NH2.1 | Advances in Understanding Volcanic Hazard and Environmental Impact
Advances in Understanding Volcanic Hazard and Environmental Impact
Including Plinius Medal Lecture
Convener: Mark Bebbington | Co-conveners: Fabio Dioguardi, Audrey Michaud-DubuyECSECS, Melody WhiteheadECSECS, Anke Zernack
| Wed, 17 Apr, 16:15–18:00 (CEST)
Room C
Posters on site
| Attendance Thu, 18 Apr, 10:45–12:30 (CEST) | Display Thu, 18 Apr, 08:30–12:30
Hall X4
Posters virtual
| Attendance Thu, 18 Apr, 14:00–15:45 (CEST) | Display Thu, 18 Apr, 08:30–18:00
vHall X4
Orals |
Wed, 16:15
Thu, 10:45
Thu, 14:00
Volcanoes are complex systems with potentially catastrophic impacts, able to generate and distribute vast sediment volumes to surrounding environments. Understanding, modelling and forecasting volcanic hazards is challenging, not least because of data issues. There is a need for the construction of robust and reliable models for forecasting volcanic hazards, both syn- and post-eruptive, and management of the resulting risks.

Syn-eruptive hazards include pyroclastic density currents, volcanic plumes and gas theoretically described by computational fluid dynamics, and experimentally modelled. But application of experimental results to large-scale natural processes is only possible via a thorough scaling analysis. Uncertainty is frequently cited as a major problem in volcanic hazard analyses and a plethora of statistical methods have attempted to quantify uncertainty in both hazard modelling and eruption forecasting. The data underlying models for both eruption occurrence and hazard propagation is multi-scale, multi-dimensional and nonlinearly correlated, and often not representative of the volcano's potential behaviour. Additional knowledge is often required to provide the causal links, and to extrapolate outside of the perceived bounds of existing data.

Post-eruption, understanding the origin, transport and emplacement mechanisms of volcanic deposits is fundamental for accurately reconstructing accumulation histories of ancient and modern volcano-sedimentary records, and for assessing future hazards and their potential economic impacts. Many knowledge gaps in these records could be reduced by bringing together multidisciplinary specialists and methods, combining classical field-based work with novel numerical modelling approaches.

Addressing risks from volcanic eruptions requires interactions between volcanologists and decision-makers, and with pre-eruption mitigation activities. These present issues around timeliness, the use of data, administrative responsibilities, and the application of laws.

The session aims at advancing volcanic hazard estimation and response through multidisciplinary approaches including
• Better describing uncertainty in volcanic hazard estimates through the use of statistical, analogue, surrogate and synthetic data
• Field studies of volcanoclastic features in sedimentary records,
• Novel statistical, experimental and computational modelling approaches, and
• Examination of the role of the state in volcanic risk management

Orals: Wed, 17 Apr | Room C

Chairpersons: Mark Bebbington, Audrey Michaud-Dubuy, Anke Zernack
Plinius Medal Lecture
On-site presentation
Jacopo Selva

Hazard models aim at making explicit our forecasting capability about future potentially adverse natural events. Hazard events are typically rare and not deterministically predictable, forcing hazard models to speak the language of certainty and uncertainty, that is, of probability. This is valid for any forecasting time window, from years to days/hours in the future (long- to short-term hazard), to the evaluation of the potential impact of an ongoing event in the next seconds/minutes/hours (warning/now-casting to urgent computing). Even though the definition of the target time window is driven by the users of the forecast (e.g. civil protections) and is not a scientific matter, the quantification of existing uncertainty given the time frame is certainly a scientific matter. Probabilistic hazard is commonly discussed mainly for long-term hazards, where large uncertainty dominates. In shorter-term forecasts, uncertainty may deacrease and practitioners are often tempted by simplified approaches that neglect uncertainty, like for eruption forecasting during volcanic crises, or for tsunami warning models after seismic or volcanic events. Nevertheless, uncertainty may still exist, and a rational scientific approach should let the results to speak about existing uncertainty, rather than to neglect it by definition. Is it possible to define a unified approach to probabilistic hazard entailing all time scales? The long-term integral hazard integrating all potential sources and generation/propagation conditions can be adapted to the different forecasting time windows, generating a unified framework in which the different time scales may feed to each other, producing homogeneous and easy-to-interpret results. This unified vision of hazard models, embracing long- to short-term hazard as well as warning and urgent computing models, is here discussed based on the recent advancements in models for volcanic, seismic and tsunami hazard and warning.

How to cite: Selva, J.: Hazard forecasting: is it a matter of time?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4270, https://doi.org/10.5194/egusphere-egu24-4270, 2024.

On-site presentation
Helen Webster, David Thomson, and James Salter

Atmospheric dispersion models are employed during volcanic eruptions to forecast the atmospheric transport and dispersion of the ash cloud. Uncertainties exist in the predicted ash cloud due to uncertainties in the ash emissions, in the atmospheric dispersion model and its parameterisations, and in the driving input meteorological data. A Bayesian inversion method has been developed for estimating the height- and time-varying profile of ash emissions using satellite retrievals of ash column load, atmospheric dispersion modelling and a prior estimate of emissions (Pelley et al., 2021). Gaussian distributions are assumed for the prior distribution of the emissions and for the errors in the satellite retrievals. An optimal emission estimate is obtained by finding the peak of the posterior probability density, subject to an imposed non-negative constraint on the emissions. The method is computationally efficient and suited for operational use.

In the original design of the Bayesian inversion method, uncertainties in the atmospheric dispersion model and its input meteorological data are not considered. Errors in the input meteorological data can lead to discrepancies between the modelled and observed ash cloud locations and can affect the performance of the Bayesian inversion method. We employ ensemble NWP (Numerical Weather Prediction) data sets to overcome issues with meteorological errors. The Bayesian framework enables a model selection approach to be adopted, where a ‘best’ meteorological data set is chosen from within the ensemble. Using the eruption of the Icelandic volcano Grímsvötn in 2011 as a case study, we illustrate the impact meteorological errors can have on ash emission estimates and show how the ‘best’ meteorological data set leads to improvements in ash cloud forecasts.

The posterior probability density is a multi-dimensional Gaussian distribution which contains information on the uncertainty in the estimated emissions. If time permits, I will describe recent attempts to obtain an ensemble of emission estimates by sampling from the posterior distribution. This is challenging because of the high dimensionality and the non-negative emissions constraint. Nonetheless, an ensemble of emission estimates from the posterior distribution would enable the uncertainty in the emissions estimate, and the associated uncertainty in the ash concentrations in the predicted ash cloud, to be quantified.

How to cite: Webster, H., Thomson, D., and Salter, J.: A Bayesian inversion method for estimating ash emissions: accounting for meteorological uncertainty & quantifying uncertainty in the estimated emissions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9544, https://doi.org/10.5194/egusphere-egu24-9544, 2024.

On-site presentation
Matteo Cerminara, Matteo Trolese, Guido Giordano, Brittany Brand, Nicholas Pollock, Francesca Cifelli, and Massimo Mattei

This study investigates the influence of topography on the internal structure and dynamics of pyroclastic density currents (PDCs), using the 1980 Mt. St. Helens eruption as a case study. By integrating paleomagnetic data and numerical models, we observe significant temperature differences (approximately 100°C) in PDC deposits on different flanks of the volcano. These variations are attributed to local topographic features affecting air entrainment in PDCs. We find that topographic drops induce a transient regime in PDCs, altering their internal temperature, velocity, and concentration. The duration of the transient phase is proportional to the ratio between the drop height and the square root of the current thickness. The influence of topography on PDC dynamics decreases with distance from these drops or when a stationary phase is reached. Taken together, our dataset allows us to estimate a local sedimentation rate of approximately 150 ± 100 mm/s for PDC deposits in a proximal reattachment region. This research emphasizes the importance of transient dynamics in understanding PDC behavior, introduces a new method for measuring sedimentation rates, and highlights the need to consider topographic effects in hazard assessments.

How to cite: Cerminara, M., Trolese, M., Giordano, G., Brand, B., Pollock, N., Cifelli, F., and Mattei, M.: Thermal transient PDC behavior induced by topographic drops: A test case at Mt. St. Helens, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19194, https://doi.org/10.5194/egusphere-egu24-19194, 2024.

