Abstract Monitoring volcanic activity requires sensitive tools capable of detecting subtle subsurface changes across eruptive cycles. While seismic methods are widely used to study volcanic unrest, few provide continuous tracking throughout eruptive stages with clearly interpretable signals. We present a geometric phase sensing approach, rooted in topological acoustics, that encodes the intrinsic geometry of the seismic wavefield. By integrating signals across a station array, the geometric phase change (Δ η ) captures wavepath-integrated medium perturbations, providing a stable measure of evolving subsurface conditions distinct from conventional waveform coherence metrics. Applied to Kı̄lauea volcano, Δ η closely tracks precursory magmatic pressurization and co-eruptive caldera collapse during the 2018 eruption, identifies two major intrusion events and post-eruptive recovery spanning five eruptions from 2020 to 2024. Δ η exhibits systematic and interpretable signatures of eruptive transitions, even under strongly perturbed ambient noise conditions. Numerical simulations corroborate these observations, indicating a sensitivity of ~15.0% per MPa to subsurface pressure changes. By leveraging geometric phase approach, we establish a monitoring framework applicable to volcanic and other dynamic Earth systems.

Due to their rarity, large-magnitude hazards are often ignored in disaster risk analysis, leaving societies with unmitigated exposure and limited preparedness. Volcanic eruptions of Volcanic Explosivity Index (VEI) 7 magnitude occur once or twice per millennium, with the last in 1815. Due to increasing populations and interdependent infrastructure, such an event happening today would be catastrophic. Assessing exposure is challenging due to the lack of past event data, limiting hazard modelling potential. We have developed a framework to assess exposure of populations, buildings, infrastructure, and cropland to VEI 7 eruptions. We assessed exposure within 100 km of 136 VEI 7 potential volcanoes, the likely extent of caldera collapse and pyroclastic density currents. We find that approximately 312 million people live within 100 km of these volcanoes. Laguna Caldera, Taal, and Wilis have the highest exposures. For tephra fall, we quantified exposure within isopach footprints from five past VEI 7 eruptions, and rotated these around the volcano to account for wind-direction variability. Among case studies, Ilopango has the highest exposure in the direction of current and future wind direction, with 115 million people, 3.2 million buildings, ~4,000 km 2 cropland exposed. Our results show that exposure is highly sensitive to wind direction and highlight the scale of potential exposure. These findings can help prioritise preparation for catastrophic eruptions by integrating VEI 7 scenarios into disaster risk analysis. • Approximately 312 million people live within 100 km of 136 volcanoes with potential for VEI 7 eruptions. • Laguna Caldera, Taal, and Wilis volcanoes rank highest in combined population, infrastructure, and cropland exposure. • Exposure to tephra fall is sensitive to wind direction.

Caldera volcano systems in compressional tectonic settings exhibit complex deformation histories shaped by the interaction between magmatic and tectonic processes. This study presents a series of analogue experiments designed to investigate how tectonic shortening induced from regional compression, represented by a fold-and-thrust belt (FTB), interacts with caldera collapse structures. Two experimental scenarios were tested: (1) collapse followed by regional compression and (2) regional compression preceding collapse. Regional shortening after collapse yielded elliptical collapse structures with a thrust-parallel elongation of the caldera outline. The models further indicate that advancing thrusts can locally reactivate suitably orientated sections of collapse-related ring-faults at the thrust front. Conversely, collapse after regional shortening did not involve significant reactivation of pre-existing thrust faults, because their low dip angles render them sub-optimally orientated for reactivation. On the other hand, models show that a thrust-related thickening of the magma reservoir roof can inhibit ring-fault localisation and propagation and can potentially lead to a thrust-perpendicular elongation of the caldera outline. Comparisons with natural calderas in the Central Andes (e.g., Jorquera, Bellavista, Puquios and Diamante calderas) and in Japan (Akaigawa caldera) reveal similar aspect ratios and structural trends, supporting the wider relevance of the experimental findings for understanding interactions between caldera formation and regional tectonics. • Analogue models reinterpret caldera systems influenced by compressional tectonics. • Compressional tectonics distort caldera faults, creating elongated geometries. • Thrust faults rotate and subside during caldera collapse within fold-and-thrust belts.

