Modeling Volcanic Processes: The Physics and Mathematics of Volcanism
Abstract
Understanding the physical behavior of volcanoes is key to mitigating the hazards active volcanoes pose to the ever-increasing populations living nearby. The processes involved in volcanic eruptions are driven by a series of interlinked physical phenomena, and to fully understand these, volcanologists must employ various physics subdisciplines. This book provides the first advanced-level, one-stop resource examining the physics of volcanic behavior and reviewing the state-of-the-art in modeling volcanic processes. Each chapter begins by explaining simple modeling formulations and progresses to present cutting-edge research illustrated by case studies. Individual chapters cover subsurface magmatic processes through to eruption in various environments and conclude with the application of modeling to understanding the other volcanic planets of our Solar System. Providing an accessible and practical text for graduate students of physical volcanology, this book is also an important resource for researchers and professionals in the fields of volcanology, geophysics, geochemistry, petrology and natural hazards.
... In contrast to the GEC-like formation scenario, a rapid maar-like vaporization and pressurization does not require the gas to be contained on a long timescale at high pressures. These results indicate that a rapid pressurization similar to molten fuel-coolant interactions driving maar explosions (Fagents et al., 2013;Sheridan & Wohletz, 1983, 1986) may be a more likely formation scenario for Titan's rampart craters in the case where the retaining cap is composed of water ice. However, this deduction is based on the tensile strength of ice, which itself is not well constrained under planetary conditions. ...
Rampart craters are a class of lakes or depressions in Titan's north polar region that have morphological attributes suggestive of an explosive origin. Two previous studies have proposed that rampart craters form via nitrogen or methane vapor explosions analogous to terrestrial maar explosions. We propose a new terrestrial analog for rampart craters: gas emission craters (GECs) found in permafrost zones. We evaluate the explosive origin of Titan's rampart craters by modeling the dispersal of material from an explosive vent. The dimensions of nine rampart craters with radar‐bright ramparts were used to model the explosion process. The model yields a range of explosion conditions (e.g., gas mass and reservoir depth) producing ejecta dispersal patterns matching the observed features. We find that gas masses of 10¹¹–10¹⁴ kg are required to produce a rampart crater. We examine two explosion scenarios: (a) rapid, maar‐like vaporization and explosion of liquid nitrogen or methane, and (b) more gradual gas accumulation and explosion akin to a GEC driven by methane released from destabilizing clathrates. If Titan's crust is composed of pure water ice, the calculated gas pressures are consistent with a rapid, maar‐like explosion mechanism. If the subsurface is predominantly composed of organic materials or clathrate, either scenario may be plausible. Further research on the composition and tensile strength of Titan's subsurface are required to discriminate between hypotheses. Nevertheless, we conclude that explosive dispersal of ejecta from a vent can account for the morphologies of Titan's rampart craters and may contribute to atmospheric methane replenishment.
... They are caused by discrete explosive events or bursting of large gas slugs . Long-duration tremor consists of a continuous vibration of the atmosphere lasting anywhere from seconds to months and is generated by a wide range of processes including continuous unsteady degassing, roiling of a lava lake surface, overlapping or closely spaced discrete explosive events, lava fountaining, and jet noise during sustained eruption columns Garces et al. 2013). Different types of infrasonic tremor exist and are classified based on their time and frequency domain characteristics (harmonic tremor, monotonic tremor, broadband tremor, and spasmodic tremor; Johnson and Ripepe 2011;Fee and Matoza 2013). ...
Infrasound signals are used to investigate and monitor active volcanoes during eruptive and degassing activity. Infrasound amplitude information has been used to estimate eruptive parameters such as plume height, magma discharge rate, and lava fountain height. Active volcanoes are characterized by pronounced topography and, during eruptive activity, the topography can change rapidly, affecting the observed infrasound amplitudes. While the interaction of infrasonic signals with topography has been widely investigated over the past decade, there has been limited work on the impact of changing topography on the infrasonic amplitudes. In this work, the infrasonic signals accompanying 57 lava fountain paroxysms at Mt. Etna (Italy) during 2021 were analyzed. In particular, the temporal and spatial variations of the infrasound amplitudes were investigated. During 2021, significant changes in the topography around the most active crater (the South East Crater) took place and were reconstructed in detail using high resolution imagery from unoccupied aerial system surveys. Through analysis of the observed infrasound signals and numerical simulations of the acoustic wavefield, we demonstrate that the observed spatial and temporal variation in the infrasound signal amplitudes can largely be explained by the combined effects of changes in the location of the acoustic source and changes in the near-vent topography, together with source acoustic amplitude variations. This work demonstrates the importance of accurate source locations and high-resolution topographic information, particularly in the near-vent region where the topography is most likely to change rapidly and illustrates that changing topography should be considered when interpreting local infrasound observations over long time scales.
... Small pressure changes can be described within the linear acoustic approximation, which assumes small pressure changes from a locally static pressure, and results in waves traveling with a (locally constant) speed of sound. Larger pressure changes cause adiabatic heating in air which locally increases the propagation speed and can lead to dramatic steepening of an initially smooth pressure wave into a discontinuity-a shock (Crighton & Scott, 1979;Garcés et al., 2013;Muhlestein et al., 2012). In an isentropic approximation (reversible process at constant entropy) a shock pulse has characteristic properties such as amplitude and duration that scale with the explosion's energy and the density of the medium in which the pulse travels (Kinney & Graham, 1985). ...
Blasting experiments were performed that investigate multiple explosions that occur in quick succession in unconsolidated ground and their effects on host material and atmosphere. Such processes are known to occur during phreatomagmatic eruptions at various depths, lateral locations, and energies. The experiments follow a multi‐instrument approach in order to observe phenomena in the atmosphere and in the ground, and measure the respective energy partitioning. The experiments show significant coupling of atmospheric (acoustic)‐ and ground (seismic) signal over a large range of (scaled) distances (30–330 m, 1–10 m J−1/3). The distribution of ejected material strongly depends on the sequence of how the explosions occur. The overall crater sizes are in the expected range of a maximum size for many explosions and a minimum for one explosion at a given lateral location. As previous research showed before, peak atmospheric over‐pressure decays exponentially with scaled depth. An exponential decay rate of d¯0=6.47×10−4mJ−1/3 was measured. At a scaled explosion depth of 4 × 10⁻³ m J−1/3 ca. 1% of the blast energy is responsible for the formation of the atmospheric pressure pulse; at a more shallow scaled depth of 2.75 × 10⁻³ m J−1/3 this ratio lies at ca. 5.5%–7.5%. A first order consideration of seismic energy estimates the sum of radiated airborne and seismic energy to be up to 20% of blast energy. Finally, the transient cavity formation during a blast leads to an effectively reduced explosion depth that was determined. Depth reductions of up to 65% were measured.
