Recent fissure-fed eruptions from the Svartsengi Volcanic System have significantly impacted Iceland’s Reykjanes Peninsula. With eruptions likely to continue intermittently for decades to centuries, exploring the controls on the locations of fissure-fed eruptions is important for hazard assessment and risk mitigation. This study maps eruptive fissures from six eruptions from December 2023 to September 2024 using satellite and aerial imagery and observes fire-fountain height evolution for four eruptions using webcam footage. We find that fissure locations are heavily influenced by topography, including features parallel to fissure strike and features formed during previous eruptions. The maximum fire-fountain heights ranged from 56 m during the January 2024 eruption to 133 m during the August 2024 eruption. Variations in fire-fountain heights in a single eruption between different fissure segments, and through time, appear to primarily be controlled by surface vent size and dike pressurisation, both of which increase mass eruption rate and lead to higher fountains. Understanding the controls on fissure location highlights areas most vulnerable to future fissure opening, which can help inform ongoing hazard assessment and risk mitigation. Digital video capture of future eruptions from multiple angles would augment monitoring and help refine models of fire-fountain evolution.

Abstract Hydrothermal systems in volcanic calderas are critical in signalling volcanic unrest, forming ore deposits, and sustaining chemosynthetic microorganisms. Analysis of a ~3500-year sequence of sediments collected from the Santorini caldera, Greece, during International Ocean Discovery Program (IODP) Expedition 398 reveals the behaviour of a prolonged paleo-hydrothermal system. Sediment geochemical and metagenomic data record vigorous hydrothermal activity and metal fluxes for ~1100 years, within a 2270-year window between two major eruptions. Sediment hydrothermally-derived trace metals are significantly enriched over background (~200-fold for As and Hg, and 10–50-fold for Mn, Sb, Mo, and V), with long-term metal fluxes (9 t yr −1 As, 2.5 t yr −1 Cu, 7 kg yr −1 Ag) comparable to fluxes from present-day geothermal fields in the Taupo Volcanic Zone. Metagenomic analysis identifies elevated metal resistance genes—signals of microbial adaptation to heightened hydrothermal stressors. Here we integrate geological and genomic evidence to decipher the paleoenvironmental and biogeochemical history of the past hydrothermal system at Santorini caldera.

We used a deep learning workflow to enhance earthquake detection during the 2025 seismic unrest between Santorini and Amorgos islands to track the evolution of the crisis in near real-time. We analysed the continuous seismic waveforms daily (1/2 - 3/3/25) as the crisis unfolded. Our analysis enhanced the earthquake catalogue from around 4,000 to 80,000 earthquakes. The enhanced catalogue allowed this international expert group to identify the volcanic-tectonic character, clearly revealing burst-like, spasmodic seismicity swarms, which is a pattern associated with fluid-driven processes from early stages of the crisis. Detailed moment tensor inversions in early events characterised by a significant non-double couple component indicated the involvement of magmatic or high-pressure hydrothermal fluids driving the unrest. Concurrent DL-enhanced tomography efforts identified a third, deep magmatic reservoir beneath Anydros Islet, consistent with pressure-driven processes. To date, volcanic-tectonic swarms in which >200 earthquakes of ML > 4 occurred within only a few weeks, largely within episodic bursts of seismicity, have not been observed elsewhere.

The first seismo-volcanological observatory in the anglophone Caribbean was established on Montserrat in 1936, in response to a volcano-seismic crisis that began with repeated felt events in 1933. Staff at Montserrat's agricultural office began routinely recording earthquake shocks in 1934. In 1936, following a scientific expedition dispatched by the Royal Society, an observatory was established at the Grove Botanical Station, Plymouth. This was run by volcano-seismic observers who managed an instrumental network, and monitored gas and steam emissions and air quality. The observatory functioned until 1946. We reconstruct the decision-making and evolution of the instrument networks as the observatory was established, and highlight the personnel involved, including the first female seismo-volcanic observer on Montserrat, Greta Scotland. Observations from the 1930s crisis emphasise the persistent seismicity and gas emissions associated with this extended episode of unrest, and suggest that there were minor phreatic explosions at the height of the crisis. We draw parallels with long-term observations of the activity of the Soufrière Hills Volcano since the 1990s.