On-site presentation
Alexis Bougouin, Henri Lhuissier, Yoel Forterre, and Bloen Metzger

The physical mechanism governing the peculiar behavior of discontinuous shear-thickening suspensions, i.e. a change from liquid-like to solid-like state with increasing applied stress, has recently been described as a frictional transition occuring at the grain scale above a critical shear stress [1, 2, 3]. This understanding offers a new view for describing complex grain-fluid flows, and especially crystal-rich lava flows, which can shear-thicken [4], or lahars, whose heterogeneities affect local friction [5].

In this context, we performed macroscopic and local measurements to characterize dam-break laboratory experiments of model shear-thickening suspensions, for which the volume and the solid fraction of the suspension are varied. Below a critical stress related to the gravitational pressure gradient, the suspension flow is close to that of a viscous Newtonian liquid, i.e. strongly decelerating and with a thickness decreasing progressively from the release side to the spreading front [6]. By contrast, above this critical stress, the front velocity becomes constant, i.e. independent of flow height, and the layer thickness is close to be uniform (Figure 1). We interpret this remarquable behavior by the formation of a highly-dissipative (shear-thickened) flow structure at the front, which keeps the suspension upstream essentially stress-free with a low (frictionless) viscosity. We model the front and provide scaling laws for its velocity in good agreement with experimental observations. These results offer a new perspective for the interpretation and modeling of heavily particle-laden geophysical flows, such as crystal-rich lava flows and lahars, which could also be essentially controlled by their highly-dissipative front.

1. M. Wyart and M. Cates (2014). Discontinuous shear thickening without inertia in dense non-Brownian suspensions. Phys. Rev. Lett., 112:098302, 2014.

2. R. Mari, R. Seto, J. Morris, and M. Denn (2014). Shear thickening, frictionless and frictional rheologies in non-Brownian suspensions. J. Rheol., 58:1693–1724, 2014.

3. C. Clavaud, A. Bérut, B. Metzger, and Y. Forterre (2017). Revealing the frictional transition in shear-thickening suspensions. Proc. Natl. Acad. Sci., 114:5147–52, 2017.

4. J. V. Smith (1997). Shear thickening dilatancy in crystal-rich flows. J. Volcanol. Geotherm. Res., 79:1-8.

5. C. Ancey (2007). Plasticity and geophysical flows : A review. J. Non-Newton. Fluid Mech., 142:4-35.

6. H. E. Huppert (1982). The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface. J. Fluid Mech., 121:43-58.

How to cite: Bougouin, A., Lhuissier, H., Forterre, Y., and Metzger, B.: Dam-break of shear-thickening suspensions: A new perspective for crystal-rich lava flows and lahars -, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1455, https://doi.org/10.5194/egusphere-egu24-1455, 2024.

On-site presentation
Edward McGowan, Tiffany Barry, and Michael Branney

Caldera-forming eruptions sequences produce a wide range of volcanogenic sedimentary deposits, from primary mesobreccia (blocks > 1m) that form from the collapse of caldera wall scarps during the eruption, to co-ignimbrite ash plumes (particles < 2mm) deposited during the waning of outflowing pyroclastic density currents, and even secondary aqueously reworked sediments deposited within caldera lakes. Understanding the temporal and special distribution of these deposits is vital to both locate and reconstruct the collapse sequence of these catastrophic events. However, research of caldera volcanoes is greatly hindered at modern examples due to subsequent burial of their own deposits.

Ordovician deposits (452 Ma) of the Borrowdale Volcanic Group (BVG) in the English Lake District are dominated by large-scale, caldera-forming deposits that have been tectonically uplifted and dissected by glacial erosion. Each of the BVG calderas have the potential to provide a wealth of knowledge regarding how calderas erupt, collapse, and continue to shape geological processes when their explosive activity ceases. However, due to intense faulting, alteration, and impersistent exposure across the Lake District, in-depth research of these calderas has been largely prevented using standard field-mapping techniques. This leaves most of the understanding for the overall nested caldera complex to be inferred.

This investigation utilizes whole-rock geochemistry as the primary method to establish correlations between potential large-scale, caldera-forming pyroclastic deposits across large distances. Once the extent of each deposit was determined, they were individually traced back to their source vents. Detailed fieldwork was then conducted to identify characteristic caldera-forming features, such as rapid thickness changes over volcanotectonic faults, and extensive intercalated mesobreccia deposits.

Geochemical analysis of immobile elements, including Nb, Th, Y, and Zr, of potential caldera-forming pyroclastic deposits has allowed for several notable correlations to be established, or disproven. Firstly, proximal outflow sheets from Langdale Caldera have been successfully correlated to pyroclastic sheets over 15 km from the caldera margin and suggest a multi-phase collapse sequence. Secondly, significant differences in the geochemistry of deposits associated with the Lincomb Tarns Formation (> 500 km2 ignimbrite) indicates the presence numerous pyroclastic sheets, originating from two separate caldera volcanoes within the Helvellyn and Ambleside areas. Finally, geochemical variations within the Haweswater ‘caldera’ infill deposit prove that sudden thickness changes, previously associated with syn-collapse volcanotectonic faulting, are the result of separate eruption events that have since between adjacently faulted.

How to cite: McGowan, E., Barry, T., and Branney, M.: A geochemical reevaluation of caldera-forming eruption deposits in the Upper Borrowdale Volcanic Group, English Lake District., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16506, https://doi.org/10.5194/egusphere-egu24-16506, 2024.

On-site presentation
Vinicio Brigante

For years now, proliferation of technological tools has been taking hold, albeit with some resistance, in the public sector since, as reflected in the agendas and public policies of EU member states, digitalization is a non-deferrable need, a prerequisite for the implementation of further reforms. This report’s purpose is to ascertain whether and how, data in AI can support administrations and stakeholders in coping with unforeseen events, such as earthquakes and volcanic eruptions. Among disaster protection risks, volcanic activity is often considered a foreseeable risk because it is thought that phenomena that presage rising magma to surface can be recognized and measured. These phenomena are called precursors although this is a simplification that does not take into account the complexity and extreme variability of volcanic phenomena and the difficulty in assessing and interpreting them. Precursor phenomena, as indicators of an ongoing process that if properly and adequately studied, analyzed and monitored, can give an idea of the state of volcano activity and its possible evolutions, allowing for the detection of possible anomalies. For this reason, data and processing by AIs can provide support and decrease errors in the calculation of phenomena even if only a quantitative reduction. Data and their processing can provide a reliable index to support prevention activities. Potential issues for the jurist involve ownership of database management, interoperability, errors in the management of the same knowledge. Assessment by AI and data has the advantage of being rapid and devoid of operator discretion. Machine learning, in fact, has a capacity of about 98 percent to correctly attribute a rock of unknown origin. Central to the discussion is to determine the ownership of data and the AI tools deputed to process them, whether to endow public facilities, or outsource this function to the private sector.

How to cite: Brigante, V.: Dialogue between technique and administration in volcanic risk management; Data issues, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22287, https://doi.org/10.5194/egusphere-egu24-22287, 2024.

Posters on site: Thu, 18 Apr, 10:45–12:30 | Hall X4

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 12:30
Chairpersons: Audrey Michaud-Dubuy, Melody Whitehead, Mark Bebbington
Shannon Williams, Frances Beckett, Susan Leadbetter, Jeremy Phillips, Anthony Lee, and Mark Woodhouse

Volcanic ash represents a hazard to aviation and a global network of Volcanic Ash Advisory Centres (VAACs) are tasked with providing advice and guidance to the aviation industry on its presence in the atmosphere. Forecasts of the expected location of the ash cloud are generated using atmospheric transport and dispersion models, initialised with a set of Eruption Source Parameters (ESPs) and driven by forecast meteorological data. In the future the VAACs will be required to adopt a Quantitative Volcanic Ash (QVA) approach of issuing probabilistic volcanic ash concentration information to the aviation industry, as such there is a need to develop a framework for producing a probabilistic forecast which incorporates both the uncertainty in forecast meteorology and in the eruption source parameters (ESPs). Variability in the meteorological forecasts is typically expressed as an ensemble of meteorological data, which can be provided to an atmospheric dispersion model to produce an ensemble of simulations in which ESPs are kept constant, and outputs are aggregated to remove the conditioning on the meteorology. Dispersion model forecasts are also sensitive to the ESPs used to initialise the simulations, notably the plume height and the mass eruption rate (MER) of volcanic ash injected into the atmosphere. The latter is difficult to measure in real-time, and for event response it is assumed to scale with the plume height. There remains a high degree of uncertainty in these linked ESPs, which can be modelled via a Bayesian linear modelling approach. We will present a method for incorporating the combined variability of ESPs and meteorological forcing into the ensemble to obtain values of exceedance probabilities for airborne volcanic ash concentrations of interest, using standard statistical techniques and numerical methods, whilst keeping computational and time costs down for efficient evaluation in an emergency. 

