The motivation comes from a very concrete problem. Volcano observatories, seismic networks, and geophysical stations in regions without cellular or wired infrastructure need radio links that can carry uninterrupted sensor data across ten to twenty kilometres. A triaxial seismometer sampling at 200 samples per second with 24 bits per axis generates a raw stream of 14.4 kilobits per second, but telemetry protocols and encapsulation overheads such as MiniSEED formatting standardise on a 115,200 bits per second serial interface at the sensor output. To prevent buffer accumulation, the wireless link must sustain goodput at or above that serial speed. LoRa, the proprietary chirp spread spectrum modulation that has become ubiquitous in smart agriculture and volcanic monitoring networks, simply cannot deliver: at the high spreading factors required for robust long-distance links, its effective air rate collapses to one to five kilobits per second, making continuous high-rate streaming fundamentally impossible.

The research team, affiliated with monitoring efforts around the active Misti and Sabancaya volcanoes in southern Peru, validated the throughput limitation empirically. In comparative benchmarks against commercial Ebyte E22 modules at 433 MHz and 915 MHz, both sub-gigahertz LoRa systems saturated at a maximum sustained goodput of just 29.38 kilobits per second, enforced by a physical packet inter-arrival floor of 65.35 milliseconds. That is a shortfall of nearly four times against the 115.2 kilobits per second target, meaning such links can carry a 100-samples-per-second seismic stream but cannot handle a 200-samples-per-second stream with any robust margin. Previous work on the 16-kilometre Misti–Arequipa path had already confirmed the geometric feasibility of the radio link while highlighting exactly this throughput wall.

OpenFLRC’s answer is to move to the 2.4 GHz industrial, scientific and medical band and exploit FLRC, or Fast Long-Range Communication, a modulation mode native to the SX1280 transceiver family. In its fastest configuration, FLRC achieves a 1.3 megabit per second air rate with a receiver sensitivity of minus 97 dBm, sufficient for multi-kilometre links. The team’s carrier board integrates an Ebyte E28-2G4M27SX radio front-end delivering up to 27 dBm, or 500 milliwatts, of output power through a Skyworks power amplifier, alongside an ESP32-S3 dual-core microcontroller running at 240 MHz with 16 MB of flash and 8 MB of PSRAM. Crucially, the design grants users bare-metal control over the radio, exposing internal hardware buffers, explicit transmit and receive timings, and direct SPI interrupts through a custom C++ library, a level of deterministic control that closed commercial LoRa modules abstract away entirely.

The engineering details reveal why the platform performs as it does. Driving a 500-milliwatt power amplifier continuously under high-rate streaming draws rapid current pulses peaking at 550 milliamperes with nanosecond-scale rise times, which would destabilise a typical breadboard or prototype supply. The carrier board embeds a five-capacitor decoupling ladder directly adjacent to the radio module’s power pins: two 150-microfarad low-ESR tantalum capacitors acting as a local bulk energy reservoir, in parallel with three high-frequency X7R ceramic capacitors. A continuous 1-ounce copper ground plane on the board’s underside, stitched to the module with thermal vias, acts as a passive heat spreader for the roughly 1.3 watts dissipated as heat during full-power transmission. The board also routes the radio’s transmit and receive enable lines through dedicated low-capacitance traces, allowing the firmware to switch the RF front-end deterministically within 2.5 microseconds and preventing destructive amplifier reflections during transmit-to-receive turnarounds.

The firmware architecture is equally deliberate. Under FreeRTOS, the dual-core processor divides labour asymmetrically: Core 0 ingests the incoming 115,200 bits per second serial stream into a lock-free circular ring buffer in RAM, while Core 1 runs a dedicated radio scheduler that fetches 117-byte chunks and pushes them to the SX1280’s FIFO over an 18 MHz SPI bus with direct memory access, shrinking each payload transfer to roughly 56 microseconds. Radio state transitions are governed strictly by a hardware interrupt that triggers a RAM-cached fast interrupt service routine, eliminating the scheduling jitter that plagues polling-based designs. The team’s timing budget analysis shows a minimum theoretical packet cycle of 840.9 microseconds, and the empirical benchmark achieved 884.3 kilobits per second of goodput at a one-millisecond packet interval, corresponding to a 73.1 percent channel efficiency relative to the raw 1.3 megabit per second air rate. Notably, 82 percent of Core 0’s processing capacity and more than 470 kilobytes of SRAM remain free for user data acquisition and edge signal processing.