We examine the extent to which movies that prominently feature volcanoes and volcanic eruptions reflect the reality of eruptions and eruptive crises. To do this, we develop an interdisciplinary methodology that draws on frameworks and earlier findings from disaster risk science, cultural theories of risk, film studies, volcanology and science communication. Variation in volcanic behaviours and their timescales are important during volcanic crises, so we compare the narrative arc (progression of the eruptive storyline in fictionalised accounts) with real eruptive arcs. We also examine the occurrences of common misconceptions about volcanoes, and volcanic eruptions, and misleading ideas about volcanologists and disaster risk (‘disaster tropes’) in volcano movies. Where eruptions are central to a film, eruptive timelines are more compressed relative to reality, typically with rapid accelerations to a single paroxysm, and the almost ubiquitous presence of physically unrealistic lava flows, regardless of eruption type. In these films, scientific response to volcanic activity can demonstrate unrealistic ideas about technical interventions enabling prediction, draw on cliched representations of scientists, and rarely feature (or misrepresent typical behaviours of) wider populations at risk. Nonetheless, some aspects of eruptive crises are well captured, particularly unrest, uncertainty and the tensions it creates. We conclude by suggesting how more realistic eruptive timelines and the inclusion of realistic scenarios could still be compatible with engaging storytelling, particularly with new developments in the modes of ‘movie’ storytelling. Finally, we consider the lessons volcanologists can learn from compelling storytelling, and the role that volcanologists could play in sharing these compelling stories.

Mercury (Hg) is a toxic trace metal. It is clear that its natural cycle has been highly disturbed by human activities, but there remains much to understand about how it operated before these perturbations. For example, the influences of glacial-interglacial climate changes on the geochemical cycle of environmental Hg remain poorly understood. While key Hg surface reservoirs are sensitive to millennial-scale climate variations, it is unclear whether these responses influence their long-term behavior. Here, we explore how the terrestrial Hg cycle responds to environmental changes over multiple glacial-interglacial cycles by analysis of a similar to 1.36-million-year-long sedimentary Hg record from the ancient Lake Ohrid (SE Europe): with the objective of understanding which processes may impact the behavior of this cycle on millennial timescales. Our analysis reveals periodic behavior in Hg between 1,360 and 780 thousand years ago (ka), but a weaker link from similar to 780 ka to present. This transition corresponds roughly to the Mid-Pleistocene transition (MPT), which is observed in climate and ice-volume proxies in both Northern and Southern Hemispheres. These data confirm that long lacustrine Hg records are modulated by, and can capture variability in, terrestrial reservoirs for Hg. We propose that the change in Hg behavior corresponds to a reduction in catchment vegetation and soil carbon, and, consequently, Hg reservoir capacity following the Mid-Pleistocene transition. Our findings demonstrate that climate-driven changes in terrestrial reservoir size and stability can significantly influence the long-term behavior of Hg, which could have major implications for our understanding of this cycle on a regional to global scale.

Sulfur plays a critical role in modulating redox cycling on Earth. Yet, sulfur's behavior during subduction and in mantle redox reactions is debated. We analyzed 34S/32S in mafic arc melt inclusions from contrasting subduction zones and modeled slab-mantle interaction to investigate the subduction zone sulfur cycle. We find that degassing may enrich or deplete the melt strongly in 34S as a function of melt redox state. After correction for this effect, arc magmas have a substantially narrow range of δ34S values (+3 ± 2‰), higher than the ambient upper mantle (-1‰). Slab-derived sulfur is oxidized, evidenced by a concurrent increase in mantle Fe3+ and sulfur contents, and contributes up to 86% of the mantle wedge's sulfur budget. Arc magma δ34S values reflect a common slab source for sulfur: the oceanic crust. Subduction zones act as a "filter" for oxidative power and 34S, effectively returning these to the surface over geological timescales.

