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The eruption of Hunga volcano on 15 January 2022 produced a higher plume and faster-growing umbrella cloud than has ever been previously recorded. The plume height exceeded 58 km, and the umbrella grew to 450 km in diameter within 50 min. Assuming an umbrella thickness of 10 km, this growth rate implied an average volume injection rate into the umbrella of 330–500 km3 s−1. Conventional relationships between plume height, umbrella-growth rate, and mass eruption rate suggest that this period of activity should have injected a few to several cubic kilometers of rock particles (tephra) into the plume. Yet tephra fall deposits on neighboring islands are only a few centimeters thick and can be reproduced using ash transport simulations with only 0.1–0.2 km3 erupted volume (dense-rock equivalent). How could such a powerful eruption contain so little tephra? Here, we propose that seawater mixing at the vent boosted the plume height and umbrella growth rate. Using the one-dimensional (1-D) steady plume model Plumeria, we find that a plume fed by ~90% water vapor at a temperature of 100 °C (referred to here as steam) could have exceeded 50 km height while keeping the injection rate of solids low enough to be consistent with Hunga's modest tephra-fall deposit volume. Steam is envisaged to rise from intense phreatomagmatic jets or pyroclastic density currents entering the ocean. Overall, the height and expansion rate of Hunga's giant plume is consistent with the total mass of fall deposits plus underwater density current deposits, even though most of the erupted mass decoupled from the high plume. This example represents a class of high (> 10 km), ash-poor, steam-driven plumes, that also includes Kīlauea (2020) and Fukutoku-oka-no-ba (2021). Their height is driven by heat flux following well-established relations; however, most of the heat is contained in steam rather than particles. As a result, the heights of these water-rich plumes do not follow well-known relations with the mass eruption rate of tephra. [ABSTRACT FROM AUTHOR]

A Bayesian linear regression to determine the bias in the Nafe–Drake relationship between compressional velocity and density provides an improved model for the density structure of Kīlauea volcano, Hawaiʻi. In previous work, we combined the results of seismic tomography with the Nafe–Drake relationship between compressional velocity and density to explain the large values of gravity disturbances overlying the summits and rift zones of the island's volcanoes. These results were used to determine mechanisms for gravitational instability of the island flanks. Here, we use laboratory measurements of the relationship of velocity and density for a wide range of Hawaiʻi island rocks as a prior in a Bayesian regression, with seismic tomography, to refine the 3-D density structure for Kīlauea volcano. This refined structure shows dense bodies (3220 kg m−3) between 5 and 8 km below sea level that underly regions of magma storage, found from geodetic and geophysical studies, beneath the summit and East Rift Zone of Kīlauea volcano. Above these bodies, density isosurfaces surround and cradle sources of pressure change determined from geodetic models, both at the summit and along the East Rift Zone. Continued subsidence of the summit following the 2018 eruption is aligned with a bowl-shaped density structure, formed primarily by density isosurfaces between 2800 and 2900 kg m−3 at 4–6 km depth. These surfaces underly the ∼3 km depth at which dyke injection initiates, are largely aseismic, and from their density values are inferred to contain high concentrations of olivine. Taken together, these density structures are consistent with an olivine-rich mush with variable porosity that increases in density with depth and provides a mechanism to form olivine cumulates both at the summit and along the rift zones. This structural framework for Kīlauea volcano is consistent with melt and mush transport occurring over a large range of depths to accommodate the growth and spreading of the volcano. [ABSTRACT FROM AUTHOR]

Volcanic islands are often subject to flank instability, resulting from a combination of magmatic intrusions along rift zones and gravitational spreading causing extensional faulting at the surface. Here, we study the Koaʻe fault system (KFS), located south of the summit caldera of Kīlauea volcano in Hawaiʻi, one of the most active volcanoes on Earth, prone to active faulting, episodic dike intrusions, and flank instability. Two rift zones and the KFS are major structures controlling volcanic flank instability and magma propagation. Although several magmatic intrusions occurred over the KFS, the link between these faults, two nearby rift zones and the flank instability, is still poorly studied. To better characterize the KFS and its structural linkage with the surrounding fault and rift zones, we performed a detailed structural analysis of the extensional fault system, coupled with a helicopter photogrammetric survey, covering part of the south flank of Kīlauea. We generated a high-resolution DEM (~ 8 cm) and orthomosaic (~ 4 cm) to map the fracture field in detail. We also collected ~ 1000 ground structural measurements of extensional fractures during our three field missions (2019, 2022, and 2023). We observed many small, interconnected grabens, monoclines, rollover structures, and en-echelon fractures that were in part previously undocumented. We estimate the cumulative displacement rate across the KFS during the last 600 ~ 700 years and found a decrease toward the west of the horizontal component from 2 to 6 cm per year, consistent with GNSS data. Integrating morphology observations, fault mapping, and kinematic measurements, we propose a new kinematic model of the upper part of the Kīlauea's south flank, suggesting a clockwise rotation and a translation of a triangular wedge. This wedge is bordered by the extensional structures (ERZ, SWRZ, and the KFS), largely influenced by gravitational spreading. These findings illustrate a structural linkage between the two rift zones and the KFS, the latter being episodically affected by dike intrusions. [ABSTRACT FROM AUTHOR]

Rocks produced by diverse processes, from condensation in space to impacts on planetary surfaces to volcanism, contain both crystals and amorphous material. Crystallinity provides information on the thermal history of the sample and is especially important in characterizing volcanic rocks and pyroclasts because lava rheology is profoundly influenced by the crystal content. Crystallinity is typically quantified via microscopy, using transmitted light or backscattered electrons. However, many samples present visibly ambiguous textures such as intimate intergrowth of crystal phases, and/or crystal sizes extending down to the nanometer scale. Here, we apply calorimetric methods involving heat capacity and enthalpy to assess the crystallinity of a series of volcanic samples. We tested three different approaches, using differential scanning calorimetry, on 30–40 mg aliquots of powdered basalts from the 2018 Kīlauea lower East Rift Zone. The first approach involves determining the magnitude of the increase in heat capacity at the glass transition, which can determine crystallinity to a 1σ precision of ±3%. The second approach is based on the enthalpy of fusion, which requires a longer more complex procedure with results that are typically more uncertain than for the heat capacity method, with a 1σ of ±6%. A final method utilizing differences in enthalpies calculated from the heat capacities required the most complex procedure and has the greatest uncertainty of ±18%. Preliminary results for lavas with microscopically determined crystallinities ranging from 11 to 98% indicate that crystallinity based on calorimetric data can be tens of percent higher than the average value identified using microscopy and petrographic analysis. Image-based methodologies applied to sections of samples reveal spatial heterogeneity and details in texture and crystallinity, whereas calorimetry-based methodologies capture the overall 'bulk sample' properties, unbiased by section effects or imaging resolution limits. These techniques are a powerful combination that can present complementary views of crystallinity. [ABSTRACT FROM AUTHOR]

The science of volcanology advances disproportionately during exceptionally large or well-observed eruptions. The 2018 eruption of Kīlauea Volcano (Hawai'i) was its most impactful in centuries, involving an outpouring of more than one cubic kilometer of basalt, a magnitude 7 flank earthquake, and the volcano's largest summit collapse since at least the nineteenth century. Eruptive activity was documented in detail, yielding new insights into large caldera-rift eruptions; the geometry of a shallow magma storage-transport system and its interaction with rift zone tectonics; mechanisms of basaltic tephra-producing explosions; caldera collapse mechanics; and the dynamics of fissure eruptions and high-volume lava flows. Insights are broadly applicable to a range of volcanic systems and should reduce risk from future eruptions. Multidisciplinary collaboration will be required to fully leverage the diversity of monitoring data to address many of the most important outstanding questions. Unprecedented observations of a caldera collapse and coupled rift zone eruption yield new opportunities for advancing volcano science. Magma flow to a low-elevation rift zone vent triggered quasi-periodic step-like collapse of a summit caldera, which pressurized the magma system and sustained the eruption. Kīlauea's magmatic-tectonic system is tightly interconnected over tens of kilometers, with complex feedback mechanisms and interrelated hazards over widely varying timescales. The eruption revealed magma stored in diverse locations, volumes, and compositions, not only beneath the summit but also within the volcano's most active rift zone. [ABSTRACT FROM AUTHOR]

The 2018 crisis of Kīlauea volcano stands as a major event in its evolution with a large down‐rift effusive eruption that drained a shallow magma reservoir at the summit. The characterization of such active magmatic systems and associated hazardous events remains a necessity and a challenge. The summit area is hydrothermally active and strongly altered as indicated by geological mapping. A unique data set of geophysical measurements was collected around Halemaʻumaʻu crater before its collapse. Magnetic data are interpreted here in combination with geological information, temperature anomalies at the surface, self‐potential measurements, and a model of electrical conductivity. 3D forward modeling shows that the main magnetic dipole‐like anomaly observed around the crater is not only caused by the crater topography but suggests the presence of an important volume of weakly magnetic material beneath the crater, which may be caused by higher temperature and/or hydrothermal alteration. 3D inversion of the data allows us to explore the first order geometry of the magnetic structures. We complement this inversion with 2D forward modeling in order to refine the geometry of major structures. This study shows the presence of major geological structures in the 2018 collapsed area that may have been associated with mechanical weaknesses and could have played a role in the geometry of the collapse. Therefore, mapping magnetic anomalies and monitoring their temporal evolution are of great interest for constraining the nature and mechanical properties of the underlying formations and their temporal evolution in order to help predict future behavior. Plain Language Summary: Kīlauea ranks among the world's most active volcanoes alternating between effusive and explosive events, implying for example, large caldera collapses. The 2018 eruption is the most recent major volcano‐tectonic event that has significantly affected the Kīlauea summit. Assessment of associated hazards is a necessity and a challenge and requires the imaging of hidden weakness zones within the volcano and the monitoring of their evolution through time. We use here a survey of magnetic measurements collected in 2015 at the Kīlauea summit in order to image the subsurface distribution of rock magnetization. These data allow us to demonstrate the presence below the Halemaʻumaʻu crater of a large volume of material characterized by weak magnetization and to delineate its geometry. This weak magnetization can be caused by high subsurface temperatures and/or rock modifications caused by interaction with hot fluid circulations. We also identify major structures that may have been weakness zones and could have played an important role in the geometry of 2018 collapse. This study suggests that the repetition of magnetic surveys over volcanoes in order to monitor the temporal evolution of their subsurface magnetization could help predict the future evolution of the volcanic system. Key Points: We present a new ground magnetic data set collected at the Kīlauea summit around the Halemaʻumaʻu crater before its collapse in 20182D and 3D modeling of these data indicate the presence of weakly‐magnetized material below the crater and along a major fissure zoneThis data set shows the presence of major structures that may have been pathways to fluids and may have played a role in the 2018 collapse [ABSTRACT FROM AUTHOR]