Validation was conducted with unusual rigour for open hardware. Rather than relying on uncontrolled over-the-air tests, the team built a conducted radio-frequency bench using a calibrated chain of SMA attenuators totalling up to 145 decibels of path loss, characterised segment by segment with a NanoVNA vector network analyser at 433 MHz, 915 MHz, and 2.44 GHz. This approach isolates true receiver sensitivity and firmware behaviour from the multipath fading, interference, and antenna pointing errors that make field measurements irreproducible. In attenuation sweeps, the sub-gigahertz LoRa links sustained near-unity packet delivery up to 130 decibels of conducted path loss, while the 2.4 GHz FLRC link held a 96.2 percent delivery ratio at 125.8 decibels before failing completely, a roughly five-decibel penalty consistent with the higher noise bandwidth of FLRC compared to narrow-band chirp spread spectrum.

Spectral measurements with a TinySA Ultra analyser confirmed the platform’s regulatory compliance. The occupied bandwidth measured between 1.336 and 1.347 megahertz across three operating channels, closely matching the configured FLRC parameters, and second-harmonic suppression ranged from 38.5 to 41.8 decibels below the carrier, comfortably within FCC Part 15.247 and ETSI EN 300 328 emission limits. The power control loop proved highly linear across an 18-decibel dynamic range. Link-budget emulation for the 16.4-kilometre Misti–Arequipa volcanic corridor, based on the ITU-R free-space model and the empirical sensitivity thresholds, indicates the link can theoretically close at that distance, though the authors recommend upgrading to 19 dBi parabolic grid antennas or adding an intermediate repeater to maintain a proper fade margin for field reliability.

The trade-offs are candidly acknowledged. The 2.4 GHz band incurs a 7.9-decibel free-space path loss penalty compared to 915 MHz, making the system dependent on line-of-sight conditions, and continuous full-power transmission demands careful thermal management in any field enclosure. The v1.0 firmware implements dedicated point-to-point streaming only, with multi-node contention protocols and the SX1280’s built-in time-of-flight ranging engine reserved for future releases. Yet the regulatory picture favours the chosen band: sub-gigahertz spectrum is fragmented regionally and subject to duty-cycle limits as low as 0.1 percent in Europe that legally prohibit continuous telemetry, whereas the 2.4 GHz band is globally harmonised with no duty-cycle restrictions, and rain attenuation over a 16-kilometre path is negligible at these frequencies.

Perhaps most striking is the price and accessibility. Each complete transceiver node costs 32.70 US dollars, built from commodity modules and a two-layer printed circuit board, and the entire project, including schematics, gerber files, firmware, bill of materials, calibration data, and benchmark videos, is published under a Creative Commons Attribution 4.0 license and certified by the Open Source Hardware Association under UID PE000005. For research groups monitoring volcanoes, earthquakes, or any high-rate phenomenon in infrastructure-poor regions, OpenFLRC demonstrates that the era of choosing between long range and sufficient bandwidth may finally be ending, and that a thirty-dollar open board can do what expensive proprietary telemetry systems have long monopolised.

