Osteoporotic vertebral fractures affect many elderly patients, and complications after common treatments such as vertebroplasty (VP) may reduce treatment satisfaction and radiographic stability. This study investigated whether the addition of posterior instrumentation with cement-augmented fenestrated pedicle screws (VP + PI) was associated with improved short-term radiographic outcomes compared with VP alone. We retrospectively analyzed 153 patients with osteoporotic vertebral fractures treated between 2017 and 2022. Patients underwent either VP alone or VP + PI. To reduce treatment-selection bias, propensity score matching was performed. Vertebral collapse was assessed on serial radiographs at 1, 3, and 6 months postoperatively, and statistical analyses were performed using SAS software. After propensity score matching, the VP + PI group had significantly lower anterior column collapse rates at 3 and 6 months postoperatively. Multivariable logistic regression confirmed that VP + PI was independently associated with a reduced risk of anterior column collapse at 6 months (adjusted OR: 0.147, 95% CI: 0.043-0.502, p = 0.0022). At 6 months, screw loosening was observed in 6 of 75 patients in the VP + PI group, and none required revision surgery during the follow-up period. VP + PI may provide better short-term radiographic stability than VP alone in selected patients with osteoporotic vertebral fractures. However, given the longer operation time and hospital stay, lack of functional outcome assessment, and limited follow-up duration, the clinical benefit and long-term safety of VP + PI require further investigation. Not applicable.

ABSTRACT The present study explores the wave generation, progression, and decay induced by the collapse of partially/completely submerged granular columns in a confined domain. The wave reflection at the opposite side of the landslide becomes important, especially in reservoirs of narrow width, leading to the consideration of a confined experimental setup. The time history of the waves recorded at fixed spatial points within the domain is characterized by the peak amplitude, time of arrival and decay. The non-dimensional peak amplitude for the same granular heights varies inversely with the fluid depth. The maximum wave amplitude is recorded at the downstream boundary, and the decay of the waves follows an exponential law that becomes asymptotic to the mean water level. The decay coefficient of the exponential law for partially submerged cases depicts that the water surface fluctuations die down faster in the middle than in the downstream extremity and near the collapse zone. For fully submerged cases, the faster dissipation is observed near the toe of the collapse zone. The post-collapse interaction of the waves with a sloping porous surface leads to a slowed dissipation of the waves in the domain and sometimes induces secondary granular motion as well.

Investigation of the bending collapse of thin double-walled multi-corner columns with foam-filled subjected to quasi-static lateral impact

Abstract Geophysical granular flows, involving rapidly flowing granular materials, can exhibit volume‐enhanced mobility. Lacking a mechanistic understanding of such size effects limits the applications of lab‐scale findings to natural events. Using discrete element method simulations, we find that increasing granular system size suppresses energy‐dissipating velocity fluctuations while promoting sustained creeping motion. This nonlocal phenomenon of granular materials enhances the mobility in various granular column collapse scenarios. This mechanism is reflected in the rheological data, which deviate from traditional rheology but are collapsed under a recent power‐law rheology that incorporates velocity fluctuations. Moreover, this size‐dependent power‐law rheology exhibits universality in transient simulations with varied flow geometries, slope angles, and base roughness. This rheologically consistent framework, spanning inertial to quasi‐static states, bridges small‐scale investigations and continuum models for large‐scale simulations, enabling improved predictive capability of the entire flow processes, from initiation to deposition, in natural geophysical flows.