Fissure-fed eruptions are a common type of volcanic activity globally. Recent fissure-fed eruptions from the Svartsengi Volcanic System have significantly impacted Iceland’s Reykjanes Peninsula. This activity may continue intermittently for decades to centuries, so understanding the controls on the locations and propagation of these fissure-fed eruptions is vital for continued hazard assessment and risk mitigation. This study maps eruptive fissures from six eruptions between December 2023 and September 2024 using satellite and aerial imagery and quantifies fire-fountain height evolution for four eruptions using webcam footage. Fissure locations are heavily influenced by topography, including features parallel to fissure strike and features formed during previous eruptions. The maximum fire-fountain heights ranged from 56 m during the January 2024 eruption to 133 m during the August 2024 eruption. Variations in fire-fountain heights in a single eruption between different fissure segments, and through time, appear to primarily be controlled by surface vent size and dike pressurisation, both of which increase mass eruption rate and lead to higher fountains. Understanding the controls on fissure propagation highlights areas most vulnerable to future fissure opening. These insights could be used to help inform ongoing hazard assessment and risk mitigation. Digital video capture of future eruptions from multiple angles would augment monitoring and help refine further models of fire-fountain evolution.

Sulfur has considerable leverage on the redox budget of subducted materials due to its presence as both sulfide (S2-) and sulfate (S6+). Recent work has revealed a discrepancy: arc magmas have positive delta S-34 values, while much of the S entering subduction zones should be hosted in pyrite, which is likely to have negative sulfur isotopic values. To address this discrepancy, we focus on the Central American subduction zone, where previous work has revealed positive delta S-34 values in parental arc magmas. We report the first comprehensive study of the sedimentary S input to any subduction zone with S concentration and sulfur-isotopic measurements of ODP Site 1040 sediments. Sedimentary S input for Central America is greater than previously thought (1.71 +/- 0.38 x 10(8) mol S/yr/100 km), although insufficient to supply the S output from the arc without contributions from subducting oceanic crust. Furthermore, similar to 90 % of the sedimentary S input is hosted in pyrite, leading to a bulk sedimentary delta S-34 of -19.5 parts per thousand. In assessing the mass balance for Central America, we find that selective removal of sulfate does not provide enough S to support arc output and thus, additional S must be mobilized by the oxidation of pyrite with several per mil rock-fluid delta S-34 fractionation to positive values. Our results agree with existing evidence that subduction zones act as efficient redox reactors, with oxidized portions of the slab (e.g., altered oceanic crust) providing the oxidizing power to supply sulfate to the arc, while a reduced and S-32-enriched complement sinks into the deeper mantle.

The April 2021 explosive eruption of La Soufrière, St Vincent, produced plumes of ash and SO2 which were observed with multiple satellite instruments. In this project these were studied with the Advanced Baseline Imager (ABI) on the Geostationary Operational Environmental Satellite (GOES) and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the three MetOp satellites.The high temporal resolution of the ABI instrument (1-10 minutes) was used to identify the approximate start and end times of each eruptive event during the 14-day eruption. There were a minimum of 35 explosive events which have been divided into four phases. The first was an initial explosive event, which was followed by a sustained event lasting over nine hours. The eruption then entered a pulsatory phase which consisted of 25 explosive events in a 65.3 hour period. Finally, there was a waning sequence of events. Over the final two phases, the duration of each event and the repose time between them was shown to increase.The IASI instrument has sensitivity to sulfur dioxide (SO2) which can be exploited to flag pixels containing SO2 and then to quantify the amount and height. Using IASI data, the SO2 plume was tracked as it was transported around the globe between –45 and 45° N. The retrievals showed a complex structure to the plume which may reflect the multiple explosive events that occurred. Most of the SO2 was shown to be in the upper troposphere and lower stratosphere. A peak SO2 mass loading of 0.31 ± 0.09 Tg occurred on 13 April a few days after the eruption began. The total mass values were converted into fluxes, with the highest fluxes occurring in the first few days of the eruption. In total it is estimated that the eruption emitted 0.63 ± 0.5 Tg of SO2.A number of similarities between the 1979 and 2021 eruptions of La Soufrière were observed in this study. These include the sequence of events with both eruptions including a pulsatory phase and the plume heights. These similarities highlight the value of these studies for better understanding eruptive events.