... Re for the S1 vent was calculated at 1.90 × 10 7 (8 MPa, throat) and 1.09 × 10 8 (15 MPa, fully expanded). In volcanic eruptions, Re can be between 10 5 and 10 8 (Clarke 2013) or as high as 10 11 (Kieffer and Sturtevant 1984). ...
Explosive volcanic eruptions eject a gas-particle mixture into the atmosphere. The characteristics of this mixture in the near-vent region are a direct consequence of the underlying initial conditions at fragmentation and the geometry of the shallow plumbing system. Yet, it is not possible to observe directly the sub-surface parameters that drive such eruptions. Here, we use scaled shock-tube experiments mimicking volcanic explosions in order to elucidate the effects of a number of initial conditions. As volcanic vents can be expected to possess an irregular geometry, we utilise three vent designs, two “complex” vents and a vent with a “real” volcanic geometry. The defining geometry elements of the “complex” vents are a bilateral symmetry with a slanted top plane. The “real” geometry is based on a photogrammetric 3D model of an active volcanic vent with a steep and a diverging vent side. Particle size and density as well as experimental pressure are varied. Our results reveal a strong influence of the vent geometry, on both the direction and the magnitude of particle spreading and the velocity of particles. The overpressure at the vent herby controls the direction of the asymmetry of the gas-particle jet. These findings have implications for the distribution of volcanic ejecta and resulting areas at risk.
... La détermination de la taille des particules permet d'obtenir les caractéristiques de fragmentation de l'éruption associée, l'interprétation génétique des dépôts pyroclastiques (de retombées ou d'écoulement) et la classification des événements volcaniques en combinaison avec la dispersion des dépôts (Walker 1971 ;Cas et Wright 1987 ;Wohletz et al. 1989 ;Fagents et al. 2013). La taille des blocs ou des bombes balistiques peut fournir des indications sur l'énergie cinétique de l'éruption ) et sur la proximité de la source éruptive (Steinberg et Lorenz 1983), tandis que le pourcentage de cendres et cendres fines (taille moyenne inférieure à 63 µm) peut fournir des indications sur l'énergie de fragmentation (Thivet et al. 2020a), mais aussi sur le danger lié à notre capacité à inhaler cette fraction de particules fines (Horwell et Baxter 2006). ...
Des téphras (ou pyroclastites) couvrant une large gamme de granulométries sont éjectés par tous les types d'éruptions. Ils engendrent de nombreux aléas. Leurs retombées peuvent être étudiés après, mais aussi durant, les éruptions. Les techniques d'étude ont beaucoup évolué et sont devenues plus quantitatives. Ceci donne accès à un nombre croissant d'informations sur les mécanismes et la dynamique des éruptions. Ce chapitre décrit les approches modernes de ces études.
Tephras (or pyroclastites) covering a wide range of grain sizes are ejected by all types of eruptions. They generate many hazards. Their fallout can be studied after, but also during, the eruptions. Study techniques have evolved a lot and have become more quantitative. This gives access to a growing amount of information on the mechanisms and dynamics of eruptions. This chapter describes modern approaches to such studies.
... (Ort et al., 2013;Fagents et al., 2013). Entre as expressões morfológicas associadas ao vulcanismo terrestre destaca-se a ocorrência de caldeiras vulcânicas, um importante elemento vulcânico associado ao ciclo tectônico (Wood, 1984 (Fig. 1b). ...
... Historical 2015, and references therein). Considering the severe and large-scale impacts of these events (Oppenheimer 2011), the volcanology community has put an emphasis on understanding and modelling the dispersal of Plinian tephra (Fagents et al. 2013). ...
In the Central Andes, large Plinian eruptions (Volcanic Explosivity Index ≥ 5) occur at a relatively high frequency, i.e. average one every 2000 to 4000 years over the past 50,000 years in Peru. Such recurring explosive activity represents a significant challenge for regions typically hosting several million people (e.g. Southern Peru, Western Bolivia and Northern Chile). With VEI 6, the 1600 CE Huaynaputina eruption is considered the largest historical eruption in South America. We have re-examined the first Plinian phase of this eruption in order to better assess critical eruption source parameters (i.e. erupted volume, plume height, mass eruption rate, eruption duration).The revised bulk volume of the tephra-fall deposit associated with the Plinian phase is approximately 13–14 km³, almost twice the previous estimate (7–8 km³ within the 1 cm isopach) based on methods including power law, Weibull function and Bayesian linear regression. Tephra was dispersed by strong winds to the WNW as far as 400 km on Peruvian territory and then in the Pacific Ocean. Seven villages were buried, killing ~ 1500 people. The revised plume height estimate, 32.2 ± 2.5 km, is consistent with the early estimations. As a result, the Huaynaputina 1600 CE first eruption phase lies in the upper part of the Plinian field close to the ultra-Plinian transition, making this event one of the largest in the past millennium which coincides with results from recent studies on palaeoclimatic impacts.
... The different parameters provide insights into the physical processes occurring during eruption (e.g., Gurioli et al. 2015 and references therein). Grain size analysis allows one to obtain the fragment population characteristics of the associated explosion, which can support a genetic interpretation of the pyroclastic deposits (fall versus flow) and a classification of the volcanic events, when combined with information about the dispersal and depositional features of the deposit (e.g., Fisher 1964;Walker 1971Walker , 1973Sheridan 1971;Sparks 1976;Fisher and Schmincke 1984;Cas and Wright 1987;Wohletz et al. 1989;Freundt and Rosi 1998;Fagents et al. 2013). Componentry analysis (the categorization of clasts as juvenile, non-juvenile, and composite fragments, White and Houghton 2006) provides information on the type of fragmentation (magmatic versus phreatomagmatic), the feeding system, and conduit processes (e.g., Wohletz 1983;Heiken and Wohletz 1985;Sheridan and Marshall 1983;Barberi et al. 1989;Taddeucci et al. 2002;Eychenne et al. 2015). ...
