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The Rocourt Tephra (RT) is a widespread stratigraphic marker distributed in Germany, Belgium, and the Netherlands , where it is used for stratigraphic correlations, dating of host sediments and of Middle Palaeolithic archaeological assemblages, sometimes including Neandertal remains. Its age is estimated between 78 and 80 ka. This tephra has been linked to the West Eifel Volcanic Field in Germany, but its corresponding source volcano is unknown. Such a discovery would make it possible to confirm or challenge the age of the tephra, because this source volcano could be dated by various methods. It would also be possible to know the composition of the magma, which cannot be determined from the altered clasts of the tephra, as well as the original mineralogical composition, thereby strengthening the validity of the marker by providing more distinctive data. Two Eifel monogenic volcanoes have been cited as potential sources, the Dreiser Weiher and the Pulvermaar, due to their large sizes and broadly similar compositions. A study of the tephra layers from these volcanoes was carried out to compare their mineral compositions with that of the Rocourt Tephra. Based on new analytical data on the composition and magmatic trends of pyroxenes, it is concluded that neither of the two volcanoes can be the source of the RT.

We present an exposure analysis of infrastructure and lifeline to tephra fallout for a future large-scale explosive eruption of Sakurajima volcano. An eruption scenario is identified based on the field characterization of the last subplinian eruption at Sakurajima and a review of reports of the eruptions that occurred in the past six centuries. A scenario-based probabilistic hazard assessment is performed using the Tephra2 model, considering various eruption durations to reflect complex eruptive sequences of all considered reference eruptions. A quantitative exposure analysis of infrastructures and lifelines is presented primarily using open-access data. The post-event impact assessment of Magill et al. (Earth Planets Space 65:677–698, 2013) after the 2011 VEI 2 eruption of Shinmoedake is used to discuss the vulnerability and the resilience of infrastructures during a future large eruption of Sakurajima. Results indicate a main eastward dispersal, with longer eruption durations increasing the probability of tephra accumulation in proximal areas and reducing it in distal areas. The exposure analysis reveals that 2300 km of road network, 18 km 2 of urban area, and 306 km 2 of agricultural land have a 50% probability of being affected by an accumulation of tephra of 1 kg/m 2 . A simple qualitative exposure analysis suggests that the municipalities of Kagoshima, Kanoya, and Tarumizu are the most likely to suffer impacts. Finally, the 2011 VEI 2 eruption of Shinmoedake demonstrated that the already implemented mitigation strategies have increased resilience and improved recovery of affected infrastructures. Nevertheless, the extent to which these mitigation actions will perform during the VEI 4 eruption presented here is unclear and our hazard assessment points to possible damages on the Sakurajima peninsula and the neighboring municipality of Tarumizu.

The island of Sumatra within the Indonesian archipelago is home to over 130 active or potentially active volcanoes with a history of explosive eruptions. Highly explosive eruptions with volcanic explosivity index (VEI) ≥ 6 in Sumatra, such as those originating from the massive Toba caldera, have been well-documented in the literature. However, moderately explosive eruptions with VEI 3–5 have received inadequate attention due to their limited preservation within the proximal stratigraphic record. This gap in knowledge hinders existing attempts to conduct hazard assessments for these potentially impactful eruptions. In this study, we address this knowledge gap by presenting a combination of geochemical, geochronological and tephrochronological datasets associated with distal tephra layers sampled from deep-sea cores collected off the coast of West Sumatra, as well as proximal pyroclastic deposits throughout central Sumatra. Our datasets reveal geochemical and stratigraphic correlations between seven distal tephra layers and their proximal sources, allowing for the quantification of their eruption ages and volumes. Notably, we identified the ~ 1.53 ka Lubuk King Tephra (LKT) eruption from Malintang volcano that discharged ≥ 1.4 km 3 dense-rock equivalent (DRE) of magma, representing the youngest known VEI 5 eruption in Sumatra. In addition, we determined Tandikat volcano as the proximal source for a pair of temporally proximate (~ 580 yr apart) VEI 5 eruptions (Tandikat II and I Tephra, TDK II and I; ~ 4.36 and ~ 4.94 ka) that produced ≥ 1.1 and ≥ 2.7 km 3 DRE of magma, respectively. We also ascertained that at least two VEI 4 eruptions occurring within the last ~ 36 kyr can be correlated to the active Marapi volcano. Furthermore, we traced distal tephra layers AB4 (~ 36.8 ka) and AB5 (~ 41.0 ka) to two distinct VEI ≥ 5 eruptions at volcanic centres in neighbouring provinces (Ranau Tuff, RAN from South Sumatra; Djudjun Tephra, DJT from Jambi). Volcanic source provenances for another six distal tephra layers remain unknown due to the lack of known proximal correlatives. Overall, our study provides an improved tephrochronological framework for late Pleistocene-Holocene explosive volcanism in central Sumatra that will help refine existing volcanic hazard assessments and enhance the integration of terrestrial and marine palaeoenvironmental archives regionally.

