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At least 271 records · Page 15Linked to original sources
USGS2025

Mount Spurr volcano, August 18, 1992: The eruption heard around Alaska

The August 18, 1992, eruption of Mount Spurr volcano, Alaska, produced an impressive Vulcanian to Subplinian eruption column reaching up to 40 km above sea level that blanketed the nearby city of Anchorage with ash. At the time of the eruption, the Alaska Volcano Observatory received reports of audible sound hundreds of kilometers from the source from a variety of azimuths from the volcano and found the pattern that did not solely depend on distance. Explosions are generally inaudible to the human ear at these distances due to the attenuation of sound in the atmosphere as the energy propagates, but low-frequency sound waves (infrasound) persist and can be used to detect and characterize eruptions. Similar reports of zones of audible sounds at great distances have been observed from notable eruptions such as Krakatau 1883, Mount St. Helens 1980, Mount Pinatubo 1991, and Hunga volcano 2022. We perform infrasound propagation modeling to help understand the unique distribution of audible reports, finding that areas with favorable infrasound propagation may help explain areas in which nonlinear propagation, including energy cascading effects into higher frequencies that are audible to the human ear, may have occurred.

Alaska↗
USGS2025

Topographic, climatic, and age controls on the reworking of volcanic debris avalanche deposits

Volcanic debris avalanches have deposited as much as 1000 km 3 of largely unconsolidated material on landscapes and remodeled existing drainage networks. The landscape disturbances created by these events pose severe, cascading downstream sedimentation hazards that can require long-term societal management, as demonstrated by decades of observations and ongoing interventions after the deposition of the 1980 debris avalanche of Mount St. Helens (United States). There, post-emplacement sediment yields caused by deposit erosion remain several times above estimated background yield and lakes impounded by the deposit still pose threats of downstream flooding. Despite the length and quality of measurements of the geomorphic evolution and consequent sediment release at Mount St. Helens, the long-term trajectory of drainage network evolution across, and the associated sediment release from, large volcanic debris avalanches remains uncertain. Observations and modeling at Mount St. Helens, however, indicate channel instability can persist many decades and may persist for centuries to millennia. We examined potential influences on the erosion and preservation of volcanic debris avalanche deposits (VDADs) by mapping valley networks developed on 89 VDADs selected from volcanic arcs across the world and spanning a variety of topographic settings and climate regimes. Using the best available topographic data (1 m lidar to 30 m radar-derived data depending on location) and aerial imagery, we estimated the areas of deposits that have been reworked relative to initial deposit footprints as a proxy for post-emplacement erosion. We found that a primary influence on reworking is the topographic confinement of the VDAD: confined, valley-filling deposits are systematically more reworked than unconfined deposits. There is no apparent relationship between deposit age and reworking for valley-filling deposits, indicating that drainage networks on deposits in confined topographic settings like at Mount St. Helens reform rapidly after emplacement. In contrast, our data indicate that the reworking of unconfined deposits has a monotonic positive relationship with age. This observation agrees with a conceptual model of channel formation at Mount Taranaki (New Zealand), which posits that an unconfined VDAD created a topographic high that initially (e.g., 2–8 ky for the Pungarehu formation at Taranaki) diverted erosion to the deposit margins. We found only a weak to moderate relationship between reworking and modern precipitation regimes, which may reflect differences between modern and paleo-precipitation conditions at many of our study sites. We also found no correlation between the size (surface area or volume) of deposits and the degree of reworking. The work presented here implies that downstream cascading sediment hazards from landscape-resetting processes like VDADs (such as thick, extensive pyroclastic flow deposits) depend on the relief and organization of the surrounding landscape.

