period based on the hypocenter distribution, waveform similarity, seismic moment, rupture length, and stress drop for volcano-tectonic (VT) and hybrid earthquakes. It was found that the hypocenters of VT earthquakes are distributed north and northwest of the summit at a depth range of 1–10 km below sea level. Deep seismicity (4–10 km) alternated with shallow seismicity (2–4 km). The last shallow seismicity, from July to mid-December 2013, was different from previous seismicity in terms of higher intensity, as determined from the seismic moment, a temporary increase in the rupture length, and the migration of hypocenters towards the summit. The seismicity of VT earthquakes was altered by a swarm of hybrid earthquakes in mid-December. The hybrid earthquakes were smaller, in terms of seismic moment (mostly <3 × 1010 Nm), than the VT earthquakes. Their hypocenters were concentrated in the shallowest depth range (−0.5 to 1.5 km below sea level) directly below the summit, their source process was repeatable (they could be grouped into six earthquake families), their dominant peak was in a low-frequency range (2.5–4.5 Hz), and they had a relatively low stress drop (<0.15 MPa). This suggests that the swarm of hybrid earthquakes was induced by a frequent repeated fracture of fluid-filled cracks due to the intrusion of magma up to directly below the summit. The transition of the earthquake family and the change in its source parameters, namely an increase in the stress drop prior to the appearance of a lava dome and then a slight decrease, may reflect a gradual change in internal pressure in the hypocentral zone through the magma intrusion process. • Detailed the magmatic intrusion process before the Sinabung magmatic eruption. • Temporal changes of source parameters of VT and hybrid earthquakes • The transition of the hybrid earthquake family and the change in its source parameters • A temporary increase in the rupture length of VT earthquakes indicates new magma intrusions. [ABSTRACT FROM AUTHOR]

Volcanic sulfur dioxide (SO 2) emission measurements are a key element of volcano monitoring strategies and underpin our understanding of magmatic degassing impacts on air quality, aircraft, and climate. Volcanic SO 2 emission monitoring is usually performed with near-field ground-based measurements, but ever-improving satellite observations increasingly offers the capacity for volcanic emission monitoring from space. Here we examine the May–August 2018 eruption at Kīlauea, Hawai'i, which produced a voluminous low-altitude gas plume. We compare SO 2 emissions calculated with three approaches: ground-based networks, dissolved sulfur (S) contents and lava effusion rates, and new satellite-derived SO 2 data. The high emission rates of this eruption posed a major challenge for near-field ground-based measurements, and corrections were needed to account for attenuation of the SO 2 signal from the optically thick plumes. Our satellite-derived gas emissions use Sentinel-5 Precursor (S5P)/Tropospheric Monitoring Instrument (TROPOMI) observations and PlumeTraj back-trajectory analysis, deriving a total mass of 1.3 to 3.3 Mt of SO 2 compared to 10.2 Mt from ground-measured fluxes (Kern et al., 2020). Our measurements deal with uncertainties such as plume aging and SO 2 oxidation as well as cloud coverage which can underestimate results. The S contents also hold their own uncertainties partly due to when sampling was possible. We find agreement between satellite-derived fluxes and those that would be produced by magma which had previously lost at least 200–750 ppm (16–85%) of its initial S content during residence in the Halema'uma'u lava lake and reservoir. Our measurements allow an estimate of the efficiency of S loss from the Halema'uma'u lava lake prior to the 2018 eruption, and this implies a lava lake magma supply rate of 0.0019–0.0072 km3 per day for 2013–2018. The 2018 eruption produced a lava volume equivalent to 5 to 19 months of magma supply to Kīlauea during 3 months of eruption. • Back-trajectory analysis of TROPOMI satellite data measured SO 2 emissions of 1.3-3.3 Mt during the 2018 Kilauea eruption. • Observations suggest the erupted lavas had partially degassed prior to the 2018 eruption. • Satellite-based SO 2 flux quantification is a useful tool when intense degassing saturates ground-based quantifications. • The 2018 Kīlauea eruption produced a lava volume equivalent to 5–19 months of magma supply to the Halema'uma'u crater. [ABSTRACT FROM AUTHOR]

Mt. Etna exhibited 62 lava fountaining events between December 13, 2020 and February 21, 2022. We analyzed tilt deformations and volcanic tremor amplitude time series, to characterize both eruptions and the preceding preparatory phases in terms of magnitude and speed of development of the volcanic phenomena, as well as to reconstruct the processes that took place inside the plumbing system and drove this intense period of activity. Based on deflation amplitudes associated with lava fountains and according with other retrieved parameters (i.e., magnitude of inflations, inflation and deflation velocities and volcanic tremor amplitudes), three periods have been distinguished. Period I displays higher values of all the aforementioned parameters, interpreted as conspicuous volumes of volatile-rich magma transferred towards the surface. Period II shows lower values evidencing lack of important new injections of magma from depth, whereas period III reveals a general increasing trend possibly related to gas flushing from magma residing in deeper portions of the plumbing system. Detailed elaborations of tilt signals allowed the identification of short-lived inflations accompanying the early stages of lava fountains during period II. Our results reveal significant correlations between amplitude and velocity of tilt and volcanic tremor signals associated with lava fountains and evidence the crucial role of gas in the inflation-deflation cycles. • The 2020–22 paroxysmal sequence at Etna has been studied via geophysical signals. • A correlation exists between deflation related to lava fountains and gas emissions. • Three periods have been identified and linked to magma recharge/discharge dynamics. [ABSTRACT FROM AUTHOR]

The Failure Forecast Method (FFM) has been used to forecast the onset of volcanic eruptions with varying degrees of success. The method involves fitting its empirical equation to precursory observables, e.g., seismic data. Current models explaining the empirical equation assume that the seismic observables used (e.g., seismic event-rate, seismic moment-rate or seismic energy-rate) are related to accelerated fracture growth. In these models, such fracture growth results in an apparent increase in seismic activity. In this study, however, we propose an alternative explanation for the increase in seismicity culminating in volcanic eruptions. We suggest that the increase in seismicity, particularly in the seismic amplitudes, can result from ascending seismic sources towards the surface and that the increase can be used for eruption forecasts using the FFM. Our argument is based on the need for magma to migrate towards the surface to produce an eruption. To test our argument, we used synthetic and field/real data and fitted them with the FFM model. The synthetic data is generated using the body wave attenuation equation, and the real data is from the Piton de la Fournaise eruption on January 2nd, 2010. We used seismic amplitudes and seismic amplitude ratios as the precursory observables and used a combination of Simulated Annealing and Bayesian Inversion algorithms to obtain the best-fit parameters of the FFM model and their posterior distributions. For the synthetic cases, we found that the method gave reasonable estimates of failure or eruption time, suggesting that the seismic amplitudes and the seismic amplitude ratios can be used for forecasting using the FFM. For the field/real cases, the results gave information about the timing of magma chamber failure, magma propagation, and the eruption onset. Our results highlight an example of modelling volcano monitoring data with the FFM that gives reasonable estimates of eruption time even if the data may not fully represent failure processes. We suggest that the result may still be reasonable owing to the empirical and asymptotic nature of the FFM combined with the underlying physics of magma and seismic migrations. • Using the increase in seismic amplitudes (RSAM) and seismic amplitude ratios caused by migrating seismic sources as the FFM observables. • Fitting the FFM to the body wave attenuation model to forecast eruption onsets • Forecasting (retrospectively) the onset of the 2010 Piton de la Fournaise eruption. [ABSTRACT FROM AUTHOR]

Magma transfer in the upper crust including emplacement at the surface of the Earth, have been regarded as largely controlled by the regional tectonic activity. While this relationship is well highlighted for systems like monogenetic, mostly basaltic, volcanic fields, the tectonic control on the transfer and emplacement of magmas in complex, polygenetic, volcanic systems, remains poorly documented in evolving tectonic settings. The Mont-Dore Plio-Quaternary volcanic complex (4.7 to 0.3 Ma) is one of such polygenetic volcanic fields as it is formed of three successive eruptive cycles: The caldera unit (3.3 to 2.2 Ma); The Aiguiller complex (2.5 to 1.5 Ma) and the Sancy stratovolcano unit (1.5 to 0.3 Ma). Analyzing fractures, fault kinematics and regional lineaments in the Variscan basement, together with attitude of dikes and volcanic centers alignments of the three volcanic units, we document the influence of the brittle structuration of the underlying basement on the volcanism distribution over time while regional stress changed. The late-Variscan N02E0, and secondary N160, striking crustal faults were reactivated since the Oligocene and channeled at depth the magma, while similarly oriented faults and fractures triggered the final storage in the shallow crust and spatial distribution of the volcanic vents. This fault system continued to act from the Miocene to the present-day uplift, associated with new N020E striking, flat-lying, fractures. An exception arises during the upper Miocene while N060E and N135E striking faults enabled the development of the caldera unit in a NW-SE extensional context. The emplacement of the three units from the mid-Pliocene to the end of the Pleistocene while a change in regional stress field conditions emerged at about 2.5 Ma exemplify the control of the brittle Variscan basement on the magmatic activity of the Mont-Dore Plio-Quaternary volcanic complex. • We studied the control of the regional tectonics on the emplacement of the Mont-Dore polygenetic volcanic complex (France). • We analyzed fractures kinematics and regional lineaments together with attitude of dikes and volcanic centers alignments. • We document the influence of the brittle structuration on the volcanism distribution over time while regional stress changed. • We highlight the relationship between reactivated brittle structures of the basement and the final emplacement of the magmas. [ABSTRACT FROM AUTHOR]

