LAV@HAZARD: A Web-Gis interface for volcanic hazard assessment

Satellite data, radiative power of hot spots as measured with remote sensing, historical records, on site geological surveys, digital elevation model data, and simulation results together provide a massive data source to investigate the behavior of active volcanoes like Mount Etna (Sicily,Italy) over recent times. The integration of these eterogeneous data into a coherent visualization framework is important for their practical exploitation. It is crucial to fill in the gap between experimental and numerical data, and the direct human perception of their meaning. Indeed, the people in charge of safety planning of an area need to be able to quickly assess hazards and other relevant issues even during critical situations. With this in mind, we developed LAV@HAZARD, a web-based geographic information system that provides an interface for the collection of all of the products coming from the LAVA project research activities. LAV@HAZARD is based on Google Maps application programming interface, a choice motivated by its ease of use and the user-friendly interactive environment it provides. In particular, the web structure consists of four modules for satellite applications (time-space evolution of hot spots, radiant flux and effusion rate), hazard map visualization, a database of ca. 30,000 lava-flow simulations, and real-time scenario forecasting by MAGFLOW on Compute Unified Device Architecture

Role of Emissivity in Lava Flow ‘Distance-to-Run’ Estimates from Satellite-Based Volcano Monitoring

Remote sensing is an established technological solution for bridging critical gaps in volcanic hazard assessment and risk mitigation. The enormous amount of remote sensing data available today at a range of temporal and spatial resolutions can aid emergency management in volcanic crises by detecting and measuring high-temperature thermal anomalies and providing lava flow propagation forecasts. In such thermal estimates, an important role is played by emissivity—the efficiency with which a surface radiates its thermal energy at various wavelengths. Emissivity has a close relationship with land surface temperatures and radiant fluxes, and it impacts directly on the prediction of lava flow behavior, as mass flux estimates depend on measured radiant fluxes. Since emissivity is seldom measured and mostly assumed, we aimed to fill this gap in knowledge by carrying out a multi-stage experiment, combining laboratory-based Fourier transform infrared (FTIR) analyses, remote sensing data, and numerical modeling. We tested the capacity for reproducing emissivity from spaceborne observations using ASTER Global Emissivity Database (GED) while assessing the spatial heterogeneity of emissivity. Our laboratory-satellite emissivity values were used to establish a realistic land surface temperature from a high-resolution spaceborne payload (ETM+) to obtain an instant temperature⁻radiant flux and eruption rate results for the 2001 Mount Etna (Italy) eruption. Forward-modeling tests conducted on the 2001 ‘aa’ lava flow by means of the MAGFLOW Cellular Automata code produced differences of up to ~600 m in the simulated lava flow ‘distance-to-run’ for a range of emissivity values. Given the density and proximity of urban settlements on and around Mount Etna, these results may have significant implications for civil protection and urban planning applications

UFGM - 2006 Annual Report

INGV, SEZIONE DI CATANIAPublished2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveope

Radiant and mass fluxes in multi-platform, multi-payload satellite-based volcano monitoring

The enormous amount of remote sensing (RS) data available today at a range of temporal and spatial resolutions aid emergency management in volcanic crises. RS provides a technological solution for bridging critical gaps in volcanic hazard assessment and risk mitigation. Detection and measurement of high-temperature thermal anomalies enable eruption monitoring and new lava flow propagation forecasts, for example. The accuracy of such thermal estimates relies on the knowledge of input parameters, such as emissivity - the efficiency with which surfaces radiate thermal energy at various wavelengths and temperatures. Emissivity is directly linked to the measurement of radiant flux and therefore affects the mass flux estimate as well as any model-based prediction of lava flow behaviour. Emissivity is not commonly measured across the range of volcanic lava compositions and temperatures, and it is generally assumed to have a constant value between 1.0 and 0.80 for basaltic lava. There is a lack of field and laboratory-based emissivity data for robust, more realistic modelling. To address this deficit, experiments on ‘aa’ lava samples were performed using data from Mount Etna (Italy), representing the range of its eruptive behaviour. In three sequential stages, emissivity was measured over the widest range of temperatures (294 – 1373 K) and wavelengths (2.17 - 15.0 μm) executable in the laboratory environment.The results show that emissivity is temperature, composition and wavelength dependent. Measured emissivity increases non-linearly with temperature decrease (cooling), exhibiting significant variations above 900 K with values considerably lower than the typically assumed 0.80. The measured and modelled emissivity values were applied to various remote sensing applications as input parameters for physical modelling of lava flows. This new evidence has significant impact on the computation of radiant heat flux from spaceborne data, as well as on modelling of lava flow ‘distance-to-run’ simulations. Furnished with improved input parameters (multicomponent emissivity), the novel approach developed here can be used to test an improved version of an unsupervised multi-platform, multi-payload volcano monitoring system