Unravelling heat and mass transfer in caldera volcanoes is critical to understanding the formation of geothermal and mineral resources. While geophysical monitoring and field work provide snapshots of the hydrothermal system, numerical simulations can quantify their dynamic behavior over time. We present three-dimensional fluid flow simulations of a cooling oblate intrusion in a caldera setting to explore the effect of a high-permeability ring fault on flow dynamics and heat and mass transfer. Hot hydrothermal systems develop only if the host rock has sufficient permeability to allow for fluid advection, which efficiently extracts heat from the intrusion. In essentially impermeable host rock, fault-bound hydrothermal circulation reaches only moderate temperatures, as heat extraction at depth is limited by conductive heat transfer. In permeable host rocks, the position and thermal structure of the hydrothermal system are strongly transient, shifting from mostly fault-hosted to caldera-infill-hosted as the system evolves. The primary control on this behavior is inward intrusion cooling, with hydrothermal upflow zones initiating along the intrusion margin and migrating inward as intrusion cooling progresses. Upflow within the ring fault is only significant while the fault coincides with such a natural upflow zone, during which it can strongly focus heat and mass transfer. Partitioning of heat and mass transfer between the fault and the caldera infill therefore changes with time as the heat source shrinks inward. Overall, the hydrothermal system evolves similarly with or without a ring fault, except during the early stages when flow through the ring fault can dominate. • Three-dimensional modelling of magmatic heat-driven fluid flow in a caldera volcano. • Ring faults can transiently localize heat and mass transfer when aligned with natural upflow zones. • Upflow zones shift from the ring fault into the caldera infill as intrusion cooling progresses and the heat source shrinks. • Sufficient bulk permeability of the surrounding rocks rather than the fault is crucial to allow heat extraction from the cooling intrusion.

Abstract Volcanic calderas are large depressions formed by the rapid collapse of overlying rock into a magma chamber during eruptions. We utilize Smoothed Particle Hydrodynamics (SPH), a continuum, meshfree numerical method, to study the 2018 caldera collapse at Kīlauea volcano in Hawaii. We model the emergence of localized and distributed inelastic deformation (shear bands) during the collapse and their relation to chamber depressurization‐induced crustal down‐sagging. The SPH method has various advantageous features, namely its ability to handle large deformations, its nonlocal properties, and its capacity to accommodate strain localization without additional enhancements to the method. We specify pressure boundary conditions along the chamber top to model depressurization of the chamber, using the pressure change time history for the 2018 event inferred from a combination of geodetic data and lava‐lake drainage. This includes non‐monotonic pressure changes associated with early partial collapse events. Our simulations help to bound the critical magma pressure that triggers collapse and provide insights into various features including the stress arching effect and the evolution and directionality of both slip planes and zones of localized deformation. Using an elastoplastic Drucker‐Prager constitutive model, we analyze the contribution of inelastic deformation before and after the initiation of collapse both adjacent to Kīlauea caldera and within the subsiding block, concluding that significant distributed plastic deformation occurs once collapse initiates. Mechanistic differences between the pressure‐driven collapses and the traditional displacement‐driven trapdoor‐problem collapse are explored.

Two large-scale volcanic eruptions occurred in the southern part of Iturup Island (Southern Kurils) in the Late Pleistocene, which resulted in the collapse of the Lvinaya Past caldera (partly flooded later), the largest one in the Kuril Island arc. It is 7 × 9 km wide, with a rim area of ca. 50 km2 and a volume of ca. 25 km3 (including a submarine part of 12.26 km3). Comprehensive geological and geochronological studies have established that these two large-magnitude caldera-forming explosive eruptions (LP-I and LP-II) were separated by a repose period of several hundred years. The age of the first eruption (LP-I) is estimated at ca. 13,500 cal yr BP. The age of the second eruption (LP-II), based on a series of radiocarbon dates, is ca. 12,300 cal yr BP. Both eruptions were of Plinian type and involved the massive ejection of silicic pyroclastic material, which is represented by pyroclastic-flow deposits and tephra. In silica and total alkali contents the pumice from the caldera-forming eruptions corresponds to low-alkali dacites and rhyodacites (SiO2 = 63.4–69.95 wt.%, total alkalies of 3.9–5.5 wt.%), whereas andesitic (SiO2 = 58.3 wt.%, total alkalies of 3 wt.%) and rhyolitic (SiO2 ≈ 74 wt.%, total alkalies of 5.6 wt.%) varieties are scarce. The total volume of erupted material from both events is tentatively estimated at 80–100 km3 (DRE = 35–45 km3), with the LP-II eruption being 30–40% more powerful than the LP-I one. We suggest that the LP-I and LP-II eruptions might have impacted both the regional and global environment.