Carboniferous plutonic activity in the Sierra Pampeanas region of NW Argentina resulted in the emplacement of several magma bodies at shallow levels, while contemporaneous volcanism was primarily recorded in the neighboring Puna region. One of these plutons, known as Los Árboles in the Sierra de Fiambalá, formed through two periods of significant felsic magma additions (326–322 Ma) and the subsequent development of tuffisites associated with subvolcanic dikes of predominantly mafic composition (315 ± 3 Ma). The presence of 2–5 -m wide tuffisite dikes, indicating subvolcanic depths (~ 1 km), provides an excellent opportunity to understand the connections between plutonic and volcanic processes. Our study reveals that for felsic magma batches to reach these subvolcanic depths, the input of synchronous mafic magmatism is a critical step. The Los Árboles pluton grew through alternating stages of accommodation by sheet intrusions, which subsequently merged during incubation into larger magma bodies with dominant lateral growth, forming a ductile halo. Both mildly alkaline mafic dike swarms and tuffisites intrude the pluton. The tuff-filled clastic dikes exhibit a variety of textural features and bulk rock compositions that indicate processes of late-stage heating and low-temperature remelting (~700 °C) of the host granite. Our findings document that magmatic plumbing systems, driven by mantle processes, can reach subvolcanic levels, induce brittle-ductile transitions in the host rock, and persist in a cold storage stage for millions of years, with temperatures below the granite solidus, and be potentially eruptive through defrosting. • Tuffisites were originated by processes of low-temperature remelting of the granite. • We document the existence of cold storage for millions of years in the upper crust. • Our plutonic-volcanic system could represent the initial phases of caldera formation. [ABSTRACT FROM AUTHOR]

The complex volcanology and petrology of the Whakamaru volcanic deposits in Aotearoa New Zealand have thus far obscured the number of eruptive phases and the relative timing of these eruption(s). We investigate pumice clasts from multiple localities to elucidate the relative timing of the eruptions, with a focus on the pre-eruptive conditions of the melt-dominated magma bodies that fed the Whakamaru eruptions and on the mushes from which these magmas were extracted. Paired whole-rock and glass compositions confirm four magma types erupted during the Whakamaru eruptions (types A, B, C, D; originally identified by Brown et al., 1998). Using the glass compositions of the pumice clasts, we calculate pre-eruptive storage temperatures (using zircon saturation geothermometry) and pressures (using rhyolite-MELTS geobarometry). Using matching whole-rock compositions from a subset of pumice clasts, we calculate extraction pressures from magma mush (also using rhyolite-MELTS geobarometry). Pre-eruptive storage pressures estimate the depths where melt-dominated magma bodies were located prior to eruption; extraction pressures, in contrast, estimate the depths at which melt was extracted from magma mush to form melt-dominated magma bodies at shallower levels of the crust. Magmas were stored at shallow depths (∼50-150 MPa) prior to eruption. Extraction pressures for types B and C are well constrained to 155-355 MPa (with an assemblage including plagioclase and quartz). Extraction pressures for types A and D depend on oxygen fugacity (f O2), as the extraction assemblage includes plagioclase and orthopyroxene (170-290 MPa for ΔNNO = 0 to +0.5 and 290-360 MPa for ΔNNO = +1 to +1.5). The four magma types likely represent independent magma bodies, with these melt-dominated magma bodies stored shallower than and separate from the mush. At least two different magma subsystems fed the Whakamaru eruptions – one subsystem sourced the type A and type D magmas, while the other sourced the type B and type C magmas. The distribution of magma types recorded in the ignimbrite deposits and in the correlated tephras (Harmon et al., 2024) reveal the sequence of eruption for the four different mappable ignimbrites. The ignimbrites to the east of the caldera (Rangitaiki ± Te Whaiti) erupted before the Whakamaru ignimbrite (sensu stricto) to the west of the caldera. The youngest Whakamaru ignimbrite eruptions likely deposited to the northwest of the caldera contemporaneously with the Manunui ignimbrite to the west of the caldera. The combination of petrological data from the ignimbrites and associated tephras suggest a complex system that included laterally juxtaposed melt-dominated magmas as well as laterally juxtaposed magma mushes that spanned much of the shallow crust, but with regions in which magma appeared in low concentration or was entirely absent. This complex pre-eruptive architecture probably contributed to the complex eruptive patterns observed for the Whakamaru eruptions. • Four magma types sourced the Whakamaru eruptions with different combinations of magma types erupted at different stages • Modeled magma storage depths reveal shallow, upper crustal magma storage levels (∼ 50-150 MPa) prior to eruption • Modeled magma extraction depths reveal that two distinct magma subsystems sourced the Whakamaru group eruptions • The timing of the ignimbrite eruptions is established using correlation with pyroclastic fall deposits • Volcanology and petrology of the Whakamaru eruptions indicate complex pre-eruptive crustal architecture and eruption history [ABSTRACT FROM AUTHOR]

Located in the northeast of Unalaska Island in the central part of the Aleutian, Alaska, Makushin volcano is one of the more active volcanoes in the United States, with the most recent eruption occurred in 1995. Pre-eruptive inflation and post-eruptive deflation were identified from 1993 to 1995 and 1996 to 2000, respectively, and were interpreted as volume changes associated with magma movement within the plumbing system. In this study, we investigate the surface deformation of Makushin from 2004 to 2021 to evaluate its present-day activity, using Synthetic Aperture Radar (SAR) interferometry technique. SAR images acquired from C-band Envisat and Sentinel-1, X-band TerraSAR-X, and L-band ALOS-2 satellites are analyzed using an advanced multiple temporal Interferometric SAR (InSAR) algorithm. The produced deformation time series are then used to track the temporal evolution of the volcanic system with Ensemble Kalman Filter (EnKF) assuming Mogi sources. The results show that Makushin is characterized by time-varying deformation episodes including quiescence, and inflation/deflation cycles at varied rates since 2004. The derived deformation histories can be well reproduced by a spatially stationary pressure source located to the east-northeast of the summit, at a depth about 6 km beneath the sea level (BSL). The inflation/deflation cycles with distinct temporal patterns are interpreted as results from volatile-dominated volume accumulation/loss in the magmatic reservoir. A secondary reservoir connected to the main magma chamber is revealed from the deformation time series. No surface displacement associated with the large earthquake swarm in 2020 is identified from the InSAR-derived deformation. The cumulative volume change in the magma reservoir is about − 6 × 10 6 m 3 from 2004 to 2021, indicating a volume/pressure deficit in the magma plumbing system. • Time-varying deformation episodes are identified at Makushin volcano from 2004 to 2021. • Volatile-dominated magmatic processes are responsible for the produced surface deformation. • A shallow secondary reservoir connected to the main magma chamber is identified. • Active surface erosions are abundant in the valleys of Makushin volcano. [ABSTRACT FROM AUTHOR]

The intraplate oceanic island of Fogo (Cape Verde islands) is in the shield-stage of its evolution. It experienced a major lateral collapse ca. 70 ka ago, after which a sequence of lavas about 2 km thick infilled the collapse scar, with eruptions continuing to the present day. Nearly 100 lavas from before and after the collapse have been sampled and analysed for bulk rock compositions. These lavas have been divided into five Formations (2 pre-collapse and 3 post-collapse), using stratigraphic principles. There is little difference in the major and trace element compositions of pre- and post-collapse lavas, and the main process that gives rise to their diversity is fractional crystallization of observed mineral phases. Pre-collapse lavas show a narrower range of bulk compositions than the post-collapse lavas, but this may be because the sampling strategy avoided these more altered and poorly exposed lavas. A group of high-P 2 O 5 lavas, erupted both before and after the collapse, may have been extensively contaminated by local seamount-stage intrusive carbonatites. A subset of 30 samples was analysed for Sr, Nd and Pb isotope ratios. They show a plume component which has interacted with two contaminants: (1) an increase in 87Sr/86Sr and decrease in 143Nd/144Nd with decreasing MgO, which indicates varying amounts of assimilation of an enriched lithospheric component coupled to fractionation (AFC), and (2) contamination of the more fractionated magmas, without further fractionation, involving the suspected carbonatite contaminant which originates from a more isotopically depleted source. Overall trends of increasing 87Sr/86Sr, and slight decreases in 143Nd/144Nd and all radiogenic Pb isotope ratios, with decreasing age of eruption, indicate a general increase in the assimilated lithospheric component throughout shield-stage activity. However, there is no clear evidence of any change in isotope compositions across the period of the collapse. All Formations show similar wide and overlapping ranges of isotope compositions, regardless of the timescales represented by each Formation. This implies that much short-term variation in the magma sources was superimposed on the overall trend of increasing lithospheric assimilation. • No evidence of major changes in geochemistry between pre- and post-collapse magmas on Fogo • Three separate sources of isotope variation in Fogo magmas: plume, enriched lithospheric component, local carbonatites • Evidence of long-term changes in magma source in Fogo, towards a more enriched source [ABSTRACT FROM AUTHOR]

