The Nevados de Chillán Volcanic Complex in the Southern Volcanic Zone (SVZ) of the Andes is one of the most active volcanic systems in Chile and has recently hosted one of the longest and best-instrumented eruptive cycles documented in the country. Here, we integrate satellite-geodetic and seismic time series spanning December 2015 to late 2025 to characterize the full eruptive cycle. We identify three main periods: (I) slight subsidence from 2015 to 2019, (II) marked inflation from 2019 to 2022 with a maximum LOS displacement of ∼ 25 cm, and (III) deflation from late 2022 onward. Inflation and deflation produced a similar spatial pattern with opposite sign and a cumulative LOS range change of ∼ 20 cm. We modeled the 2019–2022 inflation using a pressurized prolate spheroid and found that deformation throughout all three periods was mainly associated with a shallow source region centered at ∼ 5.4 km depth. The source aligns with the NW-SE-oriented Cortaderas Lineament and volcano-tectonic seismicity at 3–6 km depth. The volcano continued to inflate during the period of highest effusive output, while erupted lava volumes remained modest relative to the modeled source volume change, suggesting continued pressurization. Seismicity migrated northeastward during Period II, indicating structural control on shallow magma storage and transport. Through late 2025, deformation and seismicity declined toward pre-eruptive background conditions.
Tephra deposits are widespread across the Island of Hawaiʻi, many of which have been poorly studied. An understanding of the ages and sources of these tephras is important for assessing the frequency of explosive eruptions and thus the hazard potential from individual volcanoes on the island. This study presents new data from a 2-meter-thick section of tephra located midway up the southeastern flank of Mauna Loa volcano on the Island of Hawaiʻi. A total of 15 new radiocarbon dates constrain eruptive activity to between 6540 ± 40 cal BP (5493 BCE) and 276 ± 21 cal BP (1635 CE). The average recurrence interval for tephra deposition is estimated to be 240 years for the past ca. 9,000 years. Repose recurrence intervals vary from 15 to 882 years, indicating that the actual timing between tephra-producing explosive eruptions is more variable than the ca. 240-year average recurrence interval. The deposition and preservation of the section appears to be influenced by its location near tree line, its proximity to the trade wind inversion layer, and preservation by flanking flows. Most layers consist predominantly of fine ash with pedogenic or palagonitic alteration. Petrologic examination indicates that most of the tephra layers, although significantly altered, contain some fresh glass from which in situ geochemical data can be obtained. Thus, the outcrop provides an important type section that can be used for correlating tephra units between Kīlauea and Mauna Loa.
The 2023 eruption of Shishaldin Volcano, Alaska, provided an unusually well-monitored example of a “dry” (non-hydromagmatic) explosive basaltic eruption with sustained, buoyant plumes, and pyroclastic density currents. Here, we examine the 13 basaltic paroxysms that occurred between July and November 2023 using geostationary satellite observations, plume modeling, and volcanic lightning detection to characterize mass eruption rates and plume dynamics. We show that seven volcanic plumes reached 10–14 km above sea level, sustained for minutes to tens of minutes. Translating plume heights into mass eruption rates, using both empirical scaling and one-dimensional plume modeling, gives peak rates of 104–107 kg·s−1 and a total erupted volume of 0.05 km3 (dense rock equivalent) across the eruption sequence. Despite the moderate intensity of this eruption, automated satellite detection algorithms generally failed to detect volcanic ash. We attribute this persistent challenge to the fines-poor grain size distribution of the eruption. Volcanic lightning provides an additional window into the eruption dynamics. A total of 491 volcanic lightning flashes were detected, concentrated during seven of the most energetic phases. The timing of this electrical activity suggests that lightning only became detectable by the global lightning monitoring network when plumes ascended to atmospheric levels favorable for ice formation. Based on the available data, we infer that the low fine ash content of the plumes, combined with minimal water and ice, led to the overall modest rates of lightning (1–13 flashes per minute) compared to “wet” eruptions of similar intensity. These results show that combining satellite observations, plume modeling, and lightning detection provides a valuable timeline of eruptive intensity, even for “dry” basaltic eruptions in remote locations.