Studies of the effects of volcanic activity on the Hawaiian Islands are extremely relevant due to the past and current co‐eruptions at both Mauna Loa and Kīlauea. The Big Island of Hawaiʻi is one of the most seismically monitored volcanic systems in the world, and recent investigations of the Big Island suggest a widespread subsurface connectivity between volcanoes. Volcanic activity has the potential to add mineral contaminants into groundwater ecosystems, thus affecting water quality, and making inhabitants of volcanic islands particularly vulnerable due to dependence on groundwater aquifers. As part of an interdisciplinary study on groundwater aquifers in Kona, Hawaiʻi, over 40 groundwater wells were sampled quarterly from August 2017 through March 2019, before and after the destructive eruption of the Kīlauea East Rift Zone in May 2018. Sample sites occurred at great distance (~80 km) from Kīlauea, allowing us to pose questions of how volcanic groundwater aquifers might be influenced by volcanic subsurface activity. Approximately 400 water samples were analyzed and temporally split by pre‐eruption and post‐eruption for biogeochemical analysis. While most geochemical constituents did not differ across quarterly sampling, microbial communities varied temporally (pre‐ and post‐eruption). When a salinity threshold amongst samples was set, the greatest microbial community differences were observed in the freshest groundwater samples. Differential analysis indicated bacterial families with sulfur (S) metabolisms (sulfate reducers, sulfide oxidation, and disproportionation of S‐intermediates) were enriched post‐eruption. The diversity in S‐cyclers without a corresponding change in sulfate geochemistry suggests cryptic cycling may occur in groundwater aquifers as a result of distant volcanic subsurface activity. Microbial communities, including taxa that cycle S, may be superior tracers to changes in groundwater quality, especially from direct inputs of subsurface volcanic activity. [ABSTRACT FROM AUTHOR]

Less than a year after the 2018 Kīlauea caldera collapse and eruption, water appeared in newly deepened Halemaʻumaʻu crater. The lake—unprecedented in the written record—grew to a depth of ∼50 m before lava from the December 2020 eruption boiled it away. Surface water heightened concerns of potential phreatic or phreatomagmatic explosions but also offered a new means of possibly identifying eruption precursors. The U.S. Geological Survey Hawaiian Volcano Observatory (HVO) monitored the lake via direct visual observation, webcams, thermal imaging, colorimetry, and laser rangefinders. HVO also employed uncrewed aircraft systems to sample the water and measure near‐lake gas composition. The lake's δD and δ18O indicate a groundwater source with substantial evaporation. The initial sample had a salinity (total dissolved solids concentration) of 71,000 mg/L and was rich in sulfate (∼53,000 mg/L), iron (∼500 mg/L), and magnesium (∼10,000 mg/L). Subsequent samples were slightly more dilute. The water's pH (∼4), δ34S (+4.3‰), and surface temperatures (up to 85°C) suggest, rather than significant scrubbing of magmatic volatiles, leaching of basalt and reactions with sulfate minerals resulted in high concentrations of sulfate and other solutes. Thermodynamic modeling and precipitate mineralogy indicate that water composition was controlled by iron oxidation and sulfate dissolution. Although the lake exhibited no detectable precursors before the next eruption, and phreatic or phreatomagmatic explosions did not materialize, our multi‐parameter approach to monitoring yielded an enhanced understanding of the hydrologic, geologic, and magmatic conditions that led to the formation of the unique and short‐lived lake. Plain Language Summary: In 2019, ponded water was spotted within Kīlauea Volcano's summit crater—the first water body in the crater in written history. The presence of a crater lake was important, as it increased the chance of hazardous, explosive eruptions once Kīlauea resumed eruptive activity. However, the lake provided a new way to keep an eye on Kīlauea; other volcanic lakes have changed temperature, color, or chemistry, or even boiled away, before eruptions. We monitored Kīlauea's lake with various methods, including water sampling via drone. Data showed that the lake was fed by groundwater, not rainwater; the lake was acidic, but less so than most acid volcanic lakes; and the lake was not absorbing large amounts of volcanic gas directly. Instead, the lake's chemistry was controlled by reactions with rocks and sulfur‐bearing minerals in and near the crater. Ultimately, no changes to the lake were detected before the next eruption, most likely because of the nature of magma at Kīlauea, which is different from that at most volcanoes with crater lakes. The water lake also did not cause the eruption to be explosive, as lava merely flowed into the lake from above rather than being injected vigorously into the lake from beneath. Key Points: Kīlauea Volcano's summit water lake was sampled three times to track any potential geochemical precursors to eruptionThe lake was fed by groundwater and its chemistry was controlled by leaching of host basalt, iron oxidation, and sulfate dissolutionNo precursory changes to the lake or phreatic activity occurred, likely owing to the nature of basaltic magma and eventual dike location [ABSTRACT FROM AUTHOR]

Protecting lives and livelihoods during volcanic eruptions is the key challenge in volcanology, conducted primarily by volcano monitoring and emergency management organizations, but complicated by scarce knowledge of how communities respond in times of crisis. Social sensing is a rapidly developing practice that can be adapted for volcanology. Here we use social sensing of Twitter posts to track changes in social action and reaction throughout the 2018 eruption of Kīlauea, Hawai'i. The volume of relevant tweets explodes in early May, coincident with the beginning of the eruption; automated sentiment analysis shows a simultaneous shift towards more negative emotions. Temporal trends in topics of local Twitter conversation reveal societal actions and reflect patterns in volcanic activity, civil protection actions and socioeconomic pressures. We show how hazard and risk information is discussed and reacted to on Twitter, which helps inform our understanding of community response actions and aids situational awareness. [ABSTRACT FROM AUTHOR]

In this study we recast surface wave traveltime tomography as an inverse problem constrained by an eikonal equation and solve it using the efficient adjoint‐state method. Specifically, recognizing that large topographic variations and high surface wave frequencies can make the topographic effect too significant to ignore, we employ an elliptically anisotropic eikonal equation to describe the traveltime fields of surface waves on undulated topography. The sensitivity kernel of the traveltime objective function with respect to shear wave velocity is derived using the adjoint‐state method. As a result, the newly developed method is inherently applicable to any study regions, whether with or without significant topographic variations. Hawaii is one of the most seismically and magmatically active regions. However, its significant topographic variations have made it less accurate to investigate using conventional surface wave traveltime tomography methods. To tackle this problem, we applied our new method to invert ambient noise Rayleigh wave phase traveltimes and construct a 3D shear wave velocity model. Our results reveal features that are consistent with geological structures and previous tomography results, including high velocities below Mauna Loa Volcano and Kilauea Volcano, and low velocities beneath the Hilina Fault Zone. Additionally, our model reveals a high‐velocity anomaly to the South of Hualalai's summit, which may be related to a buried rift zone. Our findings further demonstrate that including topography can lead to a correction of up to 0.8% in the shear wave velocity model of Hawaii, an island spanning approximately 100 km with volcanoes reaching elevations exceeding 4 km. Plain Language Summary: Surface wave traveltime tomography is a commonly used technique for constructing subsurface shear wave velocity models based on surface wave traveltime measurements, which has been widely used to investigate the structures of the crust and upper mantle. The accuracy of tomography relies on effective forward modeling, that is, computing traveltime fields in a given velocity model. In this study, we employ an elliptically anisotropic eikonal equation to model the traveltime fields of surface waves on undulated topography, ensuring precise forward modeling in regions with significant topographic variations. The inversion of surface wave traveltimes is formulated as an optimization problem constrained by this elliptically anisotropic eikonal equation, which is solved using the efficient adjoint‐state method. We have applied the new tomography method to the Island of Hawaii. High shear wave velocities are revealed beneath the summits and rift zones of Mauna Loa Volcano and Kilauea Volcano, outlining the subsurface structures associated with magma storage and transportation. Key Points: An elliptically anisotropic eikonal equation is used to model the traveltime fields of surface waves on an undulated topographyAn adjoint‐state surface wave tomography method based on the anisotropic eikonal equation is developed to determine shear wave velocityThe case study in Hawaii suggests limited topography influence on velocity anomaly amplitudes in regions comparable or larger than Hawaii [ABSTRACT FROM AUTHOR]

Continental flood basalts (CFBs) are dominated by two characteristic lava morphologies. The first type, referred to as 'compound' or 'hummocky pāhoehoe,' exhibits pillow-like lava flow lobes with cross-sections of ~ 0.5–2 m and thin chilled margins. The second type, referred to as 'simple' or 'sheet lobes' preserves more massive, inflated flow interiors that are laterally continuous on scales of 100s of meters to kilometers. Previous hypotheses suggest that two factors may contribute to stratigraphic changes in morphology from 'compound' to 'simple': 1) increased eruption duration or 2) increased extrusion rate. We test the hypothesis that a large increase in extrusion rate would result in flow morphology transitioning from multiple small lobes to inflated sheet lobes due to a shift in flow propagation from intraflow resurfacing-dominated to marginal breakout-dominated. Using polyethylene glycol (PEG) wax extruded into a circular water-filled tank 130 cm in diameter, we produced larger, more complex experiments than previous studies. Our efforts simulated more complex lava fields which change flow morphology with distance from the eruptive vent, characteristic of CFBs. Whereas previous PEG studies linked extrusion rate to near-source surface morphologies, our experiments evaluated how flow propagation mechanisms change with variable extrusion rate and distance from the source. Two flow propagation styles were identified: 1) resurfacing, in which molten material breaks through the surface of a flow and covers the older crust and 2) marginal breakouts, in which molten material extends beyond the crust at the active distal margin of the flow. Flows that propagated via marginal breakouts were found to have lower proportions of resurfaced area and vice versa. We show that significant resurfacing is needed to preserve internal chilled boundaries within a flow and a low-extrusion-rate surface morphology, whereas marginal breakout-dominated flows tend to inflate the pillow-like surface morphology preserving a massive interior at great distances from the vent. Higher and more steady extrusion rates tend to decrease the extent of resurfacing and increase the distance between the source and preserved low-extrusion-rate surface morphologies. We find that an extrusion rate increase equivalent to a jump in the extrusion rate scaling factor, Ψ value, from < 1 to > 5 would be necessary to ensure a switch from resurfacing-dominated lobate morphologies to marginal breakout-dominated propagation style. This amounts to a factor of 125 increase in effusion rate for fissure eruptions and a factor of 625 for point source eruptions, assuming no change in vent geometry. This would be equivalent to an effusion rate of 0.2 m3/s, as documented in 1987–1990 Kīlauea eruptions, increasing to 125 m3/s, which was commonly measured during the 2014 Holuhraun eruption in Iceland and the 2018 eruption at Leilani Estates in Hawai'i. Thus, we propose that continental flood basalts do not require unusually large effusion rates, but instead were active for a longer and more consistent time period than smaller-volume eruptions. [ABSTRACT FROM AUTHOR]