Mayotte island experienced a large volcanic eruption 50 km offshore in 2018–2021, creating the submarine volcano "Fani Maoré". The eruption was accompanied by intense seismicity at mantle depths (20–45 km), divided into a "proximal" and a "distal" cluster centered 10 and 30 km east from the island, respectively. Previous studies suggest that two separate magma reservoirs may lie at the top and bottom of the proximal cluster. Here, we assess whether two reservoirs are a mechanically viable explanation for the proximal cluster's truncated conical shape. We developed finite-element models of pressurized magma reservoirs in a 2D axisymmetric domain, modeling the reservoirs as compliant elastic ellipsoids embedded in an elastoplastic host rock. We find that, at these depths, extremely low friction is required to generate failure at realistically low reservoir pressures. This implies in turn that mechanical weakening must occur at these depths. The weakening could be induced by fractures or pore fluid overpressure in the volcanic system. We find that two superimposed reservoirs can generate a plastic domain between them, if they are spatially close enough. Several reservoir geometries (from spherical to sill-like) are plausible. A conical fracture domain is more likely to appear for reservoirs with opposite pressure loads (i.e. one inflating, one deflating). Given the geometrical match with the proximal seismicity cluster at Mayotte, we suggest that the shallower (Moho-depth) reservoir is inflating, creating a potential hazard for Mayotte island. • Two interacting magma reservoirs can explain the earthquake distribution near Mayotte. • A 20-km deep reservoir near the island may have inflated during the recent eruption. • Shear patterns between modeled magma reservoirs depend on the applied pressure loads. • The occurrence of mantle-deep earthquakes near Mayotte may indicate mantle weakening. [ABSTRACT FROM AUTHOR]

Billowed margins of basaltic intrusions provide opportunity to study the conditions of non-explosive magma-pore water interactions and how magma propagates and interacts with unconsolidated sediment in the subsurface. Basaltic intrusions exhibiting billowed structures that formed at different paleodepths in Big Bend National Park, Texas (200–500 m) and 71 Gulch, Idaho (≤24 m) have been examined and reconstructed in three dimensions (3D) using structure for motion (SfM) techniques. To characterize billowed structure diversity, a classification system was developed utilizing 21 high-resolution 3D models of outcrops from both locations. Seven structure types are recognized: linear, sinuous, teardrop, bulbous, circular, transitional, and overprinted. Relative abundances of each structure type are similar between both localities. All structures identified were recognized along dikes, apart from one sill. Each site hosts ≥3 structure types, no one structure type is dependent on another, and the dimensions of structure types are similar at both localities with insignificant variation in mean wavelength and amplitude of crests and troughs (≤6 cm), suggesting that depth of intrusion is not a major influence in the occurrence of different structure types. Aligned plagioclase laths and stretched vesicles along margins are evidence that billow formation occurred while margins were fluid, deformable, and flowing. These observations indicate billowed structures likely form during the initial stages of intrusion while the margins are experiencing Kelvin-Helmholtz instabilities during cooling. As billowed intrusions from varying paleodepths at the two localities both occur near phreatomagmatic diatreme structures, changes in the rate or flux of magma intrusion or local heterogeneities in the host sediment and/or pore fluid content may be more responsible for explosive vs. non-explosive interactions rather than simple arrival of magma. • Billow macro and micro-textures reflect frozen Kelvin-Helmholtz instability. • Billowed structures form rapidly and are preserved shortly after dike arrival. • No significant difference in billow geometry or types from 10's to 100's of meters. • Non-explosive intrusive billows are common near phreatomagmatic vents. [ABSTRACT FROM AUTHOR]

The Chapultenango trachybasalt, located in the modern Chiapanecan Volcanic Arc (CVA) in southern Mexico, is constituted by two mafic dykes. Dyke 1 shows relatively low Th/Nb and Pb/Nb ratios compared to other CVA rocks, and exhibits primitive chemical characteristics (e.g. #Mg >65, Ni > 200, Cr > 600) typical of Ocean Island Basalts (OIB). On the other hand, Dyke 2 is almost in touch with Dyke 1, is calc-alkaline, and more evolved than Dyke 1, similar to other rocks found in El Chichón volcano. Hence this work is mainly focused on Dyke 1 that represents the least differentiated melt observed so far in the Chiapanecan Volcanic Arc, and its composition helps in characterizing the mantle source in this region. Dyke 1 OIB-like magma was likely generated by a slab window resulting from the tearing of the Cocos slab along the Tehuantepec Ridge. This tearing was likely caused by differences in physical properties between the northern and southern segments of the Cocos plate, which can be attributed to their age difference (10 Ma) and velocity convergence. This configuration permits the ascent of OIB-like melts from an enriched and relatively deep mantle, which was metasomatized by subduction components (2–6%) and then underwent partial melting (∼5%), although contamination by crustal rocks (e.g., Chiapas Massif) could not be ruled out. The resulting primitive melt therefore would have ascended rapidly, carrying some phaneritic and gabbroic fragments that exhibit similar chemical characteristics to the Chiapanecan Volcanic Arc rocks. • OIB-like magmas were generated in the Chiapanecan Volcanic Arc in southern Mexico. • Tehuantepec ridge produced a slab window in the Cocos slab allowing the ascent of enriched melts. • 2% mantle melting plus 0.8% subduction agents reproduce the Chapultenango magmas. [ABSTRACT FROM AUTHOR]

We constrain, for the first time, the storage conditions beneath recent (<5 Ma) volcanic edifices in Martinique Island, combining petrography, geochemistry, and thermobarometry. Specifically, we investigate Morne Jacob volcano (5.2–1.5 Ma), Pitons du Carbet complex (998 ka – 322 ka), Trois Îlets Volcanic field (2.35 Ma – 346 ka), and Mt. Conil – Mt. Pelée system (<550 ka). Lava samples range in composition from basalt to dacite, and in age from 4.1 Ma (Morne Jacob) to 1929 CE (Mount Pelée). For the last ∼5 Ma, the volcanoes in Martinique were fed by andesitic to dacitic magma stored in the upper 6 km of the crust, at temperatures between 900 and 1100 °C. These shallow reservoirs were frequently replenished and remobilized by basaltic and basaltic-andesite magmas originating from the lower crust with temperatures as high as 1200 °C. Erupted products contain simple to more complex mineral assemblages, and plagioclase phenocrysts exhibit textures and compositional profiles typical of antecrysts, identified as (1) normal, (2) oscillatory, (3) sieved, (4) resorbed core, and (5) resorbed rim. All complexes also show a crystallization gap in the middle crust (10–18 km). Trois Îlets, a distributed volcanic field, is the only complex that shows continuous crystallization through the entire crust, distinct magma batches and storage regions for each individual volcano. More importantly, we see drastic changes in terms of rock composition, storage conditions, and crystal populations in pre - and post – collapse lavas. Large flank collapse (> 5 km3) can induce decompression as large as 5 MPa in the upper crust and as low as 0.1 MPa down to 10–12 km. Such decompression magnitudes might be sufficient to enhance ascent of basaltic magma from depth, initiate dike intrusions in the mid to upper crust, and remobilize shallow silicic reservoirs. Such events are likely to initiate magma mixing in shallow reservoirs. This noteworthy eruption-triggering mechanism may lead to the incorporation of distinct crystal populations and subsequently contribute to heightened rates of eruption. In summary, the magma storage conditions and plumbing system architecture for the recent volcanoes in Martinique closely resemble those observed in other volcanoes within the Lesser Antilles Island Arc, such as Soufriere Hills Volcano or La Soufriere de Guadeloupe. These newly established correlations offer valuable insights that can aid in the assessment of potential future volcanic eruptions. • First estimates of temperatures and pressures for Martinique Pleistocene volcanoes. • Plagioclase equilibrium temperatures range from 969 to 1072 °C. • Plagioclase water content range from 3.1 to 6.5 H2O wt%. • Pyroxene temperatures and pressures range from 964 to 1175 °C and 0.1–8.2 kbar. • There is limited crystallization in the middle crustal layer under Martinique. [ABSTRACT FROM AUTHOR]