Subject of Research: Open-source 2.4 GHz FLRC wireless transceiver hardware for high-throughput, low-latency continuous scientific telemetry

Article Title: Open-source SX1280 2.4 GHz FLRC transceiver: Overcoming sub-GHz LoRa bottlenecks for high-rate, low-latency continuous telemetry

Article References: Choquepuma, K. J. C., Rodriguez, K. E. A., Arenas Mamani, F. A., & Hilario-Tacuri, A. (2026). Open-source SX1280 2.4 GHz FLRC transceiver: Overcoming sub-GHz LoRa bottlenecks for high-rate, low-latency continuous telemetry. HardwareX, Article e00848. https://doi.org/10.1016/j.ohx.2026.e00848

Image Credits: AI Generated

DOI: 10.1016/j.ohx.2026.e00848

Keywords: OpenFLRC, SX1280, FLRC modulation, LoRa bottleneck, wireless telemetry, volcano monitoring, seismic networks, ESP32-S3, open-source hardware, 2.4 GHz ISM band, packet delivery ratio, HardwareX

The core idea behind the new study is elegantly simple. Instead of relying on a hot light source such as lava, an artificial lamp, or direct sunlight, the proposed instrument would read sunlight that has been scattered by the sky itself. The light travels down from the sun, bounces off molecules and aerosols in the atmosphere, passes through the volcanic plume, and is collected by a telescope pointed at whatever patch of sky happens to contain the plume. Because the sky is always glowing with scattered sunlight, the instrument does not depend on a favorable solar geometry, a clear line of sight to hot rock, or an ongoing eruption. That freedom of viewing geometry is precisely what makes continuous, automated monitoring possible rather than campaign-based.

Today’s operational volcanic gas monitoring exploits exactly this trick, but only in the ultraviolet and visible part of the spectrum, where scattered sunlight is abundant. The workhorse technique, differential optical absorption spectroscopy, is deployed worldwide in networks such as the Network for Observation of Volcanic and Atmospheric Change, or NOVAC, and it measures sulfur dioxide superbly. The problem is that sulfur dioxide is only one character in a much richer chemical story. Gases such as hydrogen chloride, hydrogen fluoride, water vapor, and carbon dioxide absorb infrared light rather than ultraviolet light, so the standard UV instruments simply cannot see them. The Heidelberg team asked a deceptively straightforward question: is there enough near-infrared sunlight scattered from the sky to measure those infrared-absorbing gases with a passive Fourier transform infrared, or FTIR, spectrometer?

Answering that question required the researchers to predict, with quantitative rigor, how well such an instrument would actually perform. They built a physics-based instrument model that tracks the optical power delivered to the detector, the responsivity of the infrared photodiode, and the dominant noise sources, which shift from thermal noise in the detector’s shunt resistance under dark skies to unavoidable shot noise under bright ones. The model captures the classic trade-offs of FTIR spectroscopy: signal quality improves only with the square root of measurement time, degrades linearly with finer spectral resolution, and scales with the light-gathering capacity of the optics. Crucially, the team validated the model in the laboratory using an integrating sphere at seven different brightness levels, deliberately spanning the transition between the two noise regimes. Every measured signal-to-noise ratio fell within the model’s predicted interval, giving the authors confidence that their forecasts for a real volcano were grounded in reality rather than optimism.

To translate spectral quality into gas measurements, the researchers combined the instrument model with an information-content analysis anchored in real atmospheric observations. They chose Mount Etna in Sicily as their test case, and for good reason: Etna is one of the largest halogen point sources on the planet, one of the strongest volcanic emitters of carbon dioxide, and one of the most significant continuous gas emitters worldwide. Radiometrically calibrated measurements of the near-infrared sky brightness at Etna, recorded during a 2021 campaign, allowed the team to bracket the expected light levels, from a crisp clear sky to an aerosol-laden one, a range spanning roughly an order of magnitude. Additional sky spectra recorded from the roof of the Institute of Environmental Physics in Heidelberg let the team capture the systematic errors that plague real total-column retrievals, errors that a purely synthetic study would have missed.