How to cite: Williams, S., Beckett, F., Leadbetter, S., Phillips, J., Lee, A., and Woodhouse, M.: Incorporating eruption source parameter and meteorological variability in the generation of probabilistic volcanic ash hazard forecasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9948, https://doi.org/10.5194/egusphere-egu24-9948, 2024.

Emmy Scott, Melody Whitehead, Stuart Mead, Mark Bebbington, and Jonathan Procter

Accurate forecasts are needed to help mitigate the risks of volcanic hazards to society. Current approaches use probabilistic estimates based on sparse data, supplemented with expert judgment, to describe likely future eruption characteristics. These probabilistic eruption characteristics then inform input parameters required by hazard models.

This process requires a lot of simulations with varying input parameters to constrain uncertainty around a future eruption’s hazard characteristics. It is also computationally intensive, and the outputs may quantify, but do not reduce eruption uncertainty. As hazard models become increasingly more complex, so do the number of input parameters that need to be estimated, thus increasing the number of sources of uncertainty. As input parameters used for volcanic hazard models are fundamentally uncertain before (and often also after) an eruption, how do they affect the accuracy and utility of forecasts made using these models?

This research explores the input space of volcanic hazard models to understand the interactions between model complexity and robustness of hazard model forecasts. We use the exemplar of volcanic ash distribution models Tephra2 and Fall3D at Mt. Taranaki, Aotearoa-New Zealand (30-50% chance of eruption in the next 50 years). Sampling strategies for Tephra2 and Fall3D were developed to ensure that the input parameter space was fully covered and represent real-world values – both through independent and dependent sampling of parameters. For example, plume height is dependent on the amount of mass ejected during an eruption. A Global Sensitivity Analysis is presented here to investigate the input parameters that significantly influence model output variance. This exploration is conducted through the statistical assessment of Sobol’ indices and eFAST (extended Fourier Amplitude Sensitivity Tests) to discern the key parameters that contribute to variations in the model’s outputs. The results also shed light on which inputs are vital to robust short-term and real-time hazard forecasting, and ultimately require better understanding/quantification before an event.

How to cite: Scott, E., Whitehead, M., Mead, S., Bebbington, M., and Procter, J.: Global Sensitivity Analysis of tephra models for forecasting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1402, https://doi.org/10.5194/egusphere-egu24-1402, 2024.

Brenda Contla Hernandez, Melody Whitehead, Mark Bebbington, and Michael Rowe

Volcanic hazards are dependent on eruption size and explosivity, thus, the forecasts of these is crucial for emergency management decisions. Monitoring a volcano potentially offers valuable insights to assess when, where, and how explosive a future eruption might be. Data are collected from various monitoring equipment, such as seismometers, tiltmeters, and thermometers, that are installed at different locations and distances, from near-vent to satellite. However, establishing direct links between monitoring signals and even eruption onset remains challenging, especially for volcanoes lacking recent eruptions or without monitoring equipment installed prior to eruption. This challenge extends to eruption explosivity, where establishing links becomes even more difficult.

The Global Volcanism Program (GVP) has compiled monitoring data in bulletin reports recorded by observatories and research institutions. These reports start from 1968 and summarise volcanic activity that occurs before, during and after an eruption. Importantly, these reports include descriptions about activity and/or raw data (number of earthquakes, frequencies, plots of the seismic signals or displacements on tiltmeters) from various monitoring equipment, providing a general understanding of precursor activities preceding an eruption. This is potentially key information for forecasting eruption explosivity.

This study aims to establish a quantitative link between monitoring signals and eruption explosivity across multiple volcanoes. Data are compiled from 23 volcanoes worldwide, utilising information from the Global Volcanism Program (GVP) database and local volcano observatory reports where accessible. The different descriptions obtained by each class of monitoring equipment—whether seismic, thermal, deformation, SO2 fluxes, or crater alterations—will be statistically categorized and calibrated into predictor variables to be used in machine learning algorithms. We hope to develop a procedure for estimating the explosivity of the next eruption, as a step towards statistically forecasting future eruption styles.

How to cite: Contla Hernandez, B., Whitehead, M., Bebbington, M., and Rowe, M.: A quantitative analysis of monitoring signals and eruption explosivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1510, https://doi.org/10.5194/egusphere-egu24-1510, 2024.

Salvatore Ferrara, Warner Marzocchi, Jacopo Selva, and Laura Sandri

The management of volcanic unrest near densely inhabited areas requires collaboration between scientists, who are required to provide near real-time information, and decision makers. The ambiguity of pre-eruptive patterns and the inaccessibility and the complexity of the system lead to large uncertainties, suggesting the preference for probabilistic approaches over deterministic ones. The divergence of scientists' opinions regarding pre-eruptive phenomena can lead to extreme confusion, which inevitably translates into the difficulty of reaching an agreement for the optimal management of an emergency. Expert elicitation is a procedure for extracting a collective opinion in a relatively short time despite the incomplete knowledge of the problem and is therefore an effective tool for managing forecasts during volcanic crises in near real-time. In this work we present the results of the latest elicitation sessions at the Campi Flegrei caldera, represented by a list of weighted parameters with their respective thresholds that define the anomalous values and their interpretation, to calibrate BET_EF eruption forecasting model. Our aim is to re-calibrate it using the most recent scientific evidence linked to the increase of the activity of Campi Flegrei which has been observed in the last few years, evaluating the probability that the mechanism underlying the current unrest is a rise of magma, and the probability that this could lead to an eruption. Finally, we demonstrate a practical application showing the variation of the probability of magmatic unrest and eruption as a function of the variation of the values of the monitoring parameters ​​obtained through the elicitation.

How to cite: Ferrara, S., Marzocchi, W., Selva, J., and Sandri, L.: Forecasting the evolution of volcanic unrest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2811, https://doi.org/10.5194/egusphere-egu24-2811, 2024.

Matthew Head and Patricia M. Gregg

Geodetic observations are key for assessing the unrest status of volcanoes worldwide, providing critical information about magmatic systems and the potential for magma migration and eruption. Analysing these signals relies on a robust data-model framework. One such approach is the Ensemble Kalman Filter (EnKF), a data assimilation method that has been adapted for analyses of volcanic deformation. The EnKF sequentially assimilates and inverts geodetic observations, using a series of model states to ‘nudge’ the model parameters with each iteration, reducing the misfit between the model and observation. We construct thermomechanical Finite Element (FE) models of volcanic regions, providing the necessary flexibility to incorporate complex 3D geometries and material heterogeneity. However, these simulations are computationally expensive when incorporated into the EnKF workflow, where an ensemble of >200 model states can take several hours to evaluate. This is particularly problematic for the analysis of observational data with high temporal resolution, such as daily GPS measurements.

Here, we aim to reduce the computational cost of the EnKF-FE workflow by using regression machine learning algorithms (MLAs), focusing on reducing the number of model states that need to be evaluated by the FE models. We start by using the ‘Mogi’ deformation model, a simple analytical expression that calculates the three-component displacement field (Ux, Uy, and Uz) due to a point source. We employ a tuneable nearest-neighbour approach to identify model states that occupy a ‘similar’ parameter space, using MLAs to predict the resultant displacements. The Mogi model has significantly reduced complexity compared to that of a FE model, providing a simple platform to test different machine learning approaches. Preliminary results suggests that the k-Nearest Neighbours and Linear Regression algorithms can significantly improve the computational efficiency of the EnKF-FE workflow, with negligible impact on the inferred best-fit model parameters, when a magmatic system is in a steady-state (i.e., static overpressure). Future modelling efforts will consider FE models with a 3D deformation source within a flat-topped domain, and time-varying overpressure scenarios.