Washington↗
USGS2025

Utilizing crystal records to determine the underlying architecture and timescales of magmatic processes during the 2022 Mauna Loa eruption

Details of Mauna Loa’s plumbing system and magma storage dynamics are relatively poorly constrained, relative to nearby Kīlauea volcano. Recent studies have begun to address this gap in knowledge using geophysical imaging or olivine-focused petrology. Here, we use the crystal cargo from the 2022 summit and Northeast Rift Zone eruption to advance our understanding of Mauna Loa’s storage regions and pre˗eruptive processes. We identify textural and geochemical populations of olivine, orthopyroxene, clinopyroxene, and plagioclase macrocrysts as well as evolved glomerocrysts consisting of orthopyroxene, clinopyroxene, and plagioclase. Summit versus rift zone trends can be distinguished between specific crystal populations and are used to infer magma transfer pathways. Melt inclusion barometry from three orthopyroxene populations indicate crystallization depths of ~2–3 km which coincide with previous olivine˗hosted fluid inclusion barometry across Mauna Loa’s recent 200˗yr eruptive history. We combine orthopyroxene˗hosted melt inclusion barometry with diffusion chronometry on the same crystals using Fe˗Mg interdiffusion to estimate timescales of mixing and recharge prior to the eruption. Summit orthopyroxene yield timescales of weeks to months, aligning with geophysically recognized pre˗eruptive intrusion events and previously determined olivine timescales. Northeast Rift Zone orthopyroxene crystals have resorbed cores and yield short pre˗eruptive mixing timescales on the order of hours to days. Chemistry and timescales from the orthopyroxene populations suggest some of the 2022 magmas may have bypassed the shallowest portions of the summit reservoir system and were transferred directly into the rift zone syn˗eruptively.

Hawaii↗
USGS2025

Near-real-time geochemical monitoring of Hawaiian volcanoes using energy dispersive X-ray fluorescence (EDXRF)

Syn-eruption geochemical monitoring during volcanic activity is an important component of integrated volcanic monitoring. Volcanoes on the Island of Hawai‘i are primarily monitored by the U.S. Geological Survey’s Hawaiian Volcano Observatory using instrumental networks, field surveys, satellite observations, and petrologic monitoring. In collaboration with the University of Hawaiʻi at Hilo, an important component of this monitoring is near-real-time (generally within 24 h of sample collection) bulk-rock geochemistry using benchtop energy-dispersive X-ray fluorescence (EDXRF). Bulk-rock geochemistry, coupled with additional petrologic and geophysical analyses, are used to track eruption dynamics to help facilitate identification and understanding of changes that signal the onset of potentially hazardous activity. In this paper, we present EDXRF methodology for bulk-rock analysis used to evaluate the 2018 Kīlauea and 2022 Mauna Loa eruptions and compare this technique to other geochemical methods. Syn-eruption geochemical monitoring using EDXRF provides reliable quantitative data that is important for understanding eruption dynamics. Critical to this process are calibrating the instrument for analysis over the same range of compositions expected during volcanic activity, compiling a relevant database from past eruptions on the same instrument for comparison, and having the physical infrastructure and trained personnel to complete the analyses in a timely fashion. In addition to the scientific goals of petrologic monitoring, near-real-time geochemical analysis in Hawaii provides important information about the nature of on-going eruptions and informs decision-makers and the public about associated evolving hazards.

Hawaii↗
USGS2026

Detecting volcanic deformation in Hawaii using trustworthy multimodal deep learning techniques

Monitoring volcanoes involves a variety of data sources and methods to maintain complete continuity of coverage. Global navigation satellite system (GNSS) and interferometric synthetic aperture radar (InSAR) are commonly used complementary methods to assess the deformation state of a volcano as magma migrates beneath the surface. The amount of data these methods produce, however, is growing rapidly beyond human analysis capabilities and is becoming difficult to manage. Here, we create a novel multimodal deep learning framework to ingest InSAR and GNSS data simultaneously and classify the deformation state of the system. We apply this methodology to Mauna Loa, Hawai‘i given its wealth of InSAR and GNSS data as well as its propensity to deform on multiple timescales. Our model performs with high accuracy and is able to identify both slow and fast deformation from 2015 to 2023. The multimodal nature of our model also allows us to identify the presence of atmospheric noise in InSAR data. Furthermore, we employ explainability algorithms to show that our model is making decisions for the right reasons and to connect complex black-box machine learning mappings to current real-world geodetic interpretations of the Mauna Loa magmatic system.