The verdict on carbon dioxide is sobering. Carbon dioxide is everywhere in the atmosphere at roughly 420 parts per million, so a volcanic plume adds only a modest enhancement on top of a large and variable background. Combine that with the fact that relatively little sunlight is scattered in the near-infrared, and the numbers become brutal: even under bright skies, reaching a detection limit comparable to the expected plume enhancement takes about five minutes of averaging, and under dark conditions up to two and a half hours. Plume transects, the standard method for quantifying emissions, require many individual measurements at a precision roughly ten times better than the signal itself, which pushes the required averaging time for carbon dioxide to eight hours or even days. In practical terms, scanning a plume for carbon dioxide with this technique is out of reach, although single snapshot measurements of plume composition remain conceivable.

The halogen gases tell a completely different story. Hydrogen chloride and hydrogen fluoride have essentially no atmospheric background, so whatever the instrument sees is almost purely volcanic signal. The analysis shows that these species can be detected within seconds under bright skies and within a few minutes under dark conditions at a strongly emitting volcano like Etna. Even for the demanding precision required of plume transects, the halogens need between five minutes and three hours of averaging, which is far more favorable than carbon dioxide but still slower than the five to fifteen minutes typical of the NOVAC sulfur dioxide network. The team’s performance estimates also line up closely with historical mid-infrared measurements at Popocatépetl volcano in Mexico from 1998, which lends independent credibility to the numbers.

Perhaps the most actionable outcome of the study is a proposed multi-instrument strategy that plays to the strengths of each technique. The FTIR instrument would be paired with a co-aligned ultraviolet spectrometer measuring sulfur dioxide along the identical light path, allowing the researchers to compute gas ratios such as hydrogen chloride to sulfur dioxide directly. Those ratios, multiplied by the sulfur dioxide fluxes already delivered around the clock by established monitoring networks, would yield continuous estimates of halogen emissions, a quantity that is currently very hard to obtain. An additional sulfur dioxide camera could track the plume’s position in real time, ensuring the paired instruments always sample the plume’s core. For carbon dioxide, this route is not entirely excluded, but the authors caution that limited precision and the sensitivity of a background-dominated retrieval to radiative transfer errors make the outcome difficult to predict.

That radiative transfer challenge deserves emphasis, because it is the next great hurdle. The light path in a scattered-sunlight observation divides conceptually into three segments: the portion behind the plume where sunlight is scattered into the viewing direction, the portion inside the plume where the target gases accumulate, and the portion between the plume and the observer. Accurately modeling this path depends on aerosol load, aerosol type, and height distributions, all of which are highly variable and poorly constrained for instantaneous local measurements. For gases that exist only in the plume, such as the halogens, observations of plume geometry may suffice. For carbon dioxide, the authors suggest using methane as a proxy gas: it shares a similar background distribution, is not emitted by the volcano in relevant amounts, and absorbs at wavelengths close to the carbon dioxide lines, so it experiences nearly the same light path.

The study’s framework, an instrument noise model validated in the laboratory and coupled to an information-content analysis grounded in real measurements, is deliberately transferable. It can be applied to other instruments, spectral regions, target species, and emission sources before any hardware is built. Intriguingly, the authors point out that anthropogenic super-emitters such as power plants and industrial facilities produce carbon dioxide enhancements far larger than those of a volcanic plume, meaning that sky-scattered sunlight measurements of carbon dioxide may well prove feasible in that context even if volcanoes remain a stretch. For volcanology, the immediate path forward is clear: pair the new near-infrared capability with the ultraviolet instruments already in the field, and continuous, automated monitoring of halogen emissions, and with it a sharper window into the processes that drive eruptions, moves from aspiration to engineering.