Nontuberculous mycobacteria (NTM) are environmentally acquired opportunistic pathogens that can cause chronic lung disease. Within the U.S., Hawai'i shows the highest prevalence rates of NTM lung infections. Here, we investigated a potential role for active volcanism at the Kīlauea Volcano located on Hawai'i Island in promoting NTM growth and diversity. We recovered NTM that are known to cause lung disease from plumbing biofilms and soils collected from the Kīlauea environment. We also discovered viable Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium intracellulare subsp. chimaera on volcanic ash collected during the 2018 Kīlauea eruption. Analysis of soil samples showed that NTM prevalence is positively associated with bulk content of phosphorus, sulfur, and total organic carbon. In growth assays, we showed that phosphorus utilization is essential for proliferation of Kīlauea‐derived NTM, and demonstrate that NTM cultured with volcanic ash adhere to ash surfaces and remain viable. Ambient dust collected on O'ahu concurrent with the 2018 eruption contained abundant fresh volcanic glass, suggestive of inter‐island ash transport. Phylogenomic analyses using whole genome sequencing revealed that Kīlauea‐derived NTM are genetically similar to respiratory isolates identified on other Hawaiian Islands. Consequently, we posit that volcanic eruptions could redistribute environmental microorganisms over large scales. While additional studies are needed to confirm a direct role of ash in NTM dispersal, our results suggest that volcanic particulates harbor and can redistribute NTM and should therefore be studied as a fomite for these burgeoning, environmentally acquired respiratory infections. Plain Language Summary: Nontuberculous mycobacteria (NTM) can cause environmentally acquired lung infections in susceptible individuals. While NTM infections are linked to household exposures, there are likely non‐household routes of acquisition. Hawai'i is a geographic hotspot for NTM lung disease, but the island‐specific environmental niches for NTM remain poorly understood. Thus, a greater knowledge of where susceptible individuals acquire their infections is an important public health endeavor that may lead to actions to mitigate potential sources of NTM exposures. In the current work, we show that particulate matter collected from Kīlauea Volcano on Hawai'i Island harbors Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium intracellulare subsp. chimaera. Microbiologic, environmental, and NTM genetic data demonstrate that volcanic ash may act as a novel vehicle for the dispersal of clinically relevant NTM. Key Points: Long‐range transport of hitch‐hiking infectious agents has never been reported for volcanic eruptions globallyAsh recovered from the 2018 Kīlauea Volcano eruption harbors species of nontuberculous mycobacteria (NTM) known to cause lung diseaseGenomic evaluation reveals Kīlauea‐derived NTM are genetically similar to respiratory isolates identified on other Hawaiian Islands [ABSTRACT FROM AUTHOR]

The Hawaiian Islands represent the youngest portion of the long‐lived Hawaiian‐Emperor Seamount chain sourced from hotspot volcanism on the northwesterly moving Pacific plate. Despite being one of the best studied hotspots on Earth, our understanding of the lithospheric discontinuity structure of Hawaiʻi is inhibited by a lack of a long‐term distributed broadband seismic network and lithospheric‐scale imaging of other oceanic hotspots. In this study, we analyze 3,530 teleseismic waveforms from 1,130 events recorded at 47 stations to compute P‐wave radial receiver functions. We then incorporate an elevation correction to adaptive common conversion point stacking to create a 3D discontinuity volume of the lithospheric structure associated with an ocean island hotspot. We find a positive amplitude conversion consistently at ∼12 km below sea level, likely representing the crust‐mantle transition below much of the island. However, this conversion occurs at only ∼6 km below Kīlauea, where local tomography images a zone of high P‐wave velocities (>7 km/s) within the crust and deformation of olivine phenocrysts within a magmatic reservoir is thought to occur. At this location, seismicity also extends vertically to 35 km depth before merging with an interpreted sill complex at ∼40 km. We interpret this anomalously shallow high amplitude discontinuity as an olivine‐dominated magmatic reservoir with an estimated maximum 5% melt over the resolution of our data at crustal depths. This represents the shallow seismic signature of a much more extensive magma system extending to depth. These images provide a better understanding of the magmatic structure associated with oceanic hotspot volcanoes. Plain Language Summary: The Hawaiian Islands are the product of hotspot volcanism on the northwesterly moving Pacific plate. Our understanding on the formation of Hawaiʻi and other oceanic hotspot volcanoes is reliant on our ability to discern the process of magma formation and transportation through the mantle and up to the volcanic caldera. We have a thorough understanding of broad mantle characteristics and crustal structure beneath Hawaiʻi but lack any relatively higher resolved lithospheric seismic image given the instrumentation and data that are available. In this study, we derive a 3‐D discontinuity volume beneath Hawaiʻi. We find a discontinuity consistently at ∼12 km below sea level which we interpret to be the Moho. Beneath Kīlauea, the most active caldera on Hawaiʻi, this discontinuity shallows to ∼6 km and is unlikely to represent the Moho. These depths are consistent with high (mantle‐like) seismic velocities found in previous seismic studies. Seismicity surrounds this shallow discontinuity and extends down to ∼35 km depth possibly connecting to another magma reservoir. We interpret the shallow discontinuity beneath Kīlauea as ultramafic material formed within the crust by extensive differentiation in a low‐melt magma reservoir. These images provide a better understanding of magmatic structure associated with oceanic hotspot volcanoes. Key Points: Elevation‐corrected P‐to‐S receiver functions are used to create a 3‐D discontinuity model beneath the main Hawaiian islandA high‐amplitude positive arrival is imaged ∼6 km BSL at Kīlauea spatially coinciding with seismicity extending vertically to ∼35 km depthThis shallow arrival represents the uppermost portion of an olivine‐dominated magmatic reservoir with up to ∼5% melt [ABSTRACT FROM AUTHOR]

The 2018 eruption on the lower East Rift Zone, Hawaii, involved the opening of 24 fissures before the eruption focussed on a single point source, fissure 8 (F8). This study characterises the preserved medial F8 tephra deposit using an isopach map, maximum clast size data, and total grain size distribution analysis, shedding light on the tephra transport and dispersal mechanisms beyond the F8 cone occurring during the fountaining. The medial sheet-like deposit covers approximately 0.22 km2, best fit by a Power-Law thinning rate. The TephraFits model estimated the corresponding volume of the continuous medial tephra blanket to be ~ 2 × 104 m3, just 0.02% of the total volume erupted from fissure 8. Samples from the preserved medial deposit have grain size modes of − 3.5 to − 4 Φ, compatible with Voronoi tessellation calculations. Maximum clast size did not show a 'typical' fining relationship with distance from the vent; instead, it shows no clear pattern. One factor was that the extremely low clast density, a function of a secondary vesiculation event, enabled the pyroclasts to be re-entrained, often repeatedly, by large eddies downwind of the vent. This should be considered in future studies of prolonged fountaining episodes as the clasts involved in the medial fall are rarely well preserved in the geologic record due to their fragile nature but their presence adds complexity to the inferred eruption dynamics. [ABSTRACT FROM AUTHOR]

During eruptions, volcanoes produce air‐pressure waves inaudible for the human ear called infrasound, which are very helpful for detecting early signs of magma at the surface. Compared to violent ash‐rich explosions, recording more discrete atmospheric disturbances from effusive eruptions remains a practical challenge depending on the distance to the source. At Nyiragongo volcano (D.R. Congo), towering above a 1‐million urban area, we analyzed local infrasonic records between January 2018 and April 2022. An acoustic signature from this open‐vent volcano is detected up to the volcano observatory facilities in Goma city center about 17 km from its crater. We compared infrasound signals with space‐based observations of the intra‐crater activity (SO2 emissions, thermal anomalies, crater depth/radius). We thus obtain a comprehensive picture of Nyiragongo's eruptive activity during this period, encompassing the drainage of its lava lake during its third known flank eruption on 22 May 2021. Plain Language Summary: Similar to seismic waves propagating within the solid Earth, acoustic waves propagate in the atmosphere as a result of near‐surface volcanic activity. In contrast with powerful volcanic explosions, close‐range deployment of instruments around the active vent (for instance <15 km) is generally needed for continuously monitoring long‐living lava effusion or degassing as observed at open‐vent volcanoes, such as Kīlauea (Hawaii) or Nyiragongo (D.R. Congo). Nyiragongo hosted the world's largest lava lake up to 2021, which was drained during the third known flank eruption of this volcano on 22 May 2021. While watching for possible reawakening, we detected the infrasound signature of a nascent lava lake four months later, highlighting the crucial role of infrasound monitoring. Remote observations from space (ground deformation, gas emissions, thermal anomalies) can also provide essential information about the eruptive state of a volcano and were jointly analyzed with infrasound records. Knowing that Nyiragongo towers above the 1‐million inhabitant city of Goma, such an approach has significant implications for optimizing future monitoring efforts in a harsh field environment. Key Points: Nyiragongo volcano (D.R. Congo) is a permanent emitter of infrasound that pauses during rare flank eruptionsIntra‐crater lava eruptions (lava lake, spatter cone, lava pond) are detected up to the observatory in a dense urban area ∼17 km awayJoint analysis with space‐based observations over the period 2018–2022 provides a clear picture of the persistent unrest at this volcano [ABSTRACT FROM AUTHOR]

We would like to thank Wei and Shen (2023, https://doi.org/10.1029/2022GL102596) (W23) for their comments on our recent article on GRL. In their comments, Wei and Shen argued that tremor signal on the right side of the cross‐correlation function (CCF) of PAUD‐STCD is from Kilauea crater, and they suggested that the observed time‐delay after eruption might be attributed to the noise source change and other factors. After checking the data and the code carefully, we recognize that signal on the right side of CCF of PAUD‐STCD may be due to seismicity from the Kilauea crater. However, we demonstrate here that it does not affect our conclusions. Plain Language Summary: Wei and Shen (2023, https://doi.org/10.1029/2022GL102596) question that our velocity change measurement might be affected the volcanic tremor source change. By processing more data, we found that our results are stable. Key Points: Reply to comment by Wei and Shen (2023, https://doi.org/10.1029/2022GL102596) about the influence of the noise source for seismic velocity change measurement [ABSTRACT FROM AUTHOR]