Long‐term tephrostratigraphies of volcanic islands such as the Azores are often limited to young and incomplete subaerial records. Here, we present a Pleistocene‐Holocene marine tephra archive around the eastern islands of the Azores based on 22 marine gravity cores. We provide a new extensive data set comprising major element glass compositions of 350 marine tephra layers and 26 tephra samples collected from subaerial outcrops on São Miguel Island. The marine tephra record is dominated by trachytic glass compositions with lesser amounts of trachy‐basaltic/basaltic materials. We categorize the marine deposits into four facies: primary fall (F1), primary flow (F2), eruption‐related secondary flow (F3), and non‐eruption‐related secondary flow deposits (F4). Cores collected close to the islands contain a high proportion (>50%) of volcaniclastic material deposited during secondary processes. Using machine‐learning algorithms, we assign potential volcanic sources to individual tephra layers. Furthermore, our spatial characterization of primary/secondary deposits demonstrates the importance of carefully selecting core locations during sea‐going campaigns, as the preservation and distribution of primary and reworked tephras considerably differ depending on several factors (e.g., on paleo‐wind directions, island topography, seafloor bathymetry, and distance from source volcanoes). We also report the occurrence of mafic primary fall tephras tens to hundreds kilometers away from the closest island, indicating a potential hazard from mafic Plinian eruptions in the Azores. This study aims to improve the estimation of the eruptive frequency of the archipelago and opens new pathways for more detailed studies concerning long‐term volcanic cyclicity in the region.

The assessment of volcanic hazards is crucial to develop effective emergency plans, especially for volcanoes close to urban areas or under air traffic routes. Impact assessment for expected scenarios relies on underlying numerical models that require eruption source parameters as inputs, and forecasts drastically depend on their robust reconstruction during ongoing events. We apply a novel tephra deposit inversion workflow built on ensemble methods and data assimilation techniques to reconstruct the explosive events that occurred at Mt Etna, Italy, between 3 and 5 December 2015. Based on results from previous studies, we reconstruct this eruption using the Gaussian with Non‐negative Constraints data assimilation method. Results agree well with independent observations and highlight the potential for automatized procedures in volcanic hazard assessment.

1. Impacts of tephra deposition on vegetation are recorded in a series of 10 high temporal resolution absolute pollen diagrams from Lago Grande di Monticchio, each diagram spanning a single tephra deposition event during the last glacial-interglacial cycle. 2. Sediment accumulation rates determined by counting and measurement of annual laminations (\"varves\") provide an accurate and precise chronology, enabling the minimum recovery time after a tephra fall to be determined. 3. In most cases, pollen accumulation rate was reduced after the tephra fall, indicating reduced vegetation productivity. Tephra deposition events also led to changes in vegetation composition, although these varied in magnitude. 4. The magnitude and duration of the impacts upon the vegetation were related to the thickness of the tephra layer deposited, the thickest layers examined (>250 mm) having minimum recovery times of up to a century and thicker layers generally having greater impacts upon pollen productivity and vegetation composition. 5. Tephra chemistry also influenced the persistence of the impact. 6. The nature of the prevailing vegetation prior to the tephra fall influenced the degree and persistence of the impact. Tephra layers <30 mm thick had minimum recovery times of up to 90 years when they fell on wooded steppe vegetation, whereas cold steppe recovered much more quickly, as did forest. 7. The relative sensitivity of wooded steppe was contrary to our expectations. 8. Of individual pollen taxa, Cupressaceae emerged as particularly sensitive to tephra deposition. 9. Synthesis. Applying absolute pollen analytical methods to a sediment record with a well-supported and precise chronology obtained from a lake in a volcanic region where the vegetation has been subject to numerous tephra deposition events enabled us to explore the impacts of such events. Our results provide evidence of differential impacts upon individual plant taxa and of differential sensitivity of three vegetation types that have prevailed in the region during the last glacial-interglacial cycle. The influences of tephra thickness and chemistry on minimum recovery time were substantial. Our results are relevant to forecasting the potential impacts upon ecosystems of volcanic eruptions.

A new method for assessing volumes of tephra deposits based on only two thickness data is presented. It is based on the assumptions of elliptical shape for isopachs, a statistical characterization of their eccentricity, and an empirical relationship between their deposit thinning length scale and volumes. The method can be applied if the pair of thickness data are sufficiently distant from the volcano source, with a minimum distance ratio larger than 2. The method was tested against about 40 published volumes, from both equatorial belt and mid-latitude volcanoes. The results are statistically consistent with the published results, demonstrating the usefulness of the method. When applied in forward, the model allowed us to calculate the volume for some important tephra layers in the Mediterranean tephrostratigraphy, providing, for the first time, an assessment of the size of these eruptions or layers.