Abstract Melt re-injection after a giant caldera eruption was quantitatively investigated for the Kikai Caldera Volcano in Japan, which erupted 7300 years ago (Kikai-Akahoya eruption). Our seismic refraction survey revealed a low-velocity anomaly directly beneath the Kikai Caldera Volcano, indicating the existence of a large magma reservoir at a shallow depth of 2.5–6 km. The reservoir can be approximated by a trapezoidal shape in this 2D section, with its width being at least the same as the width of the inner caldera, and its melt fraction was estimated as 3–6%, but could be limited to 10% at most. We propose a melt re-injection model in which new melt is re-injected into this large magma reservoir at the shallow depth just beneath the caldera, which is the same magma reservoir for the Kikai-Akahoya eruption. This model may demonstrate a common feature of volcanoes that have experienced a giant caldera eruption.

• A magnetotelluric survey explores the 3D electrical resistivity distribution in the Los Humeros super-hot geothermal system (SHGS). • The resistivity model clearly reveals a highly conductive anomaly associated with the shape and depth of the cap-rock above the geothermal reservoir. • The change from high conductivity to more resistive rocks at the caprock’s base corresponds to the top of the andesitic sequence hosting the reservoir. • Our model provides a subsurface picture of the major faults and structures mapped on the surface and cut by the wells. • The resistivity model shows that at the northern end of the Maxtaloya corridor, formed by the Antigua and the Humeros faults, the top of the andesitic rocks is shallow, and houses the hottest wells. A joint geothermal project of a European and Mexican consortium (the GEMex project) was carried out between 2016 and 2020 to develop geothermal energy in the easternmost region of the Trans-Mexican Volcanic Belt. GEMex project was funded by the European Union’s Horizon 2020 and SENER-CONACYT Mexican Energy Sustainability programs. One of the key outcomes is the 3D resistivity model of the Los Humeros geothermal field in Mexico, a potentially superheated geothermal reservoir, where fluid temperature reaches close to 400 °C in some areas, based on magnetotelluric (MT) data. The model reveals a shallow resistive zone linked to post-caldera volcanic rocks; underlying this horizon is an updoming conductive anomaly caused by smectite-rich hydrothermally altered rocks that act as cap-rock. Beneath this seal-cap, a deep dome-shaped resistive anomaly is observed, likely corresponding to andesitic reservoir rocks (50–100 Ohm-m) and deeper basement rocks, possibly limestone and granodiorite. This structure aligns with temperature measurements from boreholes, where the 250–300 °C isotherms follow the shape of the top of the resistive dome. The obtained 3D model successfully identifies deep faults that facilitate hot fluid circulation and define the structural limits of the Los Potreros caldera. Faults within the caldera collapse significantly disrupt the cap-rock and the top of the andesites that host the reservoir. This information, together with results derived from other geophysical, geological, and geochemical methods, will help to infer the location and depth at which high-temperature fluids might be found. Resistivity distribution in the Los Humeros geothermal area. The white circles represent MT soundings. UTM coordinates in meters, and depth in m a.sl.

Geological and volcanological constraints on a long-lived and multi-stage collapse caldera: The Caviahue caldera, southern volcanic zone of the Andes

Lake Batur, located within a volcanic caldera in Bali, Indonesia, is subjected to anthropogenic pressures related to agriculture, aquaculture, tourism, and religious activities, which may affect its water quality and ecology condition. This study investigates the physicochemical properties of lake water and diatom assemblages preserved in lake sediments to provide insight into environmental conditions in this volcanic alkaline ecosystem. Water quality parameters, including pH, temperature, electrical conductivity (EC), and total dissolved solids (TDS), were measured. Vertical profiles of temperature and conductivity revealed stable stratification, with minimal variation below 20 m water depth. Elevated nitrogen concentrations, including nitrate (NO3−), nitrite (NO2−), and ammonium (NH4+), were observed, particularly in the southern basin, suggesting localized nutrient enrichment. Scanning electron microscopy (SEM) analysis of lake sediment samples identified ten diatom genera, including Ulnaria, Denticula, and Discostella, which are commonly associated with nutrient-enriched freshwater environments. Overall, the results indicate that Lake Batur exhibits conditions consistent with early-stage eutrophication in localized areas, highlighting the importance of continuous monitoring and targeted management strategies to protect the ecological integrity of this volcanic lake system.