The Impact of Dynamic Emissivity−Temperature Trends on Spaceborne Data: Applications to the 2001 Mount Etna Eruption

Spaceborne detection and measurements of high-temperature thermal anomalies enable monitoring and forecasts of lava flow propagation. The accuracy of such thermal estimates relies on the knowledge of input parameters, such as emissivity, which notably affects computation of temperature, radiant heat flux, and subsequent analyses (e.g., effusion rate and lava flow distance to run) that rely on the accuracy of observations. To address the deficit of field and laboratory-based emissivity data for inverse and forward modelling, we measured the emissivity of ‘a’a lava samples from the 2001 Mt. Etna eruption, over the wide range of temperatures (773 to 1373 K) and wavelengths (2.17 to 21.0 µm). The results show that emissivity is not only wavelength dependent, but it also increases non-linearly with cooling, revealing considerably lower values than those typically assumed for basalts. This new evidence showed the largest and smallest increase in average emissivity during cooling in the MIR and TIR regions (~30% and ~8% respectively), whereas the shorter wavelengths of the SWIR region showed a moderate increase (~15%). These results applied to spaceborne data confirm that the variable emissivity-derived radiant heat flux is greater than the constant emissivity assumption. For the differences between the radiant heat flux in the case of variable and constant emissivity, we found the median value is 0.06, whereas the 25th and the 75th percentiles are 0.014 and 0.161, respectively. This new evidence has significant impacts on the modelling of lava flow simulations, causing a dissimilarity between the two emissivity approaches of ~16% in the final area and ~7% in the maximum thickness. The multicomponent emissivity input provides means for ‘best practice’ scenario when accurate data required. The novel approach developed here can be used to test an improved version of existing multi-platform, multi-payload volcano monitoring systems

Large-scale volcanism on the terrestrial planets

Evidence for mafic volcanism has been found on each planet in the inner Solar System. Lava flows on these planets range in size from 10s to 1000s of kilometers in extent. I investigated large-scale lava flows on Mercury, Earth, and Mars throughout the chapters in this dissertation. Each of these lava flows provides an avenue to study the emplacement and evolution of lava on various planets and under differing conditions, the factors that affect their overall extent, and potential source areas. Chapter One investigates large-scale lava flows in the Cerberus region on Mars, specifically to understand their emplacement history, material properties, and possible magma sources. Mapping and crater counting are used to investigate these flows. The derived absolute age estimates suggest an anomalous trend of decreasing ages with increasing distance from the flow source. Through pi-group scaling, changes to the material properties of the lavas during emplacement are identified as the cause for this decreasing age trend and are attributed to increased strength, and decreased porosity, of the lava. These newly derived absolute age estimates are also used to infer the source of the magma feeding these young and extensive lava flows originated below the Cerberus region. Chapter Two focuses on long and areally extensive lava flows on Earth and Mars, in order to determine the effect of viscosity on the emplacement of 1000+ km flows. In particular, low viscosity lavas are expected to generate such large lava flows. The terrestrial and martian lava flows are interpreted to have been emplaced rapidly, with their final extents limited by the total erupted volume of lava. Through computer modeling, simulations are performed to determine the viscosity values responsible for the observed lava flow extents. The results of this work support low bulk viscosities that correspond to a basaltic composition produce the best reproductions of the martian flows. Chapter Three investigates volcanism on Mercury, which hosts broad smooth plains in three locales, which have varying interpretations for their emplacement, though volcanic processes are favored. The smooth plains units located in the annulus surrounding the Caloris impact basin contain intermingled high-reflectance red and low-reflectance blue plains. Mapping, crater counting, and spectral analyses are used to suggest the emplacement mechanism for these smooth plains. The results of this work support a volcanic origin, though impact related processes cannot be discounted