Subject of Research: Feasibility of passive near-infrared FTIR spectroscopy of sky-scattered sunlight for measuring volcanic gas emissions

Article Title: Feasibility of measuring volcanic gas composition using sky-scattered sunlight and FTIR spectroscopy

Article References: Schmitt, T. D., Sindram, M., Löw, B. A., Weis, L., Kleinschek, R., Bobrowski, N., & Butz, A. (2026). Feasibility of measuring volcanic gas composition using sky-scattered sunlight and FTIR spectroscopy. Atmospheric Measurement Techniques, 19(18), 6145-6157. https://doi.org/10.5194/amt-19-6145-2026

Image Credits: AI Generated

DOI: 10.5194/amt-19-6145-2026

Keywords: volcanic gases, FTIR spectroscopy, remote sensing, carbon dioxide, hydrogen chloride, hydrogen fluoride, sulfur dioxide, Mount Etna, scattered sunlight, near-infrared, volcano monitoring, radiative transfer

The magnitude of the intrusion is modest by volcanic standards. Stamps compares the volume to about 400 Olympic-size swimming pools, an amount that is not in itself a cause for alarm. The magma, according to the team’s numerical modeling, does not appear to be migrating closer to the crater, and the reservoir it is entering already existed prior to the event. Yet the significance of the finding extends well beyond the volume of rock involved. It demonstrates that the monitoring infrastructure installed on the volcano can detect subtle, transient deformation signals and, more importantly, that the team can interpret those signals with sufficient confidence to attribute them to specific subsurface processes. That capability lies at the heart of any credible early-warning effort for a volcano that alternates between gentle and violent behavior.

The detection itself was made possible by a ground-based geodetic network that Stamps’ group began building a decade ago. In 2016, the team installed six Global Navigation Satellite System instruments on the flanks and surroundings of Ol Doinyo Lengai. These continuously operating stations track the horizontal and vertical motions of the ground surface to a precision of about one millimeter, a level of sensitivity that allows researchers to distinguish genuine deformation of the volcanic edifice from noise introduced by atmospheric effects or equipment drift. The GNSS network is complemented by two broadband seismic stations that record earthquake activity across a wide range of frequencies, and the continuous instrumentation is supplemented by episodic benchmark measurements taken during field campaigns.

The combination proved decisive in 2024. When the GNSS stations recorded an uplift signal around the volcano, the team turned to numerical modeling to determine what subsurface source could reproduce the observed pattern of surface movement. By fitting deformation models to the geodetic data, the researchers concluded with a high degree of certainty that the signal was generated by an influx of magma into an already existing magma reservoir roughly three kilometers underground. The result validated both the sensitivity of the network and the interpretive framework the team has developed over more than ten years of observation at the site. The work was published on September 18, 2026, in Frontiers in Earth Science, with the DOI 10.3389/feart.2026.1881885.

Ol Doinyo Lengai occupies a singular position in volcano science. Its carbonatite lavas erupt at temperatures far lower than the silicate lavas produced by virtually every other volcano on the planet, and during quiet periods the volcano maintains an active lava lake that bubbles and flows effusively within its summit crater. This effusive behavior, however, is only half of the volcano’s personality. On average, Ol Doinyo Lengai produces an explosive eruption every 10 to 15 years, and these explosive episodes can pose serious hazards to the communities that live on and around its slopes. Stamps notes that the team expects another explosive eruption within their lifetime, and the central motivation of the research program is to give residents and authorities enough lead time to prepare and respond to evacuation decisions made by the Tanzania Geological Survey.

Understanding what distinguishes a benign magma intrusion from a precursor to violence is the crux of the forecasting problem, and the 2024 event provided a valuable calibration point. According to Stamps, the last time the volcano erupted explosively, the event was preceded by a magnitude 5.9 earthquake. That historical sequence suggests a set of warning indicators that the team now watches for: a significant earthquake followed by observable changes in surface deformation, and, most critically, evidence that magma is moving from a deeper storage zone to a shallower one over time. Such upward migration indicates that magma is ascending the volcanic conduit, and it is precisely the kind of progression that would elevate concern. The 2024 intrusion, by contrast, showed magma entering an existing reservoir without any sign of ascent toward the crater, which is why the team assessed it as low risk.