The 1131 CE Te Popo eruption was one of the two largest magnitude eruptions of Taranaki Mounga's most recent eruptive period and followed ~250 years of quiescence. The eruption involved three phases of column development that produced tephra fallout, followed by column collapse events that produced pyroclastic density current and ash deposits reflecting unsteady plumes and an intermittently stable conduit. This study focuses on the lithic clasts ejected during the eruption to understand the role of the shallow conduit and vent in the sub-Plinian eruption's multi-phase dynamics. We show how the conduit was comprised of older edifice lavas and intrusive lithologies that were continuously eroded to achieve more stable geometries during the eruption. Vent and crater excavation dominated early phases, before deeper erosion of intrusive accessory lithics around the fragmentation depth became more prevalent. Lining accumulation both below and above the fragmentation depth occurred continuously during fall phases before being eroded and incorporated into pyroclastic density currents during wall collapse. We propose conduit erosion processes played a significant role in evolving eruption dynamics. These results contrast with lithics ejected during the other large eruption in this period (Burrell Eruption), which occurred between multiple effusive events. The Te Popo episode offers the most likely scenario for re-awakening dynamics of Taranaki, due to the similar length of the pre-eruption repose period (since 1790 CE). • The sub-Plinian Te Popo eruption of Taranaki Mounga followed an extended period of repose (~250 years), similar to the current quiescence since the most recent eruption. • Mineralogy and textures of lithics ejected across the multi-phase eruption reflect conduit establishment through an established volcanic edifice. • Repeated fall episodes separated by column collapse PDCs, ashfall and periods of quiescence reflect unstable conduit walls, possibly due to alteration extent. • Comparing Te Popo lithic clasts to those ejected during the 1655 CE Burrell eruption reveals conduit lining and armouring by the interceding effusive eruptions.

Progressive collapsing foot deformity (PCFD) is characterized by multiplanar talar malalignment, including medial arch collapse. Although ankle arthrodesis is a well-established treatment for end-stage ankle osteoarthritis, its effect on concomitant PCFD-related parameters remains unclear. We observed that ankle arthrodesis appeared to result in radiographic changes in the medial column alignment, raising questions about whether talar stabilization might influence PCFD-related deformity. (1) Do patients with severe medial column collapse achieve greater radiographic correction after ankle arthrodesis compared with those with mild collapse? (2) Do patients with severe medial column collapse experience greater functional gains than patients with mild collapse after isolated ankle arthrodesis? (3) Do pedobarographic parameters change after ankle arthrodesis in patients with PCFD? Between January 2015 and June 2024, one surgeon performed ankle arthrodesis in 171 patients with end-stage ankle osteoarthritis. Of these, 58% (99) had radiographic evidence of medial column collapse (lateral Meary angle > 4°). After excluding patients < 18 years of age (1% [1 of 171]); those with nonunion (1% [2]), previous foot and ankle surgery (4% [7]), or neuromuscular disease (3% [5]); and those lost before 1-year follow-up (2% [4]), 47% (80) of patients remained. Patients were stratified by preoperative lateral Meary angle: mild (4° to 15°; n = 40) and severe (> 15°; n = 40). The mean ± SD age and follow-up time were 70 ± 6 years and 36 ± 21 months in the mild group and 72 ± 6 years and 34 ± 19 months in the severe group, respectively. We compared preoperative and postoperative PCFD-related radiographic parameters and functional outcomes using the Foot and Ankle Outcome Score (FAOS), the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale, and a VAS for pain. Pedobarographic analysis was performed in 10 consecutive patients preoperatively and postoperatively from the severe group who had equipment available during their follow-up visits. Patients with severe medial column collapse achieved greater radiographic correction than those with mild collapse; for example, the lateral Meary angle improved by mean ± SD 12° ± 7° in the severe group versus 6° ± 4° in the mild group (mean difference 6° [95% confidence interval (CI) 3° to 9°]; p < 0.001). Patients with severe collapse did not experience larger functional gains than those with mild collapse; the improvement in AOFAS score was no different between groups (22 ± 22 points versus 26 ± 26 points, mean difference -5 points [95% CI -16 to 6 points]; p = 0.36). Pedobarographic analysis in 10 patients from the severe group showed pressure redistribution from preoperative to final follow-up, with medial midfoot pressure remaining stable (13 versus 14 kPa; p = 0.44), while lateral forefoot pressure increased most prominently (17 versus 32 kPa; p = 0.01). Patients with severe PCFD achieved greater radiographic correction than those with mild collapse after isolated ankle arthrodesis, yet functional improvements did not differ between groups. Surgeons can consider isolated ankle arthrodesis for end-stage ankle osteoarthritis with concomitant PCFD, even in severe cases, expecting substantial deformity correction without additional procedures. Future studies should determine the threshold beyond which adjunctive procedures become necessary and assess long-term adjacent joint degeneration. Level III, therapeutic study.