Antecrysts are relic or co-magmatic phenocrysts that are common in volcanic rocks of arc settings. Their occurrence is a foundation of the crystal mush paradigm for crustal magmatism, although the putative mush is rarely erupted. The 13.6 ka Belfond eruption (Saint Lucia) produced dacite lava with glass-bearing diorite enclaves, previously shown to have synchronous zircon crystallisation extending to eruption. The cummingtonite-bearing dacite and Ca-amphibole-bearing diorite are porphyritic, and the diorite lacks cumulate features. Most of the dacite plagioclase phenocrysts record late-stage partial resorption and a high 87Sr/86Sr overgrowth not unlike the 87Sr/86Sr value of the groundmass. Their low 87Sr/86Sr interior zone indicates they are antecrystic. Furthermore, the textures and melt inclusion compositions of dacite plagioclase resemble those in the diorite enclaves. Conversely, relatively high 87Sr/86Sr overgrowths on plagioclase and cummingtonite overgrowths on Ca-amphiboles in the diorite record late-stage melt percolation. Thus, we envisage a more radiogenic dacite magma intruded a crystallising mushy diorite magma during ascent. Cummingtonite formation (PH2O = 200–300 MPa; 7–8 km) indicates this occurred in the upper crust. The Ca-amphibole and plagioclase populations in the enclaves both display disparate inter-crystal zonation patterns and, in the latter, interior zone Sr-isotope discordance. These features indicate the diorite was incrementally built by earlier magma inputs, concordant with its long zircon history. Rather than the diorite and dacite having a parent-product connection, the Belfond rocks show that magmas stalled in the crust may become mineralogically heterogeneous from prolonged inputs and that eruptible magmas gain their antecrystic cargo from interacting with such sources.
Severe Tropical Storm Trami produced a deadly lahar disaster around Taal Lake, southern Luzon, Philippines, in October 2024. The most severe impacts were in coastal communities around Taal Lake, where destructive lahars originated not from the active volcanic vent but from multiple sediment sources along the steep walls of the Taal caldera. This study investigates the processes that led to this disaster and evaluates a caldera-wide, distributed-source lahar system, here termed a non-cone-centered lahar system driven by cascading interrelationships among volcanic, geomorphic, and hydrometeorological factors. Satellite imagery, drone surveys, field mapping, sedimentological analyses, and rainfall reconstruction indicate that lahars were the dominant cause of destruction. Approximately 22.86 km2 of land was affected by landslides, mainly in Batangas Province within the municipalities of Talisay, Laurel, and Agoncillo. Substantial tephra deposits were delivered here during the January 2020 eruption of Taal Volcano. Grain-size and component analyses show that the 2024 lahar deposits were dominated by vitric, crystal, and lithic volcanic fragments derived from remobilized eruption deposits. Lahars of this magnitude occurred four years after the eruption and were likely triggered by extreme rainfall reaching up to 425.5 mm in 24 h, corresponding to an estimated 120-year return period. Field evidence of older boulder-rich deposits indicates that high-magnitude lahar activity has happened in the study area prior to historical documentation. These results demonstrate that caldera settings can sustain long-lived, spatially distributed lahar hazards, in which extreme rainfall can remobilize eruption-derived sediments from non-cone-centered sources several years after eruptive activity has ceased or significantly waned.
Pico de Orizaba (Citlaltépetl) stratovolcano, eastern Mexico, preserves a complex Holocene explosive record, yet the eruptive dynamics, source parameters, styles, and hazard implications of individual eruptive episodes remain poorly constrained. Here, we examine the 9600–9500 cal BP Lower Citlaltépetl and 9200 cal BP Upper Citlaltépetl explosive eruptions by integrating field stratigraphy from 85 outcrops, lithofacies analysis, granulometry, componentry, petrography, geochemistry, and eruption source-parameter estimates to reconstruct their eruptive sequences, magma processes, and hazards. The Lower Citlaltépetl records onset dome-collapse/vent-clearing pyroclastic density currents, evolving into a sustained sub-Plinian fallout phase, and ending with complete column collapse. Its main fallout layers were dispersed southeastward from a 25-km-high column at average mass eruption rates of 1.1 × 108 kg s−1. The total fall and pyroclastic density current dense-rock-equivalent volume was 0.1 km3, corresponding to magnitude 4.4. Juvenile products include dominant banded scoria and subordinate pumice. Petrography and geochemistry indicate that magma mixing between a shallow evolved high-Si andesite melt and an ascending mafic magma (both spanning 56–62 wt.