Understanding emplacement of rapidly-emplaced volume-limited lava flows from Mount Etna’s 2011-2012 eruption:a multidisciplinary study

While the study of emplacement in most literature focuses on long-duration cooling-limited lava flows, the short duration and rapid emplacement of many volume-limited flows impedes their analysis. This thesis aims to improve understanding of the emplacement of shortduration volume-limited lava flows by: (1) employing long-range ground-based visible timelapse data and thermo-rheological modelling to understand and analyze the importance of different factors which influence lava flow emplacement, and (2) developing a workflow for improving the application of long-range ground-based thermal cameras for studying lava flows. Results from (1) agreed with previous studies, showing strong correlations between final flow length and the following: total volume, duration, flow field width, number of bifurcations in the proximal zone of the flow, number of confluences, average and maximum advance rate in the proximal zone, and duration of fire fountaining. However, unlike previous studies, no correlation was found between final flow length and mean output rate. Visual analysis identified two flow groups based on morphology within the proximal zone of the flow, and results indicated that differences in advance rates and at-vent initial effusion rates dictated the morphology observed for the two groups. Analysing flow confinement indicated a strong relationship between final length and the distance of confinement of the primary flow. Utilising multiple regression analysis, maximum flow width, duration of flow, and maximum advance rate in the proximal zone produced the best model for flow length in terms of explanatory and predictive power. By substituting flow widths estimated from the time-lapse data for channel widths, FLOWGOmodelled effusion rates and total volumes were obtained for the primary flows of the 12 May and 19 July 2011 episodes at Mt. Etna which were within the range of values estimated by previous studies. Additionally, using FLOWGO to model flow thickness changes due to bifurcations of the primary flow produced average flow thickness estimates for the semichannelized 12 May flow that agreed with estimates from previous studies. However, no thickness estimates were possible using this method for the unconfined 19 July flow. This suggests that substituting flow width for channel width in FLOWGO for unconfined flows is inappropriate and should only be applied to flows with a more channel-like morphology. A workflow was developed to achieve objective (2) and applied to the 29 August 2011 episode at Mt. Etna to correct ground-based thermal data for atmospheric and viewing effects due to long viewing paths along two different viewing geometries (horizontal- and slant-path). Estimates of flow area, volume, and mean output rate using both viewing geometries were within the range of values reported in the literature. Estimates of surface temperature using the slant-path geometry were within the range of values given by previous studies which measured active lava channels at 0-70 metres distance; however, the complexity of the atmospheric model associated with this viewing geometry made it difficult to automate. Some errors resulted from the large pixel area (25 m2 ) of the long-range thermal data resulting in a greater area of temperature integration. The radiant heat flux profiles produced by the workflow followed the same trends as the SEVIRI-derived profile, although the intensity of the SEVIRI-derived profile was up to five times greater than the workflow profiles

Depth-averaged and 3D Finite Volume numerical models for viscous fluids, with application to the simulation of lava flows