This study investigates the sedimentation of volcanic particles from low-altitude (< 2km a.s.l.), near-daily ash plumes and clouds at Sakurajima volcano (Japan). Plume dynamics were monitored using imagery (visible wavelength) and geophysical (ash discharge rates) data. Ash fallout was characterized by using ground-based (disdrometer, particle electrical charge sensor, and sampling) and drone-mounted (optical particle counter, atmospheric sensor, and sampling) instruments. A comparison of particle size distributions and aggregate proportions between samples collected by drone 500m above the take-off sites and those collected on the ground shows that aggregation develops rapidly during sedimentation. This process involves collisions between coarse ash (up to 1mm) and fine ash particles (< 63µm). Particle binding is promoted by electrostatic attraction (forming particle clusters) or high atmospheric humidity (forming accretionary pellets). These results provide innovative in-situ evidence of ash aggregation, offering new insights into its dynamics in natural settings, crucial for improving volcanic ash dispersion forecasting.

Abstract Pyroclastic density currents (PDCs) are gravity currents that frequently form during explosive volcanic eruptions. These ground‐hugging density currents consist of high‐temperature mixtures of pyroclasts (e.g., ash, pumice), lithics, and gas. They have the potential to generate co‐PDC plumes, which detach from the underlying PDC as they buoyantly rise into the atmosphere. Co‐PDC plumes, composed of fine‐grained ash particles and hot gas, can reach heights of tens of kilometers, potentially dispersing large volumes of ash over continental scale areas, impacting the environment, and posing a risk to aviation. Owing to their formation mechanism, co‐PDCs have unique characteristics, such as fine particle sizes (e.g., &lt;90 μm) and a high‐aspect ratio, irregular‐shaped, source geometry. Here, we consider how the release of ash into the atmosphere from a co‐PDC plume may differ to that from a typical Plinian eruption column, and the implications for operational modeling of the resulting ash cloud for the provision of advice to the aviation industry. We use the Numerical Atmospheric‐Dispersion Modelling Environment (NAME), which is used by the London Volcanic Ash Advisory Centre. We performed a sensitivity analysis to determine which co‐PDC source parameters are important for modeling the associated ash clouds. We show that variations in the source geometry, that is, the total area and aspect ratio, have a minor impact after the first ∼6 hr in the atmosphere.

Abstract Volcanic ash formed during explosive volcanism reacts with SO 2 gas molecules in volcanic conduits and eruption clouds, resulting in the formation of CaSO 4 . When ash is removed from the eruption cloud, the SO 2 gas molecule is scavenged from the eruption cloud. The CaSO 4 growth is rate‐limited by Ca 2+ diffusion at high temperatures. Here, we estimate the amount and efficiency of SO 2 scavenged by volcanic ash in eruption clouds (eruption column and pyroclastic flow) and the conduit for the 1991 Pinatubo eruption by combining a 3D numerical simulation of volcanic clouds and diffusion modeling. Our calculation showed that the amount of SO 2 scavenging in the pyroclastic flow was almost the same order of magnitude as that in the conduit. This can be explained by considering that pyroclastic flow forms a larger hot region just above the vent, and thermal energy cannot be easily consumed by mixing with the ambient air. This result sheds light into the potential of pyroclastic flows to be more efficient at high‐temperature SO 2 scavenging than previously thought. We estimated the actual efficiency of SO 2 scavenging during the 1991 Pinatubo eruption (3.5–9 hr), and the estimated value was compared with the satellite data of SO 2 injected into the stratosphere (20 Mt). Our results suggest that 8.0%–90% SO 2 emitted could be scavenged from the eruption cloud during the 1991 Pinatubo eruption. Our model results indicate that including thermal evolution of eruption cloud structures can lead to more accurate predictions of SO 2 scavenging during large volcanic eruptions.