Hawaii↗
USGS2026

Spatial and temporal geochemical variations of lava flows and tephra deposits from the December 2020 to September 2024 eruptions of Kīlauea volcano

Kīlauea volcano underwent dramatic morphological changes in 2018. That year recorded the end of the 35-year-long eruption of Puʻuʻōʻō (1983–2018) and 10-year-long (2008–2018) Halemaʻumaʻu lava lake and emplacement of the ~4-month-long lower East Rift Zone lava flows that coincided with ~500 m of summit caldera collapse. Starting on December 20, 2020, eruptions resumed at Kīlauea’s summit. There were five summit eruptions between December 2020 and September 2023, which ranged in duration from more than a year to as short as a week. Following these summit eruptions, seismicity and deformation increased in the upper Southwest Rift Zone in 2024, culminating in a ~8.5-h-long eruption in this region on June 3, 2024. Increased seismicity and deformation then shifted to the upper and middle East Rift Zone and after several months culminated in an eruption just west of, and within, Nāpau Crater in the middle East Rift Zone from September 15 to 20, 2024. Despite vast morphological changes at Kīlauea’s summit, the geochemical compositions (i.e., whole rock and glass) that erupted from December 2020 to September 2023 are all remarkably similar to each other. Whole-rock compositions appear distinct from the preceding 2008–2018 Halemaʻumaʻu lava lake and phase 3 (i.e., summit or uprift-derived mafic lavas) of the 2018 lower East Rift Zone lava flows, although glass compositions appear to have more overlap with 2018 lower East Rift Zone glasses. The June 3, 2024, upper Southwest Rift Zone spatter and lava flows exhibit a dramatic enrichment in whole-rock MgO that is not recorded in glass, which reflects accumulation of olivine (e.g., antecrysts or xenocrysts) during dike emplacement, and is consistent with the abundance of olivine in the lava flows (5–10%). June 2024 Southwest Rift Zone whole-rock and glass compositions overlap with those erupted at the summit from December 2020 to September 2023, whereas some whole-rock trace (i.e., Sc, Sr, and Zr) and major elements (i.e., CaO) are suggestive of mixing with a magmatic component that had fractionated plagioclase and pyroxene and/or a new parental magma influencing the summit reservoir system. The September 15–20, 2024, eruption at Nāpau Crater in the middle East Rift Zone involved the most differentiated magma since eruptive activity resumed in December 2020, with its magma fractionating olivine + plagioclase + pyroxene. The September 15–20, 2024, composition resembles Puʻuʻōʻō lava flows that erupted in, or near, Nāpau Crater in 1983 (episode 1), 1997 (episode 54), and 2011 (episode 59), with episode 59 having a compositional cluster that is most similar to that of the September 2024 lava flows. The data presented and provided herein open new research perspectives for long-term analyses of geochemical variations following caldera collapse at Kīlauea volcano and facilitate comparisons with other basaltic caldera systems worldwide.

Hawaii↗
USGS2026

Between quiescence and crisis: Hawaiian Volcano Observatory communication and response strategies on the Island of Hawaiʻi

Over the past two centuries, eruptions of Mauna Loa volcano have damaged infrastructure and destroyed several communities on the Island of Hawaiʻi. Future eruptions will impact existing population centers and critical infrastructure, which continue to grow each year. The U.S. Geological Survey Hawaiian Volcano Observatory has developed and practiced methods to promote eruption preparedness in communities on the Island of Hawaiʻi, particularly over the past three decades during which Mauna Loa was quiescent while Kīlauea volcano erupted frequently. Here, we summarize the observatory’s efforts to increase awareness of hazards associated with Hawaiian volcanoes and describe how lessons learned during responses to past volcanic crises on Kīlauea were applied prior to and during the 2022 Mauna Loa eruption, highlighting new response communication challenges encountered during the event. Additionally, we identify potential avenues for future communication/outreach on the Island of Hawaiʻi, such as expanding efforts in communities located in high-hazard areas and striving to be more culturally and linguistically inclusive in our communication techniques.