Abstract Deposits of thick volcanic and volcaniclastic series can be interpreted as either related to regional tectonics (commonly extensional or transtensional tectonics) or local volcanic mechanisms (caldera collapse). In order to distinguish between these two end-member mechanisms, we propose the use of magnetic techniques, namely analysis of Anisotropy of Magnetic Susceptibility (AMS) and paleomagnetism, and analysis of geological structures. These techniques have been applied to the Estac Basin (Central Pyrenees), an inverted Late Carboniferous–Permian basin now involved in the antiformal stack of the Pyrenean belt. AMS data provide directions of flow of volcanic rocks that can be interpreted in terms of palaeo-slopes and therefore can be related to structures contemporary with deposition and Late Carboniferous–Permian volcanic activity. The maximum of the magnetic lineation (i.e. volcanic paleoflow) direction is bimodal, with (i) an absolute maximum (as occurring in most South-Pyrenean Late Carboniferous–Permian basins) along a WNW–ESE direction and (ii) a secondary magnetic lineation along an N–S direction. Paleomagnetic data obtained from the volcanic products show a primary magnetization or early remagnetization compatible with the Late Carboniferous–Permian paleomagnetic reference direction and allow us to reconstruct an early folding probably related to the warping of the basin. The magnetic and structural data can be interpreted according to a volcano-tectonic subsidence model in which E–W faults played a major role and caldera collapse contributed to the important thickness of the volcaniclastic deposits.

Abstract Three voluminous inflated lobate lava flow complexes on the distal rifts of Axial Seamount are much larger than other known flows in the global spreading system. Each complex is 65–100 km 2 , is up to 130 m thick, and is ∼3.0–4.6 km 3 , almost 100 times the volumes of historical Axial flows. These extraordinary flows are 5–7 times thicker than typical drained ponds in sheet flows. They thickened as impounded lava accumulated under chilled crusts. As flows expanded, molten interiors partially drained and flow tops collapsed. Levees built around collapses when interiors are repressurized. This formation sequence was preserved when the levee around one deep pond breached and drained the interconnected ponds. The complexes formed during moderately high‐rate eruptions. Lavas from the south rift complex are plagioclase phyric mid‐ocean ridge basalt (MORB) and those from the north rift complex are nearly aphyric and slightly more evolved. Glass compositions are similar to those of the summit and most rift lavas, implying that they resided in the summit magma reservoir where depleted ridge‐derived magma and more enriched hot‐spot‐derived magma mixed. The distal south rift complex formed ∼1259 ± 119 years BP (or ∼691 CE; based on 14 C dating of planktic foraminifera from core bases), a date that is statistically indistinguishable from the dates of phreatomagmatic deposits at the summit and formation of the present‐day caldera. The north rift voluminous flows erupted ∼12,870 ± 173 years BP. The southwest complex, although partly mapped, remains unsampled, and is still older. Eruptions of these earlier voluminous lava complexes may also have coincided with prior caldera collapses.

A hydrogeochemical investigation was conducted at Takezaki Spring, located in the Nango Valley within the Aso Caldera – one of the largest caldera volcanoes in the world – where the spring is thought to be formed by the mixing of multiple groundwater flow systems. The study was conducted from October 2024 (wet season) to June 2025 (dry season). Seasonal variations in dissolved ion concentrations and stable isotope ratios of oxygen and hydrogen revealed that, toward the dry season, the contribution of groundwater from the central cone flow system – characterized by a larger and more stable flow – became increasingly dominant in the spring discharge. In addition, a marked rise in the oxygen isotope ratio and an increase in discharge was observed after mid-April, when paddy field irrigation commenced upstream. These observations suggest that irrigation water may have significantly contributed to spring discharge even during the dry season. Analysis using multiple hydrological tracers clarified the seasonal and temporal variability of end-members from the wet to the dry season.