One of the most stubborn uncertainties in volcanology is timing. Some volcanoes erupt explosively every time they erupt, making their behavior relatively predictable once unrest is detected. Ol Doinyo Lengai is more complicated, alternating between effusive and explosive eruptions in a pattern that is not fully understood. A key reason the team continues to monitor the volcano intensively is to constrain this particular volcano’s time delay, the interval between detectable precursory activity and an actual explosive eruption. Every additional episode of recorded deformation, seismicity, and magma transport adds to a decade-long baseline of observations that gradually reveals how the volcano’s subsurface system transitions from storage to ascent to eruption. The longer and richer the record becomes, the more skillfully the team can match patterns of surface observation to processes occurring underground.

The monitoring effort at Ol Doinyo Lengai is also notable for its ground-based character. Satellite-based observations, including those contributed through NASA, provide valuable context and broad spatial coverage of deformation across the region. But Stamps emphasizes that her team is currently the only group conducting continuous ground-based GNSS monitoring and consistent ground-based seismic monitoring at the volcano. Ground instruments offer continuous temporal sampling and millimeter-level precision that orbital observations alone cannot match, particularly for small, short-lived deformation episodes like the 2024 bulge, which might be missed or ambiguously characterized by intermittent satellite acquisitions. The redundancy and complementarity of the two approaches strengthen the overall early-warning picture.

The practical payoff of this work accrues directly to the people who live in the shadow of the volcano. More than a decade of observations has given the team a substantially better understanding of which underground magma movements correspond to which surface signals, and that empirical link is the foundation of any effort to anticipate when the volcano is edging closer to an explosive eruption. For residents of the surrounding area, the difference between a well-instrumented volcano and a poorly instrumented one can be measured in the time available to act. The Tanzania Geological Survey, which holds formal responsibility for evacuation decisions, now has access to a continuously refreshed, quantitatively interpreted stream of deformation and seismicity data from one of the rift’s most active and most unpredictable volcanoes.

The 2024 bulge may have been modest, equivalent to 400 swimming pools of magma settling into a reservoir it already knew, but as a test of scientific and operational readiness it was passed convincingly. A transient deformation signal was detected in near real time, modeled rigorously, attributed to a specific source at a specific depth, and correctly evaluated as non-threatening. Each such episode sharpens the interpretive tools that will be needed when the volcano’s behavior changes in more consequential ways. Given the volcano’s average recurrence interval of 10 to 15 years between explosive eruptions, the question is not whether the next one will come but whether the warning signs will be recognized in time. On the evidence of this study, the instruments are in place, the baseline record is deepening, and the science of translating millimeters of ground motion into meaningful forecasts is steadily maturing at one of Earth’s most remarkable volcanoes.

Subject of Research: Magma intrusion and surface deformation monitoring at Ol Doinyo Lengai volcano in Tanzania

Article Title: Interpreting a volcano’s ‘bulges’ and predicting the next explosive eruption

Article References: Interpreting a volcano’s ‘bulges’ and predicting the next explosive eruption. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Ol Doinyo Lengai, volcano monitoring, magma intrusion, GNSS, Tanzania, explosive eruption, East African Rift, surface deformation, carbonatite lava, seismic monitoring, early warning system, Frontiers in Earth Science

Hunga volcano, which rises from the Tonga-Kermadec arc about 65 kilometres north of Tongatapu, had already signalled its unrest in December 2021, with a sequence of eruptions that built a small temporary island and peppered the surrounding sea with floating pumice. Then, in the early afternoon of 15 January local time, the system transitioned almost instantaneously into a climactic phase. Explosions tore through the shallow edifice, whose vent lay only a few tens of metres below sea level, and the resulting plume punched through the tropopause into the mesosphere, the highest volcanic plume ever reliably documented. What the new analysis makes clear is that the extraordinary violence of the eruption was tightly coupled to the structural failure of the volcano itself: as the eruption evacuated magma from a shallow reservoir, the roof of the system foundered, and the caldera floor dropped by hundreds of metres in a remarkably short interval.