Gravity-driven granular flows, including debris flows and landslides, represent significant hazards to society. A clear understanding of the relationship between granular column collapse and controlling factors, such as initial geometry and basal conditions, is therefore critical for engineering mitigation. This study examines the collapse of granular columns within varied particle sizes, initial widths, and basal boundary conditions. Key parameters, such as kinematic velocity, collapse acceleration, motion duration, and final deposit morphology, are systematically analyzed. The results highlight the influence of column dimensions and basal friction on collapse dynamics: in dimensionless terms, the size effect is negligible, while basal friction predominantly influences the late stage of collapse, with limited impact during the initial and intermediate phases. Furthermore, in the functional relationships linking runout distance or deposit height to the initial aspect ratio, variations in basal conditions alter only the coefficients, leaving the exponents unchanged. Notably, these exponents also remain invariant with changes in particle size.

Abstract Granular avalanches exhibit striking parallels to natural geophysical flows, including debris flows, landslides, and pyroclastic flows, whose instability, rheology, and deposition morphology are governed by particle‐scale dynamics and bulk interactions within granular systems. To rigorously investigate fluid‐particle coupling in such multiphase environments, this study employs coupled lattice Boltzmann‐discrete element method simulations, which are validated by our experimental observations, to analyze the collapse of buoyant granular columns in subaqueous settings. The insights gained are extended to elucidate the behavior of large‐scale geophysical flows, such as submarine gravity currents. In particular, the dynamics of buoyant granular flows are shown to follow a scaling relationship similar to that observed in the 2022 Hunga Tonga‐Hunga Ha'apai volcanic plume although their underlying mechanisms might be different. This scaling transition signifies a dual regime shift, occurring both within the granular phase and at the interstitial fluid‐grain interface. By incorporating buoyancy effects where the particle density is lower than the ambient fluid, this work advances existing scaling laws for granular column collapses. Furthermore, the results provide critical insights into the multiphase physics that governs visco‐collisional geophysical flows, bridging microscale interactions to macroscale flow behaviors in natural and industrial contexts.

Transient granular flows immersed in a viscous fluid are prevalent in geological hazards (e.g., submarine landslides) and civil engineering applications (e.g., fresh concrete delivery), where particle segregation plays a critical role in shaping flow dynamics and mobility. The present study investigates density-driven segregation in immersed granular column collapses, a crucial, yet challenging, phenomenon due to complex fluid-particle interactions at the particle scale. Using the coupled LBM-DEM simulation tool that was validated by laboratory experiments, this study investigated the effects of different particle density ratios and fluid viscosities on density segregation through macro-/micro-analyses. Results show that higher density ratios lead to more pronounced segregation, with light particles migrating to the surface and heavy particles concentrating near the base, enhancing the overall mobility of the flow. Microscopically, light particles experience larger normalized average contact and hydrodynamic forces, but lower coordination numbers than heavy particles, indicating stronger driving pressures promoting their relatively upward transport. Furthermore, density segregation is primarily driven by an imbalance between gravity and buoyancy-like forces, with drag forces playing a minimal role in vertical segregation. These insights advance our understanding of density segregation in immersed granular flows and have significant implications for improving predictive models of submarine landslides and other fluid-laden granular hazards.