Wavelength‐dependent mid‐infrared (400–1,800 cm−1; 5.56–25 μm) optical constants (real and imaginary indices of refraction; n and k) are determined using reflectance spectra at a spectral sampling of 4 cm−1 for several silicate glasses of varying SiO2 wt% which include (a) basaltic volcanic glass from Kīlauea, Hawaii, (b) synthetic andesite, (c) two synthetic dacites, (d) obsidian volcanic glass from Mount Lassen, California, (e) synthetic rhyodacite, and (f) rhyolitic volcanic glass from Mexico. Because glasses are optically isotropic, no specific orientation was required for spectral measurements, and polished glass samples were measured at random orientations using micro‐FTIR spectrometer. Lorentz‐Lorenz dispersion theory and Fresnel reflectance model for high symmetry materials were used to model the optical constants by optimizing oscillator parameters in modeled spectra to match laboratory spectra. A genetic algorithm (GA) approach automatically finds the natural oscillators and their parameters for each spectrum, and then uses these parameters in a non‐linear least squares optimization routine. The study compared spectral parameters such as Christiansen feature, reststrahlen bands (RBs), and the peaks centered around 860–1,100 (peak 1) and 400–480 cm−1 (peak 2) of n and k to their respective SiO2 wt% of the glasses. CF, RBs, peak 1 of n and k, and peak 2 of n shift to higher wavenumbers with increased SiO2 wt%, whereas peak 2 of k shifts to lower wavenumbers with increased SiO2 wt%. Derived optical constants of these glasses will improve quantitative abundance mapping of volcanic materials on the surfaces of silicate targets in the Solar System. Plain Language Summary: The effective mapping of minerals and their abundances on a planet's surface from orbit is enabled by understanding the nature of the interaction of light of varying wavelengths with the planetary surface. The reflected/emitted light from the surface directly depends on the optical properties of the materials and their interaction with each other. In this study, we numerically modeled the mid‐infrared optical constants of silicate glasses using a genetic algorithm (GA) approach. The GA allows the model to automatically locate the natural harmonic oscillators and their parameters that are responsible for creating the spectral signals that can be detected by spectrometers on orbital spacecraft. Derived optical constants of the glasses could be used in radiative transfer models for quantitative mineral mapping applications. Glasses on planetary surfaces are common in volcanic and/or impact materials and the mid‐infrared spectral range has been widely used to map the surface mineralogy of planets including the Moon and Mars. Mapping the composition and abundance of these glasses therefore will help us to understand the thermal evolution of the planets themselves. Key Points: MIR optical constants (5.56–25 μm; 400–1,800 cm−1) and their oscillator parameters were modeled for seven silicate glasses of varying SiO2 wt%MicroFTIR reflectance spectra of the glasses studied were measured for the spectral region 5.56–25 μm (400–1,800 cm−1)Genetic algorithm was adopted to automatically find the natural oscillators and their parameters for the glasses studied [ABSTRACT FROM AUTHOR]

We use seismic ambient noise correlation and coda wave interferometry to estimate velocity variations at high temporal resolution, during the pre‐eruptive period and the onset of the 2018 eruption of Kīlauea volcano. A progressive velocity increase is observed from March to the end of April. It is followed by rapid decrease starting a few days before the onset of the East Rift Zone (ERZ) eruption and then by sharp velocity drop when the eruption started. The change of trend from velocity increase to decrease is progressively delayed by a few days from the summit caldera toward the ERZ. The location of the velocity perturbations shows a migration of the sources of velocity changes from the summit caldera toward the ERZ before the eruption. Using a model of pressure source, we show that the simultaneous caldera inflation and velocity increase probably result from an anisotropic distribution of fault and crack orientations. The velocity decrease could be due to damaging processes above the shallow reservoir and to plastic deformations around the caldera. We introduce a forward model of rock damage associated with the volcano‐tectonic seismicity to calculate the velocity decrease. The good agreement between the calculated and the observed velocity variations shows that a large part of the velocity decrease results from damage of the medium. The delayed onsets of velocity decrease and the source migration of velocity perturbations are probably related to progressive fault openings in the Southern and Eastern parts of the caldera and to magma transfer toward the ERZ. Plain Language Summary: Magma migration from the summit reservoir to the lower East rift zone induced changes in the medium properties of the Kīlauea volcano. Pre‐eruptive seismic velocity variations, measured using ambient noise correlation, were caused by the caldera inflation and damage related to the volcano‐tectonic seismicity. Our work shows that the calculated decrease of velocity using a rock damage model associated with the volcano‐tectonic seismicity provides a good agreement with the observed velocity variations. The delayed onsets of velocity decrease and the source migration of velocity perturbations are probably related to progressive fault openings in the Southern and Eastern parts of the caldera and to magma transfer from the summit reservoir to the ERZ. Key Points: A progressive velocity increase is followed by a rapid decrease delayed by a few days from the caldera toward the East rift zoneThe velocity decrease could be due to damaging processes above the shallow reservoir and to plastic deformations around the calderaThe delayed onsets of velocity decrease and the source migration of velocity perturbations are related to fault openings and magma transfer [ABSTRACT FROM AUTHOR]

Recent geodetic data has clearly imaged significant contraction of rift zones during effusive eruptions, which is attributed to deformation of active, elongated feeders, challenging the rigid conduit paradigm. In this work we develop a physical model to understand the impact of conduit deformation on the eruptive dynamics. Numerical calculations show that magma overpressure increases the width of the conduit, resulting in higher discharge rates than would be expected from the rigid case. At the same time, conduits with high aspect ratio, have larger compressibility and can store significant amount of magma, thereby acting as secondary reservoirs. The net result is that rift zones can maintain high fluxes over prolonged periods of time, leading to large volume eruptions and biasing magma compressibility estimates. We apply our findings to the 2018 Kīlauea eruption where episodic collapse of the summit led to pressure pulses that propagated down‐rift and that were recorded by both tiltmeters and peaks in the effusion rates. Inversion of the data indicates a conduit with a height of 700–800 m and a maximum opening of 4 m, located at a depth of 2.5 km in the Upper East Rift Zone, becoming shallower in the Puʻu ʻŌʻō region and propagating sub‐horizontally in the Middle and Lower East Rift Zone. Based on these properties we infer that up to 30% of the erupted volume can be attributed to magma stored in the rift zone. In agreement with recent studies, we find that magma over‐pressure was low at the end of the 2018 eruption. Plain Language Summary: Deformation of the volcanic edifice shows a contraction of the conduits feeding eruptions. We have developed a physical model to understand how such deformation affects the amount of magma extruded and for how long the eruption will last. The results of the model indicate that elastic conduit deformation allows for larger volumes of magma to surface more quickly, compared to cases where the conduit behaves rigidly. One important finding was that elastic conduits act as secondary magma reservoirs. We applied the model to estimate the properties of the storage and transport system of the 2018 Kīlauea eruption. We found that the conduit had a height of about 750 m and a maximum opening of 4 m. The conduit is located at a depth of about 2.5 km in the Upper East Rift Zone, becoming shallower in the Pu'u 'Ō'ō region and propagating sub‐horizontally in the Middle and Lower East Rift Zone. As much as 30% of the total erupted volume could have originated from the conduit itself. Indeed, the pressure that drove the flow of the magma was low at the end of the eruption. Key Points: Geodetic data show significant deformation of rift zones during eruptionsA physical model of elastic conduit is derived to understand deformation effects on eruption dynamicsThe model is applied to 2018 Kīlauea eruption to invert the parameters of its plumbing system [ABSTRACT FROM AUTHOR]

SUMMARY: Calderas are kilometer-scale basins formed when magma is rapidly removed from shallow magma storage zones. Despite extensive previous research, many questions remain about how host rock material properties influence the development of caldera structures. We employ a mesh-free, continuum numerical method, Smoothed Particle Hydrodynamics (SPH) to study caldera formation, with a focus on the role of host rock material properties. SPH provides several advantages over previous numerical approaches (finite element or discrete element methods), naturally accommodating strain localization and large deformations while employing well-known constitutive models. A continuum elastoplastic constitutive model with a simple Drucker–Prager yield condition can explain many observations from analogue sandbox models of caldera development. For this loading configuration, shear band orientation is primarily controlled by the angle of dilation. Evolving shear band orientation, as commonly observed in analogue experiments, requires a constitutive model where frictional strength and dilatancy decrease with strain, approaching a state of zero volumetric strain rate. This constitutive model also explains recorded loads on the down-going trapdoor in analogue experiments. Our results, combined with theoretical scaling arguments, raise questions about the use of analogue models to study caldera formation. Finally, we apply the model to the 2018 caldera collapse at Kīlauea volcano and conclude that the host rock at Kīlauea must exhibit relatively low dilatancy to explain the inferred near-vertical ring faults. [ABSTRACT FROM AUTHOR]

Temporal variations in lava chemistry at active submarine volcanoes are difficult to decipher due to the challenges of dating their eruptions. Here, we use high-precision measurements of 226Ra-230Th disequilibria in basalts from Kama‘ehuakanaloa (formerly Lō‘ihi) to estimate model ages for recent eruptions of this submarine Hawaiian pre-shield volcano. The ages range from ca. 0 to 2300 yr (excluding two much older samples) with at least five eruptions in the past ∼150 yr. Two snapshots of the magmatic evolution of Kama‘ehuakanaloa (or “Kama‘ehu”) are revealed. First, a long-term transition from alkalic to tholeiitic volcanism was nearly complete by ca. 2 ka. Second, a systematic short-term fluctuation in ratios of incompatible elements (e.g., Th/Yb) for summit lavas occurred on a time scale of ∼1200 yr. This is much longer than the ∼200-yr-long historical cycle in lava chemistry at the neighboring subaerial volcano, Kīlauea. The slower pace of the variation in lava chemistry at Kama‘ehu is most likely controlled by sluggish mantle upwelling on the margin of the Hawaiian plume. [ABSTRACT FROM AUTHOR]

The search for pre‐eruptive observables that can be used for short‐term volcanic forecast remains a scientific challenge. Pre‐eruptive patterns in seismic data are usually identified by analyzing seismic catalogs (e.g., the number and types of recorded seismic events), the evolution of seismic energy, or changes in the tensional state of the volcanic medium as a consequence of changes in the volume of the volcano. However, although successful volcanic predictions have been achieved, there is still no generally valid model suitable for a large range of eruptive scenarios. In this study, we evaluate the potential use of Shannon entropy as short‐term volcanic eruption forecasting extracted from seismic signals at five well studied volcanoes (Etna, Mount St. Helens, Kilauea, Augustine, and Bezymianny). We identified temporal patterns that can be monitored as short‐term eruptive precursors. We quantified the decay of Shannon entropy prior to eruptions, noting that changes appear between 4 days and 12 hr before. When Shannon entropy is combined with the temporal evolution of other features (i.e., energy, kurtosis, and the frequency index), we can elaborate physical models according to the occurring volcanic processes. Our results show that pre‐eruptive variation in Shannon entropy is a confident short‐term volcanic eruption monitoring tool. Plain Language Summary: Volcanic eruptions represent a major natural hazard. Despite decades of research, the forecasting of volcanic eruptions remains a scientific challenge. Subsurface volcanic processes generate seismic waves, which can be measured at the surface using seismometers. To date, the most successful examples of eruption forecasting have been based on seismic data. However, we still lack a early warning model that can be applied across the wide range of eruption styles seen around the world. In this study, we implemented a new approach for the analysis of seismo‐volcanic data aimed at warning eruptions. We used advanced signal processing algorithms to analyze continuous seismic signals from a suite of well‐studied volcanoes (Mount St. Helens, Mt. Etna, Kilauea, Augustine, and Bezymianny) in order to create a new database of features found within the seismic signals. We found that pre‐eruptive variation in the Shannon entropy (a statistical parameter associated to the coherence of the seismic sources) of seismic signals offers a successfully feature for short‐term volcanic eruption alert. The relationship between pre‐eruptive seismic signals and Shannon entropy is based on changes in the probability distributions of the type of seismic waves, independent of the signal source. Key Points: While successful volcanic forecasting has been achieved, there is no generally valid model suitable for large range of eruptive scenariosWe used feature extraction to analyze seismic data from five well studied volcanoes to identify short‐term eruptive precursorsShannon entropy has a uniform temporal pattern of pre‐eruptive change and is a recurrent and transferable feature [ABSTRACT FROM AUTHOR]