Regional geologic histories are key to mitigating the impact of geologic hazards on nearby communities, but standard geochronology remains costly and labor-intensive. In contrast, surface roughness derived from high-resolution topographic data is an emerging technique for relative and absolute dating of geomorphic features, yet its applicability to volcanic terrains remains largely unexplored. Here, we evaluate if changes in lava flow roughness can be reliably quantified and used as a proxy for lava flow age. We compile an inventory of 17 predominantly postglacial lava flows in the Mount Adams Volcanic Field (Washington, USA) spanning 4–31 ka, including 6 radiometrically dated flows. We calculate surface roughness for each lava flow from 1 m LiDAR Digital Elevation Models using a moving-window standard deviation of slope metric. We fit both linear and exponential models to the roughness–age relationship and evaluate model performance using nonlinear least-squares regression, corrected Akaike Information Criterion (AICc), and Monte Carlo simulations. Results demonstrate that surface roughness decreases systematically with age and is best described by an exponential decay function (R2 = 0.96), with a well-constrained surface roughness decay constant corresponding to a characteristic smoothing timescale of 6 ka. These results, which represent proof of concept, demonstrate that lava flow surfaces undergo progressive smoothing consistent with diffusive geomorphic processes. This approach, the first of its kind for lava flows, offers a rapid and inexpensive tool for reconstructing volcanic histories and may improve hazard assessments for volcanoes worldwide.
Three of the most recent rhyolite eruptions in Europe occurred approximately 800 years ago on the island of Lipari, Aeolian Islands, Sicily. These eruptions produced ash and lava deposits that share many of the physical and chemical traits known to exist in hybrid explosive-effusive silicic systems like the Mono Craters and Medicine Lake (USA), in addition to the recently active rhyolite volcanoes Chaitén (2008) and Cordón Caulle (2011), Chile. Here, we present a study on the microtextures, H2O concentrations, and δD values of pyroclastic and effusive deposits of three rhyolite eruptions on Lipari (Lami, Forgia Vecchia, and Rocche Rosse). Textural features of obsidian pyroclasts are, within our parameters of analysis, identical among the three centers. The three vents furthermore display overlapping bulk H2O concentrations (0.08–1.22 wt.
The process of remobilization of tephra fallout by wind or water has been documented during and after explosive eruptions, with important impacts in health, infrastructure and environment. Existing studies focus on large stratovolcanoes, even though this process may also occur in monogenetic fields. In this work, we address the relevance, controlling factors and characteristics of the processes and deposits related to this phenomenon for scoria cones, which are the main volcano type in this setting. In a systematic literature review, we found a limited number of publications mentioning this process that mostly consist of individual case studies. Based on the analysis of this dataset, we make a synthesis of the existing data and present a first model of tephra remobilization at scoria cones. In this model, we distinguish between (1) the proximal zone, where erosion and transport occur by rilling, gullying and landsliding on the cone slopes, and (2) medial to distal zones where channel erosion, flooding, wind deflation, gullying and ponding along lavas, also take place. The main controlling factors are the climatic conditions that determine the agent and intensity of erosion and transport, and topography which influences transport and deposition. We identify critical gaps in the literature. Sedimentary data on the deposits is sparce and only available for a few cones in specific contexts. Also, the rates of erosion and redeposition are poorly constrained. We demonstrate that closing these gaps is important to better estimate the total volume of tephra emitted by scoria cone eruptions, reconstruct the environmental conditions of past eruptions, and assess hazards in urbanized active monogenetic fields.