Abstract. Volcanic emissions from the Tajogaite volcano, located on the Cumbre Vieja edifice on the island of La Palma (Canary Islands, Spain), caused significant public health and aviation disruptions throughout the eruption (19 September–13 December 2021, officially declared over on 25 December). Nonetheless, it is considered the most significant volcanic event in Europe over the past 75 years due to the substantial amount of SO2 released into the atmosphere. The Instituto Geográfico Nacional (IGN), the authority responsible for volcano surveillance in Spain, implemented extensive operational monitoring to track volcanic activity and to provide a robust estimation of the volcanic plume height using a video-surveillance network. In parallel, the State Meteorological Agency of Spain (AEMET), in partnership with other Spanish ACTRIS (Aerosol, Clouds, and Trace Gases Research Infrastructure) members and collaborating institutions, conducted an unprecedented instrumental deployment to evaluate the impacts of this volcanic event on atmospheric composition. This effort included a network of aerosol profilers surrounding the volcano. A total of four profiling instruments were installed on La Palma: one MPL-4B lidar and three ceilometers. Additionally, a pre-existing Raman lidar on the island contributed valuable data to this study. These efforts are undertaken due to the importance of monitoring volcanic plume height in terms of air quality (necessary for the implementation of effective civil protection policies), volcanic activity surveillance (for tracking and forecasting eruptive behaviour), and, from a scientific perspective, for improving our understanding of the climatic and radiative impacts of this type of aerosol. In this study, the eruptive process was characterised in terms of the altitude of the dispersive volcanic plume (hd), measured by both IGN and AEMET-ACTRIS, and the altitude of the eruptive column (hec), measured by IGN. Modulating factors such as seismicity and meteorological conditions were also analysed. The consistency between the two independent and complementary datasets (hd,IGN and hd,AEMET) was assessed throughout the eruption (mean difference of 258.6 m). Our results confirmed the existence of three distinct eruptive phases, encompassing a range of styles from Strombolian explosive to effusive activity. While these phases have been characterised in previous studies, the results of the present work provide complementary information and novel insights from an alternative observational approach, which may be of use in future volcanic crises and will be applied to operational surveillance during such events. A subsequent comparison of hd,AEMET with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol layer height product (ALHCALIOP) revealed a systematic underestimation by the satellite product, with a mean difference of 392.2 m. Finally, the impact of using hec in estimating SO2 emissions from the NASA MSVOLSO2L4 satellite-based product was evaluated. When a fixed (standard) plume altitude of 8 km was used instead of the observed hec, the total SO2 emission was significantly underestimated by an average of 56.2 %, and by up to 84.7 %. These findings underscore the importance of accurately determining the volcanic plume height when deriving SO2 emissions from satellite data.

The 2021 Tajogaite eruption (La Palma, Canary Islands) provides a unique opportunity to investigate magma dynamics in magmatic systems where developed and monogenetic volcanoes coexist. Here, we present an integrated, interdisciplinary study combining petrological, geochemical, and geophysical data to reconstruct the pre- and syn-eruptive processes that controlled the evolution of the eruption. Whole-rock and mineral chemistry, diffusion chronometry in olivine crystals, gas geochemistry, GNSS, InSAR, seismicity and eruptive column height monitoring were jointly analyzed to constrain magma storage conditions, magmatic processes and the temporal evolution of the plumbing system. Our multidisciplinary results reveal a multi-stage magmatic history, involving at least three pre-eruptive intrusions (2017–2018, 2020, and in the weeks before the 2021 eruption) that progressively revived the system. Olivine diffusion modeling indicates that the 2021 eruption was triggered by a late-stage intrusion in early September, with ascent times of 10–30 days. Throughout the eruption, additional deep magma injections were recorded through changes in crystal chemistry, ground deformation, and eruptive dynamics. The earliest erupted magmas of the 2021 eruption were more evolved and hosted olivine crystals with oscillatory zoning, reflecting conduit opening and rapid ascent. During the second half of the eruption, the system transitioned to a regime marked by the development of a crystal mush zone, where magma accumulated without immediate eruption. This evolution was evidenced by prolonged olivine residence times and a characteristic 5-day lag between deformation peaks and maximum eruptive column heights during this period. Therefore, to further improve eruption forecasting in monogenetic systems and to resolve the formation of transient magma storage zones in the upper crust that might control the eruption dynamics, we highlight the critical importance of integrating petrological and geophysical monitoring.