How to cite: Head, M. and Gregg, P. M.: Improving the efficiency of ensemble-based volcano deformation analyses using Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8093, https://doi.org/10.5194/egusphere-egu24-8093, 2024.

Sheng-Rong Song and Yi-Chia Lu

The Coastal Range of eastern Taiwan is located at the plate boundary of Philippine Sea and Eurasia plates, which is the arc-continent collision zone. Abundant huge blocks, especially in Wushihpi area, which are predominantly composed of the volcanic rocks, are interbedded in the Paliwan Formation. Based on the field surveys, different occurrences of volcanic lithofacies have been recognized in outcrops. They are pillow breccias with and without white vesicle fillings, hyaloclastites, peperites rich and poor in zeolite fillings, lahars, lava flows with columnar structures, weathered brownish and reddish blocks in tuffaceous conglomerates and limestones. Those lithofacies can be grouped into three volcanic facies, the shallow marine, transitional from submarine to subaerial facies and subaerial facies. Those facies occur together chaotically and contact sharply. It infers that the volcanic rocks occurred in Wushihpi of Coastal Range is debris avalanche deposits and the source may come from different volcanic sequences of the Tulunshan volcanics, the major eruption products of Luzon Arc. Meanwhile, similar occurrences of debris avalanche deposits as huge blocks are also widely distributed in whole Coastal Range from the north to the south and Lutao. Those observations suggest that the sedimentation of debris avalanche and tectonics of slope failures may play major roles for denudation of volcanic arc during Taiwan arc-continent collision. 



How to cite: Song, S.-R. and Lu, Y.-C.: Volcanic Debris Avalanche Deposits in the Coastal Range, Eastern Taiwan: Implications for Sedimentation and Tectonics of Arc-Continent Collision, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7190, https://doi.org/10.5194/egusphere-egu24-7190, 2024.

Yongsik Gihm, Min-Cheol Kim, and Yong-Un Chae

In extensional and transtensional basins, the dual action of basin-forming tectonism and explosive volcanic activity results in deposition of complex volcano-sedimentary successions. Since both aspects contemporaneously affect sediment-dispersal systems, it is difficult to distinguish one from the other by analyzing volcano-sedimentary successions. To discriminate tectonic influence, basin fills of the Miocene, pull-apart Janggi Basin were investigated. Here, the contemporaneous influence of tectonic subsidence and explosive volcanism formed <966 m thick, conformable volcano-sedimentary successions composed of laterally extensive, pumice-bearing, unwelded pyroclastic deposits and nonmarine sedimentary rocks formed under humid climatic conditions. Based on Laser Ablation – Multiple Collector – Inductively Coupled Plasma Mass Spectrometry zircon U-Pb age data, these successions were deposited from 21.1 ± 0.2 to 20.1 ± 0.1 Ma. After deposition of basinwide, tens of metres thick, and unwelded pyroclastic deposits, the directly overlying facies successions (FS-1 and FS-2) show contrasting depositional features to the classical model of volcaniclastic sedimentation. Facies succession-1 is represented by fluvial conglomerates composed mostly of (sub)rounded pebble and cobble sourced from basement. The supply of basement-derived clasts through fluvial systems resulted from development of physiographic relief during or soon after the eruption by syndepositional tectonic subsidence. Facies succession-2 occurs directly on pyroclastic deposits that cover FS-1 and show coarsening-upward trends, and is composed of basal lacustrine mudstones and overlying resedimented volcaniclastic sandstones showing a progradational geometry, interpreted as a result of progressive filling of the lake by remobilized volcaniclastic sediments. Occurrence of basal lacustrine laminated mudstones indicates that syndepositional creation of the accommodation by tectonic subsidence exceeded forceful input of pyroclastic and remobilized volcaniclastic sediments, resulting in a delayed sedimentary response to explosive volcanic eruptions. This study shows that, despite voluminous production of volcaniclastic sediments, tectonic activity controlled sediment type and stacking patterns. Therefore, these depositional features allow to discriminate tectonic effects from complex volcano-sedimentary successions, enabling to reconstruct basin evolution. 

How to cite: Gihm, Y., Kim, M.-C., and Chae, Y.-U.: Finding tectonic signals from ancient volcano-sedimentary successions: an example from the Miocene Janggi Basin, SE Korean Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6834, https://doi.org/10.5194/egusphere-egu24-6834, 2024.

Anke Zernack, Erlend Kirkeng Jørgensen, Anthony Newton, and Anders Romundset

Ocean-rafted pumice is found on modern and paleo-beaches from the North Atlantic to the South Pacific. Correlation of ocean-rafting events to their volcanic source can help date sedimentary records and landforms, while geochemical fingerprinting of artefacts made from ocean-rafted pumice provides age constraints for pumice-bearing archaeological sites. These pumices also record large explosive eruptions that might not be preserved near the volcano due to extensive erosion or a submarine volcanic source and as such can be used for petrological and geochemical investigations.

This study explores links between spatiotemporal patterns of Holocene pumice deposition along the Norwegian coastline and prehistoric human use of this versatile resource. We first focused on a suite of pumice pieces from archaeological contexts of variable isostatic uplift in Northern Norway with most showing evidence of use as abrasive tools. These samples were geochemically correlated to individual Holocene eruptions or groups of tephras (SILK) from the Katla Volcanic System in Iceland. Our age data revealed that the estimated eruption dates typically predate the contexts by several hundred and up to 2-3,000 years, probably reflecting abundance and availability of certain pumice types at the time.

To investigate how distal resource availability is influenced by geological processes like eruption frequency, ocean-currents, and deposition/preservation we conducted field surveys of two coastal stretches with different climates, geomorphic settings and uplift histories. On Varanger Peninsula in Northern Norway strong Holocene uplift rates and sea-level changes have built a unique record of raised shorelines that provide windows into fossil beach ridges up to the marine limit, covered in little vegetation. We found that pumice was abundant on specific paleo-shorelines and in defined geomorphic settings but absent from older beach ridges. Most samples correlated with the <7 ka Katla record and the distinct mid-Holocene transgression high-stand accumulated the largest variety of pumice types and clast sizes. One sample cluster overlaps with SILK tephra compositions but does not correlate to any known Katla units while a single pumice plots outside the field defined by Katla eruptives, resembling compositions known for Jan Mayen.

In contrast, the Trøndelag and Nordland coast in Southern Norway is heavily vegetated and pumice was only found at isolated sites that displayed the right conditions, important factors being: a) the paleo-setting of the beach (e.g., currents, orientation, morphology) favouring accumulation in the first place, b) rapid uplift and limited erosion enabling preservation of the stranded pumice and c) exposure of pumice-bearing beach ridges (sections cut by rivers/erosion, roads/construction) as subsequent burial by sediment, soil and vegetation further reduces access to previously available pumice resources. This supports our hypothesis of pumice only being readily available for limited periods of time following eruption, rafting and onshore deposition. We will further test this assumption by integrating compositional information of archaeological pumice pieces from a recent archaeological excavation in Lofoten into our data-set.

Overall, our study provides a better understanding of the nature and frequency of Holocene silicic eruptions from Katla while also improving age control for existing relative sea-level curves and archaeological contexts in Norway.

How to cite: Zernack, A., Jørgensen, E. K., Newton, A., and Romundset, A.: Distal records of Katla’s explosive past: Ocean-rafted pumice found in archaeological contexts and raised shorelines in Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7206, https://doi.org/10.5194/egusphere-egu24-7206, 2024.