Localized crater deformation can shed insight into shallow magma processes and eruption hazards. To study localized crater deformation at Nyiragongo volcano (Democratic Republic of the Congo), we processed Interferometric Synthetic Aperture Radar (InSAR) time series using RADARSAT-2 Ultra-Fine satellite data spanning 2012–2016. This observation was possible thanks to a period between mid-2012 and early 2016 during which the lava lake did not overflow the bottom of the crater. We observed persistent crater floor subsidence and inverted the InSAR displacements during August 2013–December 2015 to model candidate deformation sources with analytic solutions in a homogeneous elastic half-space. We identified a deflating source modeled as a sill at 90 m depth beneath the crater surface. The sill solution is an oversimplified but useful model of the observed deformation rather than a physically realistic intrusion. Thus, we instead interpret the model to represent a composite signal of cooling lava lake overflows accumulated in the crater. Our study demonstrates the capabilities of imaging localized deformation patterns using high spatial resolution SAR data.
Uncrewed aerial vehicles (drones) are capable of performing a variety of volcanic measurements quickly and safely. However, most battery-powered drones are limited to flight ranges of only a few kilometers, requiring personnel to be present on-site for each survey. As a result, travel time and personnel availability often limit the frequency of observations and the ability to respond immediately to changes in volcanic activity. To enable near-daily flights at a restless volcano, a semi-autonomous drone docking station (droneport) was installed at Kusatsu-Shirane volcano and operated remotely via the internet from September 2025 to March 2026 (184 days), including during winter. Except for a period of 72 days when takeoff was not possible due to the snow intrusion into the enclosure and the freezing of the anemometer, the system enabled the drone to operate fully without on-site personnel. Our near-daily flights quantitatively documented changes in the area and brightness of dark gray discoloration of the crater lake. Comparison with lake water chemistry and geodetic observations suggests that variations in the discoloration reflect changes in magmatic fluid supply. By sharing real-time aerial video with stakeholders such as the Japan Meteorological Agency, we demonstrate that repeated flights using a droneport can help assess the volcanic alert level. The droneport enables rapid drone launch without exposing operators to risk, even when access to the crater area is restricted by regulations or snow. Droneports provide a useful platform for near-daily observations and for capturing unexpected events, including changes in surface activity.
Acıgöl caldera (Central Anatolia, Turkey) offers an exceptional natural laboratory to investigate how small-scale eruptions and large caldera-forming events may become closely coupled during the evolution of silicic volcanic systems. Here we reconstruct the eruptive evolution of the Upper Acıgöl Tuff (UAT; 164 ka) using proximal volcano-stratigraphy integrated with glass chemical fingerprints and published geochronology. The intra-caldera stratigraphic record documents a continuous succession of deposits, including a phreatomagmatic tephra ring, debris-avalanche deposits, lithic-rich Plinian fallout, caldera-forming ignimbrite, and post-collapse lava-dome emplacement. The lack of evidence for long hiatuses between these units, including the absence of paleosols or reworked horizons, continuous stratigraphic contacts, local interbedding, and faulting that affects multiple units prior to lava-dome emplacement, is consistent with rapid emplacement and partial overlap among these eruptive processes. Our observations indicate that the Taşkesik maar eruption occurred during the early stages of the UAT caldera-forming event. Although not a deterministic precursor, this small-scale eruption marked an early phase of the cascading eruptive events that culminated in magma chamber decompression, roof subsidence, and ignimbrite emplacement during caldera collapse. Taşkesik and the UAT are thus regarded as closely related eruptive phenomena within a progressively evolving caldera system. These findings highlight the importance of integrating small-volume intra-caldera eruptions into conceptual models of caldera unrest and volcanic hazard assessment.