Changing hydrology impacts the biogeochemical cycling of elements such as mercury (Hg), whose transport and transformation in the environment appear linked to hydroclimate on diverse timescales. Key questions remain about how these processes manifest over different timescales and about their potential environmental consequences. For example, millennial-scale Hg–hydroclimate interactions in the terrestrial realm are poorly understood, as few sedimentary records have sufficient length and resolution to record abrupt and long-lasting changes in Hg cycling and the relative roles of depositional processes in these changes. Here, we present a high-resolution sedimentary Hg record from tropical Lake Bosumtwi (Ghana, western Africa) since ∼ 96 ka. A coupled response is observed between Hg flux and shifts in sediment composition, the latter reflecting changes in lake level. Specifically, we find that the amplitude and frequency of Hg peaks increase as the lake level rises, suggesting that Hg burial was enhanced in response to an insolation-driven increase in precipitation at ∼ 73 ka. A more transient, 3-fold increase in Hg concentration and accumulation rate is also recorded between ∼ 13 and 4 ka, coinciding with a period of distinctly higher rainfall across northern Africa known as the African Humid Period. Two mechanisms, likely working in tandem, could explain this correspondence: (1) an increase in wet deposition of Hg by precipitation and (2) efficient sequestration of organic-hosted Hg. Taken together, our results reaffirm that changes in hydroclimate, directly and/or indirectly, can be linked to millennial-scale changes in tropical Hg cycling and that these signals can be recorded in lake sediments.

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 (similar to 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.

The numerous volcanic centres in the Main Ethiopian Rift (MER) present significant but poorly understood hazards to local populations. The MER is also an important site to gain insights into tectonic processes as it captures the transition from continental rifting (to the south) to incipient seafloor spreading (to the north). Peralkaline magmas account for around 90% of the volcanic products found in the MER. Determining the conditions under which these magmas evolve is critical to understanding rift-related volcanism and its associated hazards. Corbetti Caldera has an extensive record of large-scale, predominantly aphyric, peralkaline rhyolite eruptions. However, little is known about the mafic magmas from which these highly differentiated melts have evolved. Here we present data from the only basaltic deposit found within the caldera, coupled with whole rock, glass and mineral analysis of the peralkaline products, to investigate magma storage conditions at Corbetti. We demonstrate that magma mixing played a role in the evolution of the basaltic magmas and use RhyoliteMELTS modelling to show Corbetti's peralkaline magmas likely evolved at pressures between 100 and 250 MPa, from a magma with an initial water content of 0.5-1 wt%, at or below the QFM buffer. Mineral hygrometry on the sparse crystal populations corroborates the RhyoliteMELTS modelling, suggesting that the basaltic magma had 0.1-1.2 +/- 0.32 wt% H2O, and the peralkaline magmas an average of similar to 5.5 +/- 1.25 wt% H2O. These results also match melt inclusion data for Corbetti and other peralkaline systems. We also provide new Ar-40/Ar-39 ages for two eruptions, a pre-caldera rhyolitic lava flow (206.7 +/- 0.9 ka) and a post-caldera peralkaline ignimbrite (160 +/- 0.8 ka). These results add to our understanding of the history of Corbetti and the storage conditions of peralkaline magmas within a continental rift setting and highlight the hydrous nature of Corbetti's magmas and the role that H2O plays during explosive eruptions.