Shannen Mills, Jonathan Procter, Anke Zernack, Stuart Mead, Ian Schipper, Andrew Stevenson, Benedicta Arhatatari, Darren Thompson, and Joseph Fleming

Depressurisation from edifice collapse events can impact the subvolcanic plumbing system as a propagation wave moves down through the system shifting the fragmentation zone. Understanding how this influences the eruptive behaviour at a volcano is important for understanding changes in hazards following a large edifice collapse event. Mt. Taranaki has experienced at least 16 collapse events within its > 200 kyr history. Two of the largest collapse events the 27.3 ka Ngaere and 24.8 ka Pungarehu debris avalanches occurred in close succession and were encompassed by the Poto and Paetahi tephra formations, made up of 28 subplinian eruptions over ~ 4,000 years. This eruptive period provides a unique opportunity to examine and understand the influence that edifice collapse events have on the subvolcanic plumbing system. Using 3D Micro-Computed Tomography at the Australian Synchrotron bubble textural analysis was undertaken to investigate the changes in pyroclastic textures from large explosive eruptions and how these change following an edifice collapse event. The high-resolution 3D scans indicate that the eruptive products from the Poto and Paetahi Formations are dominated by small bubbles (2.7 x 10-7 mm3) with high bubble number densities ranging from 2.56 x 1015 cm-3 to 1.74 x 1016 cm-3. Bubble size distributions for the Poto and Paetahi Formations indicate a range of bubble nucleation and growth processes occurring within the subvolcanic plumbing system below Mt. Taranaki initiating at different depths. Early onset of bubble nucleation and periods of magma stalling are indicated by the presence of large, coalesced bubbles within the eruptive products, while the dominance of smaller bubbles indicates a fast ascent of magma within the system with nucleation occurring higher up in the system. Changes are seen in the textural characteristics of pyroclasts produced following the 27.3 ka 5.85 km3 Ngaere collapse which depressurized the shallow magmatic system and shifted the fragmentation zone. Following the 24.8 ka 7.5 km3 Pungarehu collapse ~2,500 years later the same influence is not seen, due to the cone not having enough time to rebuild between edifice collapse events. The results from this study show that the depressurisation and subsequent propagation wave are dependent on the height above the plumbing system not just the mass removed and therefore two major collapses in close proximity do not show the same systematic impact on the fragmentation zone.

How to cite: Mills, S., Procter, J., Zernack, A., Mead, S., Schipper, I., Stevenson, A., Arhatatari, B., Thompson, D., and Fleming, J.: Using pyroclastic textures as an index for understanding the impact edifice collapse has on the subvolcanic plumbing system. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7230, https://doi.org/10.5194/egusphere-egu24-7230, 2024.

Jonathan Procter, Shannen Mills, Anke Zernack, Stuart Mead, Andrew Stevenson, and Benedicta Arhatari

Volcanic communities near long-lived stratovolcanoes are susceptible to the significant threat associated with edifice collapse events which produce volcanic debris avalanches. These events can have runout distances > 100 km and are the largest mass flows on Earth with volumes ranging from 0.1 to 100 km3 which have the potential to bury large sectors of the landscape posing a severe risk to people and infrastructure. However, the emplacement mechanisms of these large destructive phenomena are still poorly understood with the inability to accurately quantify the physical parameters such as frictional regimes, velocity, and temperature which contribute to the extreme runout. The internal structure and minerology of the avalanche deposits hold the key to understanding the transportation mechanisms. During transportation inter-particle collision and shearing occurs reducing grainsize and generating new minerals such as Pseudotachylytes, Frictionites and Silica polymorphs along shear zones between larger clasts and along the base of the flow. Twenty-five volcanic debris avalanches and rock avalanches of varying sizes were sampled from New Zealand and the USA to provide a representative variety of flow types to better understand transportation mechanisms. Using 3D Micro-Computed Tomography at the Australian Synchrotron the internal structure of the avalanche deposits were analysed to identify different minerals and structures present. Analysis of the microstructures of the samples show a variety of different fracture patterns that can be categorized based on the different source lithologies sampled as well as the different rheological emplacement conditions from the collapse and flow.  Features seen at the micro-scale mimic larger centimeter to meter scale features traditionally observed in the flow.  Investigating the formation of new minerals along collision and shear zones can provide insights on the physical constraints of the flow e.g., velocity and temperature. Data from this study will provide quantitative input parameters forming the foundation for developing a model for transportation and emplacement of long-runout volcanic debris avalanches. Data from these models can be used to assess the volcanic debris avalanche hazards from volcanoes globally, better informing risk assessments.

How to cite: Procter, J., Mills, S., Zernack, A., Mead, S., Stevenson, A., and Arhatari, B.: Characterising transport and emplacement mechanisms of volcanic debris avalanches through 3D Micro Tomography. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7208, https://doi.org/10.5194/egusphere-egu24-7208, 2024.

Letizia Pace, Capolongo Domenico, Capparelli Giovanna, Clausi Gabriele, Dioguardi Fabio, and Sulpizio Roberto

Volcaniclastic debris flows are highly concentrated flows of rock debris, mud and water in which the sediment is of volcanic origin. These phenomena can be syneruptive, posteruptive, or unrelated to an eruption. To be generated, the coexistence of steep slopes, unconsolidated sediments and an adequate amount of water is necessary.

The aim of this project is to investigate the role of water circulation in the initiation processes of debris flows to enhance our ability to anticipate potential new debris flows in the Campanian Volcanism area, focusing on the Sarno area. Sarno is a small municipality located in the Vesuvius Volcanism area (western side of the Campanian Apennines) that is sadly infamous for the major debris flow events that, on the 6th of May 1998, destroyed the town and killed around 150 people.

The study area exhibits a convergence of geomorphological and lithostratigraphic settings that contribute to enhancing its exposure to hazards: i) the presence of a calcareous bedrock with very steep slopes (30-45°) mantled by ii) an alternation of colluvium and pyroclastic deposits, and iii) natural scarps and man-made cuts that further worsen the stability conditions.

This research employs a multimethodological approach including i) geotechnical and rheological analyses of the sediments; ii) X-ray Diffraction for the mineralogical characterisation, particularly of the clay fraction; iii) large-scale experiments to investigate the role of water circulation in the sediments during simulated rainfall in the triggering of volcaniclastic debris flows; iv) in situ Time-Domain Reflectometry measurements at Pizzo D’Alvano for soil moisture vertical distribution and v) simultaneously acquisition-surveys by using a drone-mounted passive radiometer for spatial soil moisture distribution. Integrating these methods aims to achieve understanding of the water content distribution in the debris flow initiation process that could be potentially used in the rainfall-triggered landslide early-warning systems.

How to cite: Pace, L., Domenico, C., Giovanna, C., Gabriele, C., Fabio, D., and Roberto, S.: The role of hydrological circulation in the initiation process of debris flows in the Campanian volcanic terrain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16350, https://doi.org/10.5194/egusphere-egu24-16350, 2024.

Claudia Principe

The two "hottest" areas of Italy from the point of view of forecasting and mitigating volcanic hazard at the moment are the Phlegraean Fields and Vesuvius. At the Phlegraean Fields the bradyseismic crisis continues with noticeable changes in the fumarole regime and bradyseismic movements in the Solfatara area. Depending on the various conceptual models created by the various groups of scientists working in this area, it is possible to foresee different possible future scenarios, also assuming the persistence of magmatic degassing and conductive heat transfer from the magma to the overlying rocks and the absence of external, such as the occurrence of one or more regional earthquakes and the release of fresh magma into the reservoir located 8 km deep.

At Vesuvius, different scenarios are possible for the reactivation of the most famous volcano in the world. The first scenario involves the emplacement, maturation and eruption of magma from a sub-surface magma chamber, following the pattern of the last large explosive eruption which occurred in 1631 with the occurrence of a small-scale Plinian eruption. A disastrous scenario but one that requires fairly long warning times. A further scenario, proposed more recently, involves the ascent of magma along fractures linked to regional tectonic trends and its emplacement through rapidly moving flows with probable opening at the base of the volcanic edifice and much shorter warning times.

How can we manage these different situations in terms of Civil Protection and resilience?

How to cite: Principe, C.: Managing different eruptive scenarios at Phlegraean Fields and Vesuvius, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22302, https://doi.org/10.5194/egusphere-egu24-22302, 2024.