The Whakamaru group eruptions (349 ± 4 ka; Downs et al., 2014) are the largest known eruptions in the history of the young Taupō Volcanic Zone, Aotearoa New Zealand. The complex field relationships of the ignimbrites have thus far obscured the timing and history of their eruption(s). We present new evidence from fall deposits correlated with the Whakamaru eruptions to complement the ignimbrite record. Two coastal sections are characterized in detail. We group the tephra horizons into three packages: the older, smaller Tablelands and Paerata tephras; the overlying Kohioawa tephras (correlated with Whakamaru group eruptions); and the younger Murupara and Bonisch tephras. Major- and trace-element compositions suggest these tephras represent six distinct high-silica magma types, with the Kohioawa tephras representing three distinct magma compositions that are atypical of the TVZ. The distribution of Kohioawa magma types (types A, B, and C) changes through time, with the oldest deposits containing exclusively type A magma, the middle deposits containing types A and B, and the youngest deposits containing all three Kohioawa types. A combination of horizon-scale mineralogy and rhyolite-MELTS modeling suggests that only Kohioawa types B and C are saturated in sanidine – the presence of sanidine is atypical in Taupō Volcanic Zone magmas but has been previously documented in the Whakamaru group ignimbrites. Rhyolite-MELTS geobarometry reveals shallow storage pressures (∼50–150 MPa) for Kohioawa magmas. At least three different melt-dominated magma bodies sourced the Kohioawa tephras – these magma bodies were laterally juxtaposed and co-erupted for most of the Whakamaru eruptions. Magmas that preceded and post-dated the Whakamaru eruptions have more typical TVZ compositions, emphasizing the unique features of the Whakamaru system. • Pyroclastic fall deposits are correlated to the Whakamaru group eruptions using tephra deposits ∼90 km from the caldera • Three magma bodies, distinguished by glass chemistry and presence/absence of sanidine, sourced the Whakamaru group eruptions. • Modeled storage depths revealshallow, upper crustal magma bodies sourced the Whakamaru group eruptions (50–150 MPa; ∼ 2–6 km) • Different magma bodies were involved at different times during the eruption(s) [ABSTRACT FROM AUTHOR]

This study proposes the entire detection of the surface deformation of a volcanic area using interferometric synthetic aperture radar (InSAR) with geostatistics to specify the locations and shapes of the sources causing the deformation. We selected the Tangkuban Parahu area, West Java, Indonesia, as our study site and used a Sentinel-1 dataset. In this study, we combine persistent scatterer and small baseline subset InSAR with a geostatistical technique, i.e., turning bands simulation. This combination can compensate for undetected displacement pixels and decompose the line-of-sight displacement into vertical and horizontal east–west displacements using both the ascending and descending mode results and the least-squares method. This two-dimensional geostatistics and multitemporal InSAR approach is referred to as 2D GMT-InSAR. A detailed displacement pattern is revealed by 2D GMT-InSAR for undetected pixels in low-coherence areas. Then, the vertical displacement pattern in the study period from 2014 to 2019, mainly uplift with local subsidence, is reproduced via the joint use of the Mogi and Okada models for circular and rectangular parallelepiped sources of the deformation, respectively. Via a Bayesian inversion, one circular source, equivalent to a magma reservoir, and one dyke source are identified. The displacement pattern is likely caused by pressure increases in the magma reservoir, associated with the volcanic activation, and in the dyke, associated with the gas and fluid flows from the reservoir, which induced a phreatic explosion in July 2019. A connection of the dyke with the old Sunda volcanic system is found; this new finding is a result of the caldera collapse during the Sunda volcanic eruption. • Up–down and east–west displacements were revealed via turning bands simulations • Volcanic uplift before a 2019 eruption was detected by InSAR with geostatistics • Inversion of interpolated InSAR data was effective to estimate magma reservoir system • Two shallow magma reservoirs were located at depths of ∼1100 m and 3700 m • These reservoirs were likely formed by collapse and evolution of a nearby volcano [ABSTRACT FROM AUTHOR]

Since 1.25 Ma, three volcanic systems in the western U.S. Cordillera hosted rhyolitic eruptions of ≳300 km3 dense rock equivalent creating the Yellowstone (0.63 Ma), Long Valley (0.76 Ma), and Valles (1.25 Ma) calderas. Their similar time scales since caldera-forming eruptions and rich histories of seismic research motivate a review of seismic constraints on the modern magma reservoirs beneath these calderas from the uppermost mantle to the upper crust. Across the Cordillera upper mantle seismic velocities are generally below the continental average and each of the calderas is underlain by exceptionally low velocities consistent with the presence of mantle melt, ≲3%. Concentrated upper mantle low-velocity anomalies are found beneath the eastern Snake River plain southwest of Yellowstone caldera and beneath Long Valley caldera. Valles caldera is located above a broadly distributed low-velocity anomaly associated with the Rio Grande Rift and Jemez volcanic lineament. At lower crustal depths potential magma reservoirs exhibit weaker seismic velocity anomalies and greater variability among the results of different tomographic inversion methods compared to shallower depths. At middle-to-upper crustal depths, ~5–15 km, seismic tomography provides evidence of magmatic reservoirs beneath all three calderas, and scattered wave imaging supports sharp upper, lateral, and/or lower boundaries of each inferred magma reservoir. Estimates of average melt fractions in these reservoirs vary from ~9–23% based on recent tomography, with localized melt fraction estimates as high as ~30–60% based on sharp interfaces detected by scattering and ray bending analyses. The wide range of inferred melt fractions likely results from contrasting sensitivities of different seismic imaging methods combined with spatially heterogeneous melt fractions and uncertainties in mapping seismic velocities to silicate melt fractions. Seismic radial anisotropy beneath Yellowstone and Long Valley calderas indicates that middle-to-upper crustal reservoirs are organized as sill complexes with relatively crystal-poor and crystal-rich layers, suggesting magma storage in many weakly connected volumes. Future estimates of (an)isotropic seismic velocities and melt fractions across 3D reservoirs may be improved through expanded applications of full waveform tomography to body and surface waves and increasingly dense array studies facilitated by combinations of broadband and rapidly-deployable shorter-period seismographs. Advanced seismic imaging offers potential for improved delineation of magma reservoir boundaries and constraints on intra-reservoir structures such as sill complexes that provide insight into magma reservoir mechanics and compositional heterogeneity. • Review of seismic imaging beneath the Yellowstone, Long Valley, and Valles calderas • Ongoing supply of mantle melt is likely, particularly at Yellowstone and Long Valley. • Imaging in the lower crust is more variable between methods than in the upper crust. • Evidence of a middle-to-upper crustal magma reservoir, ~5–15 km, at each system • Anisotropy at ~5–15 km depth suggests magma organized in sill complexes. [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]

Volcanic activity at Mt. Etna in the last decade has mostly been manifested by sequences of short paroxysmal episodes characterised by powerful lava fountains and high eruption columns. On the 23 February 2013, an exceptionally intense episode occurred at the New South-East Crater, producing a fountain >800 m high (among the highest ever recorded at Etna) and a ~9 km eruption column that dispersed ash >400 km from the vent. Textural and petrographic analyses of lapilli revealed that magma erupted during the high-intensity phase is characterised by low microlite contents (<7 area%), high vesicularity (76–83%), and high vesicle number densities (6–8.2 × 106 cm−3). The short-lived initial Strombolian explosions removed viscous magma from the conduit, enabling the rapid ascent of gas-rich, microlite-poor magma and the eruption of an 800 m high fountain and 9 km high eruption column. For the 23 February eruption, the high vesicularity and low microlite content of the pyroclasts support the hypothesis that volatile-rich magma was the driver of the high intensity lava fountain. This eruptive event, along with three other recent events at Etna over the last 15 years, can be defined as subplinian based on eruption rate and column height, but also generated incandescent 800–1000 m fountains. For these reasons, we propose to term this event, and others at Etna characterised by similar eruption features and parameters, as subplinian fountaining events. • 23rd Feb. 2013 event produced a lava fountain >800 m high and an 8.7 km column. • Highly vesiculated, microlite-poor magma erupted during the high-intensity phase. • Gas-rich magma is the driver of the high intensity fountain and eruption column. • The event has subplinian features and is labelled a subplinian fountaining event [ABSTRACT FROM AUTHOR]

Surtseyan eruptions have long been studied from their edifice deposits, emplaced subaqueously or subaerially. Here we characterize a Surtseyan eruption from both edifice and ash-sheet deposits using a combination of techniques. The volcano studied is Black Point, which erupted into Lake Russell about 13,000 years ago from a water depth of 105 m, producing a total of ~0.8 km3 of tephra. The techniques, applied to samples acquired by targeted sampling based on geological observations in the field, include geochemical characterization of the eruption products, grain-size analysis of the ash-size fraction at proximal and medial sites, three-dimensional characterization of vesicles in lapilli, and particle-shape analysis for ash grains using the recently introduced freeware PARTISAN©. The aim of this combined approach is to determine how the eruption evolved through its course, from before magma fragmentation to the mechanisms of formation, transport and deposition of the tephra. Field observations are consistent with the ash-sheet deposits forming from eruption-fed density currents, and/or fallout through the water column from a subaerial plume +/− umbrella cloud. Geochemical correlation links the mound deposits, as well as the tuff rings, with a stratigraphic sequence at about 2 km west from the edifice. Both show non-linear but broadly correlative geochemical variations in deposits from the subaqueous stage of the eruption through the subaerial one. Pyroclast vesicle textures indicate that volatile expansion played only a minor role in magma fragmentation, and that there was a high level of bubble coalescence and hence outgassing during the eruption. We infer that fragmentation was mostly phreatomagmatic, resulting from explosive interactions between rising magma and water-saturated sediments. Two-dimensional particle-shape analysis of ash grains shows a large variability in the shape parameters of convexity and solidity; this tells us little about fragmentation style but serves as a proxy for magma vesicularity. The most interesting aspect of this eruption is that none of the shape parameters, or qualitative observations, show any sort of systematic change during the course of the eruption, despite the eruption having begun in 100 m of water and ended up subaerial. • Study of dispersal from a Surtseyan eruption (Black Point volcano, California) • Geochemical link between edifice deposits and proximal ash sheet • Proximal and medial ash was mostly transported and emplaced by eruption-fed density currents. • One medial deposit shows features of deposition via a subaerial plume. • Pyroclasts shown by 3D micro-tomography and 2D particle-shape analysis to lack significant change over 100 m eruptive depth. [ABSTRACT FROM AUTHOR]