Comparison of Interferometric SAR Phase Linking Methods for Distributed Scatterer: A Sentinel-1 Case Study over the Kīlauea Volcano Caldera

Highlights • Caldera volcanism is associated with rifting on the South Aegean Volcanic Arc. • We integrate drill core and seismic records of volcanism and lithospheric rifting. • The rift basins NE of Santorini acted as depocenters for eruption-fed megabeds. • Rapid rifting preceded a transition to highly explosive activity at Santorini. • Tectonic stresses amplified the normal internal processes of the volcano. • Santorini and Kos Volcanoes may be coupled by regional lithospheric stresses. Abstract Many highly hazardous, caldera-forming explosive eruptions occur in extensional tectonic regimes, but the role of lithospheric rifting in modulating caldera volcanism remains enigmatic. IODP Expedition 398 deep-drilled the volcano-sedimentary infills of submarine half-grabens around Santorini caldera on the continental South Aegean Volcanic Arc. Here we use the volcanic tephra archives to produce a high-resolution eruptive chronostratigraphy for Santorini, to ground-truth seismic stratigraphy, and to extract an integrated timeline of volcano-tectonic couplings. The rift basins contain several submarine volcaniclastic megabeds from the caldera-forming eruptions of Santorini and one from the Kos caldera. The thickest megabed succession is < 250,000 yrs old and lies on a seismic reflection onlap surface that records a phase of rapid rifting. Sedimentation lagged behind subsidence during this rifting phase, creating bathymetric troughs. Integrating submarine core-seismic and onland datasets, we propose that rifting may have driven the transition of Santorini from a prolonged state of effusive and minor explosive activity (∼550 – 250 ka) typical of arc stratovolcanoes to one of repeated caldera-forming eruptions (<250 ka). Rapid rifting may have amplified the normal internal dynamics of the magmatic system in three ways, driving the volcano into a sustained, highly explosive state: (1) an increase in the supply of mantle-derived basalt, (2) enhanced shearing, permeability, and melt percolation in the transcrustal magmatic system, and (3) the development of horizontally extensive magma reservoirs. Broadly simultaneous transitions into caldera-forming activity of the widely separated Santorini and Kos Volcanoes suggest that the two magmatic systems are linked by plate-scale lithospheric stresses.

Unmanned Aerial Vehicles (UAVs) can deliver rapid, spatially resolved measurements of volcanic gases that often precede eruptions, yet most deployments remain manual or preplanned and are slow to react to seismic unrest. In the present work, we present a simulation-validated design of an earthquake-triggered, autonomous workflow for early detection of CO2 anomalies, demonstrated through a conceptual case study focused on the Santorini caldera. The system ingests real-time seismic alerts, generates missions automatically, and executes a two-stage sensing strategy: a fast scan to build a coarse CO2 heatmap followed by targeted high-precision sampling at emerging hotspots. Mission planning includes wind-and terrain-aware flight profiles, geofenced safety envelopes and a facility-location approach to landing-site placement; in a Santorini case study, we provide a ring of candidate launch/landing zones with wind-contingent usage, illustrate adaptive replanning driven by heatmap uncertainty and outline calibration and quality-control steps for robust CO2 mapping. The proposed methodology offers an operational blueprint that links seismic triggers to actionable, georeferenced gas information and can be transferred to other island or caldera volcanoes.

Understanding the carbon cycle in Antarctic coastal systems is vital for evaluating the role of polar oceans in regulating atmospheric CO2 and global climate feedbacks. However, these areas remain poorly sampled and are underrepresented in existing carbon flux models. This dataset offers high-resolution environmental observations collected in February 2025 from surface waters and inland stations in Deception Island, an active volcanic caldera in the South Shetland Islands, Antarctica. It includes measurements of surface seawater pCO2, temperature, salinity, wind speed, air temperature, solar radiation, tidal elevation, and seismic signals (long-period and tremor events), along with related spatiotemporal metadata. To enhance direct observations, we applied a data-driven modeling approach using deep learning techniques. A Bidirectional Long Short-Term Memory (Bi-LSTM) neural network was trained on multivariate sequences to estimate seawater pCO2, with model performance evaluated through five cross-validation folds. The final datasets contain both measured and Bi-LSTM-estimated pCO2 values. All data and processing steps adhere to FAIR principles to support research on air-sea gas exchange, remote sensing calibration, and Antarctic carbon system dynamics.