The rates and pathways of material transport from subducting plates to arc volcanoes control the long-term chemical evolution of the atmosphere, continents, and mantle. Arc magma compositions are commonly used as proxies for the state of the slab directly below a volcanic vent, under the assumption of vertical transport from the slab to the surface. Here, we present new boron (B) isotope and trace element data that challenge this assumption. Measurements of olivine-hosted melt inclusions from 900 km along and 200 km across the Southern Andean Volcanic Zone reveal remarkably coherent trends, indicating: (1) That the B isotope composition of the slab component sampled by erupted magma is invariant with slab depth, contrary to the expectation that the slab composition should progressively change with dehydration, and (2) that slab overprinting decreases with the distance from a long-lived arc-front stratovolcano in both along- and across-arc directions. These observations indicate that slab liquids generated across a large depth range are subsequently homogenized and focused both parallel and perpendicular to the trench. Similar geochemical behavior is apparent in other arc segments. We hypothesize that along-arc focusing is the consequence of periodic-in-space, solid-state, abortive upwelling from the slab surface, and that this produces persistent zones of elevated mantle melting consistent with the characteristic narrow geometry and isolated, long-lived stratovolcanoes of volcanic arcs. This framework implies that the structures of volcanic arcs have a deep origin, and can be used to better interpret global variations in subduction fluxes and their relationship with subduction parameters.

The 2020-21 eruption of La Soufriere, St Vincent began with extrusion of a viscous lava dome, which was destroyed upon transition to a major explosive phase. Here we present petrological data to reconstruct the processes leading up to these events. Bulk-rock SiO2 contents range from 52.8 to 55.4 wt%, classifying the lava and the subsequent scoria as basaltic andesite, the latter being slightly more mafic. Macrocrystal chemistry and modes (plag-cpx-opx-tmt-ol) and crystallinity (45-50 vol%) are largely identical for both phases of the eruption. Pyroxenes are homogenous and precipitated mostly from andesitic melts. Conversely, plagioclase shows strong normal zonation resulting from magma ascent and stalling at multiple crustal levels. Clinopyroxene thermobarometry reveals that crystallization predominantly took place between 8 and 13 km depth at temperatures of 997(-35)(+18) degrees C. A lack of evidence for mafic recharge and changes in volatile content and the omnipresence of xenoliths, suggests pre-eruptive destabilization of an andesitic-dacitic melt pocket that disrupted and entrained antecedent mush. Olivine diffusion profiles show that this interaction preceded the onset of eruption. Low dissolved sulfur contents (<= 270 ppm S) place constraints on the total SO2 gas release. Meltmush disruption appears to be a dominant driver of eruptions at La Soufriere.

Advances in air and space sensor technology reveal new opportunities and innovative ways to remotely sense the Earth’s subsurface. Considerable spatial coverage, fast and frequent image acquisition and very high radiometric, spectral, spatial and temporal resolution imaging systems can now detect near subsurface anomalies with impressive accuracy. The merits are extensive, with archaeological prospecting, environmental risk mitigation, natural resource exploration, defence and security and speleological research all benefitting from subsurface imaging capabilities over unknown territory, difficult terrain, hazardous environments and inaccessible ground. In this paper, we categorise the ground indicators and potential field characteristics of a general subsurface anomaly before reviewing and documenting over seventy air and space subsurface detection techniques using: photogrammetry, multispectral sensors, thermal infrared, hyperspectral imaging, synthetic aperture radar (SAR), airborne light detection and ranging (LiDAR), airborne gravity and aeromagnetics. The capabilities of each technique are evaluated by reviewing their ability to detect specific characteristics from subsurface anomalies and then they are tabulated by investigable feature and sensor type in seven technique tables. Research trends in motive, sensor type and subsurface anomaly characteristic are discussed and a short review of the major ground-truthing techniques used to verify airborne and spaceborne observations is considered. To close, we take a brief look at future research opportunities with very high resolution (VHR) datasets, multi-branch convolutional neural networks (CNNs) and active remote sensing in variable potential fields.