Textural parameters such as density, porosity, pore connectivity, permeability, and vesicle size distributions of vesiculated and dense pyroclasts from the 9.4-ka eruption of Kilian Volcano, were quantified to constrain conduit and eruptive processes. The eruption generated a sequence of five vertical explosions of decreasing intensity, producing pyroclastic density currents and tephra fallout. The initial and final phases of the eruption correspond to the fragmentation of a degassed plug, as suggested by the increase of dense juvenile clasts (bimodal density distributions) as well as non-juvenile clasts, resulting from the reaming of a crater. In contrast, the intermediate eruptive phases were the results of more open-conduit conditions (unimodal density distributions, decreases in dense juvenile pyroclasts, and non-juvenile clasts). Vesicles within the pyroclasts are almost fully connected; however, there are a wide range of permeabilities, especially for the dense juvenile clasts. Textural analysis of the juvenile clasts reveals two vesiculation events: (1) an early nucleation event at low decompression rates during slow magma ascent producing a population of large bubbles (>1 mm) and (2) a syn-explosive nucleation event, followed by growth and coalescence of small bubbles controlled by high decompression rates immediately prior to or during explosive fragmentation. The similarities in pyroclast textures between the Kilian explosions and those at Soufrière Hills Volcano on Montserrat, in 1997, imply that eruptive processes in the two systems were rather similar and probably common to vulcanian eruptions in general.
... Owing to the complex geodynamic process in the epicentral area and its vicinity, the respective swarm might relate to volcanic or tectonic processes or one may trigger the other. In general, earthquake swarm activities are classified into tectonic or volcanic earthquake swarms, although, a swarm may be triggered by coupling of tectonic or magmatic processes where one can trigger the other ( Fagents et al., 2013). The basic question addressed in this paper is whether the source of the peculiar seismicity was triggered by tectonic or magmatic processes. ...
The Harrat Lunayyir (HL) earthquake swarm of 2009 originated in the HL volcanic field and attracted global attention mainly due to three factors: (i) its relatively short life span that ushered a large frequency of the swarm population (30,000 events in < 2 years), (ii) the swarm epicenter zone was contained within a small crustal volume under the HL and (iii) the migratory nature of the swarm following the tectonic trend of a normal fault zone beneath HL. The HL belongs to the Large Igneous Province of Saudi Arabia (LIP-SA) where it correlates to the Great Dikes locally. Our aim in this study is to describe the spatial distribution of the hypocenters, b-value character, and Coulomb stress failure (CSF) in an attempt to analyze the underlying geodynamic process that caused the swarm. We utilize the relocated hypocenters monitored by local networks to examine the b-value characteristics for the swarm. This is best represented in a cross section showing two domains of higher b-value anomalies: two patches occurring at shallow depth and at the deeper crust to the SE from the mainshock originated at the shallower depth northwestward. Consistently positive ΔCFF pattern with a large percentage of aftershocks imply how the mainshock rupture controlled the aftershocks activity. This implies that the failure along the NNW fault trend is due to the prevailing ambient stress field imparted to the swarm. We model this by CSF associated with the mainshock for three time dependent situations: (a) foreshock and aftershock epicenters, (b) foreshock hypocenters, and (c) aftershock hypocenters. In actuality, multiple factors might have controlled the aftershock activity as we speculate that positive Coulomb stress was associated in an area where the higher b-value prevails. The CSF produced by the mainshock illustrates how the stress dissipated along the NNW normal fault zone that interrupts the Great Dykes along the Red Sea coast. These results further suggest that the crustal heterogeneity under HL act as an asperity in the epicentral area, whose origin may relate to magma intrusion into upper crust. However, seismic survey is required for detailing this geologic inference.
... The resulting deposit accumulates in a radial pattern around the volcano only where wind is absent; more typically, it is dispersed in the direction of the prevailing winds throughout the eruption (Figure 3.3). As a general rule, deposit thickness and particle size distribution reduce with distance from the volcano: decreases that can be well fitted by a Weibull distribution (Bonadonna & Costa, 2013). Aggregation of particles can lead to secondary maxima in deposit thickness and particle sizes at varying distances from the volcano (Figure 3.3). ...
All explosive volcanic eruptions generate volcanic ash, fragments of rock that are produced
when magma or vent material is explosively disintegrated. Volcanic ash is then convected
upwards within the eruption column and carried downwind, falling out of suspension and
potentially affecting communities across hundreds, or even thousands, of square kilometres.
Ash is the most frequent, and often widespread, volcanic hazard and is produced by all
explosive volcanic eruptions. Although ash falls rarely endanger human life directly, threats to
public health and disruption to critical infrastructure services, aviation and primary production
can lead to potentially substantial societal impacts and costs, even at thicknesses of only a few
millimetres. Communities exposed to any magnitude of ash fall commonly report anxiety about
the health impacts of inhaling or ingesting ash (as well as impacts to animals and property
damage), which may lead to temporary socio-economic disruption (e.g. evacuation, school and
business closures, cancellations). The impacts of any ash fall can therefore be experienced
across large areas and can also be long-lived, both because eruptions can last weeks, months or
even years and because ash may be remobilised and re-deposited by wind, traffic or human
activities.
Given the potentially large geographic dispersal of volcanic ash, and the substantial impacts that
even thin (a few mm in thickness) deposits can have for society, this chapter elaborates upon
the ash component of the overviews provided in Chapters 1 and 2. We focus on the hazard and
associated impacts of ash falls; however, the areas affected by volcanic ash are potentially much
larger than those affected by ash falling to the ground, as fine particles can remain aloft for
extended periods of time. For example, large portions of European airspace were closed for up
to five weeks during the eruption of Eyjafjallajökull, Iceland, in 2010 because of airborne ash
(with negligible associated ash falls outside of Iceland). The distance and area over which
volcanic ash is dispersed is strongly controlled by wind conditions with distance and altitude
from the vent, but also by the size, shape and density of the ash particles, and the style and
magnitude of the eruption. These factors mean that ash falls are typically deposited in the
direction of prevailing winds during the eruption and thin with distance. Forecasting ash
dispersion and the deposition ‘footprint’ is typically achieved through numerical simulation.