The quantitative core of the study lies in the comparison of multibeam echo-sounder surveys. A regional bathymetric mapping campaign in 2016 had captured the pre-eruption shape of Hunga’s submarine flanks and summit in detail, and repeated surveys carried out in the aftermath of the eruption, together with additional high-resolution mapping, allowed the researchers to compute a precise difference map of the seafloor. The results show that the collapse removed on the order of several cubic kilometres of rock from the edifice, deepening the caldera and reshaping the inner walls. Vertical changes of as much as several hundred metres were measured across broad areas of the caldera floor, confirming that this was a coherent piston-like subsidence of the reservoir roof rather than scattered slumping of loose material on the flanks.

To place that structural change on a timeline, the team turned to the geophysical signals recorded as the collapse unfolded. Seismic stations around the Pacific recorded an extraordinary sequence of very-long-period signals, a slow, rhythmic pulsing superimposed on the eruption’s broadband shaking that previous work had linked to repeated pressure oscillations in the coupled magma-seawater system. The new study shows that these pulses align closely in time with the inferred stages of caldera subsidence, indicating that the collapse did not occur as a single instantaneous drop but proceeded in discrete steps as the caldera block settled incrementally onto the diminishing magma body. Hydroacoustic and barometric records, including the Lamb wave that swept around the atmosphere, provide independent timing anchors, allowing the collapse history to be synchronized with the eruption’s global signals.

The mechanics inferred from these data are consistent with classical models of caldera formation but with an emphatically submarine twist. As magma withdrew rapidly from a shallow reservoir, the overlying roof lost support and failed along ring-shaped fractures. Seawater flooded into the vent region, and the intimate mixing of magma and water drove the eruption’s exceptional explosivity, a process long recognized in theory but seldom observed at this scale. Crucially, the collapse itself may have sustained the eruption: each increment of subsidence decompressed the remaining magma, accelerating volatile exsolution and feeding the next explosive pulse. The result was a positive feedback between structural failure and explosive discharge that explains how a volcano whose vent lay underwater could outshine, in atmospheric effect, any eruption of the satellite era.

The volume budget that emerges from the study also resolves a puzzle about the eruption’s products. Estimates of the ash and pumice deposited on land, on the seafloor, and dispersed through the atmosphere fall short of the volumes implied by the erupted magma in some reconstructions, and the new accounting of collapse volume helps close that balance. The subsided caldera accounts for a large fraction of the material removed from the reservoir, while a substantial volume of fragmented juvenile rock remained trapped as dense deposits within the deepened caldera basin, never reaching the surface as visible ash. This partitioning matters for interpretation: it shows that the caldera acts as a sediment trap that can hide a large share of an eruption’s output from conventional tephra inventories, a bias that likely affects volume estimates at many submarine volcanoes.

Beyond Hunga itself, the findings sharpen hazard assessment for the dozens of shallow submarine volcanoes in the Tonga-Kermadec arc and in comparable settings worldwide, from the Aeolian arc to the Kermadec subduction system’s northern neighbours. Shallow-water vents are notoriously difficult to monitor, and Hunga demonstrated that such systems can escalate from low-level activity to a globally significant climax with little warning. The recognition that caldera collapse can proceed in rapid, stepped fashion within hours, generating devastating tsunami through both displacement of seawater by the collapse and by the pyroclastic flows that raced across the seafloor, gives tsunami modellers a concrete, physically grounded scenario to test. The Hunga event generated tsunami waves that claimed lives as far away as Peru, underscoring that submarine collapse hazards are not confined to the volcano’s immediate shoreline.

Methodologically, the study exemplifies the power of merging datasets that individually capture only fragments of a fast-moving natural experiment. Pre- and post-eruption bathymetry fixes the geometry of collapse; very-long-period seismology constrains its tempo; atmospheric pressure waves and satellite imagery bound the eruption’s explosive energy; and petrological work on the erupted juvenile clasts ties the geophysical record to the magma’s storage conditions and volatile content. None of these threads alone could distinguish between competing interpretations, such as phreatomagmatic excavation versus gravitational sliding, but together they converge on a coherent narrative of reservoir-roof failure synchronously coupled to explosive discharge. The approach offers a template that can be applied retrospectively to other recent submarine eruptions and prospectively in monitoring network design.