Mauro Di Vito, Mattia de'Michieli Vitturi, Laura Sandri, Antonio Costa, Marina Bisson, Sandro de Vita, Domenico Doronzo, Roberto Gianardi, Mauro Rosi, Ilaria Rucco, Roberto Sulpizio, Giovanni Zanchetta, and Elena Zanella

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting on population and infrastructures. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma-Vesuvius and Campi Flegrei volcanoes, as well as the nearby Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. Our recent studies focus on the analysis of the pyroclastic fall and flow deposits, and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius, 472 CE (Pollena) and 1631. Historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database. Stratigraphic, sedimentological, and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter estimations. The field data analyses show that in both eruptions the dispersal area of the primary pyroclastic deposits is wider than previously known. Such distribution of the deposits directly affects the one of the lahar deposits, even because a significant remobilization took place during and after the studied eruptions, involving the distal phreatomagmatic ash. From these analyses, it was possible to constrain the timing of the deposition, and to estimate the thicknesses, velocities and dynamic pressures (impact parameters) of the lahars. A new shallow layer model based on depth-averaged variables, named IMEX-SfloW2D, was developed for the simulation of lahar dynamics. A thorough sensitivity analysis was carried out to identify the critical processes (erosion and deposition) and parameters (numerical and physical) controlling lahar runout, using both synthetic and real cases topographies. Effects of erosion and deposition were investigated by comparing field data with the output of simulations including vs. excluding these processes. By comparing observed and simulated flow thickness and area covered by the flows, and their evolution over time, it can be shown that the inclusion of erosion and deposition is important to properly simulate the impact parameters of lahars, particularly on uneven terrain. Lastly, a novel workflow for Probabilistic Volcanic Hazard Assessment (PVHA) for lahars was developed and applied to the Vesuvius case study. Such a workflow explores the effect of uncertainty of the flow initial conditions on the impact parameters of lahars on the target area, by sampling coherent sets of values for the input model parameters and running thousand simulations. The simulation outputs were processed to produce hazard curves, hazard maps, and probability maps for the maximum flow thickness, and hazard surface and probability maps for joint thresholds in flow thickness and dynamic pressure. It is believed that the latter hazard products represent a novel product in PVHA for lahars around Vesuvius volcano and can be applied worldwide. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas, even at distances of several to tens of km from active volcanoes like Vesuvius.

How to cite: Di Vito, M., de'Michieli Vitturi, M., Sandri, L., Costa, A., Bisson, M., de Vita, S., Doronzo, D., Gianardi, R., Rosi, M., Rucco, I., Sulpizio, R., Zanchetta, G., and Zanella, E.: Lahars as repeated hazardous phenomenon around Vesuvius volcano (Italy) during and after impacting explosive eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19093, https://doi.org/10.5194/egusphere-egu24-19093, 2024.

Carla Tranquilino, Lizeth Caballero, Mario Flores Guzmán, Damiano Sarocchi, and Fabio Dioguardi

Lahars are two-phase gravity flows which behavior strongly depends on the interaction between the solid phase (large clasts) and the liquid phase (interstitial fluid or matrix). In particular, the rheological behavior of the interstitial fluid is the parameter with the greatest influence on the lahar movement, since the interstitial fluid controls the transportion and sedimentation of the solid phase. The characteristics that define the rheological behavior of the interstitial fluid are particle volumetric concentration, size distribution, and sediment composition. Because of these, here we present the rheological characterization of syn-eruptive and post-eruptive lahars occurred at Popocatepetl volcano, Mexico.

The interstitial fluid characterization was carried out by a strain rate dependence test using a rotational viscometer with a coaxial cylinder geometry. We studied volcanic sediments with different densities and compositions (pumice and lava fragments) sampled from syn- and post-eruptive lahar deposits (at room temperature). In addition, we studied the range of the volumetric sediment concentration that defines the flowage based on the geotechnical characteristics of sediments.

The results suggest a Bingham-type behaviour model with yield strength values between 10-2 and 100 Pa, for shear rate conditions between 50 and 100 s-1. In addition, an inverse relationship of apparent viscosity throw values between 10-2 and 10-1 Pa s at  the same shear rates, suggesting a thinning behaviour. The data suggest exponential relationships between volumetric sediment concentration and yield strength or apparent viscosity. The fitting coefficients describe volcanic sediments, unlike those found in the literature and often used in lahar simulations for hazard modelling, which are derived from the study of soil materials and mine tailings.

The interstitial fluid of syn-eruptive lahars with monolithologic composition (pumice fragments) has yield strength and apparent viscosity values higher than those of syn-eruptive and post-eruptive lahars with heterolithologic composition (pumice and lava fragments). In addition, the dominant clay-sized interstitial fluid has apparent viscosity values between two and three orders of magnitude higher than the dominant silt-sized interstitial fluid.

Finally, the rheological behavior of the studied lahar samples will contribute to solving  the constitutive equations that describe their movement under a viscoelastic flow behavior for the studied shear rates. Furthermore, this information could be implemented in numerical simulations with similar volcanic sediment characteristics and deformation conditions to those studied, with the aim of estimating the inundation area that would be affected by the occurrence of a similar event.



How to cite: Tranquilino, C., Caballero, L., Flores Guzmán, M., Sarocchi, D., and Dioguardi, F.: First approach to the rheological behaviour of syn-eruptive and post-eruptive lahars., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8213, https://doi.org/10.5194/egusphere-egu24-8213, 2024.

Silvio Kmetyko, Martin Mergili, and José Luis Palma

The Villarrica or Rukapillan is one of the most active volcanoes in South America. In Chile it is the volcano with the highest risk to human life and infrastructure. An eruption on 3rd of March 2015 triggered several lahars that affected four different valleys, where they caused the destruction of touristic infrastructure and parts of the local road network. Adequate numerical simulations of such events can build an important basis for risk management. Various software tools are available to accomplish such task, each of which has its potentials and limitations. This work compares two sets of numerical simulations of the lahars that occurred in the valley Zanjón Seco during the 2015 eruption. The first set is conducted with r.avaflow, a physically-based open-source simulation framework for mass flows and process chains which runs in the GRASS GIS environment. The second is realized with Laharz, a statistically-based tool which runs in an ArcGIS environment. Strengths and weaknesses of both simulation tools in regard to the adequate reconstruction of the observed lahar events reproducing such volcanic hazards are discussed. For this purpose, the model outputs are evaluated against the lahar deposits mapped in the valley and qualitatively compared with each other.

How to cite: Kmetyko, S., Mergili, M., and Palma, J. L.: Numerical modelling of the lahars generated during the 2015 eruption at Volcán Villarrica (Chile), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9844, https://doi.org/10.5194/egusphere-egu24-9844, 2024.

Guillaume Carazzo and Geoffrey Robert

Volcanic plumes associated with propagating pyroclastic density currents can rise tens of kilometers into the atmosphere, dispersing fine ash particles over large areas with a potential hazard for aviation safety. Such plumes originate from the buoyancy reversal of the pyroclastic density currents caused by the entrainment and heating of ambient air combined with the sedimentation of coarse particles. Several experimental and numerical studies investigated the formation, dynamics and impacts of these plumes but the mechanisms controlling the mass partitioning between the buoyant rising plume and the dense propagating current have received less attention despite its crucial importance for hazard assessment. Here, we present a new laboratory study aimed at investigating the controls on the mass partitioning during the plume lift-off. The experimental set-up is designed to simulate a gravity current of ethanol and ethylene glycol (EEG) flowing under a sloping roof in a tank of fresh water. The EEG mixture is less dense than fresh water but may become denser when mixed with water allowing us to generate a plume associated with the gravity current. Depending on the source conditions, the turbulent gravity current may either fully lift-off to form a buoyant plume, separate in a dense propagating flow and a buoyant plume, or propagate along the slope with no plume formation. We show that the transition between the three regimes is strongly controlled by the Richardson number defined at the source and by the slope. The results are consistent with the theoretical predictions of a simple 1D model and provide constraints on the mass partitioning during the formation of the plume.

How to cite: Carazzo, G. and Robert, G.: A laboratory study of plumes associated with pyroclastic density currents, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17769, https://doi.org/10.5194/egusphere-egu24-17769, 2024.