In this chapter, we discuss volcanic ash fall hazard modelling that has been implemented at the
global and local (Neapolitan area, Italy) scales (Section 3.2). These models are probabilistic, i.e.
they account for uncertainty in the input parameters to produce a large number of possible
outcomes. Outputs are in the form of hazard maps and curves that show the probabilities
associated with exceeding key hazard thresholds at given locations. As with any natural hazard,
these results are subject to uncertainty and the local case study describes how ongoing research
is working to better quantify this uncertainty through Bayesian methods and models. Further
to the ash fall hazard assessments, we discuss the key components required to carry these
hazard estimates forward to risk: namely identification of likely impacts and the response
(vulnerability) of key sectors of society to ash fall impact. The varied characteristics of volcanic
ash, e.g. deposit thickness and density, particle size and surface composition, the context, e.g.
timing and duration of ash fall, and resilience of exposed people and assets can all influence the
type and magnitude of impacts that may occur. We draw from data collected during and
following past eruptions and experimental and theoretical studies to highlight likely impacts for
key sectors of society, such as health, infrastructure and the economy (Section 3.3). In many
parts of the world, the failure, disruption or reduced functionality of infrastructure or societal
activities, e.g. ability to work or go to school, is likely to have a larger impact on livelihoods and
the local economy than direct damage to buildings. Broad relationships between ash thickness
(assuming a fixed deposit density) and key levels of damage is also outlined (Section 3.4);
however, vulnerability estimates are typically the weakest part of a risk model and detailed
local studies of exposed assets and their vulnerability should ideally be carried out before a
detailed risk assessment is undertaken.
Greater knowledge of ash fall hazard and associated impacts supports mitigation actions, crisis
planning and emergency management activities, and is an essential step towards building
resilience for individuals and communities. This chapter concludes with a discussion on where
some of the important advances in ash fall hazard and risk assessment may be achieved,
providing a roadmap for future research objectives.
... Very few attempts have been made to interpret and revise the ground information in order to better constrain the initial eruptive conditions: Connor and Connor (2006) used an inversion techniques and recently Gudmundsson et al. (2012); Stevenson et al. (2015) performed an integration of ground measurements and satellite observations. The importance of estimating eruptive source parameters (GSD and erupted mass) with a good accuracy is also due to the growing use of dispersal codes for ash hazards assessment purposes (Sparks et al., 1997; Textor et al., 2005; Folch, 2012; Fagents, Gregg, and Lopes, 2013). Indeed, numerical models for ash dispersion are generally initialized with source conditions inferred from field observations. ...
Since the seventies, several reconstruction techniques have been proposed,
and are currently used, to extrapolate and quantify eruptive parameters from
sampled deposit datasets. Discrete numbers of tephra ground loadings or
stratigraphic records are usually processed to estimate source eruptive values.
Reconstruction techniques like Pyle, Power law and Weibull are adopted as
standard to quantify the erupted mass (or volume) whereas Voronoi for
reconstructing the granulometry. Reconstructed values can be affected by large
uncertainty due to complexities occurring within the atmospheric dispersion and
deposition of volcanic particles. Here we want to quantify the sensitivity of
reconstruction techniques, and to quantify how much estimated values of mass
and grain size differ from emitted and deposited ones. We adopted a numerical
approach simulating with a dispersal code a mild explosive event occurring at
Mt. Etna, with eruptive parameters similar to those estimated for eruptions
occurred in the last decade. Then we created a synthetic deposit by integrating
the mass on the ground computed by the model over the computational domain
(>50000 km2). Multiple samplings of the simulated deposit are used for
generating a large dataset of sampling tests afterwards processed with standard
reconstruction techniques. Results are then compared and evaluated through a
statistical analysis, based on 2000 sampling tests of 100 samplings points. On
average, all the used techniques underestimate deposited and emitted mass. A
similar analysis, carried on Voronoi results, shows that information on the
total grain size distribution is strongly deteriorated. Here we present a new
method allowing an estimate of the deficiency in deposited mass for each
simulated class. Finally a sensitivity study on eruptive parameters is
presented in order to generalize our results to a wider range of eruptive
conditions.
... Although the collapse of an ejecta plume does not necessarily cause sorting or grading processes, Stöffler et al. (2013) described a 50 cm-thick layer of graded ''primary suevite'' deposited from the collapse of a primary ejecta plume of the Ries impact event. Gravitationally driven sorting and grading processes are furthermore known from volcanic ignimbrites and fallout deposits that are usually covered by fine-grained volcanic ashes (e.g., Schminke, 2005;Fagents et al., 2013). Similar sorting processes should be expected for the collapse of the proposed clast-rich and melt particle-bearing Steinheim ejecta plume, leading to the relative enrichment of the ash-like particles at the top of the basin breccia. ...