Data collected during well-observed eruptions can lead to dramatic increases in our understanding of volcanic processes. However, the necessary prioritization of public safety and hazard mitigation during a crisis means that scientific opportunities may be sacrificed. Thus, maximizing the scientific gains from eruptions requires improved planning and coordinating science activities among governmental organizations and academia before and during volcanic eruptions. One tool to facilitate this coordination is a Scientific Advisory Committee (SAC). In the USA, the Community Network for Volcanic Eruption Response (CONVERSE) has been developing and testing this concept during workshops and scenario-based activities. The December 2020 eruption of Kīlauea volcano, Hawaii, provided an opportunity to test and refine this model in real-time and in a real-world setting. We present here the working model of a SAC developed during this eruption. Successes of the Kīlauea SAC (K-SAC) included broadening the pool of scientists involved in eruption response and developing and codifying procedures that may form the basis of operation for future SACs. Challenges encountered by the K-SAC included a process of review and facilitation of research proposals that was too slow to include outside participation in the early parts of the eruption and a decision process that fell on a small number of individuals at the responding volcano observatory. Possible ways to address these challenges include (1) supporting community-building activities between eruptions that make connections among scientists within and outside formal observatories, (2) identifying key science questions and pre-planning science activities, which would facilitate more rapid implementation across a broader scientific group, and (3) continued dialog among observatory scientists, emergency responders, and non-observatory scientists about the role of SACs. The SAC model holds promise to become an integral part of future efforts, leading in the short and longer term to more effective hazard response and greater scientific discovery and understanding. [ABSTRACT FROM AUTHOR]

Micromagnetic Tomography (MMT) is a new technique that allows the determination of magnetic moments of individual grains in volcanic rocks. Current MMT studies either showed that it is possible to obtain magnetic moments of relatively small numbers of grains in ideal sample material or provided important theoretical advances in MMT inversion theory and/or its statistical framework. Here, we present a large‐scale application of MMT on a sample from the 1907‐flow from Hawaii's Kilauea volcano producing magnetic moments of 1,646 grains. We produced 261,305 magnetic moments in total for these 1,646 grains, an increase of three orders of magnitude compared to earlier studies to assess the robustness of the MMT results, and a major step toward the number of grains that is necessary for paleomagnetic applications of MMT. Furthermore, we show that the recently proposed signal strength ratio is a powerful tool to scrutinize and select MMT results. Despite this progress, still only relatively large iron‐oxide grains with diameters >1.5–2 μm can be reliably resolved, impeding a reliable paleomagnetic interpretation. To determine the magnetic moments of smaller (<1 μm) grains that may exhibit pseudo‐single domain behavior and are therefore better paleomagnetic recorders, the resolution of the microcomputed tomography and magnetic scans necessary for MMT must be improved. Therefore, it is necessary to reduce the sample size in future MMT studies. Nevertheless, our study is an important step toward making MMT a useful paleomagnetic and rock‐magnetic technique. Plain Language Summary: The magnetic information of volcanic rocks is an invaluable archive of the behavior of the Earth's magnetic field through time. Recently, a new technique, Micromagnetic Tomography, was proposed that promises to determine the magnetic signals of individual iron‐bearing grains in these rocks. This would greatly improve our ability to obtain and interpret the magnetic information stored in them. Here, we go beyond the proof‐of‐concept of this exciting new technique and show that it is indeed possible to obtain statistically robust results for a set of rather large grains, with diameters >1.5–2 μm, in a sample from the 1907‐flow from Hawaii's Kilauea volcano. Key Points: We studied a sample from the 1907‐flow of Kilauea (Hawaii) with well‐known rock‐magnetic properties using Micromagnetic Tomography (MMT)We performed 16,874 MMT inversions to characterize the magnetic moments of 1,646 grains, resulting in 261,305 magnetic momentsMagnetic moments were found only for grains >1.5–2 μm that exhibit multidomain behavior, but these MMT results are statistically robust [ABSTRACT FROM AUTHOR]

The mechanisms that led to the exceptionally large Kīlauea 2018 eruption are still poorly understood and actively debated. External processes such as rainfall events or flank sliding have been proposed to play a triggering role. Here, we present field, geophysical, and petrological observations to show that internal changes within the magmatic plumbing system most likely led to the eruption. Chemical zoning in olivine crystals records the intrusion of primitive magma that is concurrent with deep seismicity and inflation at the volcano's summit. Magma replenishment and pressurization of the summit reservoirs already started around 2014 and accelerated towards the eruption. Kīlauea volcano was therefore primed to experience a shift in eruptive activity in 2018. This pressure increase associated with reservoir replenishment may have been sufficient to overcome a previously blocked conduit. These findings imply that precursory signs of years of protracted magma intrusion and pressurization of the system may be recognizable in the future, which could lead to improved hazards mitigation. [ABSTRACT FROM AUTHOR]

On 20 December 2020, after more than 2 years of quiescence at Kīlauea Volcano, Hawaiʻi, renewed volcanic activity in the summit crater caused boiling of the water lake over a period of ∼90 min. The resulting water‐rich, electrified plume rose to 11–13 km above sea level, which is among the highest plumes on record for Kīlauea. Although conventional models would infer a high mass flux from explosive magma‐water interaction, the plume was not associated with an infrasound signal indicative of "explosive" activity, nor did it produce a measurable ash‐fall deposit. We use multisensor data to characterize lava‐water interaction and plume generation during this opening phase of the 2020–21 eruption. Satellite, weather radar, and eyewitness observations revealed that the plume was rich in water vapor and hydrometeors but transported less ash than expected from its maximum height. Volcanic lightning flashes detected by ground‐based cameras were confined to freezing altitudes of the upper cloud, suggesting that the ice formation drove the electrification of this plume. The low acoustic energy from lava‐water interaction points to a weakly explosive style of hydrovolcanism. Heat transfer calculations show that the lava to water heat flux was sufficient to boil the lake within 90 min. Limited mixing of lava and water inhibited major steam explosions and fine fragmentation. Results from one‐dimensional plume modeling suggest that the models may underpredict plume height due to overestimation of crosswind air‐entrainment. Our findings shed light on an unusual style of volcanism in which weakly explosive lava‐water interaction generated an outsized plume. Plain Language Summary: On 20 December 2020, after more than 2 years without an eruption at Kīlauea Volcano, lava erupted through the debris along the summit crater wall and flowed downslope into a hot, acidic water lake. The lava quickly heated and boiled the water, generating a volcanic cloud or plume that reached 11–13 km above sea level, among the highest plumes on record for Kīlauea. After 90 min, the lake had boiled away, leaving behind a new, growing lava lake. In this study, we investigated the processes that occurred during the interaction between the lava and the water lake and the tall plume that developed. Based on observations from weather radar, eyewitnesses, camera footage, acoustic measurements, and numerical modeling, we show the following: (a) interaction between the lava and water did not cause explosions, (b) the plume contained very little ash but carried abundant water vapor that formed ice at higher altitudes, which created lightning, and (c) heat transfer from lava to the water caused the plume to rise much higher than expected for an ash‐poor eruption. Key Points: Weakly explosive water‐lava interaction boiled Kīlauea's summit crater lake in 90 min and created an 11–13 km high, ash‐poor plumeThe water‐rich plume produced multiple lightning flashes generated by hydrometeor charging microphysicsLava supplied heat to the plume via boiling without contributing mass, which led to a taller plume than expected [ABSTRACT FROM AUTHOR]

Liu et al. (2022, https://doi.org/10.1029/2021GL093691) used Rayleigh waves extracted from the cross‐correlation of ambient noise recorded by two stations to monitor the seismic velocity variations associated with the 2018 Kı̄lauea eruption. However, their study ignored the fact that the tremors on the Island of Hawai'i were dominated by a source at the Kı̄lauea summit before the eruption. Close inspection of the waveforms of the station pair PAUD‐STCD shows a simple, mistakenly identified wave traveling direction in Liu et al. (2022, https://doi.org/10.1029/2021GL093691). A correct wave traveling direction agrees with the noise source model, where the dominant tremor source should be at the Kı̄lauea summit. Because of the drastic change in the tremor source after the eruption, the cross‐correlation of the tremor records may reflect predominantly changes in the source rather than in the medium properties between the two stations. Plain Language Summary: More and more studies are using seismic records to understand the volcano eruption process. A very recent study monitored the dyke intrusion near the Pu'u'ō'ō right after the start of the 2018 Kı̄lauea eruption, by observing increased seismic wave arrival times. However, after re‐inspecting the data, we find their study understood the source location emitting the seismic waves wrong. Thus, their observed increased seismic wave arrival times can no longer be explained by the proposed dyke intrusion in the rift zone. We further suspect that the temporal variations of the seismic source contributed greatly to the arrival time variations. Key Points: The tremor signals appeared on the ambient noise cross‐correlation functions (CCFs) should be from the Kı̄lauea summit, not Pu'u'ō'ōThe tremor sources changed after the beginning of the eruptionThe apparent temporal variations of the CCFs related to the tremors reflected the change of noise source rather than medium velocity [ABSTRACT FROM AUTHOR]

Recharges of magma underneath basaltic volcanoes can occur as precursory events prior to an eruption but are not always revealed in geophysical data streams or erupted lavas compositions. In contrast, phosphorus within primitive, Mg‐rich (Fo89‐90), olivine can preserve recharge information lost by the mixed melt. Evidence of rapid growth and dissolution are preserved only in phosphorus X‐ray intensity maps, which reveal that Mg‐rich olivine from eruptions occurring between 2008 and 2020 at Kīlauea Volcano (Hawaiʻi) experienced at least two episodes of magma intrusion. We develop numerical diffusion models that evaluate the fidelity of the Fe‐Mg compositional archive by quantifying three factors that influence Fo population distributions: (a) the frequency at which an Mg‐rich basaltic liquid (in equilibrium with Fo90 olivine) intrudes the reservoir, (b) the pre‐existence of a polymodal distribution of olivine crystal sizes and their shapes (c) the effects of sectioning on apparent olivine core compositions. We find that most crystals lose their initial Mg‐rich composition if they are held at temperatures relevant to summit magma storage conditions (1,160–1,190°C) for more than 10 years. Thus, previous assertions that Mg‐rich olivine crystals at Kīlauea are scavenged from centuries‐old stored magmas are unrealistic. Our method permits critical evaluation of contrasting explanations of heterogeneous Fe‐Mg contents of olivine cargo: (a) different total durations of mush storage with partial diffusive erasure of compositional traits, or (b) coexistence of multiple chemically distinct magmas. Our approach provides general guidance for the conservative interpretation of temporal information preserved within olivine Fe‐Mg compositional archives. Plain Language Summary: Geochemical characterization of olivine crystals is a valuable petrological tool that provides clues into the composition of primitive (Mg‐rich) basaltic melts. Olivine from three recent Kīlauea eruptions (2008 and 2020 Halemaʻumaʻu lava lake at the Kīlauea summit, 2018 lower East Rift Zone) are analyzed for their iron (Fe), magnesium (Mg) and phosphorus (P) compositions. Analyzing concentration changes in slow diffusing elements like P in olivine and in fast diffusing elements like Fe‐Mg helps to understand growth, dissolution, and diffusive re‐equilibration cycles in the crystals. These cycles are inferred to have been caused by magma intrusions for all three eruptions. Then, we develop an interpretative framework that incorporates the disparate patterns of chemical heterogeneity revealed in the chemical maps of sectioned olivine crystals. Using numerical diffusion models, we evaluate how the frequency of Mg‐rich primitive intrusions, the size of the olivine crystals, and crystal sectioning affect the Fe‐Mg content within a given olivine population. We show that the variable compositions of olivine crystals erupted in Kīlauea lavas cannot result from remobilization of century‐old crystal mush. Key Points: Olivine crystals from three recent Kīlauea eruptions have sharp truncations in phosphorus zoning that mark olivine dissolution event(s)Dissolution‐recrystallization of high‐Fo olivine at Kīlauea can occur in less than a yearFo contents in Kīlauea olivine crystals reflects either a high frequency of magma recharges (>10 events/y) or short diffusion times (<5 years) [ABSTRACT FROM AUTHOR]