Ilaria Rucco, Fabio Dioguardi, Mauro Antonio Di Vito, Nikhil Nedumpallile-Vasu, Damiano Sarocchi, and Raffaella Ocone

Granular materials are widely involved in several processes, from the food, cosmetic, and pharmaceutical industries to natural phenomena such as pyroclastic density currents and landslides. Therefore, the study and understanding of their behaviour and rheology are of paramount importance in terms of hazard assessment and for developing and implementing mathematical and numerical models. The simulations try to reproduce the complexity of the flows taking into account several parameters, but, despite the advances in the theoretical descriptions of granular flows, a gap still exists between the empirical models and the experimental observations.

In this work, we present the results of the characterization of volcanic samples carried out with the FT4 Powder Rheometer (Freeman Technology). Shear tests, compressibility tests, and wall friction tests were performed to characterize the flowability of the powders. We particularly focus on the wall (or basal) friction angle, which describes the interaction of the particles with a variable-roughness substrate. Some glass beads have also been investigated, as a reference value. The results show how the ratio between the roughness of the surface and the average particle size of the samples influences the wall friction angle. Moreover, the comparison with the glass beads also reveals the influence of the irregular shape of the particles.

How to cite: Rucco, I., Dioguardi, F., Di Vito, M. A., Nedumpallile-Vasu, N., Sarocchi, D., and Ocone, R.: Evaluation of the wall friction angle of dry volcanic materials from laboratory experiments., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18995, https://doi.org/10.5194/egusphere-egu24-18995, 2024.

Carolina Figueiredo, Halil Sarp Esenyel, Ulrich Kueppers, and Donald Bruce Dingwell

During explosive volcanic eruptions involving felsic magmas, angular porous pyroclasts are generated and ejected into the atmosphere. As these pyroclasts are mechanically weak, transport processes after fragmentation can alter their shape. Rotary tumbling experiments have been used to mimic particle-particle interaction during Pyroclastic Density Currents (PDC) or sedimentation and to understand the role of transport mechanisms on fine ash generation and changes in pyroclast morphology. We used clasts generated by Hornby et al. (2020) to statistically quantify the shape evolution of pre- and post-tumbling pyroclasts. Two types of Laacher See pumice were used as starting material. LSB (Laacher See Bims) was industrially processed by ROTEC® by wet sieving, while ULST (Upper Laacher See Tephra) represents pristine clasts from fall units of the Laacher See eruption. Four sets of tumbling experiments (T1, T2, T3A, T3B) were performed. All lasted in total 120 minutes and ash generation was quantified after 15, 30, 45, 60 and 120th minutes. In T1 experiments, ash generated was added back into the drum after each increment but left out and stored separately in T2 experiments. In T3 steel balls were added to the drum to simulate the impact of lithics on the mechanical response of pumice lapilli. All other boundary conditions of T3A experiments mimic those of T1 while T3B experiments mimic T2. We quantified three values for each set of clasts: 1) amount of ash generated (dry sieving), 2) clast volumes (following Pisello et al., 2023), and 3) clast morphology. For the latter, we used shadowgraphs of 100 clasts per sample set independently, processed the images on Photoshop (clast contours delimitation and binarization) and calculated shape parameters (Convexity, Solidity, Form factor and Axial ratio, see Liu et al., 2015) using ImageJ. As expected, a striking distinction between starting material and tumbled clasts was found. We present data for 1) ash generation efficiency (≤ 53%), 2) clast volume (reduction), and 3) shape parameters (≤ 0.15 increase) to evidence the importance of pyroclast overprinting during transport-related processes. As clasts collected from fall units (see ULST here or Pisello et al., 2023) are angular, particle-particle interaction during gas-pyroclast flow inside conduits is found to have been of minor importance.

How to cite: Figueiredo, C., Esenyel, H. S., Kueppers, U., and Dingwell, D. B.: Shape evolution of pyroclasts in tumbling experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22220, https://doi.org/10.5194/egusphere-egu24-22220, 2024.

Loredana Nada Elvira Giani and Gianluca Casagrande

The aim of the paper is to identify a key to understanding that allows us to overcome the regulatory trilemma that has emerged, seeking to offer a perspective according to which the exceptional event, an expression of the (ineliminable) complexity of reality, is included (in the competent political and institutional fora) in a broader case, encompassing contingencies. And this is not to foresee them, often asking science to do the impossible, nor to block activities considered dangerous through an exaggeration of the principles of prevention and precaution, but simply to allow the legal system to assume a broader vision, inclusive of the unusual case in point, to provide a toolbox of possible reactions to be triggered in the event (even remote) of the occurrence of an exceptional event.

How to cite: Giani, L. N. E. and Casagrande, G.: Trilemma, complexity, administration and exceptional events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22289, https://doi.org/10.5194/egusphere-egu24-22289, 2024.

Annarita Iacopino

This paper aims to analyse the path of administrative jurisprudence on how the principles of prevention and precaution behave, the role they assume for the public decision-maker and the judge's review. In this perspective, priority is given to examining the nature and ratio of the two principles, as well as the relationship between them. It is then necessary to define their sphere of operation and the essentially “methodological and bidirectional” dimension in which they move. They, in fact, offer rules for proceeding and not for deciding, thus allowing the identification of the path of proceduralisation of public decisions in situations of danger (prevention) or in situations of risk (precaution), enabling the minimisation of risks, respectively, through intervention on the causes of the possible emergence of danger and through the identification of the solution that makes it possible to balance the minimisation of risks with the maximisation of benefits. In an emergency phase, as in the case of compulsory vaccination, this may require operating in a “counter-intuitive” manner with the imposition of instruments-therapies- that ensure more benefits than risks, since the potential risk of an adverse event for an individual is far less than the actual damage to society as a whole. In all these hypotheses, the scientific basis represents a guarantee of the reasonableness of the choices, since the public decision-maker's assessment must be based on acquisition of the best science of the moment and on the rigour of the relevant method; a “reserve of science” whose reasonableness and proportionality is subject to the administrative judge's review.

How to cite: Iacopino, A.: Precaution and prevention in the jurisprudence of the administrative judge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22292, https://doi.org/10.5194/egusphere-egu24-22292, 2024.

Vanessa Manzetti

The Court of Auditors is assigned the scrutiny of the economic-financial balance of the Public administrations in order to protect the economic unity of the Italian Republic.  Such prerogatives have a great importance in the framework outlined by art. 2 §1 of the Constitutional Law n.1/2012, which, in line with the European Union legal system, recalls the Public Administrations as a whole to ensure balanced budgets and the sustainability of the public debt. This means that the surveys of the Court of Auditors in the performance of its functions (judicial, control and advisory) should indirectly also reveal the emergency costs.

The paper will examine some fundamental documents such as the Report on the financial management of the local authorities 2019-2021, the deliberations of the Regional Audit sections of the Court on budgets of the local health authorities, as well as the Reports on the result of the controls on the financial management of the companies subject to the control of the Court of Auditors ex art. 12 of the Law n. 259 of 1958. The examination will also focus on the controls that the Regional Control Sections of the Court of Auditors carries out on the budgets and final accounts of Local Authorities to verify the compliance with the annual objectives set by the Internal Stability Pact and the compliance with the obligation provided by article 119 § 6 of the Italian Constitution. These controls aim also to verify the debt sustainability and the absence of irregularities that could jeopardize the balance economic-financial aspects of the Local Authorities.

An important perspective to better quantify the costs of the emergency is also identified by article 103 of the Italian Constitution which attributes to the Court of Auditors the jurisdiction on public accounting, civil, military and war pensions, as well as the jurisdiction on the liability of public accountants, public administrators and public officials in judgements concerning the management of the public money. This approach could also lead to reflect on the relationship between public debt and emergency, and on the possibility of judgments raised by a party before the Court of Auditors. Lastly, the examination of the Opinions drawn up by the Court of Auditors in the exercise of its advisory function could be also useful to trace the unclear perimeter of the costs of the emergency

How to cite: Manzetti, V.: Costs of emergency and the role of Court of Auditors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22298, https://doi.org/10.5194/egusphere-egu24-22298, 2024.