Mine tailings are commonly stored in off-stream reservoirs and are usually composed of water with high concentrations of fine particles (microns). The rupture of a mine-tailings pond promotes, depending on the characteristics of the stored material, the fluidization and release of hyperconcentrated flows that typically behave as non–Newtonian fluids. The simulation of non–Newtonian fluid dynamics using numerical modelling tools is based on the solution of mass and momentum conservation equations, particularizing the shear stress terms by means of a rheological model that accounts for the properties of the fluid. This document presents the extension of Iber, a twodimensional hydrodynamic numerical tool, for the simulation of non–Newtonian shallow flows,
especially those related to mine tailings. The performance of the numerical tool was tested throughout benchmarks and real study cases. The results agreed with the analytical and theoretical solutions in the benchmark tests; additionally, the numerical tool also revealed itself to be adequate for simulating the dynamic and static phases under real conditions. The outputs of this numerical tool provide valuable information, allowing researchers to assess flood hazard and risk in mine-tailings spill propagation scenarios
The Miocene volcanic-intrusive complex in the Slovenský Raj Mountains, middle Slovakia, comprises a swarm of subalkaline basalts and basaltic andesites with alkaline basalts, trachybasalts and basaltic trachyandesites. Basaltic to doleritic feeder dykes and sporadic hyaloclastite lavas are exposed in contact with the Triassic Bódvaszilas Formation of the Silica Nappe. The primary clinopyroxene, plagioclase, and Fe-Ti oxide assemblage also contains calcite spheroids inferred to represent carbonatitic melt. These spheroids are associated with subsolidus chlorite, actinolite, mag-netite, titanite, calcite, and epidote. Micropoikilitic clinopyroxene, albite, and Ti-magnetite formed due to rapid quenching. There was an incorporation of host rock carbonate during the eruption. The erupted products are the result of magmatic differentiation of the parental basaltic tholeiitic magma with a redox of ∆QFM = +1 to +3, affected by varying degrees of 0%-50% fractionation and the assimilation of carbonate material in a shallow magmatic reservoir. REE geochemistry shows N-MORB-like type patterns with both La N /Yb N and La N /Sm N < 1 at near constant Eu/Eu* (~0.9). This is supported by εNd (t=13 Ma) values of +8.0 to +7.4 determined from the basaltic rocks. The REE values can be modeled by 1% fractional melting of garnet peridotite mixed with 7% melting of spinel peridotite of PM composition (1:9 proportions). SIMS and LA-ICP-MS U/Pb analysis of zircons yields a concordant age of 12.69 ± 0.24 Ma and a 13.3 ± 0.16 Ma intercept (Serravallian) age. The Middle Miocene volcanic activity was related to subduction-collision processes along the boundary of the Cenozoic ALCAPA (Alps-Carpathians-Pannonia) microplate and the southern margin of the European plate.
The eruption of Cumbre Vieja (also known as Tajogaite volcano, 19 September–13 December 2021, Spain) is an example of successful emergency management. The lessons learnt are yet to be fully disclosed as is whether the response can be further improved. The latter may include tools to predict lava flow inundation rheological characteristics, amongst other issues related to volcanic eruptions (i.e., ash fall and gas emission). The aim of this study was to explore if a scientific open-source, readily available, lava-flow-modelling code (VolcFlow) would suffice for lava emplacement forecasting, focusing on the first seven days of the eruption. We only the open data that were released during the crisis and previously available data sets. The rheology of the lava, as well as the emission rate, are of utmost relevance when modelling lava flow, and these data were not readily available. Satellite lava extent analysis allowed us to preliminarily estimate its velocity, the average flow emitted, and flow viscosity. These estimates were numerically adjusted by maximising the Jaccard morphometric index and comparing the area flooded by the lava for a simulated seven-day advance with the real advance of the lava in the same timescale. The manual search for the solution to this optimization problem achieved morphometric matches of 85% and 60%. We obtained an estimated discharge rate of about 140 m3/s of lava flow during the first 24 h of the eruption. We found the emission rate then asymptotically decreased to 60 m3/s. Viscosity varied from 8 × 106 Pa s, or a yield strength of 42 × 103 Pa, in the first hours, to 4 × 107 Pa s and 35 × 103 Pa, respectively, during the remainder of the seven days. The simulations of the lava emplacement up to 27 September showed an acceptable distribution of lava thickness compared with the observations and an excellent geometrical fit. The calculations of the calibrated model required less time than the simulated time span; hence, flow modelling can be used for emergency management. However, both speed and accuracy can be improved with some extra developments and guidance on the data to be collected. Moreover, the available time for management, once the model is ready, quasi-linearly increases as the forecasting time is extended. This suggests that a predictive response during an emergency with similar characteristics is achievable, provided that an adequate rheological description of the lava is available.
“Pyroclastic fallout” is the process of fallout of the particles, which is one of the most common processes in volcanology and is generally associated with all types of explosive eruptions. This chapter shows how the study and monitoring of pyroclastic fallout products play a key role in volcanic risk assessment. The pyroclastic fallout process is, in its simplest formulation, the sedimentation of pyroclasts through the atmosphere and their deposition on the Earth's surface. For fallout deposits, the subdivision into proximal, medial or distal deposits depends on the size of the eruption considered. During eruptive crises a sampling of the eruptive products is generally carried out in the hours following the beginning of each eruption. Geochemical and petrographic analysis of pyroclasts can constrain the initial conditions from the magma chamber to the surface via the conduit. Total grain size distribution represents the theoretical eruptive mixture injected into the atmosphere during volcanic explosive eruptions.
Two distinct types of rare crystal-rich mafic enclaves have been identified in the rhyolite lava flow from the 2011–12 Cordón Caulle eruption (Southern Andean Volcanic Zone, SVZ). The majority of mafic enclaves are coarsely crystalline with interlocking olivine-clinopyroxene-plagioclase textures and irregular shaped vesicles filling the crystal framework. These enclaves are interpreted as pieces of crystal-rich magma mush underlying a crystal-poor rhyolitic magma body that has fed recent silicic eruptions at Cordón Caulle. A second type of porphyritic enclaves, with restricted mineral chemistry and spherical vesicles, represents small-volume injections into the rhyolite magma. Both types of enclaves are basaltic end-members (up to 9.3 wt% MgO and 50–53 wt% SiO2) in comparison to enclaves erupted globally. The Cordón Caulle enclaves also have one of the largest compositional gaps on record between the basaltic enclaves and the rhyolite host at 17 wt% SiO2. Interstitial melt in the coarsely-crystalline enclaves is compositionally identical to their rhyolitic host, suggesting that the crystal-poor rhyolite magma was derived directly from the underlying basaltic magma mush through efficient melt extraction. We suggest the 2011–12 rhyolitic eruption was generated from a primitive basaltic crystal-rich mush that short-circuited the typical full range of magmatic differentiation in a single step.