This Ph.D. project was initially born from the motivation to contribute to the depth-averaged and 3D modeling of lava flows. Still, we can frame the work done in a broader and more generalist vision. We developed two models that may be used for generic viscous fluids, and we applied efficient numerical schemes for both cases, as explained in the following. The new solvers simulate free-surface viscous fluids whose temperature changes are due to radiative, convective, and conductive heat exchanges. A temperature-dependent viscoplastic model is used for the final application to lava flows. Both the models behind the solvers were derived from mass, momentum, and energy conservation laws. Still, one was obtained by following the depth-averaged model approach and the other by the 3D model approach. The numerical schemes adopted in both our models belong to the family of finite volume methods, based on the integral form of the conservation laws. This choice of methods family is fundamental because it allows the creation and propagation of discontinuities in the solutions and enforces the conservation properties of the equations. We propose a depth-averaged model for a viscous fluid in an incompressible and laminar regime with an additional transport equation for a scalar quantity varying horizontally and a variable density that depends on such transported quantity. Viscosity and non-constant vertical profiles for the velocity and the transported quantity are assumed, overtaking the classic shallow-water formulation. The classic formulation bases on several assumptions, such as the fact that the vertical pressure distribution is hydrostatic, that the vertical component of the velocity can be neglected, and that the horizontal velocity field can be considered constant with depth because the classic formulation accounts for non-viscous fluids. When the vertical shear is essential, the last assumption is too restrictive, so it must relax, producing a modified momentum equation in which a coefficient, known as the Boussinesq factor, appears in the advective term. The spatial discretization method we employed is a modified version of the central-upwind scheme introduced by Kurganov and Petrova in 2007 for the classical shallow water equations. This method is based on a semi-discretization of the computational domain, is stable, and, being a high-order method, has a low numerical diffusion. For the temporal discretization, we used an implicit-explicit Runge-Kutta technique discussed by Russo in 2005 that permits an implicit treatment of the stiff terms. The whole scheme is proved to preserve the positivity of flow thickness and the stationary steady-states. Several numerical experiments validate the proposed method, show the incidence on the numerical solutions of shape coefficients introduced in the model and present the effects of the viscosity-related parameters on the final emplacement of a lava flow. Our 3D model describes the dynamics of two incompressible, viscous, and immiscible fluids, possibly belonging to different phases. Being interested in the final application of lava flows, we also have an equation for energy that models the thermal exchanges between the fluid and the environment. We implemented this model in OpenFOAM, which employs a segregated strategy and the Finite Volume Methods to solve the equations. The Volume of Fluid (VoF) technique introduced by Hirt and Nichols in 1981 is used to deal with the multiphase dynamics (based on the Interphase Capturing strategy), and hence a new transport equation for the volume fraction of one phase is added. The challenging effort of maintaining an accurate description of the interphase between fluids is solved by using the Multidimensional Universal Limiter for Explicit Solution (MULES) method (described by Marquez Damian in 2013) that implements the Flux-Corrected Transport (FCT) technique introduced by Boris and Book in 1973, proposing a mix of high and low order schemes. The choice of the framework to use for any new numerical code is crucial. Our contribution consists of creating a new solver called interThermalRadConvFoam in the OpenFOAM framework by modifying the already existing solver interFoam (described by Deshpande et al. in 2012). Finally, we compared the results of our simulations with some benchmarks to evaluate the performances of our model

Extending the Global Sensitivity Analysis of the SimSphere model in the Context of its Future Exploitation by the Scientific Community

In today’s changing climate, the development of robust, accurate and globally applicable models is imperative for a wider understanding of Earth’s terrestrial biosphere. Moreover, an understanding of the representation, sensitivity and coherence of such models are vital for the operationalisation of any physically based model. A Global Sensitivity Analysis (GSA) was conducted on the SimSphere land biosphere model in which a meta-modelling method adopting Bayesian theory was implemented. Initially, effects of assuming uniform probability distribution functions (PDFs) for the model inputs, when examining sensitivity of key quantities simulated by SimSphere at different output times, were examined. The development of topographic model input parameters (e.g., slope, aspect, and elevation) were derived within a Geographic Information System (GIS) before implementation within the model. The effect of time of the simulation on the sensitivity of previously examined outputs was also analysed. Results showed that simulated outputs were significantly influenced by changes in topographic input parameters, fractional vegetation cover, vegetation height and surface moisture availability in agreement with previous studies. Time of model output simulation had a significant influence on the absolute values of the output variance decomposition, but it did not seem to change the relative importance of each input parameter. Sensitivity Analysis (SA) results of the newly modelled outputs allowed identification of the most responsive model inputs and interactions. Our study presents an important step forward in SimSphere verification given the increasing interest in its use both as an independent modelling and educational tool. Furthermore, this study is very timely given on-going efforts towards the development of operational products based on the synergy of SimSphere with Earth Observation (EO) data. In this context, results also provide additional support for the potential applicability of the assimilation of spatial analysis data derived from GIS and EO data into an accurate modelling framework