Magma opening new fluid pathways through the crust can generate migrating seismic sources following the trail of the magma. By using Seismic Amplitude Ratio Analysis (SARA), it is possible to detect this seismic migration simply from the amplitudes of continuous data recorded at different stations in a network, without having to do any picking of seismic phases. In this study, we present a modified method – Red-flag SARA, which adapts SARA for real-time monitoring. Red-flag SARA provides a quantitative tool to analyse amplitude ratios between stations in a network and detect temporal changes in these ratios. Since such changes imply seismic source location variations, Red-flag SARA is a handy tool during seismic crises to quickly answer the question of whether seismic activity, and therefore magma, is migrating or not. We tested Red-flag SARA on synthetic data and validated it using real data from two volcanoes – Piton de la Fournaise, Reunion Island, and Gede, Indonesia, for three scenarios: 1) magma migration ending as intrusion, 2) migration leading to eruption and 3) a burst of seismicity with no magma migration. • Magma migration can be detected through Red-flag Seismic Amplitude Ratio Analysis. • A quantitative tool suitable for real-time monitoring • Offers insight about the dynamics of the processes driving detected magma migration [ABSTRACT FROM AUTHOR]

With seven major eruptions in the 20th century, Mount Cameroon is one of the most active volcanoes in Africa. However, information on the volcano's plumbing system is still relatively scarce. In order to contribute to filling this knowledge gap, a geochemical, clinopyroxene geobarometry, and Sr Nd isotope study was carried out on samples collected from the 1922 and lower 1999 lava flows found on the SW flank of the volcano. Petrographic evidence shows a common crystallising mineral assemblage of olivine and clinopyroxene and/or plagioclase scattered in a microlite-rich groundmass. The total alkali-silica classification diagram shows that the lavas of 1922 exhibit basanitic compositions those of 1999 are predominantly basanites with some few hawaiites. The Sr isotope ratios for the 1999 samples in this study show values somewhat lower and higher than the limits obtained for historic Mount Cameroon samples so far. While major and trace element trends indicate fractional crystallisation processes, chemical and mineral disequilibrium textures are indicative of open-system processes such as magma mixing and magma chamber recharge. Variations in incompatible trace element ratios, which hardly change during fractional crystallisation, are also suggestive of open-system processes. Plots of K 2 O and Nb show a mixing trend between samples from these eruptions, implying a common magma chamber where remnant material from preceding eruptions was incorporated into succeeding eruptions. Clinopyroxene geobarometric calculations show this common dominant crystallisation depth at 23–29 km. • Sr isotope ratios for the 1999 samples are somewhat different than limits so far obtained for previous Mt. Cameroon lavas. • Bulk rock element trends indicate fractional crystallization, while disequilibrium textures indicate magma mixing/recharge. • Plots of K 2 O and Nb show a mixing trend between samples from these three eruptions implying a common magma chamber • Clinopyroxene geobarometric calculations show common dominant crystallisation depth at 23-29 km for these samples. [ABSTRACT FROM AUTHOR]

Villarrica volcano is one of the most active volcanoes of the Andes (rest cycles of 5.4 ± 3.9 years) and erupts products of basaltic to basaltic-andesite compositions and in styles from Hawaiian to Vigorous Strombolian. We compare whole-rock geochemistry and mineral abundances, textures and compositions of the most voluminous basaltic lavas of the 20th century, which were erupted in 1921, 1948 and 1971. The analyzed lavas show a restricted range in whole-rock compositions (51.7–52.4 wt% SiO 2), but there is an increasing trend of MgO content from 1921 (~5.3 wt% MgO) to 1948 (~7.0 wt% MgO) and a decreasing trend from 1948 to 1971 (~6.0 wt% MgO). Two groups of plagioclase compositions are observed in all lavas: An-poor (~An 60) and An-rich (~An 80). An-poor compositions are the most abundant in all lavas and were commonly formed in both the earliest (cores) and latest stages (external rims and small and nearly unzoned phenocrysts) of plagioclase crystallization, whereas An-rich plagioclase formed around An-poor cores during intermediate stages. Additionally, precipitation of An-poor plagioclase in both rims and cores could simultaneously have occurred in highly dissolved An-rich antecrysts. Equilibrium temperatures of plagioclase-olivine-clinopyroxene of about 1090 °C were obtained in crystal clots of the three lavas. Thermometry calculations obtained from MELTS simulations of plagioclase formation indicate a heating (thermal mixing) of the reservoir at ~0.5 kbar of up to 100 °C with respect to the crystal clots temperatures. Incorporation of small amounts of volatile-rich and hotter mafic magma of similar composition (cryptic mixing) into the Villarrica reservoir, could heat it, probably in a more efficient way than heat conduction alone. A longer interaction of the hot mafic magma within the reservoir could cause crystallization of An-rich plagioclase, dissolution of An-poor plagioclase (i.e. increase in An-rich/An-poor modal content ratios) and compositional modifications toward MgO-rich and volatile-rich compositions, that ultimately result in higher intensity of eruption. • Three lavas of the Villarrica Volcano erupted in the 20th century were studied. • Similar pre-eruptive processes that include heating and water addition are recognized. • Heating is about 100 °C (from ~1090 to ~1190 °C) at ~0.5 kbar. • Incorporation of volatiles and hot mafic magma (cryptic mixing) is likely to occur. • Longer duration of heating event could cause higher eruption intensity. [ABSTRACT FROM AUTHOR]

Sector collapses affect volcanic edifices across all tectonic settings and involve a rapid redistribution of mass, comparable in scale to the largest magmatic eruptions. The eruptive behaviour of a volcano following sector collapse provides a test of theoretical relationships between surface loading and magma storage, which imply that collapse-driven unloading may lead to changes in eruption rate and erupted magma compositions. Large sector collapses are infrequent events globally, with all historical examples being relatively small in comparison to many of the events documented in the geological record. As a result, exploration of the impacts of sector collapse on eruptive behaviour requires detailed investigation of prehistoric collapses, but this is often hindered by poorly-resolved stratigraphic relationships and dating uncertainties. Nevertheless, observations from a number of volcanoes indicate sharp changes in activity following sector collapse. Here, a global synthesis of studies from individual volcanoes, in both arc and intraplate settings, is used to demonstrate a number of common processes in post-collapse volcanism. Multiple examples from large (>5 km3) sector collapses in arc settings show that collapse may be followed by compositionally anomalous, large-volume and often effusive eruptions, interpreted to originate via disruption of a previously stable, upper-crustal reservoir. These anomalous eruptions highlight that magma compositions erupted during periods of typical (i.e. unperturbed by sector collapse) volcanism may not be representative of the range of compositions stored within a vertically extensive crustal reservoir. If eruptible magma is not present, upper-crustal reservoirs may rapidly solidify following collapse, without further eruption, allowing more mafic compositions to ascend to the surface with only limited upper-crustal modification, resulting in edifice regrowth at temporarily elevated eruption rates. Subsequent re-establishment of an upper-crustal reservoir further supports a relationship between surface loading and crustal storage, but long-term chemical and mineralogical differences between pre- and post-collapse evolved magmas imply that a newly-developed reservoir can overprint the influence of a preceding reservoir, forming a spatially and compositionally distinct plumbing system. These broad patterns are replicated in intraplate settings, despite differences in scale and melting processes; current evidence suggests that post-collapse evolution of intraplate volcanoes can be explained by unloading-induced destabilisation of the magma plumbing system, rather than increased melt production. What emerges from an apparently diverse set of observations is a systematic behaviour that strongly supports a coupling between edifice growth and magma ascent, storage and pressurisation. Eruption rates, erupted compositions, and the style of volcanism at any particular system may thus be modulated from the surface, and long-term shifts in surface behaviour may occur without any changes in the deep parts of magmatic systems. Observations of sharp post-collapse changes in erupted compositions, including the ascent of primitive mafic magmas, also require a crystal-dominated mid- to upper-crustal reservoir, consistent with recent models of crustal magmatic systems. • Global synthesis of volcano-magmatic evolution following sector collapse • Decompression-driven reservoir disruption leads to anomalous post-collapse eruptions. • Rapid regrowth via mafic volcanism; subsequent re-establishment of shallow storage • Implies direct modulation of shallow plumbing system development by surface load • Common patterns in intraplate and arc settings [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]