The 2022 Hunga eruption severed Tonga’s international submarine cable, blanketed agricultural land in corrosive ash, and displaced communities, even as the exact interplay of processes driving its ferocity remained uncertain for months afterwards. By demonstrating that the seafloor of the volcano collapsed with extraordinary speed during the eruption’s climactic hours, the new research closes a central gap in that understanding and turns a catastrophic event into a benchmark for volcano science. As mapping technology and ocean-bottom instrumentation spread across the world’s volcanic arcs, events like Hunga will increasingly be captured in real time, and the lessons recorded here, about stepped collapse, magma-water feedback and hidden deposit volumes, will shape both the science and the preparedness of coastal nations living above active submarine volcanoes.

The Hunga collapse also provides a rare modern analogue for historical events that shaped early volcanological thinking. The 1883 eruption of Krakatau in Indonesia, which likewise involved a shallow marine vent and generated deadly seaborne tsunami, has long been interpreted as involving caldera-scale destruction of the edifice, but it was documented only through aftermath surveys and eyewitness accounts. The minute-by-minute geophysical record assembled for Hunga offers what those earlier events never could: a direct, instrumentally timed view of how a volcanic edifice fails during a climactic submarine eruption, allowing reinterpretation of historical catastrophes through a modern observational lens.

The stepped character of the subsidence carries particular significance for seismologists. Very-long-period signals of the kind recorded during Hunga are produced by slow, volumetric pressure changes in shallow magmatic and hydrothermal systems, and their rhythmic repetition during the collapse suggests that each increment of roof failure perturbed the underlying magma-seawater system in a repeatable way. Such signals, once calibrated against the bathymetric difference maps, could in principle serve as real-time indicators that a submarine edifice is actively foundering, giving warning of tsunami potential while an eruption is still under way.

The study also illustrates how much of an eruption’s story remains hidden beneath the sea surface. Because Hunga’s vent lay underwater, much of the fragmentation, transport and deposition of juvenile material occurred out of sight, and only the combination of seafloor mapping and geophysical inversion could recover the full mass balance. This hidden component helps explain why eruption magnitude scales derived from atmospheric and tephra observations alone can underestimate submarine events, and why repeated bathymetric surveys should be treated as an essential component of post-eruption response in volcanic arcs.

For the Tonga-Kermadec arc specifically, the results underscore the value of baseline mapping. The 2016 pre-eruption survey proved decisive, and the study implicitly argues for systematic, repeated multibeam coverage of shallow submarine volcanoes before crises occur, since without such baselines the geometry of any future collapse would be irrecoverable.

Subject of Research: Rapid submarine caldera collapse during the 2022 climactic eruption of Hunga volcano, Tonga

Article Title: Rapid submarine caldera collapse during the 2022 climactic eruption of Hunga volcano (Tonga)

Article References: Ribó, M., Cronin, S. J., Park, S.-H., Garvin, J., Yeo, I. A., Clare, M. A., Watson, S. J., Kang, S.-G., Sielfeld, G., Slayback, D. A., Choi, Y., Jung, J., Yoo, J., Hutton, B., Stern, S., White, J. D. L., Brenna, M., Hunt, J., Mackay, K., … Kula, T. (2026). Rapid submarine caldera collapse during the 2022 climactic eruption of Hunga volcano (Tonga). Nature Geoscience. https://doi.org/10.1038/s41561-026-02099-7

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02099-7

Keywords: Hunga volcano, Tonga, submarine caldera collapse, 2022 eruption, caldera formation, bathymetry, very-long-period seismicity, phreatomagmatic eruption, tsunami, magma-water interaction, volcano monitoring, Tonga-Kermadec arc