Complex crystal cargo in basaltic eruptions has the potential to yield diverse insights on pre- and syn-eruptive timescales of magma storage and transport. Research on eruption products from the 1959 eruption from Kīlauea Iki Crater at Kīlauea volcano (Hawai'i) demonstrates that time-series samples collected during an eruption can yield a wealth of information not accessible by studying the fall deposit alone. Major element zoning in olivine crystals illustrates four environments of magma storage that were variably mixed and progressively involved in the eruption. Diffusion timescales retrieved from crystals < 1 mm in size are typically much shorter than those from crystals > 1 mm, illustrating the additional complexity of information recorded by different grain sizes and olivine populations. The timescales can be divided into two groups: (1) t > 100 days reflect longer-term magma recharge into Kīlauea's deep (8–10 km) reservoir system and (2) t < 100 days broadly correspond to a period of unrest and inflation beginning ~ 3 months prior to eruption. Some timescales reflect syn-eruptive processes, where diffusion began after the eruption onset. Progressive changes in zoning populations in the time-series scoriae samples illustrate how quickly diffusive re-equilibration can erase older magmatic histories and information and underscores that studies on fall deposits can lead to an incomplete record of magmatic processes. Thus, diffusion timescales from fall deposits alone should be cautiously interpreted with the caveat that they may be missing a substantial part of the total eruptive event and, therefore, the record of magmatic histories inferred from crystal cargo. [ABSTRACT FROM AUTHOR]

The intrusion of magma into Kīlauea's lower East Rift Zone in May 2018 led to the largest eruption along this segment of the volcano in over 200 years. As magma drained from the rift zone, leading to the collapse of Pu'u 'Ō'ō, pressure at the summit initially remained elevated and dropped at a slower rate compared to historical intrusion events. The anomalously long timescale of summit deflation suggests that the dike was fed from multiple sources. Here we show that dikes can serve as "dipsticks" of magma reservoirs and that the co‐evolution of dike growth and reservoir deflation constrains key magma transport parameters. Using coupled dike‐chamber models constrained by ground deformation and seismicity, we test four configurations of magma plumbing in order to illuminate which reservoirs and transport pathways were activated during the intrusion phase (30 April to 3 May) of the 2018 event. Slow summit deflation relative to the rate of dike propagation is best explained by a model in which the dike initiates from a compressible magma reservoir in the East Rift Zone, which then drains magma upstream from the Halema'uma'u reservoir through a shallow transport system. We use a Bayesian Markov chain Monte Carlo (MCMC) approach to estimate storage parameters for both reservoirs as well as the effective conductivity of the shallow magma transport system in the East Rift Zone, finding good agreement with independent estimates. Our results suggest that the rupture of reservoirs from within the East Rift Zone presents a unique hazard at Kīlauea. Plain Language Summary: We investigate early phases of the 2018 unrest at Kīlauea Volcano, Hawai'i. Between 30 April and 3 May, small earthquakes accompanied magma movement through the lower East Rift Zone (LERZ). At the same time, the ground surface at the summit and the lava lake within the Halema'uma'u crater began to drop, indicating that magma was being withdrawn from the shallow summit reservoir. If the shallow summit reservoir were the only source of magma for the LERZ intrusion, we would expect the timescales of magma intrusion into the LERZ and out of the summit region to be similar. However, the rate of ground subsidence at the summit is anomalously slow given the rate of magma movement through the rift zone. We propose that an additional source of magma fed the intrusion, and we test physics‐based models for the growth of a dike fed by multiple magma chambers. By comparing the model output to data, we constrain the additional source of magma to be a large and/or compressible reservoir within the East Rift Zone. We estimate how easily magma can flow through the shallow East Rift Zone. Our work highlights the hazard posed by magma stored within the flanks of the volcano. Key Points: Deflation of Kīlauea's summit was anomalously slow during the intrusion of magma into the lower East Rift Zone in 2018Dynamic models suggest the dike broke out from a shallow East Rift Zone reservoir, buffering pressure upstream in the Halema'uma'u reservoirTemporal evolution of dike growth and summit deflation constrain magma conductivity through a shallow East Rift Zone transport pathway [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 short‐range impacts of volcanic aerosols from the eruption of the Kilauea volcano on the genesis of tropical cyclone (TC) Wukong in 2018 are investigated by numerical simulations, as distinct from the studies on the aerosol climate effects. The aerosol−radiation and aerosol−cloud effects are isolated through sensitivity experiments. For the aerosol−radiation effect, the radiative cooling at the low levels and heating above by aerosols southeast of Wukong's periphery induce stable sinking and decrease latent heating in the environment far from the storm center. Therefore, the sea‐level pressure increases there, enhancing low‐level radial inflow to the storm, inner‐core convection and the release of latent heat, which is conducive to TC genesis. For the aerosol−cloud effect, volcanic aerosols in storm circulation can be converted into cloud condensation nuclei, invigorating inner‐core convection, and subsequently favoring TC genesis. However, the nonlinear effect resulting from the interaction between aerosol−radiation and aerosol−cloud effects is not conducive to TC genesis, because it weakens the aerosol−cloud effect through the deposition of aerosols and also limits the aerosol−radiation effect through the increasing of peripheral convection. Plain Language Summary: The role of sulfate aerosols released by volcanic eruptions in climatological tropical cyclone (TC) activities over different basins or hemispheres remains uncertain. These aerosols, composed of either solid or liquid particles, not only change the heating or cooling of atmosphere by scattering and absorbing sunlight, but also participate in cloud formation and evolution by conversion into nuclei of cloud droplets. Impacts of aerosol−radiation and aerosol−cloud interaction on a TC formation process during a volcanic eruption still lacks of detailed study for real cases. We investigate whether these effects of aerosols from the Kilauea volcanic eruption were beneficial or not to the formation of TC Wukong in 2018. The aerosol−radiation effect enhances cooling at the low levels of Wukong's environment and increases the sea‐level pressure there, which drives air to flow inward and is beneficial to TC genesis. On the other hand, lots of aerosols ingested into the storm invigorates the convection near the storm center, is also helpful. Instead, the interaction between the above two effects offset partly their own positive contributions to TC genesis. Our findings suggest that considering the interaction of volcanic aerosol−cloud−radiation is necessary to improve our understanding and prediction of TC activities. Key Points: Enhanced radiative cooling at low layer of Wukong's periphery induced by aerosols from Kilauea volcanic eruption advanced its genesisMicrophysical effect of the aerosols partly entering into Wukong's inner core invigorated convection so as to favor its genesisThe nonlinear interaction between the aerosol−radiation and the aerosol−cloud effects contributed negatively to Wukong's genesis [ABSTRACT FROM AUTHOR]

The contrasting dynamics between Mauna Loa and Kīlauea have been studied over the last 100 years from multiple viewpoints. The fact that dynamic changes of one volcano trigger a dynamic response of the other volcano indicates a connection may exist. Petrological works show a direct relationship between the magmatic systems of these two volcanoes is not possible. We analysed DInSAR data and GPS measurements of ground deformation patterns associated with the activity of Mauna Loa and Kīlauea volcanoes. The DInSAR SBAS dataset spans the interval between 2003 and 2010, and was acquired along ascending and descending orbits of the ENVISAT (ESA) satellite under different look angles. Of the 10 tracks that cover the Big Island (Hawai'i), 4 cover both volcanic edifices. Using GPS measurements, we computed the areal strain on 15 triplets of stations for Kīlauea volcano and 11 for Mauna Loa volcano. DInSAR data was analysed by applying Independent Component Analysis (ICA) to decompose the time-varying ground deformation pattern of both volcanoes. The results revealed anticorrelated ground deformation behaviour of the main calderas of Mauna Loa and Kīlauea, meaning that the opposite response is seen in the ground deformation of one volcano with respect to the other. At the same time, Kīlauea exhibits a more complex pattern, with an additional component, which appears not to be correlated with the dynamics of Mauna Loa. The GPS areal strain time series support these findings. To corroborate and help interpret the results, we performed inverse modelling of the observed ground deformation pattern using analytical source models. The results indicate that the ground deformation of Mauna Loa is associated with a dike-shaped source located at 6.2 km depth. In comparison, the anticorrelated ground deformation of Kīlauea is associated with a volumetric source at 1.2 km depth. This excludes a hydraulic connection as a possible mechanism to explain the anticorrelated behaviour; instead, we postulate a stress-transfer mechanism. To support this hypothesis, we performed a 3D numerical modelling of stress and strain fields in the study area, determining the elastic interaction of each source over the others. The most relevant finding is that the Mauna Loa shallow plumbing system can affect the shallowest magmatic reservoir of Kīlauea, while the opposite scenario is unlikely. Conversely, the second independent component observed at Kīlauea is associated to a sill-shaped source located at a depth of 3.5 km, which is less affected by this interaction process. [ABSTRACT FROM AUTHOR]

The Advanced Himawari Imager (AHI) and Advanced Baseline Imager (ABI), respectively aboard Himawari-8 and GOES-R geostationary satellites, are two important instruments for the near-real time monitoring of active volcanoes in the Eastern Asia/Western Pacific region and the Pacific Ring of Fire. In this work, we use for the first time AHI and ABI data, at 10 min temporal resolution, to assess the behavior of a Normalized Hotspot Index (NHI) in presence of active lava flows/lakes, at Krakatau (Indonesia), Ambrym (Vanuatu) and Kilauea (HI, USA) volcanoes. Results show that the index, which is used operationally to map hot targets through the Multispectral Instrument (MSI) and the Operational Land Imager (OLI), is sensitive to high-temperature features even when short-wave infrared (SWIR) data at 2 km spatial resolution are analyzed. On the other hand, thresholds should be tailored to those data to better discriminate thermal anomalies from the background in daylight conditions. In this context, the multi-temporal analysis of NHI may enable an efficient identification of high-temperature targets without using fixed thresholds. This approach could be exported to SWIR data from the Flexible Combined Imager (FCI) instrument aboard the next Meteosat Third Generation (MTG) satellites. [ABSTRACT FROM AUTHOR]