Volcán de Agua, also known locally as Hunahpú, is a largely unstudied volcano in Guatemala, situated less than 10 km south of the city of Antigua Guatemala, between the active volcanoes of Pacaya and Fuego. The population centres of Ciudad Vieja, Santa María de Jesús, Amatitlán and Palín also lie within 15 km of Agua’s summit, with a total population of approximately 550,000. There is little published work on either its eruptive behaviours or bulk chemistry, with no documented historical eruptions. Dating of its past activity is unknown, and the style of activity remains poorly constrained. Other volcanoes along the Guatemalan cordillera have shown a range of activities in the last two centuries, ranging from effusive to Strombolian at Pacaya in the south to the VEI 2–6 explosive eruptions at Santa Maria to the north west. As part of this study, we analysed samples from surface-exposed deposits that provide evidence for at least one phase of basaltic activity that generated pyroclastic density current (PDC) deposits. These deposits are poorly sorted and contain very angular to sub-rounded, weakly vesicular clasts. The deposit’s geometry suggests an overbank flow, indicating that it escaped an established drainage channel as the current changed direction. Charcoal fragments identified within the deposit were subjected to reflectance analysis, which indicates a depositional temperature of approximately 300 °C. Radiocarbon dating of this charcoal yielded an age of 15,454 ± 41 BP. This represents the first published date of eruptive activity at Agua. Given the location of the dated deposit and lack of capping deposits, it may be possible that Agua has been inactive throughout the Holocene.
The Best-Fit Assessment for Numerical Models (BAM) is a Python-based, open-source, modular, and versatile statistical tool designed to primarily evaluate the performance of numerical models in volcanology. BAM was developed to assess models that simulate the transport and deposition of volcanic mass flows, namely pyroclastic density currents, lava flows, lahars, and debris avalanches. BAM makes use of matrix arrays in the form of raster pairs, chiefly meant to compare the footprint of flow model outputs against user-provided observed geological evidence, such as mapped deposits. This comparison is achieved via a best-fit assessment, which, firstly, includes the computation of length metrics (e.g., percent-length ratio), a confusion matrix (i.e., statistical contingency table), and traditional similarity metrics (e.g., the Jaccard similarity coefficient, Dice-Sørensen coefficient, precision, and sensitivity). Secondly, BAM introduces an approach to incorporate any branching of the footprint geometry, termed the skeleton-aggregated percent-length ratio, and a method to more strictly evaluate areas of overestimation or underestimation, the function-transformed false positives and false negatives, respectively. These transformed results are reincorporated into the traditional similarity metrics to yield innovative and insightful function-transformed similarity metrics, completing the best-fit assessment procedure. This collection of measures establishes BAM as a robust framework to validate, calibrate, and benchmark numerical models focused on inundation areas for volcanic mass flows.
The K-alkaline, Quaternary Roman Magmatic Province (RMP) includes several active and quiescent caldera-forming volcanoes along the Italian Tyrrhenian margin, which have erupted tens of intermediate to large volume ignimbrites, poorly studied in terms of erupted volume and associated plumbing system, with few noticeable exceptions like the 40 ka Campanian Ignimbrite from Campi Flegrei. Here we reappraise the 433 ka Tufo Rosso a Scorie Nere sabatino (TRSNs) ignimbrite from the Bracciano caldera. Using new field data, we calculate the erupted DRE volume to be 67–170 km3, corresponding to a mass of 0.87–4.35 × 1014 kg, which classifies the eruption as VEI 7 and magnitude 7, and the second largest identified within the RMP, after 181–265 km3 DRE of the Campanian Ignimbrite. This new volume estimate is one order of magnitude larger than previously suggested and suggests that the volumes of many other ignimbrites from the RMP may be severely underestimated, potentially qualifying the RMP as an ignimbrite flare-up system. Geochemical characterization of the TRSNs residual glass allows us to test the efficiency of rhyolite-MELTS geobarometry for phonolite compositions and discuss the geometry and structure of the plumbing system leading to the TRSNs caldera-forming event. These data highlight the occurrence of a zoned magma reservoir, which fed first the initial Plinian phase, followed by the main ignimbrite and caldera-forming phase.
This study provides insights on modification of the drainage network within the urban area of Catania (southern Italy) by the recurrent volcanic eruptions of Mount Etna that occurred throughout the Holocene. The oldest lava flows identified within the urban area were emplaced around 5000 BC, culminating in the most recent lava flow that reached the city in 1669. By integrating historical documentation, field observations, and geotechnical borehole data, the original morphological configuration of the area was reconstructed to delineate the pre-eruptive surface drainage system prior to burial by lava flows. The geometry and depth of the paleovalleys were further constrained through estimation of the thickness of the lava flows filling these preexisting depressions. The results highlight a substantial reorganization of the local geomorphology, wherein former valleys were transformed into topographic highs, markedly altering drainage pathways and infiltration dynamics. This long-term landscape evolution continues to exert a persistent control on the spatial distribution and movement of groundwater. In particular, the principal subsurface flow directions align with the axes of the ancient surface drainage network, while the thickest lava sequences constitute the most productive groundwater reservoirs owing to their enhanced secondary permeability.