The climactic eruption of Mount Mazama in Oregon, North America, resulted in the deposition of the most widespread Holocene tephra deposit in the conterminous United States and south-western Canada. The tephra forms an isochronous marker horizon for palaeoenvironmental, sedimentary and archaeological reconstructions, despite the current lack of a precise age estimate for the source eruption. Previous radiocarbon age estimates for the eruption have varied, and Greenland ice-core ages are in disagreement. For the Mazama tephra to be fully utilised in tephrochronology and palaeoenvironmental research, a refined (precise and accurate) age for the eruption is required. Here, we apply a meta-analysis of all previously published radiocarbon age estimations (n = 81), and perform Bayesian statistical modelling to this data set, to provide a refined age of 7682–7584 cal. yr BP (95.4% probability range). Although the depositional histories of the published ages vary, this estimate is consistent with that estimated from the GISP2 ice-core of 7627 ± 150 yr BP (Zdanowicz et al., 1999).

The simultaneous or sequential occurrence of several hazards—be they of natural or anthropogenic sources—can interact to produce unexpected compound hazards and impacts. Since success in responding to volcanic crises is often conditional on accurate identification of spatiotemporal patterns of hazard prior to an eruption, ignoring these interactions can lead to a misrepresentation or misinterpretation of the risk and, during emergencies, ineffective management priorities. The 2021 eruption of Tajogaite volcano on the island of La Palma, Canary Islands (Spain), was an 86 day-long hybrid explosive-effusive eruption that demonstrated the challenges of managing volcanic crises associated with the simultaneous emission of lava, tephra and volcanic gases. Here, we present the result of a small-scale impact assessment conducted during three-field deployments to investigate how tephra fallout and lava flow inundation interacted to cause compound physical impact on buildings. The study area was a neighbourhood of 30 buildings exposed to tephra fallout during the entire eruption and by a late-stage, short-lived lava flow. Observations highlight, on one hand, the influence of clean-up operations and rainfall on the impact of tephra fallout and, on the other hand, the importance of the dynamics of lava flow emplacement in controlling impact mechanisms. Overall, results provide an evidence-based insight into impact sequences when two primary hazards are produced simultaneously and demonstrate the importance of considering this aspect when implementing risk mitigation strategies for future long-lasting, hybrid explosive-effusive eruptions in urban environments.

Marine fallout ash beds can provide continuous, time‐precise records of highly explosive arc volcanism that can be linked with the climate record. An evaluation of revised Plio‐Pleistocene (0–4 Myr) tephrostratigraphies from Ocean Drilling Program Sites 881, 882, and 884 confirms cyclicity of the Kamchatka‐Kurile arc volcanism and a marked increase just after the intensification of the Northern Hemisphere glaciation at 2.73 Ma. The compositional constancy of the Kamchatka‐Kurile volcano‐magma systems through time points to external modulation of volcanic cyclicity and frequency. The stacked tephra record reveals periodic peaks in arc volcanicity at ∼0.3, ∼1.0, ∼1.6, ∼2.5, and ∼3.8 Myr that coincide with maxima of the global ice volume variability that have been linked with the amplitude modulation of the precession (0.3, 1.0 Myr) and obliquity (1.6, 2.5 and 3.8 Myr) bands. A simple model of a decreasing obliquity variance across the mid‐Pleistocene Transition at constant precession variance produces an excellent correlation of ash bed cycles with the variability of global benthic δ18O (r2 = 0.75), which implies that climate, and not direct orbital forcing, modulates Kamchatka‐Kurile arc volcanism. The rising influence of precession variance in the Kamchatka‐Kurile ash bed record after the mid‐Pleistocene Transition contrasts with the dominant 100 kyr signal in the benthic δ18O global ice volume variability, which may either reflect limitations of the ash bed record or an regional rather than global influence of ice volume variability. Our results indicate that climate influences the Kamchatka‐Kurile arc volcanism, which may influence climate only by feedback. Plain Language Summary Volcanic ash and dust produced during catastrophic explosive volcanic eruptions, such as those of Mount Pinatubo or El Chichón, can cause short‐term global cooling on the scale of a few years. It has long been speculated whether the Earth's long‐term cooling over the past few million years has been augmented by an increase in explosive volcanism about 2.58 million years ago. In order to investigate causal links between the climate evolution and volcanism during the past 4 million years, we obtained a time‐precise and temporally highly resolved record of the Kamchatka‐Kurile arc volcanism from the centimeter‐thick ash beds that were embedded in marine sediments after large eruptions downwind the volcanic sources. When the ash bed record is compared to climate evolution, it clearly shows that explosive volcanic eruptions—regardless of their short‐term effects—do not contribute directly to the long‐term global cooling. Instead, the variations of the Earth's powerful climate system modulate these explosive volcanic eruptions, as the periodic waxing and waning of the large ice shields affect the magma‐producing systems deep in the Earth's interior. However, climate‐active gases and particles produced during periods with more vigorous arc volcanism may still enhance the ice cycles. Key Points Marine fallout ash beds record cyclicity and acceleration of the Plio‐Pleistocene (0–4 Myr) explosive Kamchatka‐Kurile arc volcanism Ash bed cyclicity correlates with the obliquity and precession variance of the global ice volume Climate, and not direct orbital forcing, modulates the Plio‐Pleistocene volcanicity of the Kamchatka‐Kurile arc