Hawaii↗
USGS2026

Syn-emplacement crystallization of Mauna Loa 2022 lava flows, Hawaiʻi

Advances in near-real-time forecasts of lava flow advance rates, final travel distance, and areal coverage are transforming hazard response, particularly in locations such as Hawaiʻi that experience frequent lava flow activity. The most severe threats are posed by rapidly advancing channelized ʻaʻā flows, such as those that characterized the November–December 2022 eruption of Mauna Loa volcano. To constrain rheological inputs to flow forecasting models during the eruption, samples were collected from the two most persistent lava flows and rapidly assessed for downflow changes in crystallinity and vesicularity. As observed in other channelized lava flows, the lava lost bubbles and cooled during transport, with consequent increases in groundmass crystallinity and bulk viscosity. Lava rheology, however, is controlled by more than bulk bubble and crystal contents; also important are the melt viscosity and the size and shape distributions of bubbles and crystals. Here we further interrogate the sample suite to document a down flow increase of almost two orders of magnitude in melt viscosity alone (a function of cooling combined with compositional change) and assess the extreme anisotropy of the plagioclase crystals as a function of size and flow type (pāhoehoe or ʻaʻā). When combined with previous studies, these data constrain observed relations between surface morphology, flow temperature and crystal content and indicate that remote assessments of morphological transitions and core lava temperature could be used for channel-wide monitoring of rheological evolution for assimilation into flow models.

Hawaii↗
USGS2026

Lava flow emplacement dynamics during the Mauna Loa 2022 eruption

On November 27, 2022, Mauna Loa erupted for the first time in 38 years, threatening a major highway on the Island of Hawaiʻi. The opening phases of the eruption were focused at the volcano’s summit, before magma propagated into the upper Northeast Rift Zone to erupt at four fissure segments that localized at fissure 3 by December 2. This fissure produced a braided ʻaʻā flow that traversed the steep north flank at >1 km/hr, before slowing as slopes shallowed. Effusion rates peaked in the early hours of the eruption and then steadied at around 100 m3/s at fissure 3. Lava effusion became variable and dropped abruptly on December 7. The eruption ended on December 10 with a final flow length of 18 km. We tracked lava effusion rates, flow advance, channel dynamics, and 3-D flow field development with field and remote sensing observations throughout this eruption to inform lava flow forecasts and investigate ʻaʻā flow dynamics. Flows were mapped using optical and infrared imagery, uncrewed aircraft systems, and airborne single-pass InSAR. Video- and time-lapse cameras were deployed to record lava fountaining and channelized flow at frequent intervals, supplemented by field measurements. Analyses of these data built a detailed record of effusion rates and associated flow dynamics. We combine these high frequency observations of the proximal flow field with broader thermal and 3-D mapping of the evolution in the medial and distal flow field to examine ʻaʻā flow dynamics from source to toe. Within the steep, medial section of the flow field, channel blockages caused back-ups and overflows as the eruption progressed. Disrupted lava supply to the distal flow field and low slopes resulted in stalling, widening, and thickening at the toe. Overall, 142 million m3 of lava covered 36 km2 over 13 days. Our results inform the controls on development and evolution of lava flow fields, with implications for forecasting primary flow advance and secondary flow field growth.

Hawaii↗
USGS2026

Growth and erosion of volcanic islands since 1963 analyzed by multi-sensor satellite data and historical records

Most volcanic activity is taking place in the oceans. Depending on water depth, eruption recurrence times and volumes, a new island can form. The power of erosional forces, the type of erupted material and the efficiency of secondary processes determine the island’s lifetime. Since the famous eruption of Surtsey (Iceland) in 1963, at least another 23 volcanic islands have appeared. Some islands remained intact for years or decades, whereas others disappeared within just weeks or months. In this study, we analyzed satellite data to determine growth and erosion rates of the volcanic edifices related to these 24 islands. We combined multi-sensor (optical, thermal, radar) satellite data time series with information from literature and the Global Volcanism Program database. We developed a comprehensive dataset, including 19 parameters, on the islands’ lifetime, shape, area, volume, eruption style and duration, environmental conditions, development of sedimentary deposits, and the geomorphic evolution of the island over time. Our dataset is available in a database format. This database allows us to test eight hypotheses about factors influencing the islands’ lifetime. Our results show that instead of one single critical factor, a combination of different factors influences the life history of volcanic islands. For instance, we show that larger islands do not necessarily live longer. The mechanical properties of the eruption products affect the island’s structural integrity. Irrespective of the material, a minimum initial area of around 50,000 m 2 seems to be a reasonable threshold to give the island a chance to exist longer.