The Minoan eruption's extensive tephra deposits across the Eastern Mediterranean have been constrained by limited terrestrial data, particularly from the Anatolian mainland. This study presents the first documentation of the Bayır Tephra (BT), discovered in colluvial deposits 260 km E-NE of Santorini near the Yatağan Fault. Geochemically correlated with Minoan pyroclastics, the BT comprises two distinct stratigraphic layers, both exhibiting a bimodal grain size distribution: BT-01 (8 cm thick, white, micropumice-dominant, linked to the Plinian phase) and BT-02 (54 cm thick, grey, non-vesicular glass shard-dominant, linked to the co-ignimbrite phase). Using the BT data and an updated Anatolian dataset, a new isopach map was produced using the Radial Basis Function (RBF) method. Analysis of the tephra distribution yields a new Four-Stage Model for ash cloud dynamics: T1) Initial eastward drift toward Rhodes; T2) A crosswind-induced bifurcation mechanism, resulting in the N-NE deflection of the main plume and the simultaneous separation of a weaker SE lobe; T3) Continued N-NE movement with crosswinds forming an Aeolian Ashfall Edge to the East; and T4) Final widespread ash drift towards the Black Sea. This model proposes that the bilobate tephra distribution (SE and NE) is controlled primarily by wind dynamics, rather than separation between Plinian and Co-ignimbrite plume axes. The ashfall volume is calculated as 59.3 km3 (35 km3 DRE), mass as 7.4 × 1013 kg, and the Eruption Magnitude is updated to 7.1. These refined parameters provide a reliable baseline for future risk and hazard assessments.
Volcanic eruptions shape the landscape. While some events may locally cause mass loss (e.g. gravitational failure, explosive excavation, or collapse following magma withdrawal), constructive processes are dominant: volcanic deposits create new land, cover the landscape, and build new cones around vents. The 2021 Tajogaite eruption (La Palma, Spain) produced a cinder cone complex that was initially 187 m taller than the pre-eruption topography (January 2022). This new volcanic edifice presented an unparalleled chance to quantitatively track its post-eruptive morphological changes. To this end, we are using seven UAS surveys with visible optical cameras between January 2022 and July 2024. This unique dataset allows us to constrain these changes at high temporal and spatial resolution. Over the course of our observation period, the cone “shrank” by more than 11 m in height and lost almost 0.79 × 106 m3 of volume. The rate of these changes was highest at the beginning (6.3 cm height loss/day between January and March 2022) and then decreased exponentially. Towards the end of the observation period (August 2023 to July 2024), the average rate was 0.5 cm/day. These quantifications show that surface processes (wind, rain) accounted for only approximately 10
The emplacement of high-viscosity magma at shallow crustal levels involves a risk for volcanic eruptions but may also produce accessible heat sources for geothermal exploration. Assessing the volcanic risk and the geothermal potential of newly forming and existing sub-volcanic intrusions requires an understanding of their growth and subsequent cooling dynamics. As these processes cannot be directly observed in nature, modelling can deliver useful insights. Here, we present a series of finite element method (FEM) models that simulate the dynamics of magma movement and cooling during the formation of a shallow cryptodome inflating from a sill. The melt and solid volume fraction and temperature-dependent physical properties of the crystallizing magma are determined by simulations conducted with the Rhyolite-MELTS code. The results of the FEM models allow us to investigate the role of magma influx rate on the fluid dynamics and magma cooling inside the intrusion during and after magma influx. We conclude that magma inflow dynamics governs the volume and distribution of eruptible magma, as well as the duration for which the magma remains sufficiently hot to either be remobilized for an eruption or used as heat source for geothermal energy production. These results advance our understanding of the hidden processes that occur in growing and cooling sub-volcanic intrusions in nature.