Augustine is an active stratovolcano occupying almost entirely a small island in the Cook Inlet in Alaska. In this study, we use the arrival time data from local seismicity recorded by 15 permanent seismic stations deployed on the flanks of Augustine Volcano by the Alaska Volcano Observatory and invert them by the body wave local earthquake tomography. The resulting model includes the 3D distributions of the P and S wave velocities (Vp and Vs), Vp/Vs ratio and the relocated seismic events. The resolved area extends down to the depth of 2 km below sea level (b.s.l). At shallow depths, within the edifice, we observe a contrasted anomaly with very high Vp , low Vs and very high Vp/Vs , which represents the rigid volcano core composed of igneous rocks (high Vp), but strongly fractured and saturated with fluids and melts (low Vs). At larger depths, below sea level, we retrieve a columnar anomaly of high Vp/Vs ratio representing the magma conduit. On the top of this anomaly, there is a zone with low Vp/Vs coinciding with the strong seismicity cluster, which is associated with the degassing of deep fluids. • We use local earthquake data to build the 3D tomography model of Vp, Vs and Vp/Vs ratio beneath the Augustine Volcano. • Within the edifice, we reveal a contrasted body with high Vp and low Vs representing the rigid core saturated with fluids. • At larger depths, a columnar anomaly of high Vp/Vs indicates the location of the magma conduit. [ABSTRACT FROM AUTHOR]

Vulcanian eruptions are very common at many volcanoes around the world that erupt intermediate to silicic magmas. This type of eruption generates a wide variability of bombs and blocks preserving information onto the conduit processes that strongly control the dynamics of these events. After 84 years of repose, a new cycle of eruptive activity of Tungurahua volcano (Ecuador) started in October 1999, consisting of recurrent low-to-moderate explosive phases, which included sporadic stronger Strombolian to sub-Plinian pulses, as well as Vulcanian outbursts. The 1 February 2014 eruption was one of the most important Vulcanian events and was characterized by highly energetic explosions resulting from a plug conduit failure that generated a ∼ 9 km-high eruptive column and fallback pyroclastic density currents. Four different types of blocks and bombs were found in the deposits of the pyroclastic density currents: dense fragments (DB), breadcrust bombs (BCB), cauliflower bombs (CFB) and foliated, banded bombs (FB). All the different types of bombs have homogenous andesitic bulk-rock compositions but different, highly evolved matrix glass compositions ranging from rhyolitic for BCB to dacitic for CFB and DB, suggesting the occurrence of contrasting shallow crystallization processes within the conduit. The wide variability of the bombs in terms of patterns of surface cracks, external morphologies, internal density and vesicularity gradients records different conditions of formation from a same magma composition. The combination of morphological measurements, compositional data and textural analysis allow us (i) to infer the pre-eruption physical and rheological state of the conduit plug, (ii) to reconstruct the short-scale lateral and vertical gradients characterizing the plug, and (iii) to clarify the specific mechanism controlling the formation conditions of CFB, still poorly defined in the literature. • Rheological zoning in the conduit is recorded in juvenile bombs and blocks • Cauliflower bomb (CFB) formation does not depend on composition • Condition for CFB formation related to differences in magma viscosity • Magma-water interaction does not play a primary role in the formation of CFB [ABSTRACT FROM AUTHOR]

The origin of gaps or zoning in the composition of erupted products is critical to understanding how sub-volcanic reservoirs operate. We characterize the compositionally zoned magma that produced the 2053 ± 50 cal. yr BP Paso Puyehue Tephra from the Antillanca Volcanic Complex in the Andean Southern Volcanic Zone (SVZ). The 3.7 km3 Paso Puyehue Tephra is zoned from dacite (69 wt% SiO 2) lapilli and ash comprising the lowermost 80% of the deposit that abruptly transitions upward into basaltic andesite scoria (54 wt% SiO 2) making up the remaining ∼20%. Variations in whole-rock, matrix glass, and mineral compositions through the deposit allow us to estimate pre-eruptive magma storage conditions and to develop a model of how this magma body was generated. Our findings suggest that amphibole-bearing basaltic andesitic magma stored at ∼8.0 ± 1.3 km depth fractionally crystallized and cooled from 1048 ± 1.1 to 811 ± 28.6 °C under highly oxidizing conditions to produce silicic a melt that upon extraction and rise, pooled at ∼6.4 ± 1.2 km depth at temperatures as low as 810 °C before eruption. MELTS models suggest that crystallization of a basaltic andesite parent magma with 4 wt% dissolved H 2 O can produce the dacite under conditions predicted by mineral thermobarometers with phase compositions comparable to those measured in minerals. Pervasive normal zoning at the rims of plagioclase crystals—most pronounced at the transition between dacite and basaltic andesite, and compatible vs. incompatible trace element concentrations, suggest that magma mixing was limited and likely occurred at the interface between the dacitic and basaltic andesitic magmas during ascent within the conduit upon eruption. Compositionally bimodal tephras are increasingly recognized throughout the SVZ with several interpreted to reflect basaltic recharge and mixing into extant rhyolitic reservoirs. In further contrast to other SVZ rhyolitic products, e.g., from the nearby Cordón Callue and Mocho Choshuenco volcanoes, the Paso Puyehue magma was highly oxidized. This may reflect enhanced delivery of H 2 O from the subducting plate into the mantle wedge, which in turn may facilitate efficient extraction and separation of buoyant, low-viscosity rhyolitic melt from crystal-rich basaltic andesitic parent magmas and the co-eruption of both end members. • We describe a compositionally zoned Tephra deposit in southern Chile. • The compositional zoning originated via fractional crystallization, not magma mixing. • The erupted magma body was stored more deeply under more oxidizing conditions than magmas erupted from the nearby Cordon Caulle volcano. [ABSTRACT FROM AUTHOR]

Volcanic eruptions in basaltic systems represent the most frequent expression of volcanic activity in the World, whose surface manifestations range from effusive lava flows to more explosive events. Their eruptive dynamics and style are largely controlled by the degassing of magma. In this study, we analyze seismic tremors recorded during 23 eruptions that occurred at Piton de la Fournaise volcano (La Réunion, France) during 2014–2021 and show that their properties are strongly linked to the magma degassing. We apply the network covariance matrix method to build a catalog of tremor sources associated with all 23 eruptions, to measure their time-frequency properties, and to locate their sources. We then conduct a multi-disciplinary analysis by comparing the seismic tremor observations with images of the eruptive sites, lava flow rate measurements, impulsive earthquakes, as well as deformation and magma composition data. The tremor depth distribution is found to be well correlated with magma gas content, indicating that the tremor generating mechanism is largely controlled by the shallow magma degassing under the eruptive site. The resulting seismic tremor signals analysis enable to track changes in degassing regimes and associated eruptive styles at the surface, thus improving monitoring and knowledge of the eruptive dynamics of the studied volcano. • Seismic monitoring network data analysis enables to measure spatial, temporal and spectral properties of co-eruptive tremor. • Shallow magma degassing at Piton de la Fournaise controls seismic tremor properties and generating mechanism. • Tremor data along with others observatory data reveal different eruptive phases linked to the evolution of degassing regimes. [ABSTRACT FROM AUTHOR]

Volatile exsolution is widely considered to be capable of generating magmatic overpressure and triggering volcanic eruptions. Despite its role as an eruption trigger, exsolution-driven overpressurisation is relatively poorly understood. Part of the problem is that thermodynamic models do not consider how the behaviour of small quantities of magma scales up to reservoir level – where variations in temperature and crystallinity become important. In contrast, many thermomechanical models focus only on magma injection, and do not consider how overpressure evolves spatially or temporally, when related to crystallisation and volatile exsolution. Here, we use Rhyolite-MELTS to track exsolution-driven overpressure during cooling for a variety of natural compositions, storage pressures, initial volatile contents and magmatic X H2O (molar H 2 O/ (CO 2 + H 2 O)). We then couple these outputs to a thermal model to determine the timescales and spatial extent of overpressurisation with varying volatile content. We find that the highest overpressures occur in magmas which are initially at their H 2 O solubility limit, with the addition or removal of H 2 O resulting in a decrease in peak overpressure. We also find that maximum overpressure decreases with the addition of CO 2 (decreasing X H2O) at typical magma storage pressures of 100–230 MPa. The higher overpressures generated at the volatile 'sweet spot' have a greater potential to trigger eruptions – or to favour their initiation by making the system more susceptible to other triggers, such as magma injection. The reduction in overpressure with increasing or decreasing initial H 2 O suggests that triggering by volatile exsolution is less likely for these magmas. Peak overpressure at the volatile sweet spot also coincides with an increased incidence of explosive eruptions at water contents ∼4–5.5 wt%. This suggests that higher magmatic overpressures may produce more explosive eruptions, by driving faster initial ascent rates and decreasing outgassing efficiency in the conduit. Our thermal modelling demonstrates that, for small magmatic systems, exsolution-driven overpressurisation can operate on timescales which are much shorter than the crustal relaxation timescale. In these cases, overpressure cannot be dissipated by a visco-elastic crustal response, and therefore has the potential to trigger a volcanic eruption. • Highest overpressure occurs for magmas initially at H 2 O solubility limit. • Overpressure increases with increasing X H2O. • Critical overpressure can be attained within crustal relaxation timescales. • High overpressures may drive faster ascent rates and influence eruption style. [ABSTRACT FROM AUTHOR]