This study examines household preparedness for volcanic eruptions of Kīlauea and Mauna Loa in Hawai'i. Specifically, correlation and regression analyses were conducted to test which variables (i.e., demographics, risk perception, hazard intrusiveness, affective response, hazard agent characteristics, risk area, and community bondedness) have significant effects on two measures of hazard adjustment (i.e., household emergency preparedness and perceived stakeholder preparedness). Regression results showed that community bondedness, household income (i.e., one of the demographics), and risk area predicted household emergency preparedness. In addition, community bondedness and risk area predicted perceived stakeholder preparedness. These results indicate that future research should include more detailed examinations of people's hazard adjustments, the psychological reactions that motivate those hazard adjustments, and the antecedents of those psychological reactions. Finally, the data revealed that Kīlauea and Mauna Loa respondents had, on average, low levels of risk perception and hazard intrusiveness, so it is important for local emergency managers to increase residents' volcano hazard awareness and preparedness for future volcanic threats. [ABSTRACT FROM AUTHOR]

The initial melts erupted by a Hawaiian volcano have a range of alkalic compositions but are rarely observed as they are covered by enormous volumes of shield stage tholeiites. A remarkable record of the early evolution of Hawaiian volcanoes, however, is preserved by a volcanic sandstone dredged from the submarine flank of Kilauea, which contains a suite of petrogenetically related pre-shield basanite to nephelinite glasses. Here we show that the systematic variation in the rare earth element (REE) patterns of these samples requires the fractional crystallisation of garnet. A fractionating assemblage of Ca-rich garnet (32%), omphacitic clinopyroxene (63%), and minor phlogopite can explain the variation in the major and trace element contents of the suite. The results suggest fractional crystallisation of eclogite from a primitive Hawaiian melt near the base of the lithosphere (>90 km) and that a deep magma chamber is the first stage in the development of a Hawaiian volcano. Rare glasses of earliest melts produced by a Hawaiian volcano can only have formed by the crystallisation of garnet implying a magma chamber near the base of the lithosphere [ABSTRACT FROM AUTHOR]

Monitoring of active volcanic systems is a challenging task due in part to the trade‐offs between collection of high‐quality data from multiple techniques and the high costs of acquiring such data. Here we show that magnetic data can be used to monitor volcanoes by producing similar data to gravimetric techniques at significantly lower cost. The premise of this technique is that magma and wall rock above the Curie temperature are magnetically "transparent," but not stationary within the crust. Subsurface movements of magma can affect the crustal magnetic field measured at the surface. We construct highly simplified magnetic models of four volcanic systems: Mount Saint Helens (1980), Axial Seamount (2015–2020), Kīlauea (2018), and Bárðarbunga (2014). In all cases, observed or inferred changes to the magmatic system would have been detectable by modern magnetometers. Magnetic monitoring could become common practice at many volcanoes, particularly in developing nations with high volcanic risk. Plain Language Summary: Scientists monitor volcanoes and try to predict volcanic eruptions using a variety of techniques. In this study, we show how a relatively inexpensive magnetometer can be used to monitor volcanoes by tracking magma movement below the surface. Rocks produce a magnetic signal that can be measured using a magnetometer, but magma produces no magnetic signal. We construct magnetic models showing that when magma migrates below the surface, it affects the magnetic field because it is displacing or melting the rocks. The volcanoes that we model are Mount St. Helens (pre‐1980 eruption), Axial Seamount (from 2015 to 2020), Kīlauea, Hawaii (pre‐2018 eruption), and Bárðarbunga (pre‐2014 eruption). Magnetic volcano monitoring may become standard practice at many volcanoes, particularly in developing nations with low monitoring budgets but high volcanic risk. Key Points: Magnetic models of four volcanic systems are presented, showing that movement of magma produces measurable magnetic signalsMagnetic data can be used for low‐cost volcano monitoring in a wide variety of settings and environmental conditionsThis monitoring technique has several advantages over existing methods, but consistent workflows and best‐practices need to be developed [ABSTRACT FROM AUTHOR]

Results from nine microgravity campaigns from Kı̄lauea, Hawaiʻi, spanning most of the volcano's 2008–2018 summit eruption, indicate persistent mass accumulation at shallow levels. A weighted least squares approach is used to recover microgravity results from a network of benchmarks around Kı̄lauea's summit, eliminate instrumental drift, and restore suspected data tares. A total mass of 1.9 × 1011 kg was determined from these microgravity campaigns to have accumulated below Kı̄lauea Caldera during 2009–2015 at an estimated depth of 1.3 km below sea level. Only a fraction of this mass is reflected in surface deformation, and this is consistent with previously reported discrepancies between subsurface mass accumulation and observed surface deformation. The discrepancy, amongst other independent evidence from gas emissions, seismicity, and continuous gravimetry, indicate densification of magma in the reservoirs below the volcano summit. This densification may have been driven by degassing through the summit vent. It is hypothesized that during the final years of the summit eruption, magma densification resulted in a buildup of pressure in the reservoirs that may have contributed to the lower East Rift Zone outbreak of 2018. The observed mass accumulation beneath Kı̄lauea could not have been detected through other techniques and illustrates the importance of microgravity measurements in volcano monitoring. Plain Language Summary: Kı̄lauea, Hawaiʻi, is one of the best known shield volcanoes in the world. In 2008, a summit eruption began and lasted for over a decade, ending with an outbreak in 2018 from the volcano's lower East Rift Zone (ERZ) that destroyed hundreds of homes. Over the course of the 2008–2018 summit eruption, nine microgravity campaigns were completed around the volcano's caldera. These campaign measurements provide unique insight into mass changes below the surface of the volcano that would not have been detected otherwise. The results show that during 2009–2015, mass was steadily accumulating in the magma reservoirs below Kı̄lauea's summit. Usually, the accumulation of mass below volcanoes is accompanied by surface inflation, but for Kı̄lauea it was found that the mass increase was much larger than expected for the observed increase in volume, indicating densification of gas‐rich magma in the reservoir. Magma densification may lead to a mass increase without significantly increasing the source volume. The subsequent pressure increase may have contributed to the 2015 summit intrusion and the 2018 lower ERZ eruption. Key Points: Nearly a decade of microgravity campaign data from Kı̄lauea during its 2008–2018 eruption are analyzed using a weighted least squares approachSubsurface mass accumulation between 2009—2015 of order 1.9 × 1011 kg at 1.3 km depth b.s.l. without commensurate surface deformationCompression and densification of gas‐rich magma may have accommodated increased pressurization in the magmatic system [ABSTRACT FROM AUTHOR]

Flowing lava and water have dramatically different physical properties but can form similar hydraulic structures, including undular hydraulic jumps, or standing wave trains. In water flows, undular hydraulic jumps are evidence of critical flow (Froude number ∼1) and open‐channel hydraulic theory provides a powerful tool for estimating flow depth and velocity. Monitoring these parameters in an active lava channel is inherently challenging, but essential for calculating lava discharge (effusion rate), a primary control on the rate of flow front advance and ultimate flow runout distance. We analyze undular hydraulic jumps in both water and lava flows to assess the conditions under which they form and, by extension, the potential use of critical flow theory to estimate, in real time, lava flow velocity, depth, and discharge. Experimental data for water flows show that these structures mark the transition from supercritical to subcritical flow. Undular hydraulic jumps in the near‐vent lava channel of the 2018 lower East Rift Zone eruption of Kīlauea, Hawaiʻi also reflect critical flow conditions; their wavelengths scale with flow depth and velocity, consistent with hydraulic theory. Calculated lava effusion rates are similar to estimates made using more traditional approaches (Jeffreys', 1925, https://doi.org/10.1080/14786442508634662, equation based on lava viscosity, density, and channel slope) and with lava volumes derived from topographic‐change mapping. From this we conclude that critical flow phenomena show great potential to track flow dynamics and inform hazard assessment for a wide range of geophysical fluids. Plain Language Summary: Flowing water and lava have very different physical properties, but under certain flow conditions, each will form arrays of evenly spaced standing waves (wave trains). In water, these are known to form at "critical flow" when there is a specific ratio between flow depth and flow velocity. However, conditions for forming standing wave trains in lava have not been measured. We investigated the relationship between the spacing of waves in a train, and the flow speed and depth, using both data from experiments with water and measurements made during the 2018 lava flow at Kīlauea volcano. We found that waves form in each fluid at the same ratio of flow speed and depth, and that the spacing of waves in a train shows a fixed mathematical relationship to these parameters. There is considerable practical importance to this finding. During a volcanic eruption, direct measurement of flow speed is difficult and dangerous, and depth is impossible, and yet both are needed to predict how far and how fast lava will travel. The critical flow characteristics of lava, and potentially other hazardous flows such as mudflows, allow assessment of flow behavior and potential hazards in real time. Key Points: Undular hydraulic jumps, or standing wave trains, form in both water and active lava at critical flow (Froude number ∼1)Wavelengths scale with flow depth and velocity following hydraulic theory in water flume experiments and Hawaiian lava flow dataApplication to wave trains in active lava flows provides rapid estimates of key flow parameters and effusion rates for hazard assessment [ABSTRACT FROM AUTHOR]

In 2002 and 2003 a collaborative effort was undertaken between Lawrence Berkeley National Laboratory, Sandia National Laboratories, the U.S. Geological Survey (USGS) Menlo Park, the USGS Hawaiian Volcano Observatory, and Electromagnetic Instruments Inc. to study the Kīlauea volcano in Hawaii using the magnetotelluric (MT) technique. The work was motivated by a desire to improve understanding of the magma reservoirs and conduits within Kīlauea and the East and Southwest Rift zones, which has implications for understanding Kīlauea's plumbing system. An improved understanding of the rift zones has implications in understanding large‐scale landslides that are generated in the Hilina Slump, which produce significant impacts on coastal communities. Up to eight stations operated simultaneously, with multiple remote reference sites, and data were processed using multi‐station robust processing techniques. In total, data were acquired at 70 sites over the Southwest and East rift zones. Good to excellent quality data were obtained even in the harshest conditions, such as those encountered on the fresh lava flows of the East Rift Zone, where electrical contact resistances are on the order of 100 kΩ. A three‐dimensional (3D) MT model study was done to guide interpretation of the observed MT measurements. Synthetic modeling demonstrates that conductive bodies in the upper 3 km can be spatially resolved where MT station sampling is good. Resistivity anomalies in the 3D inversions have a high degree of spatial correlation with previously published seismic velocity anomalies beneath Kīlauea. Melt fractions between 0.096 and 0.117 are calculated for the Kīlauea and Puʻuʻōʻō low resistivity anomalies, respectively. Plain Language Summary: Magnetotelluric (MT) data collected on the Island of Hawaiʻi on Kīlauea volcano and its associated rift zones in 2002 and 2003 have been inverted to produce a three‐dimensional resistivity model. The resistivity model is compared to published models of seismic velocity and Vp/Vs ratio derived from earthquake data acquired by the Hawaiian Volcano Observatory. In areas where the velocity models have good data coverage and high sensitivity, such as over the summit magma chamber, the MT derived resistivity, and the seismic derived Vp and Vp/Vs models have a very high degree of spatial correlation. The high correlation between independent models increases the confidence in both models. Melt fractions of 0.096 and 0.117 are calculated from the inverted resistivities for low resistivity anomalies beneath Kīlauea and Puʻuʻōʻō respectively. This work demonstrates that high‐quality MT data can be acquired in the difficult field conditions present on an active volcano and points the way forward for future improved acquisitions. Key Points: Inverted three‐dimensional (3D) resistivity has high spatial correlation with seismic Vp/Vs from Dawson et al. (1999)Melt fractions of 0.096 and 0.117 are predicted for magma bodies beneath Kīlauea and Puʻuʻōʻō respectivelyThe Kīlauea summit magma chamber is well imaged between 0 and −2 km elevations by 3D resistivity [ABSTRACT FROM AUTHOR]