Bulletin of Volcanology↗
USGS2026

Examples of eruption response teams from the Alaska Volcano Observatory

During times of eruption response, volcano observatories need to organize themselves differently than during normal operations. The number of formal operational roles grows to ensure that critical responsibilities are covered, including management of all activities at the observatory as well as increased staffing to ensure proper surveillance of data and issuance of timely notices and warnings. The scope and approach differ for each observatory and, in fact, for different eruptions. The Alaska Volcano Observatory (AVO) maintains an extensive monitoring program and issues forecasts and warnings about volcanic eruptions and unrest in Alaska. Since 2000, AVO has used formal roles to perform these duties and has implemented a variety of team approaches to respond to larger eruptions. For the Augustine (2006) and Redoubt (2009) eruptions, management scaled from 3 up to ~ 8 people in a command team to cover all aspects of the response. During these and other eruptions (e.g., Okmok, 2008), an operations room was staffed continuously to cover real-time responsibilities pertaining to monitoring and issuing alerts while the command team focused on overall management. More recently, such as for Bogoslof in 2016–2017 and Shishaldin in 2019 and 2023, AVO used a virtual real-time response team to handle warning tasks and variations of an Observatory Volcanic Event Response Team (OVERT; Moran et al. 2024) to manage overall observatory response activities. In 2025, AVO employed a formal OVERT for the first time to oversee its response to unrest at Mount Spurr. Frequent implementation, nimble scaling, constant evaluation, flexibility, and good communication make the team approach effective. We present examples of several response teams used over the last 25 years, and lessons learned from them, in the hope that these will be helpful to other observatories facing crisis responses. These examples may also allow stakeholders and the public to better understand how observatories work.

Alaska↗
USGS2026

Geochemistry of the 2022 Mauna Loa eruption: A comparison with earlier historical summit reservoir eruptions, with implications for magma supply and recharge

On November 28th, 2022, following a record historical repose period of 38 years, Mauna Loa erupted about 145 × 10 6 m 3 of lava and tephra over a 15-day period. The eruption was confined to the summit caldera region and the upper Northeast Rift Zone and is remarkably homogeneous in composition in both time and space. In these respects, it is typical of prior shallow summit reservoir magma bodies, recently estimated to be at a depth of around 1–2 km beneath the caldera. In contrast with these earlier magma bodies, which typically contain 6.7–7.1% MgO and are perched at the low-MgO end of olivine-control trends, the 2022 lava and tephra are more evolved with 6.24 + / − 0.03% MgO. This implies a temperature difference of around 11 °C with the prior 1984 magma. The simplest explanation is that over 38 years, cooling and crystallization of the remaining 1984 magma body has significantly exceeded magma recharge, giving rise to the evolved 2022 magma. The problem with this model is that we know from a variety of geophysical observations that in those 38 years, Mauna Loa has been erratically inflating, with heightened periods since around 2000 attributed to magma recharge. To reconcile these differences, we suggest instead that the 1984 magma cooled and crystallized much more extensively, from 1166 °C to around 1106 °C, co-crystallizing plagioclase, clinopyroxene, pigeonite and subsequently enstatite instead of pigeonite. At this point, the residual 1984 magma would have an MgO content around 4.2% and been about 50% solidified. Subsequent recharge and mixing by dominantly reservoir magmas, derived from a deeper 3–4-km intermediate magma reservoir, eventually produced the 2022 magma.