The Wulanhada Volcanic Field (WVF) in northern China consists of a few tens of well-preserved monogenetic volcanoes, where Holocene eruptions have occurred, but is rarely known. Understanding the internal structure of the crustal magma plumbing system beneath the WVF is of great significance for the study of volcanic eruption mechanisms and the assessment of volcanic risks and hazards. We present the crustal electrical resistivity models across the WVF obtained from two-dimensional (2-D) and three-dimensional (3-D) inversion of magnetotelluric profile data, which show some robust and meaningful features. Two high-resistivity anomalies (>1000 Ω·m) occupy almost the entire upper and middle crust. They may serve as an impermeable barrier to impede the ascent of deep magmatic fluids and/or melts. However, there is also a sub-vertical anomaly with moderate resistivity separating two high-resistivity anomalies. We inferred that it may represent a crustal-scale buried fault that provided a pathway for magma ascent during past eruptions and controlled the spatial distribution of the Holocene volcanic group in the WVF. A remarkably high-conductivity anomaly (3–10 Ω·m) in the middle-lower crust is explained to be the presence of ~0.8–7.5% partial melts. It may represent a magma reservoir that exists as a crystal-rich mush zone. Considering the presence of the magma reservoir and pathway beneath the WVF, the volcanic risks and hazards of future eruptions should not be ignored. The results shed light on the structure of the buried volcanic edifice in the WVF and need to be verified by more specific work in the future. • The crustal magma plumbing system beneath the Wulanhada volcanic field (WVF) is preliminarily investigated by MT imaging. • The upper-middle high-resistivity crust may impede the ascent of deep magmatic fluids and/or melts. • A sub-vertical conductive anomaly may represent a pathway for magma ascent during past eruptions. • A remarkable conductor in the middle-lower crust may indicate the presence of the magma reservoir beneath the WVF. [ABSTRACT FROM AUTHOR]

Paramushir is the northernmost island of the Kuril Arc comprising several Holocene volcanoes, of which two are presently active: Ebeko and Chikurachki. We present the first crustal-scale three-dimensional seismic shear-wave velocity model of the northern part of Paramushir derived with the use of data of 20 temporary stations operated in 2021–2022 and one permanent station. The continuous seismic data were used to obtain the Rayleigh wave dispersion curves for periods ranging from 0.5 s to 12 s through computing ambient seismic noise cross-correlation functions. Then the 3D shear wave velocity distribution was constructed by seismic tomography. The synthetic tests demonstrate that the model has sufficient resolution down to 7–10 km depth. We observe a series of low-velocity anomalies at the depths of 4–6 km below the volcano-origin Vernadsky Ridge. They may likely represent magma reservoirs that are responsible for Holocene eruptions along the ridge. These anomalies are overlain by the high-velocity anomalies associated with the rigid cover consisting of an upper-crustal granite-granodiorite body and consolidated magma intrusions. Along the eastern flank of Ebeko we reveal a thin low-velocity anomaly at a depth of ∼1 km that can be interpreted as a water-saturated layer. The contact of this layer with hot magma intrusions leads to the formation of a large amount of steam that is ejected during the frequent phreatic eruptions of Ebeko and from numerous fumaroles in the summit area. On the other hand, this layer, which is following down to the Pacific Coast, might be promising for the geothermal energy exploitation. • We present the first seismic model of the Paramushir Island based on ambient noise tomography. • A shallow high-Vs anomaly beneath volcanic Vernadsky Ridge represents the rigid cover composed of consolidate igneous rocks. • Below 6 km depth, the low-velocity anomalies below Ebeko and other volcanoes on the ridge represent magma storages. • A low-velocity layer at ∼1 km depth likely indicates the migration paths of meteoric fluids important for geothermal survey. [ABSTRACT FROM AUTHOR]

We studied nine pumice fall deposits of the Young Merapi stage (<2.2 ka – 1,788 CE) observed in the western and southern flanks of Merapi volcano. All deposits include a wide variation of lithics (10–42% C lithic), with thicker deposits (i.e., more voluminous eruption) being more lithic-rich and vice versa. Two different magma types (hereafter referred to as type I and type II) were identified based on petrography, bulk-rock, glass, and feldspar microlite compositions. Type I magma has abundant amphibole and pyroxene, is rich in calcium (>9 wt% CaO bulk), poor in both silica (50.8–53.7 wt% SiO 2 bulk and 62.3–66.6 wt% SiO 2 glass) and strontium (<580 ppm, bulk-rock), and has more calcic feldspar microlites (An 38 – 79). Type II magma also contains abundant amphibole, but has less pyroxene and is poorer in calcium (<9 wt% CaO bulk), higher in both silica (53.2–54.5 wt% SiO 2 bulk and 63.3–70.8 wt% SiO 2 glass) and strontium (>580 ppm), with less calcic feldspar microlites (An 31 – 77). These two magma types alternately fed the explosive eruptions during the Young Merapi stage; however, their juvenile products are distinctive in terms of syn -eruptive microtextures (i.e., matrix-vesicles and microlites). Pumices from type II magma have a higher matrix-vesicle number density (MVND) and microlite number density (MND) values than those of pumices from type I magma (1.0–6.5 × 1015 and 1.8–7.4 × 1015 m−3, and 0.6–2.3 × 1015 and 0.7–1.8 × 1015 m−3, respectively). A positive correlation between MVND with SiO 2 and MND suggests that a colder (i.e., less calcic feldspar microlites indicate lower temperature and vice versa) and more evolved (higher SiO 2) magma facilitates more extensive matrix-bubble nucleation and deeper microlite crystallization than hotter magmas, allowing type II magma to erupt more explosively than type I magma. • Two magma reservoirs (type I and II) sourced the explosive eruptions during the Young Merapi stage (<2.2 ka – 1,788 CE). • Type II was colder and more evolved than type I, facilitating more extensive syn-eruptive vesiculation and crystallization. • The estimated magma decompression rates vary from 5.3 to 19.3 MPa/s, equivalent to that of the 2008 CE eruption of Chaitén. [ABSTRACT FROM AUTHOR]

La Primavera is a Quaternary rhyolitic volcanic complex located in the northwestern part of the Trans-Mexican Volcanic Belt. It consists of lavas, domes, and composite volcanoes emplaced between 143.5 and 25.5 ka, both inside and outside the caldera rim. Post-caldera volcanism occurred between ∼95 and 25.5 ka, erupting 2 lavas, 22 domes, and 5 composite volcanoes. Here, we present new petrographic descriptions, mineral chemistry, and whole-rock chemical compositions of juvenile fragments from the post-caldera pyroclastic units originated from the Nejahuete, San Miguel, Planillas, and Tajo composite volcanoes. Based on their major, trace, LREE (light rare earth elements), and isotopic compositions, we identify four compositional groups: 1) Colli dome (low-LREE and low-Zr), 2) E to N pyroclastic units (low-LREE and intermediate-Zr), 3) B to D pyroclastic units, and 4) GP to A pyroclastic units (high-LREE and high-Zr). Based on their composition, we propose a three-step model to explain the genesis of the post-caldera magmas: 1) injection of a calc-alkaline subduction-related melt modified by an OIB mantle-derived component (e.g., the Gachupín basaltic-andesite) into the magmatic chambers and generation of at least two crystal mushes, one formed from crystallization of a mantle-derived magma (i.e, Gachupín), and the other from a differentiated residual liquid derived from the same mantle-derived magma, 2) formation of the REE-poor and REE-rich compositions of the La Primavera magmas by different degrees of partial melting of the crystal mushes, and 3) generation of the REE-intermediate compositions of the La Primavera magmas by mixing of the REE-poor and REE-rich melts produced from partial melting of the crystal mushes to generate the LREE and Zr variations of the La Primavera magmas. • Post-caldera activity of La Primavera erupted four chemically different rhyolitic magmas. • Chevkinite and Fe-hedenbergite crystals occur in the post-caldera rhyolitic rocks. • Mixing of interstitial liquids obtained from variable partial melting of different crystal mushes took place. • Three different magma chambers fed the post-caldera rhyolitic magmas of La Primavera. [ABSTRACT FROM AUTHOR]