Abstract Magma and pressure transport between Kīlauea's summit reservoirs and along its East Rift Zone (ERZ) are dynamic even in the absence of surface eruptions. However, these processes do not always produce surface manifestations and may sometimes elude detection by current geological and geodetic monitoring. Here we monitor subsurface seismic velocity changes across Kīlauea's system from 2013 to 2018 and integrate these observations with concurrent measurements of ground deformation and lava lake elevation. We corroborate years‐long seismic velocity decreases around the summit caldera, which are particularly pronounced at southern stations, consistent with sustained pressurization of the South Caldera reservoir (SCR) from a deep magma supply. Following the 2015 summit intrusion, accelerated rates of velocity decrease, summit inflation, and lava lake rise suggest an increased magma supply to the SCR. Notably, we identify an anomalous 7‐month period (late 2016–mid 2017) of disrupted magma/pressure transfer between the SCR and Halema'uma'u magma reservoir (HMR), as evidenced by dropping lava lake levels despite continued summit inflation and SCR pressurization. This period coincided with pressurization observed beneath Pu'u'ō'ō, indicating pressure/magma diversion from the summit toward the ERZ and the episode terminated with a M5.3 flank earthquake in June 2017 that restored the connectivity between the SCR and HMR and triggered shallow crustal pressurization beneath the summit caldera for the subsequent 2–3 months. Our findings reveal significant perturbations in Kīlauea's magmatic plumbing system approximately one year before the catastrophic 2018 eruption, highlighting seismic velocity monitoring's value for detecting subtle changes of the volcano.

During an earthquake rupture, both dynamic and static stress drop play a key role in controlling how much energy is radiated as seismic waves, how large is the fault slip, and how quickly the rupture spreads out of the nucleation zone. Using a time-domain analysis of P- and S-wave log-displacement records, we estimate seismic moment, rupture velocity, static stress drop, and source radius of 56 Md 3+ earthquakes detected during the 2020-2025 seismic crisis at Campi Flegrei caldera, Italy. Fractures propagated at sub-shear velocities (0.4-0.9 of the shear wave velocity) along 100-1000 m in radius fault surfaces. Independent stress release estimates show a statistically significant inverse relation with the rupture velocity. The measured low seismic radiation efficiency, with a median value of 0.1, suggests that only a small portion of the stress drop is radiated as seismic waves, implying that a significant amount of energy is likely dissipated through frictional and inelastic processes, including off-fault damage. The findings suggest that in this volcanic caldera, earthquakes with higher stress drop may enhance fault-surrounding damage, which acts as a natural barrier to rupture propagation. Consequently, this mechanism could limit rupture extent and constrain the maximum magnitude of earthquakes in the area. Earthquakes at Italy’s Campi Flegrei caldera show unusually low seismic radiation efficiency, with most energy dissipated through off-fault damage and frictional processes, according to a time-domain-based analysis of seismic catalogue data.

Abstract Mauna Loa is the largest active volcano on Earth, comprising ∼51% of the Island of Hawai‘i’s landmass and posing significant risks to the island’s communities, infrastructure, and natural environment. Historical eruptions have produced lava flows that have reached the ocean in as little as 3 hr. The timing and location of such lava flows in the past 200 yr underscore how critical determination of the location and geometry of magma storage and structure is for volcanic hazard assessment and eruption forecasting. Now, after nearly 38 yr of volcanic quiescence, Mauna Loa has erupted again. On 27 November 2022, fissures initiated within the summit caldera and then migrated to the northeast rift zone, where they generated a large lava flow that threatened a major highway. To improve our understanding of the geometry of this magma system, we deployed a temporary nodal array on Mauna Loa in the summer of 2024. This increased our seismic coverage sufficiently to image this magmatic system. This nodal array consists of 33 seismometers distributed on and around the volcano and was deployed for over three months to record seismic signals. The primary objective of this project is to resolve the high-resolution seismic velocity structure and characterize seismic features associated with magma storage and ascent pathways. In this article, we present an overview of the deployment, evaluate the quality of the data, and show example recordings to evaluate the suitability of the data set for future seismic investigations, including earthquake relocation, seismic tomography, and receiver function analysis. Comparisons with nearby permanent broadband and short-period seismic stations demonstrate that the nodal array recorded high-quality waveforms, making it a valuable resource for constraining the magmatic system beneath Mauna Loa at multiple scales.