Hawaii↗
USGS2026

Steps toward a satellite-based global volcano monitoring and early warning system: From pilot to demonstrator to GVEWERS

The consequences of volcanic eruptions span a broad range. Large explosive eruptions that recur every several hundred to thousands of years can impact global climate, but even small eruptions of a magnitude that takes place multiple times each year someplace on Earth can have devastating effects given the large number of people who live near volcanoes. Ground-based monitoring is inadequate or lacking at many of the world’s active volcanoes, but satellite observations can fill important gaps and provide operational awareness of volcanic unrest and eruptions. The need for satellite monitoring of volcanoes has been articulated in numerous international agreements, and for some datasets, like thermal and ultraviolet imagery, daily or sub-daily monitoring has been incorporated into operational volcano surveillance. Utilization of high-resolution synthetic aperture radar (SAR) and optical datasets, however, has lagged. Since 2014, the Committee on Earth Observing Satellites (CEOS) has sponsored a series of projects designed to enhance access to, and utilization of, high-resolution SAR and optical satellite imagery for volcano monitoring. The efforts have culminated in the development of the Global Volcano Early Warning and Eruption Response from Space (GVEWERS) initiative—a global and sustainable program intended to support volcano hazards assessment and mitigation. GVEWERS builds on lessons learned from a decade of CEOS volcano projects while also providing a foundation for continuing to improve the accessibility and exploitation of satellite data for better anticipating and responding to hazardous volcanic eruptions.

Bulletin of Volcanology↗
USGS2026

What a difference a day makes: When and where are daily satellite observations of morphology and deformation needed during volcanic eruptions and unrest?

Daily high-spatial-resolution satellite imagery at active volcanoes could be used to anticipate eruptions and save lives, but is only rarely available or used in real time. Specifically, daily repeat coverage of ground deformation, topography, and surface morphology at volcanoes is now possible using high-spatial resolution optical and radar imagery (< 10 m/pixel). However, multiple satellites are needed—either constellations of four or more sibling satellites or a “virtual constellation” using several different types of satellites. As part of the Global Volcano Early Warning and Eruption Response from Space (G-VEWERS) project of the Committee on Earth Observation Satellites (CEOS), we review case studies at both erupting and restless volcanoes to identify scenarios where near-daily radar (both backscatter images and interferometric products) or optical data captured noteworthy changes, including Merapi and Mount Agung, Indonesia; La Soufrière, St. Vincent; Colima, Mexico; Kīlauea, Hawaiʻi; and Fagradalsfjall, Iceland. Finally, we consider the resources needed to scale this globally. There are 40–50 volcanoes erupting at any given time, but currently only about 10% have daily imaging at high-spatial-resolution. The allocations of high-spatial-resolution imagery available through G-VEWERS and other open datasets (~10,000 scenes/year) are < 60% of what is needed (~17,000 scenes/year) for daily imaging of all restless and erupting volcanoes. We therefore propose criteria to prioritize where daily satellite high-spatial-resolution observations may be useful continuously or under emergency conditions based on the threat and the type of volcano/eruption.

Bulletin of Volcanology↗
USGS2026

Thermal infrared and ultraviolet remote sensing of sulfur dioxide gas emitted during the 2018 lower East Rift Zone eruption of Kilauea, Hawaiʻi

Ultraviolet (UV) remote sensing is widely used to detect volcanic sulfur dioxide (SO₂) due to its high sensitivity and favorable spatial and temporal resolution. However, significant discrepancies have been reported between ground-based and satellite-based UV observations of dense volcanic plumes. A notable example is the 2018 lower East Rift Zone eruption of Kīlauea, where SO₂ emission rates derived from ground-based Differential Optical Absorption Spectroscopy (DOAS) measurements differed substantially from those obtained by the spaceborne Tropospheric Monitoring Instrument (TROPOMI). In this study, we investigate these differences by applying thermal infrared (TIR) satellite retrievals using a modified version of the SO₂-ALTA algorithm to Moderate Resolution Imaging Spectroradiometer (MODIS) observations. The resulting TIR-derived SO₂ fluxes are compared with ground-based DOAS data, satellite UV observations, and petrological estimates of gas emissions. Our results show strong agreement between TIR-derived fluxes, ground-based DOAS measurements, and petrological estimates, particularly during the peak and plateau phases of the eruption. In contrast, satellite UV-derived SO₂ emissions are systematically lower. We find that TIR observations are more effective in quantifying high-concentration SO₂ plumes in the near-vent region, while UV measurements are more sensitive under lower-concentration conditions but more affected by scattering in optically dense plumes. These findings highlight the complementary strengths of UV and TIR remote sensing techniques and emphasize the importance of accounting for plume density and observation geometry when interpreting satellite SO₂ retrievals.