We developed a numerical thermodynamics laboratory called “Thermolab” to study the effects of the thermodynamic behavior of nonideal solution models on reactive transport processes in open systems. The equations of the state of internally consistent thermodynamic data sets are implemented in MATLAB functions and form the basis for calculating Gibbs energy. A linear algebraic approach is used in Thermolab to compute Gibbs energy of mixing for multicomponent phases to study the impact of the nonideality of solution models on transport processes. The Gibbs energies are benchmarked with experimental data, phase diagrams, and other thermodynamic software. Constrained Gibbs minimization is exemplified with MATLAB codes and iterative refinement of composition of mixtures may be used to increase precision and accuracy. All needed transport variables such as densities, phase compositions, and chemical potentials are obtained from Gibbs energy of the stable phases after the minimization in Thermolab. We demonstrate the use of precomputed local equilibrium data obtained with Thermolab in reactive transport models. In reactive fluid flow the shape and the velocity of the reaction front vary depending on the nonlinearity of the partitioning of a component in fluid and solid. We argue that nonideality of solution models has to be taken into account and further explored in reactive transport models. Thermolab Gibbs energies can be used in Cahn‐Hilliard models for nonlinear diffusion and phase growth. This presents a transient process toward equilibrium and avoids computational problems arising during precomputing of equilibrium data.
Volcanology, seismology and Earth Sciences in general, like all quantitative sciences, are increasingly dependent on the quantity and quality of data acquired [...]
The realistic representation of atmospheric pollutant dispersal over areas of complex topography presents a challenging application for meteorological models. Here, we present results from high–resolution atmospheric modeling in order to gain insight into local processes that can affect ash transport and deposition. The nested Weather Research and Forecasting (WRF) model with the finest resolution of 50 m was used to simulate atmospheric flow over the complex topography of Sakurajima volcano, Japan, for two volcanic eruption cases. The simulated airflow results were shown to compare well against surface observations. As a preliminary application, idealized trajectory modeling for the two cases revealed that accounting for local circulations can significantly impact volcanic ash deposition leading to a total fall velocity up to 2–3 times the particle’s terminal velocity depending on the size. Such a modification of the estimated particle settling velocity over areas with complex topography can be used to parametrize the impact of orographic effects in dispersal models, in order to improve fidelity.
LLUNPIY (lahar modeling by local rules based on an underlying pick of yoked processes, from the Quechua word “llunp’iy“, meaning flood) is a cellular automata (CA) model that simulates primary and secondary lahars, here applied to replicate those that occurred during the huge 1877 Cotopaxi Volcano eruption. The lahars flowing down the southwestern flanks of the volcano were already satisfactorily simulated in previous investigations of ours, assuming two possible different triggering mechanisms, i.e., the sudden and homogeneous melting of the summit ice and snow cap due to pyroclastic flows and the melting of the glacier parts hit by free-falling pyroclastic bombs after being upwardly ejected during the volcanic eruption. In a similar fashion, we apply here the CA LLUNPIY model to simulate the 1877 lahars sprawling out the Cotopaxi northern slopes and eventually impacting densely populated areas. Our preliminary results indicate that several important public infrastructures (among them the regional potable water supply system) and the Valle de Los Chillos and other Quito suburban areas might be devastated by northward-bound lahars, should a catastrophic Cotopaxi eruption comparable to the 1877 one occur in the near future.
Large outflow channels on ancient terrains of Mars have been interpreted as the products of catastrophic flood events. The rapid burial of water-rich sediments after such flooding could have led to sedimentary volcanism, in which mixtures of sediment and water (mud) erupt to the surface. Tens of thousands of volcano-like landforms populate the northern lowlands and other local sedimentary depocentres on Mars. However, it is difficult to determine whether the edifices are related to igneous or mud extrusions, partly because the behaviour of extruded mud under Martian surface conditions is poorly constrained. Here we investigate the mechanisms of mud propagation on Mars using experiments performed inside a low-pressure chamber at cold temperatures. We found that low viscosity mud under Martian conditions propagates differently from that on Earth, because of a rapid freezing and the formation of an icy crust. Instead, the experimental mud flows propagate like terrestrial pahoehoe lava flows, with liquid mud spilling from ruptures in the frozen crust, and then refreezing to form a new flow lobe. We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars, and that similar processes may apply to cryovolcanic extrusions on icy bodies in the Solar System. Experimental mudflows under Martian surface conditions propagate similarly to terrestrial pahoehoe lava flows, suggesting mud (rather than igneous) volcanism can explain some flow morphologies on Mars.
This paper presents various phenomena obtained by localized microwave-heating (LMH) of basalt, including effects of inner core melting, lava eruption and flow (from the molten core outside), plasma ejection from basalt (in forms of fire-column and ball-lightning), and effusion of dust (deposited as powder by the plasma). The experiments are conducted by irradiating a basalt stone (~30-cm3 volume, either naturally shaped or cut to a cubic brick) in a microwave cavity, fed by an adaptively-matched magnetron (~1 kW at 2.45 GHz). Effects of LMH and thermal-runaway instability in basalt are observed and compared to theory. Various in- and ex-situ diagnostics are used in order to characterize the dusty-plasma observed and its nanoparticle products. The resemblance of the experimental phenomena obtained in small laboratory scale to gigantic volcanic phenomena in nature is noticed, and its potential relevance to further volcanic studies is discussed. In particular, we show that LMH could be instrumental for laboratory demonstrations and simulations of miniature-volcano effects, such as lava flows, formation of volcanic glass (obsidian), eruption of dusty-plasma and volcanic ash, and ejection of ball lightning. These findings might be significant as well for various applications, such as drilling and mining, microwave-induced breakdown spectroscopy (MIBS), mineral extraction, and powder production directly from basalts.