Interactive 3D simulation of Taal Volcano eruption plumes

Abstract. The Atmospheric LIDar (ATLID) instrument of the ESA's Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) satellite mission launched in May 2024 provides high-resolution vertical profiling of aerosols and clouds at 355 nm. Fully operational since July 2024, ATLID has been witness to a significant perturbation of stratospheric aerosol budget following the eruptions of Ruang volcano (Indonesia) in late April 2024. Using ATLID together with limb-viewing satellite instruments (OMPS-LP and SAGE III), we quantify the stratospheric aerosol perturbation generated by the Ruang eruption and characterize the global transport of volcanic aerosols. To evaluate the ATLID performance in the stratosphere, its data are compared with collocated ground-based lidar observations at various locations in both hemispheres and overpass-coordinated balloon flights carrying AZOR backscatter sonde. The intercomparison with suborbital observations suggests excellent performance of ATLID in the stratosphere and proves its capacity to accurately resolve fine structures in the vertical distribution of stratospheric aerosols. Using various satellite observations, we show that Ruang's eruptive sequence in April 2024 produced eruptive columns reaching 25 km altitude, and resulted in a doubling of the tropical stratospheric aerosol abundance for several months. The eruption timing in austral Fall and its high-altitude reach fostered efficient poleward transport into the southern extratropics during austral Winter 2024. By the time of the austral Fall 2025, the sulphate aerosols from Ruang have spread across the entire Southern hemisphere and were most probably entrained by the 2025 Antarctic polar vortex, potentially enhancing the polar stratospheric cloud occurrence.

ABSTRACT Gravity‐driven granular flows are a fundamental geological hazard. Among the various dynamic aspects of granular flow that are still being explored, the consideration of the bedding angle stands out as particularly significant. In this study, granular columns with different bedding angle and varying aspect ratios ( AR s) (initial height/initial length) were examined by discrete element method simulations. The results showed that the entire collapse process can be categorized into three distinct stages: initiation, collapse, and accumulation. The runout distance of the granular column with a larger bedding angle extends farther at the same time point. Two distinct final deposit profiles were identified with reduced trapezoidal and triangular shapes. A comparison of the absolute values of the maximum differential sedimentation angles shows a clear increase with the bedding angle. The highest value of maximum kinetic energy consistently occurs in the model with a bedding angle of 90° across all aspect ratios. The maximum dissipated energy increases as AR increases. The bedding angle significantly influences the extent of coordination number (CN) reduction, with larger bedding angles resulting in a more pronounced decrease in CN. As the bedding angle increases, the degree of anisotropy in the particle system intensifies. As the granular column collapses, the degree of anisotropy gradually diminishes. Increasing the aspect ratio significantly amplifies the degree of anisotropy.

Physical and MPM modelling of sand column collapse with different moisture and density conditions

Granular flow, such as hopper discharge and debris flows, involves complex multi-scale, multi-phase, and multi-physics coupling, posing significant challenges for numerical simulation. Over the past two decades, methods like the Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH), and Depth-Averaging Method (DAM), have been developed to address these problems. However, their applicability across different scales remains unclear due to differences in physical assumptions and numerical algorithms. Therefore, a comprehensive evaluation is critically needed. This study selects three typical methods (DEM, SPH, and DAM) to examine their convergence behavior, boundary condition implementation, and limitations in physical and numerical modeling. We numerically studied three extreme deformation flow cases with the three chosen methods. These cases include granular column collapse at the particle scale, flow-structure interaction at the laboratory scale, and reconstruction of the 2015 Shenzhen Guangming landslide at the field scale. By comparing the granular flow dynamics, deposition morphology, and structure interactions, and also the simulation accuracy and computational efficiency, we show the applicability of the three models across different scales. Further, we provide practical guidance for model selection in large-deformation flow problems in a granular system of different scales.

Abstract Buoyancy-driven fluid flows, such as tornadoes, hurricanes, and Rayleigh-Bénard convection (e.g., boiling water), exhibit a fundamental feature known as stratification: hotter (lighter) fluid rises while colder (heavier) fluid sinks. This process is described by the Boussinesq equations. Motivated by real-world applications, this paper explores via the Boussinesq equations how stratification is influenced by the Reynolds number and different boundary conditions (slip and no-slip). It is well known that the dynamics of fluids with no-slip boundary conditions is still not well understood in the high Reynolds number regime. First, we rigorously establish the large Reynolds number limit of viscous Boussinesq flow with an explicit convergence rate under the stress-free boundary condition. Second, we present a linear stability analysis for perturbations near the hydrostatic equilibrium, the stationary eventual temperature profile. Third, numerical simulations reveal the stratification is faster under the higher Reynolds numbers and the slip boundary condition. In particular, we observe the boundary plume eruptions that facilitate stratification and the seesaw-like oscillations for the large Reynolds numbers.