Risks, major infrastructure and public procurement
(withdrawn after no-show)
Aristide Police
Volcano engineering for food resiliency: uncertainty and ethics
(withdrawn after no-show)
Anders Sandberg

Posters virtual: Thu, 18 Apr, 14:00–15:45 | vHall X4

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 18:00
Chairpersons: Fabio Dioguardi, Anke Zernack, Audrey Michaud-Dubuy
Morgan Hetherington, Alan Cuthbertson, Sue Dawson, and Fabio Dioguardi

Explosive volcanic eruptions, which are characterized by the discharge of ash and gas from the vent into the atmosphere, are an example of a naturally occurring buoyant jet.  These buoyant jets can significantly impact the surrounding environment; for example, the presence of fine ash particles in the atmosphere can damage aircraft engines, potentially leading to engine failure. Therefore, during an explosive eruption, volcanic ash advisory centers (VAACs) consistently monitor the concentration of ash in the atmosphere using numerical models. These numerical models require the definition of a source term (i.e., source mass eruption rate, plume height and total grain size distribution), which is often obtained from simpler one-dimensional models. One-dimensional models derived from well-established theories successfully replicate the dynamics of the initial buoyant jet; however, they assume time-averaged source conditions which are not observed in field-scale vulcanian and strombolian style eruptions. As such, there is a disconnect between these well-established theories assuming time averaged source conditions and reality. This disconnect may introduce uncertainties in ash concentration forecasts, potentially resulting in practical implications such as unnecessary airspace closures or flights operating in hazardous conditions. The present contribution utilizes scaled laboratory experiments to quantify the influence of source variability on the dynamics of buoyant jets and evaluates potential deviations from time-average assumptions.

Scaled laboratory experiments were conducted in an acrylic tank measuring 1200x670x450 mm, filled with water to a depth of 870 mm. A vertical pipe, 18 mm in diameter, was used to release fresh water (density ρ = 1000 kg/m³), which was combined with dye or particles, into saline water (ambient density  = 1000 - 1030 kg/m³). This configuration resulted in the generation of a vertical buoyant jet.  The flow rate was controlled and measured using a valve and ultrasonic flow meter. For the generation of unsteady discharges, a solenoid valve was employed, facilitating pulsed source conditions with discharge intervals ranging between ½ second to 2 seconds. Image analysis techniques, specifically light-induced fluorescence (LIF) and particle image velocimetry (PIV), were employed to measure buoyant jet characteristics, including concentration profiles, velocity fields, and jet geometry. These characteristics were measured under both steady and unsteady source conditions, facilitating a comparative analysis of the changes in behaviour arising from source condition variations.

The experimental results were compared with integral assumptions of one-dimensional models. These findings will be presented, and their significance will be explored within the context of vulcanian and strombolian style eruptions.

How to cite: Hetherington, M., Cuthbertson, A., Dawson, S., and Dioguardi, F.: Understanding the dynamics of unsteady buoyant Jets: an experimental analogue of Vulcanian and Strombolian style eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15962, https://doi.org/10.5194/egusphere-egu24-15962, 2024.

Emergency organization and State duty of prevention
(withdrawn after no-show)
Marco Macchia
Programming as risk part of emergency governance
(withdrawn after no-show)
Giovanna Iacovone
Marco Calabrò and Allessandro di Martino

The topic of exceptions to the ordinary rules of public contracts in the management of risks and emergencies resulting from volcanological phenomena allows for numerous considerations on the aspects of public contracts and administrative law. The topic must obviously be analysed through an interdisciplinary approach focusing on the relationship between technology and law. For example, to verify the legitimacy of the application of derogatory regulations, it is necessary to consider the three-phase structure of volcanic risk: risk assessment, hazard assessment and mitigation of the event. The centrality of the technical issues requires, first of all, an examination of the legal profiles: the first aspect concerns the delimitation of both the concept of "paramount urgency" - a prerequisite for derogating from the ordinary rules - and of which events (whether they have already occurred or have not yet occurred) are susceptible to fall within the scope of the provision. In this context, this research focuses on the practices of individual local authorities from which a significant interpretative and methodological distance emerges.

A further profile of interest concerns organisational issues: this work aims to examine the benefits of a centralisation of competences in the hands of the regions, from two points of view. The first concerns the attempt to reduce potential corruption phenomena that could occur in territories where unpredictable maintenance events frequently occur. The second is based on the consideration that leaving the choice to individual local administrations could lead to different assessments of 'extreme urgency' conditions between neighbouring authorities Centralisation would therefore go in the direction of uniformity of decisions.

There are, in conclusion, two other aspects that deserve further study. The first concerns the need for ex-post controls, linked to the centrality of the assessment of the conditions of extreme urgency, which risks being ineffective given the extremely tight timeframe. The second seeks to understand whether the derogation to the procurement regime also drags on the regime of landscape authorisations or environmental impact assessments: if this were not the case, and if therefore ex ante intervention were still necessary, the process of simplifying the activities of economic operators would inevitably be thwarted. In addition to the theoretical reflections carried out on the derogation to the ordinary regime of contracting in cases of volcanic risk, this work will also analyse the so-called Campi Flegrei Decree, which allows recourse to the derogatory techniques mainly for two reasons: to provide for the acquisition of instrumental resources necessary to ensure the effective management of civil protection activities; and to provide for the setting up of temporary areas and services for the reception of the population.

How to cite: Calabrò, M. and di Martino, A.: Exceptions to the ordinary rules for awarding public contracts: the volcanic risk paradigm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22294, https://doi.org/10.5194/egusphere-egu24-22294, 2024.

Decoding decision discrepancy: Unravelling noise in seismic authorizations
(withdrawn after no-show)
Simone Busetti and Maria Stella Righettini
Marina d'Orsogna and Federico Valentini

The catastrophic events linked to natural phenomena that periodically strike Italy generate an increasingly irremediable rift between the State and the population, which is also tangible in the litigation that has become an increasingly frequent consequence of disasters in recent times. The media clamour that judicial events take on increasingly generates an image of a State that is impeccable in the solidarity phase but remains highly negligent in risk prevention policies. Compared to this vision, the recent commitment of the legislator to prevent the damaging effects of bradyseism in the Phlegraean Fields area goes against the trend.

However, many of the prevention activities identified, which can be implemented thanks to the appropriations provided, risk being compromised on a practical level due to the considerable rate of abuse in the area concerned, which makes the territory more fragile and the population less safe.     

It is strategically necessary to increase the level of public safety in an area that, on this point, presents undeniable criticalities: among the measures that can be implemented, it is desirable, for example, to perform an immediate analysis of the seismic vulnerability of the public and private building stock so as to allow preventive safety measures. In addition, an update of the General Evacuation Plan is needed, which currently, according to studies, would not allow the area, with its very high population density, to be cleared in a few hours.

How to cite: d'Orsogna, M. and Valentini, F.: Environmental surveillance and volcanic risk. Bradyseismic crisis and vulnerability of built-up areas: new intervention strategies on public and private heritage., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22379, https://doi.org/10.5194/egusphere-egu24-22379, 2024.

Emanuele Fratto Rosi Grippaudo and Luigi Rufo

This paper aims to analyse the use of artificial intelligence tools to implement an active contact tracing system for individuals living in at-risk territories. Thus, not only a 'state of alert' communication system, but a 'contact tracing' system similar to that used in some States during the SARS pandemic COVID-19. From a legal point of view, it is necessary to balance the right to privacy with the right to health/right to life. In this perspective, the necessary prerequisites will be analysed: state regulation, rigorously proportionate and, furthermore, the security of the data. This must be placed on a server that is strictly publicly owned and managed, to prevent tracing being used as a bargaining chip, and ensure that the personal data collected by the platform or application are only those necessary to warn users of the danger and are not used for any other purpose, without prejudice to the possibility of using them in aggregate or in any case anonymous form, for statistical or scientific research purposes only.

How to cite: Fratto Rosi Grippaudo, E. and Rufo, L.: Data privacy in volcanic hazard scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22382, https://doi.org/10.5194/egusphere-egu24-22382, 2024.

Risk and volcanoes: guarantee perspectives
(withdrawn after no-show)
Ruggiero Dipace
Sociological perspective of volcanic risk: volcanic risk and building resilient processes
(withdrawn after no-show)
Rita Biancheri
Civil Protection Department. Territorial organization and governance profiles
alessandro paire