The study of rejuvenated-stage volcanism provides insight into spatiotemporal changes to the geochemical structure of the Hawaiian mantle plume and the varying interaction with non-plume sources over an extended period of melting beneath volcanic centres. We present new geochemical and Hf-Pb-Sr-Nd isotope data from 6 samples of rejuvenated-stage volcanism on West Maui, the southernmost and youngest island within the Hawaiian chain to exhibit rejuvenation. Major and trace element geochemistry reveal four discrete silica undersaturated eruptions produced by 3–11% partial melting of a garnet peridotite mantle source of metasomatized upper asthenosphere. High Ba/Th ratios (>200) overlap with rejuvenated-stage lavas from Niʻihau, indicating that a minor carbonatite presence persists within the source of rejuvenated-stage lavas along the Hawaiian chain. Puʻu Laina lavas on West Maui have εHf = +15 and εNd = +8.9, which are among the most depleted values of rejuvenated lavas and plot on or below the terrestrial mantle array. These values are close to that of the most depleted lavas from the North Arch and along with rejuvenated lavas from Kauaʻi and East Molokaʻi trend towards the Pacific MORB. Pyroxenite xenoliths and lavas from Kaʻula and Oʻahu, and lavas from Niʻihau extend to higher εHf values at a given εNd indicating a long-lived depleted source independent of the MORB mantle. West Maui rejuvenated lavas form a steep 208Pb/204Pb-206Pb/204Pb trendline and together with North Arch and East Molokaʻi lavas are shifted towards lower 208Pb/206Pb values typical of Pacific MORB. We propose that the across-plume heterogeneity seen in rejuvenated lavas on Kauaʻi and Niʻihau persists at the southern end of the Hawaiian chain where West Maui and East Molokaʻi rejuvenated lavas, like Kauaʻi and North Arch, preferentially source upper asthenosphere as opposed to an ancient depleted source. This across-plume heterogeneity within rejuvenated-stage lavas closely resembles the Kea and Loa-trend differences in shield stage geochemistry and indicates that similar geodynamic processes are responsible for both. • Radiogenic Pb, Hf, Nd, and Sr isotopes in Hawaiian rejuvenated lavas. • Depleted component of the Hawaiian plume reflects asthenospheric source. • Bilateral zonation of the Hawaiian plume evident during rejuvenated volcanism. [ABSTRACT FROM AUTHOR]

The Frac-Digger method based on seismological data of the Kamchatka Branch Federal Research Center United Geophysical Survey Russia Academy of Sciences (KB FRC UGS RAS) was applied to reveal the 3D distribution and chronology of injections of dykes and sills from the deep and shallow magma chambers of Klyuchevskoy volcano preceding the eruptions of Bezymianny volcano during period from 2000 to 2020. The orientation of magma injections (dykes and sills) and mechanisms of volcano-tectonic earthquakes reveal radial horizontal extensional stress conditions in volcanic structures and sometimes local radial compression around magma chambers. Geochemical history of eruption samples shows the parentage of Klyuchevskoy magma for Bezymianny volcano products, tracing magma transport patterns. The result is a 3D conceptual model of the magma-feeding system of Bezymianny volcano from Klyuchevskoy volcano. • Magma activity of Klyuchevskoy volcano precedes eruptions of Bezymianny volcano. • Dyke injections from the 30 km-deep magma chamber of Klyuchevskoy fed most of Bezymianny eruptions. • Magma injections from the shallow magma chamber of Klyuchevskoy may also cause Bezymianny eruptions. [ABSTRACT FROM AUTHOR]

• Since the 2021 uplift, no significant gravity change is detected outside the center caldera. • A 150 μGal gravity decrease from 1988–2017 may indicate subsurface mass eviction. • A 100 μGal gravity increase from 2017–2021 may indicate subsurface mass buildup. In August 2021, Askja volcano in Iceland returned to the spotlight after a sudden onset of rapid uplift followed decades of continuous subsidence. In this study the extended record of microgravity data from Askja between 1988 to 2017 is revisited, and new microgravity data from 2021 and 2022 are introduced, which were collected after the uplift had started. Askja caldera had been steadily subsiding since at least 1984 and was characterised by a net decrease in microgravity, potentially signalling the contraction of its magma chamber or eviction of magma either laterally or to deeper levels. The microgravity data indicate that despite ongoing subsidence between 2017 and early 2021, a significant gravity increase can be detected in the center of the caldera between 2017 and August 2021. This increase may be introduced during – or leading up to – the period of uplift. The new microgravity data also indicate that during the period of 40 cm uplift after August 2021 to fall 2022, gravity changes approach the free-air gradient, suggesting subsurface density decreases as a driving process. This process may relate to the vesiculation of magma previously emplaced in the volcano roots, a change in the hydrothermal system, or replacement of dense basaltic magma with less dense rhyolitic magma, or a combination of these processes. However, uncertainties for this period are elevated and may obscure a gravity signal expected from additional mass accumulation. The timing and high uncertainties of some campaigns make it challenging to be conclusive on the driving process behind the uplift, but future microgravity campaigns could help solve the ambiguity. The study also provides a description of potential pitfalls in microgravity campaigns and recommendations on how the reliability of microgravity data can be improved. [ABSTRACT FROM AUTHOR]

We analyzed continuous Global Positioning System (GPS) data from Sinabung to capture and model the migration of magma from the pre-eruptive and syn -eruptive time period between June 2013 and January 2016. We divided this time into four periods of significant deformation: two extensional stages followed by two contractional stages. Using a grid search method, we determined the location and volume change of a Mogi source for each deformation stage. Cumulative volume changes during the contraction periods were approximated by an exponentially decaying function with time. Period 1 began in June 2013 with slight extension, for which an inflation source was modeled at a depth of 3–8 km below sea level (bsl) and a volume change of 0.3–1.8 Mm3. Seismicity in period 1 was marked by a notable increase in deep high frequency volcano tectonic earthquakes (VTs) beginning in July 2013 and shallow VTs in September 2013. Period 2 began in late October 2013 with accelerated extension, with at least 1 cm extension in the baseline length. During period 2 the modeled inflation source ascended to a shallower depth of 0.9 (0.4–2.1) km below sea level (bsl) beneath Sinabung with a change in volume of + 0.39 (+ 0.18–+0.60) Mm3, and with accelerated rates of volume increase during the time period when the magma migrated to the surface. Seismicity during period 2 was marked first by an increase in the incidence of shallow volcano-tectonic (VT) earthquakes and later by repetitive self-similar hybrid events as the magma migrated to the surface. Period 3 began in January 2014, after the appearance of the lava dome, and was marked by rapid steady contraction of ~ 3 cm through March 2014. The modeled source located at 8.4 (7.4–9.9) km bsl beneath the eastern flank of Sinabung with a volume change of − 20.51 (− 26.89 to − 14.12) Mm3. Period 4 began in April 2014 with decelerating contraction, and the modeled deformation center shifted to the northeast, reaching a depth of 12.2 (10.1–14.8) km bsl between Sinabung and Sibayak volcanoes and a change in volume of − 88.26 (− 123.87 to − 52.66) Mm3. Approximately 2/3 of the total volume change related to contraction occurred between January 2014 and May 2016, and the current activity of Sinabung is expected to decrease gradually and almost terminate in the early 2020s, assuming no new intrusion or deformation rate changes. Both of the eruptions at Sinabung in 2010 and Unzen in 1991–1995 show characteristics of ground inflation and subsequent deflation, indicating magma migration and effusion processes similar to the current Sinabung activity. The inflation before the 2010 Sinabung eruptions likely started before 2007 and is an indication of magma intrusion before the 2010 and 2013 eruptions. • We analyzed continuous data of GPS at Sinabung volcano, Indonesia. • Extension before the lava dome appearance and subsequent contraction was detected. • The inflation sources migrated from deeper part to shallower beneath the summit. • The deflation sources moved away to easterly direction to deeper. • The exponential decay function allows estimation of the trend of eruptivity. [ABSTRACT FROM AUTHOR]

Basic principles controlling tensional failure of a solid are applied in this work to investigate the role played by angularities. The conditions explored apply equally to the initial rupture of sections of the walls of a magma chamber or reservoir and to the propagation of the leading edge of a three dimensional intrusion. The results show that even when the internal pressure inside a cavity might be uniform, the resulting stress on the material surrounding it can have contrastingly different values depending on its position relative to any angularities. Such variability explains why similar volumes of magma, trapped under similar conditions at depth and therefore having equivalent buoyancy, sometimes may feed a tapping event and fail to do so at other times. In addition, it can be appreciated why sometimes veins and dykelets only a few millimeters thick are formed whereas on other occasions it is possible to create a dyke several meters wide filled with magma of similar composition and intruding very similar country rock. The approach followed here also provides an alternative mechanism for the formation of blunt-ended dykes, and outlines the form in which those intrusions are likely to evolve under certain circumstances. • Angularities approximated as elliptical cavities • Stress Concentration Factors calculated with analytical solutions • Stress due to angularities of different acuteness calculated. • Behavior of cusps and edges contrasted. • Influence of angularities in magma tapping events outlined. [ABSTRACT FROM AUTHOR]