Vesiculation of hydrous melts at 1 atm was studied in situ by synchrotron X-ray tomographic microscopy at the TOMCAT beamline of the Swiss Light Source (Villigen, Switzerland). Water-undersaturated basaltic, andesitic, trachyandesitic, and dacitic glasses were synthesized at high pressures and then laser heated at 1 atm. on the beamline, causing vesiculation. The porosity, bubble number density, size distributions of bubbles, and pore throats, as well as their tortuosity and connectivity, were measured in three-dimensional tomographic reconstructions of sample volumes, which were also used for lattice Boltzmann simulations of viscous permeabilities. Connectivity of bubbles by pore throats varied from ~ 100 to 105 mm−3, and for each sample correlated with porosity and permeability. Consideration of the results of this and previous studies of the viscous permeabilities of aphyric and crystal-poor magmatic samples demonstrated that at similar porosities permeability can vary by orders of magnitude, even for similar compositions. Comparison of the permeability relationships from this study with previous models (Degruyter et al., Bull Vulcanol 72:63–74, 2010; Burgisser et al., Earth Planet Sci Lett 470:37–47, 2017) relating porosity, characteristic pore-throat diameters, and tortuosity demonstrated good agreement. Modifying the Burgisser et al. model by using the maximum pore-throat diameter, instead of the average diameter, as the characteristic diameter reproduced the lattice Boltzmann permeabilities to within 1 order of magnitude. Correlations between average bubble diameters and maximum pore-throat diameters, and between porosity and tortuosity, in our experiments produced relationships that allow application of the modified Burgisser et al. model to predict permeability based only upon the average bubble diameter and porosity. These experimental results are consistent with previous studies suggesting that increasing bubble growth rates result in decreasing permeability of equivalent porosity foams. This effect of growth rate substantially contributes to the multiple orders of magnitude variations in the permeabilities of vesicular magmas at similar porosities.
Ultramafic magmas (MgO ≥ 18 wt%) are generally thought to be primary mantle melts formed at temperatures in excess of 1600 • C. Volatile contents are expected to be low, and accordingly, high-Mg magmas generally do not yield large explosive eruptions. However, there are important exceptions to low explosivity that require an explanation. Here we show that hydrous (hence, potentially explosive) ultramafic magmas can also form at crustal depths at temperatures even lower than 1000 • C. Such a conclusion arose from the study of a silicate glass vein, ~1 mm in thickness, cross-cutting a mantle-derived harzburgite xenolith from the Valle Guffari nephelinite diatreme (Hyblean area, Sicily). The glass vein postdates a number of serpentine veins already existing in the host harzburgite, thus reasonably excluding that the melt infiltrated in the rock at mantle depths. The glass is highly porous at the sub-micron scale, it also bears vesicles filled by secondary minerals. The distribution of some major elements corresponds to a meimechite composition (MgO = 20.35 wt%; Na 2 O + K 2 O < 1 wt%; and TiO 2 > 1 wt%). On the other hand, trace element distribution in the vein glass nearly matches the nephelinite juvenile clasts in the xenolith-bearing tuff-breccia. These data strongly support the hypothesis that an upwelling nephelinite melt (MgO = 7-9 wt%; 1100 ≤ T ≤ 1250 • C) intersected fractured serpentinites (T ≤ 500 • C) buried in the aged oceanic crust. The consequent dehydroxilization of the serpentine minerals gave rise to a supercritical aqueous fluid, bearing finely dispersed, hydrated cationic complexes such as [Mg 2+ (H 2 O) n ]. The high-Mg, hydrothermal solution "flushed" into the nephelinite magma producing an ultramafic, hydrous (hence, potentially explosive), hybrid magma. This hypothesis explains the volcanological paradox of large explosive eruptions produced by ultramafic magmas.
Acoustic pressure is largely used to monitor explosive activity at volcanoes and has become one of the most promising technique to monitor volcanoes also at large scale. However, no clear relation between the fluid dynamics of explosive eruptions and the associated acoustic signals has yet been defined. Linear acoustic has been applied to derive source parameters in the case of strong explosive eruptions which are well-known to be driven by large overpressure of the magmatic fluids. Asymmetric acoustic waveforms are generally considered as the evidence for supersonic explosive dynamics also for small explosive regimes. We have used Lattice-Boltzmann modeling of the eruptive fluid dynamics to analyse the acoustic wavefield produced by different flow regimes. We demonstrate that acoustic waveform well reproduces the flow dynamics of a subsonic fluid injection related to discrete explosive events. Different volumetric flow rate, at low-Mach regimes, can explain both the observed symmetric and asymmetric waveform. Hence, asymmetric waveforms are not necessarily related to the shock/supersonic fluid dynamics of the source. As a result, we highlight an ambiguity in the general interpretation of volcano acoustic signals for the retrieval of key eruption source parameters, necessary for a reliable volcanic hazard assessment.
The use of islands as ‘model systems’ has become particularly relevant for examining a host of important issues in archaeology and other disciplines. As papers in this special issue of the Journal of Island and Coastal Archaeology demonstrate, islands can serve as critical and ideal analytical platforms for observing human populations in the past and their evolutionary histories within complex and insular human ecodynamics. In this paper we address the issue of how islands are also important models for future sustainability and as corollaries for the survival of humans generally. In a sense, island cultures and ecosystems can be seen as microcosms of the issues we have faced as humans, and provide important insights for understanding the fate of our species, particularly as it pertains to the exploration and colonization of new worlds.
All modes of surface transportation can be disrupted by visibility degradation caused by airborne volcanic ash. Despite much qualitative evidence of low visibility on roads following historical eruptions worldwide, there have been few detailed studies that have attempted to quantify relationships between visibility conditions and observed impacts on network functionality and safety. In the absence of detailed field observations, such gaps in knowledge can be filled by developing empirical datasets through laboratory investigations. Here, we use historical eruption data to estimate a plausible range of ash-settling rates and ash particle characteristics for Auckland city, New Zealand. We propose and implement a new experimental set-up in controlled laboratory conditions, which incorporates a dual-pass transmissometer and solid aerosol generator, to reproduce these ash-settling rates and calculate visual ranges through the associated airborne volcanic ash. Our findings demonstrate that visibility is most impaired for high ash-settling rates (i.e. > 500 g m⁻² h⁻¹) and particle size is deemed the most influential ash characteristic for visual range. For the samples tested (all < 320 μm particle diameter), visibility was restricted to ~ 1–2 m when ash settling was replicated for very high rates (i.e. ~ 4000 g m⁻² h⁻¹) and was especially low when ash particles were fine-grained, more irregular in shape and lighter in colour. Finally, we consider potential implications for disruption to surface transportation in Auckland through comparisons with existing research which investigates the consequences of visual range reduction for other atmospheric hazards such as fog. This includes discussing how our approach might be utilised in emergency and transport management planning. Finally, we summarise strategies available for the mitigation of visibility degradation in environments contaminated with volcanic ash.