The 2018 eruption of Kīlauea Volcano was a dynamic event involving explosions, collapses, and fountaining at multiple vents spread over tens of kilometers. The permanent infrasound network operated by the USGS Hawaiian Volcano Observatory (HVO) was well prepared to observe the collapse of the summit, and additional deployments permitted infrasound observations during fissuring in the lower East Rift Zone (LERZ). We provide a summary of infrasound observations, including lava lake spattering, collapses, explosions, rockfall, and lava fountaining, using seismicity and tilt at times to help constrain our interpretations. At the summit of Kīlauea Volcano, we document the process of partial caldera collapse and examine a set of "proto-collapse" events that precede the widely observed events but share many of the same qualities as the larger collapses. For the initial twelve collapse events, we compare the timing of collapse onset to other observations and illustrate the repeatable characteristics of the recorded waveforms and infrasound characteristics associated with each episode of caldera collapse. In the LERZ, we match the acoustic signals with visual observations, including fissure migration, explosions near fissures, and littoral explosions. Lastly, we document and discuss the performance of infrasound alarms during the 2018 Kīlauea eruption. In general, alarming became successful in detecting collapse events at the summit of the volcano after tuning and became a key discriminant in the initial determination of collapse events, especially when visual observations were not available. [ABSTRACT FROM AUTHOR]

The period of heightened volcanic and seismic activity at Kīlauea volcano on the island of Hawai'i, USA from late spring through summer 2018 included a remarkable quasi‐periodic sequence of caldera collapse events. From mid‐May to early‐August, 62 collapse events, each releasing the seismic energy equivalent of a Mw 5.0 ± 0.4 earthquake, occurred about every 1–2 days with over 300 M ≥ 2.5 earthquakes between sequential collapses. This region, experiencing very high rates of seismicity and frequent large magnitude events, is a good candidate to apply a regional seismic hazard assessment. Nowcasting is a type of statistical analysis that uses small magnitude events to estimate the occurrence of large magnitude events. This is done utilizing the concept of natural time in which time is counted by small magnitude event occurrences between large magnitude events, not in clock time (days passed). This method has produced a "nowcasted" set of large earthquakes that are in good agreement with the actual cataloged events in prior studies analyzing non‐volcanic regions. Previously applied to tectonic earthquakes and induced seismicity over longer time frames, this is the first test of nowcasting large caldera collapse events in volcanic associated seismicity and on a relatively short time scale. The technique produced limited "success" nowcasting 37 collapse events that agreed with the catalog of actual events. A temporal dependence of successful nowcasting during the sequence was found that may correlate to previously identified and analyzed physical changes in the volcanic system. Key Points: We applied earthquake nowcasting to 37 caldera collapse events, yielding close agreement with the actual recorded set of collapse eventsKīlauea volcano saw a temporal change in the natural time relationship that can be related to changes in the physical systemThis nowcasting method revealed limited success in a volcanic setting compared to prior tectonic earthquake applications [ABSTRACT FROM AUTHOR]

The stabilized channel is a crucial element of an 'a'ā flow system, delivering lava to forward extending zones of dispersed flow. However, the term stable implies that channel geometries, lava properties, and dynamics are invariable. However, just how stable are these in space and time? To answer this question, we constrain the degree of variation for an extremely well-exposed stabilized channel on Kīlauea (Hawai'i), carrying out mapping, facies analyses, and sampling down the entire 5.5-km length of the channel-levee unit. Though active for only 3 days, flow and emplacement dynamics were highly unstable, experiencing both temporal and spatial variation. This resulted in a complex construction history and solidified channel form, where construction comprised three emplacement phases: initial, free-flowing, and late-stage ponded. These three emplacement phases were coupled with variation in underlying substrate, slope, and volume flux. These temporally and spatially varying conditions combined to result in four channel types and geometries (tubed, stable, ponded, and braided); five lava facies (smooth pāhoehoe, rough/spiney, slabby, transitional, and 'a'ā); and four levee types (initial-rubble, surge-fed overflow, pond-fed overflow, and accretionary). Complexity in channel form was reflected in cooling rates that ranged from 6.6 °C km−1 for free-flowing conditions to 17.7 °C km−1 for ponded lava. Likewise, vesicularities ranged from gas-rich (as high as 74% vesicles) to outgassed (as low as 27%). Due to the high degree of variance at this system, we suggest that feeder channel is a better term for this component of a channel-fed 'a'ā lava flow field. This term stresses the role of the channel in feeding zones of dispersed flow and is not a term that implies channel form and flow dynamics are unchanging. Although flow conditions can be complex, flow for some periods can be stable. If depths, widths, temperatures, and crystallinities during phases of below-bank stability can be identified, then the system can be modelled. We show this by fitting down-channel variation in flow properties for stable periods to output of the FLOWGO thermorheological model. In doing this, we provide a dataset that can guide and benchmark models aimed at simulating the dynamics and properties of channel-fed systems. [ABSTRACT FROM AUTHOR]

Cataloguing damage and its correlation with hazard intensity is one of the key components needed to robustly assess future risk and plan for mitigation as it provides important empirical data. Damage assessments following volcanic eruptions have been conducted for buildings and other structures following hazards such as tephra fall, pyroclastic density currents, and lahars. However, there are relatively limited quantitative descriptions of the damage caused by lava flows, despite the number of communities that have been devastated by lava flows in recent decades (e.g., Cumbre Vieja, La Palma, 2021; Nyiragongo, Democratic Republic of Congo, 2002 and 2021; Fogo, Cape Verde, 2014–2015). The 2018 lower East Rift Zone (LERZ) lava flows of Kīlauea volcano, Hawaiʻi, inundated 32.4 km2 of land in the Puna District, including residential properties, infrastructure, and farmland. During and after the eruption, US Geological Survey scientists and collaborators took over 8000 aerial and ground photographs and videos of the eruption processes, deposits, and impacts. This reconnaissance created one of the largest available impact datasets documenting an effusive eruption and provided a unique opportunity to conduct a comprehensive damage assessment. Drawing on this georeferenced dataset, satellite imagery, and 2019 ground-based damage surveys, we assessed the pre-event typology and post-event condition of structures within and adjacent to the area inundated by lava flows during the 2018 LERZ eruption. We created a database of damage: each structure was assigned a newly developed damage state and data quality category value. We assessed 3165 structures within the Puna District and classified 1839 structures (58%) as destroyed, 90 structures (3%) as damaged, and 1236 (39%) as unaffected. We observed a range of damage states, affected by the structural typology and hazard characteristics. Our study reveals that structures may be damaged or destroyed beyond the lava flow margin, due to thermal effects from the lava flow, fire spread, or from exposure to a range of hazards associated with fissure eruptions, such as steam, volcanic gases, or tephra fall. This study provides a major contribution to the currently limited evidence base required to forecast future lava flow impacts and assess risk. [ABSTRACT FROM AUTHOR]

The article offers information related to evolving of magma temperature and summit eruption of Kīlauea Volcano. It discusses a framework for inferring subsurface magma dynamics associated with prolonged eruptions in near real time that synthesizes petrologic and geophysical volcano monitoring approaches.

Volcano monitoring, eruption response, and hazard assessment at volcanoes in the United States of America (US) fall under the mandate of five regional volcano observatories covering 161 active volcanoes. Working in a wide range of volcanic and geographic settings, US observatories must learn from and apply new knowledge and techniques to a great variety of scientific and hazard communication problems in volcanology. Over the past decade, experience during volcanic crises, such as the landmark 2018 eruption of Kīlauea, Hawaiʻi, has combined with investments and advances in research and technology, and the changing needs of partner agencies and the public, to transform the operations, science, and communication programs of US volcano observatories. Scientific and operational lessons from the past decade now guide new research and growing inter-observatory and external communication networks to meet new challenges and improve detection, forecasting, and response to volcanic eruptions in the US and around the world. [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]

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]

Inflationary deformation and very long period (VLP) earthquakes frequently accompany basaltic caldera collapses, yet current interpretations do not reflect physically consistent mechanisms. We present a lumped parameter model accounting for caldera block/magma momentum change, magma chamber pressurization, and ring fault (assumed vertical) shear stress drop. Pressurization of the underlying magma chamber is represented by a tri‐axial expansion source, and the combined caldera block/magma momentum change by a vertical single force. The model is applied to Kīlauea 2018 caldera collapse events, accurately predicting near field static/dynamic ground motions. In addition to the tri‐axial expansion source, the single force contributes significantly to the VLP waveforms. For an average collapse event with fully developed ring fault, Bayesian inversion constrains ring fault stress drop to ∼0.4 MPa and the pressure increase to ∼1.9 MPa. That the predictions fit both geodetic and seismic observations confirms that the model captures the dominant caldera collapse mechanisms. Plain Language Summary: Episodic caldera collapses at basaltic volcanoes can be hazardous, and forecasting them requires physically consistent interpretations of geophysical observations. We use a physics‐based approach to explain caldera collapse induced ground motions, such as during the 2018 collapse of Kīlauea. We show that, the most fundamental physical mechanisms of caldera collapse involve a pressure increase in the underlying magma chamber, due to rapid reduction of its volume, and a time‐varying force, due to the acceleration of caldera block/magma. The physics‐based model will allow for more accurate interpretations of seismic data collected from less well monitored caldera collapses. Key Points: Caldera block/magma momentum change and chamber pressurization parsimoniously explain co‐collapse inflation and very long period eventsCoupled tri‐axial expansion source and vertical single force arise in the point source limit, contributing to very long period waveformsInversion constrains co‐collapse shear strength drop, pressurization, and mass of caldera block/magma during Kīlauea's 2018 events [ABSTRACT FROM AUTHOR]