Focusing on the study of existential risk, this chapter shows how academic research publications can be systematically reviewed using semi-automated processes such as crowdsourcing and machine learning. These publications can then be accumulated in an open-access database, if relevant, forming a reusable evidence base for policy and risk analysis. The authors use The Existential Risk Research Assessment (TERRA), a living bibliography about existential risk, as an example of the semi-automated processes in action, noting the successes and challenges of such a semi-automated tool. This chapter allows for speculation concerning the future of a publication base like TERRA and the authors encourage readers themselves to participate in TERRA, to contribute to a bigger and better future bibliography.

The element mercury (Hg) is a key pollutant, and much insight has been gained by studying the present-day Hg cycle. However, many important processes within this cycle operate on timescales responsive to centennial- to millennial-scale environmental variability, highlighting the importance of also investigating the longer-term Hg records in sedimentary archives. To this end, we here explore the timing, magnitude, and expression of Hg signals retained in sediments over the past ∼ 90 kyr from two lakes, linked by a subterranean karst system: Lake Prespa (Greece, North Macedonia, and Albania) and Lake Ohrid (North Macedonia and Albania). Results suggest that Hg fluctuations are largely independent of variability in common host phases in each lake, and the recorded sedimentary Hg signals show distinct differences first during the Late Pleistocene (Marine Isotope Stages 2–5). The Hg signals in Lake Prespa sediments highlight an abrupt, short-lived peak in Hg accumulation coinciding with local deglaciation. In contrast, Lake Ohrid shows a broader interval with enhanced Hg accumulation and, superimposed, a series of low-amplitude oscillations in Hg concentration peaking during the Last Glacial Maximum, which may result from elevated clastic inputs. Divergent Hg signals are also recorded during the Early and Middle Holocene (Marine Isotope Stage 1). Here, Lake Prespa sediments show a series of large Hg peaks, while Lake Ohrid sediments show a progression to lower Hg values. Since ∼ 3 ka, anthropogenic influences overwhelm local fluxes in both lakes. The lack of coherence in Hg accumulation between the two lakes suggests that, in the absence of an exceptional perturbation, local differences in sediment composition, lake structure, Hg sources, and water balance all influence the local Hg cycle and determine the extent to which Hg signals reflect local- or global-scale environmental changes.

The rigorous assessment of volcanic hazards relies on setting contemporary monitoring observations within an accurate, longer-term geological context. Revealing that geological context requires the detailed fieldwork, mapping and laboratory analysis of the erupted materials. However, many of the world’s most dangerous volcanic systems are located on or near coasts (e.g., the Phlegraean Fields and Vesuvius in Italy), islands (e.g., the volcanic archipelagos of the Pacific, south-east Asia, and Eastern Caribbean), or underwater (e.g., the recently erupting Hunga Tonga–Hunga Ha’apai volcano), meaning that much of their erupted material is deposited on the sea bed. The only way to sample this material directly is with seafloor sediment cores. This perspectives paper outlines how marine sediment cores are a vital yet underused resource for assessing volcanic hazards by: (1) outlining the spatio-temporal scope of the marine volcanic record and its main deposit types, (2) providing existing examples where marine sediments have contributed to volcanic hazard assessments; (3) highlighting the Sunda Arc, Indonesia as an example location where marine sediment cores are yet to contribute to hazard assessments, and (4) proposing that marine sediment cores can contribute to our understanding of very large eruptions that have a global impact. Overall, this perspectives paper aims to promote the utility of marine sediment cores in future volcanic hazard assessments, while also providing some basic information to assist researchers who are considering integrating marine sediment cores into their volcanological research.