Hawaii↗
USGS2026

Timescales of cumulate mobilization and mixing for the 1868 A.D. eruption of Mauna Loa, Island of Hawai‘i

The deadly 1868 A.D. eruption of Mauna Loa’s lower Southwest Rift Zone (Island of Hawai‘i) included a M7.9 earthquake and associated tsunami and landslides, demonstrating the severe hazards posed by Earth’s largest active subaerial volcano. To better understand the relationship between intense seismic activity, dike emplacement, magma storage, transport histories, and mobilization of olivine cumulates at Mauna Loa, we examine compositional zoning of olivine in the 1868 lava flows. Samples range from basalt (< 10% olivine) to picrite (30–40% olivine). The olivine cargo is heterogeneous (Fo 78.2–89.2 ; forsterite = [Mg/(Mg + Fe) × 100]) but dominated by ~ Fo 89 cores that lie above the Fe-Mg equilibrium field of host glasses. Crystal rims < Fo 80 are due to post-eruptive modification in slow cooling lava flows. Minor element compositions fall within the range of other Mauna Loa olivine erupted in the past 200 years. Olivine crystals exhibit both normal and complex Fo zoning patterns that yield timescales of diffusive re-equilibration that range from 3 to 258 days, with 72% of crystals recording 71 days or less. These timescales correspond to magmatic priming of the summit reservoir system ~ 2 months prior to the eruption and the M7.9 earthquake likely facilitated the transport of the crystal-rich summit-derived magmas downrift shortly prior to eruption. If the recently proposed faster Fe-Mg diffusion coefficient is used, timescales instead range from < 1 day to 25 days, with most recording 1 week or less. In this scenario, most of the olivine zoning would have to have been generated after the M7.9 earthquake perturbed the system.

Hawaii↗
USGS2026

Satellite observations, plume dynamics and volcanic lightning from the 2023 eruption of Shishaldin Volcano, Alaska

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 10 4 –10 7 kg·s −1 and a total erupted volume of ~ 0.05 km 3 (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.

Alaska↗
USGS2026

An extensive and short-lived episode of mid-Holocene fayalite- bearing high-silica rhyolite eruptions at Mono Craters, California

Having last erupted ~ 700 years ago, the Mono Craters volcanic chain is an active system with a history of explosive and effusive high-silica rhyolite eruptions. Approximately ~ 30 lava domes and flows range from ~ 42 to ~ 0.7 ka, form a ~ 15 km curvilinear trend, and change mineralogy (biotite-, orthopyroxene-, or fayalite-bearing) and crystallinity through time. However, the eruptive chronology of this system is incompletely understood. We report new 238 U- 230 Th isochron ages for nine fayalite-bearing domes from paired zircon and allanite crystal surfaces that reveal a major shift in eruptive frequency and volume over the history of the chain, with extrusion of > 0.45 km 3 of high-silica rhyolite lava between 7.1 and 5.2 ka. This contrasts with older biotite- (~ 42–20 ka) and orthopyroxene-bearing (~ 12–9 ka) domes, each of which erupted smaller volumes over a more protracted period. Whole-rock compositions suggest these older domes tapped separate domains within a shared magmatic system because the former are higher in Sr and Ba whereas the latter are lower in SiO 2 , higher in Zr, and more enriched in light rare-earth elements. Titanomagnetite chemistry and zircon saturation temperatures also reflect changing magma compositions and conditions associated with these domes. Fayalite-bearing domes, in contrast, have uniform whole-rock and titanomagnetite compositions which support rapid extrusion of magma over an interval short enough to prevent Fe-Ti oxides from recording any changes in magmatic conditions. The youngest lavas were also produced in a short-lived episode ~ 700 years ago, showing that multivent, geologically brief eruptive episodes occur repeatedly at Mono Craters.

California↗