Multi-phase controls on lava dynamics determined through analog experiments, observations, and numerical modeling

Volcanic eruptions pose hazards to life and insfrastructure, and contribute to the resurfacing of earth and other planetary bodies. Lavas and magmas are multi-phase suspensions of silicate melts (liquids), solid crystals, and vapor bubbles, and solidify into glass and rock upon cooling. The interactions between phases place important controls on the dynamics and timescales of magma and lava transport and emplacement. The purpose of this thesis is to explore the role of multiphase interactions in controlling eruption dynamics and inform conceptual and numerical models for hazard prediction. In Chapters 1 and 2, centimeter to meter scale analog experiments are used to explore the multi-phase rheological properties and flow behaviors of bubble- and particle-bearing suspensions. Optical imaging of dam-break experiments presented in Chapter 1 expand existing experimental parameter ranges for lava analogs to higher bubble concentrations than existing datasets (up to 82% by volume bubbles and 37% by volume particles). I develop a constitutive relationship for threephase relative viscosity, and demonstrate that at the low strain-rate conditions relevant to many natural lava flows, accounting for the rheological effect of bubbles can result in the prediction of slower runout speeds. Chapter 2 expands upon the work of Chapter 1 using different analog materials observed using nuclear magnetic resonance imaging (MRI) phase-contrast velocimetry (PCV) to measure velocity in the flow interior of three-phase dam-break experiments. I find that for high-aspect ratio particles (sesame seeds), phase segregation into shear bands readily occurs, even at low particle fraction (20%) and results in strain localization. I suggest that the presence of shear bands can lead to faster flow runout than predicted using assumptions of bulk rheology. Chapter 3 analyzes thermal infrared (IR) time-lapse photography and videography of Hawaiian to Strombolian explosive activity during the 2021 eruption of Cumbre Vieja volcano, La Palma, Canary Islands, Spain. Images are analyzed to find time series of apparent plume radius, velocity, and apparent volume flux of high-temperature gas and lava. I compare with other measures of eruptive activity, including remote observations of plume height, SO₂ flux, effusive flux, tremor, and events at the volcano edifice including edifice collapses and the opening of new vents. I find correlations between tremor and explosive flux, but no correlation with SO2 flux or effusive flux, which I interpret as evidence of bubble segregation, highlighting the role of phase segregation and temporal variability in material properties in natural systems. Finally, in Chapter 4, I develop a novel finite element model to explore the interaction between a viscous flow with a solidified crust, and the effect of these interactions on lava flow and lava dome emplacement. I develop a model that couples a temperature-dependent viscous interior with an elastic shell flowing into air, water, or dense atmospheres. The model expands upon existing numerical simulations used in volcanology to have direct applications to lava flows and domes on the sea floor, which accounts for a large portion of the volcanism on Earth, and volcanism on other planetary bodies. Additionally, the formation of levees or solidified flow fronts that fracture and lead to a restart of flow. These lava flow breakouts pose a significant hazard, but there are currently no volcanological community codes capable of using a physics-based approach to predict the timing or location of breakouts. The model in Chapter 4 is the first to allow for assessment of the likelihood of failure at the scale of a flow lobe. Chapter 4 describes the model formulation and verification, and validation against centimeter-scale molten basalt experiments. The dissertation as a whole integrates work using a variety of methods including analog experiments, observations of natural eruptions, and numerical simulations to contribute to our understanding of the effects of multi-phase interactions on volcanic eruptions