Realistic models of lithologic structure are critical for predicting flow and transport through heterogeneous volcanic aquifers. Existing models of lava flows based on physical processes are able to realistically simulate flow geometry and lithology, but the computational intensity limits applicability in generating entire aquifers. Fast surface-based models have been developed for hazard mapping, but these do not incorporate 3D geometry or lithology critical for hydrogeologic applications. Here we develop a hybrid modeling method (HMM) based on a combination of a process-based model (PBM) and a surface-based model. The methodologies are presented and compared to a known single flow and to each other in a full aquifer simulation. Results indicate that both the PBM and HMM simulations reasonably reproduce the flow geometry (length, branching, thickness) of the 1984 eruption of Mauna Loa in Hawai’i. Simulations of a volcanic aquifer built from 100 flows with the PBM and HMM are similar in spatial distribution and overall proportions of lithology (aa, transitional, pahoehoe, ash), flow geometry, and aquifer geometry. Thus, the hybrid method is an efficient method to generate geologically realistic models of volcanic aquifer structure. Model realism and parameterization can be improved as more field data become available.
The dynamics and styles of volcanic eruptions are governed by a variety of physical and chemical processes. Different eruptive styles, which are superficial expressions of the mode of degassing, originate from basaltic magmas, from lava lakes to lava fountains and strombolian eruptions.
The interrelationship between degassing dynamics, physical properties of magma and geometric irregularities of volcanic conduits have been investigated through a set of experiments performed on analogue material, silicone oil, whose fluid-dynamic properties scale basaltic systems. The experiments were performed by injecting compressed air into experimental conduits with either smooth surface and cylindrical shape or alternatively with complex geometry. In particular, the geometric irregularity of natural systems has been reproduced in a laboratory resine conduit created by applying the mathematical / geometric concept of fractals.
Combinations of variables such as viscosity (10, 100 and 1000 Pa s), geometry (cylindrical and fractal) and inclination (90 ° -45 °) of the conduit and the amount of injected gas (20,30 and 70x10-3l/s) were made to explore a wide range of the investigated parameters.
The different flow regimes observed during the experiments and the transition from each degassing regime have been quantitatively investigated, together with the investigation of the slugging frequency and the study of the individual velocities of the gas slugs and their geometric dimensions. Calculated a-dimensional parameters allowed for a comparison with natural systems and literature data. Several relationships have been established between frequency, gas flux rate and viscosity that may play a relevant role in the study of volcanology and in particular in defining the correlation between eruptive style and degassing behaviour at depth.
The hazards, also known as perils, are grouped here according to the nature of the dominant process that drives them. In any multi-hazard environment, it is essential to understand which perils govern likely losses. This chapter describes how the peril, in both its physical process (hazard) and impact (risk) via vulnerability, is simplified and encapsulated in event sets and exposure-based portfolio risk management tools called 'catastrophe models'. The occurrence of tropical cyclones (TC) is known as an event, and catastrophe models calculate losses from ensembles or event sets generated using stochastic combinations of cyclogenesis, track, size and intensity. TC damage is modelled as a damage ratio (DR). Coastal flooding associated with storm surge and inland flooding resulting from heavy rainfall are the two most important secondary perils associated with TCs. Storm surge can drive losses for some storms and is included in most US models and increasingly in the Asia Pacific region.
Active volcanoes are mechanically dynamic environments, and edifice-forming material may often be subjected to significant amounts of stress and strain. It is understood that porous volcanic rock can compact inelastically under a wide range of in situ conditions. In this contribution, we explore the evolution of porosity and permeability – critical properties influencing the style and magnitude of volcanic activity – as a function of inelastic compaction of porous andesite under triaxial conditions. Progressive axial strain accumulation is associated with progressive porosity loss. The efficiency of compaction was found to be related to the effective confining pressure under which deformation occurred: at higher effective pressure, more porosity was lost for any given amount of axial strain. Permeability evolution is more complex, with small amounts of stress-induced compaction (< 0.05, i.e. less than 5 % reduction in sample length) yielding an increase in permeability under all effective pressures tested, occasionally by almost 1 order of magnitude. This phenomenon is considered here to be the result of improved connectivity of formerly isolated porosity during triaxial loading. This effect is then overshadowed by a decrease in permeability with further inelastic strain accumulation, especially notable at high axial strains (> 0.20) where samples may undergo a reduction in permeability by 2 orders of magnitude relative to their initial values. A physical limit to compaction is discussed, which we suggest is echoed in a limit to the potential for permeability reduction in compacting volcanic rock. Compiled literature data illustrate that at high axial strain (both in the brittle and ductile regimes), porosity ϕ and permeability k tend to converge towards intermediate values (i.e. 0.10 ≤ϕ≤ 0.20; 10-14≤k≤10-13 m2). These results are discussed in light of their potential ramifications for impacting edifice outgassing – and in turn, eruptive activity – in active volcanoes.
The Baekdusan volcano was formed through three stages of activity: (a) a basalt shield (aging between 22.6 and 1.48 Ma), (b) a trachytic comendite stratocone (aging between 1.19 and 0.02 Ma), (c) a trachyte-comendite ignimbrite deposits (aging from 20 ka till date). Volcanic seismicity, ground deformation, and volcanic gas geochemistry yield new evidence for magmatic unrest of the volcano between 2002 and 2006. The monitoring data suggest that Mt. Baekdusan is a potentially active volcano and that its close monitoring is needed. One of the possible volcanic hazards from this volcano is the pyroclastic density currents. In order to evaluate the small-scale pyroclastic flow emplacement scenario of the 1903 AD eruption, Titan2d mass-flow model is used. The 1668–1702 AD and the Millennium eruption are characterized by 4–5 and ~7 VEI, respectively. The Millennium eruption can be considered as the last colossal super-eruption like Tambora, and so Baekdusan volcano could have even a global effect. The parameters used are as follows: volume (5–10 × 10⁷, 1 × 10⁹, 2 × 10¹⁰ m³), the vents of the 1903, 1668–1702, and Millennium eruptions; the pyroclastic flow runout calculated in the field are small (3,000 m :1903 eruption), intermediate (5,000 m :1668–1702 eruptions), and large (7–80,000 m, Millennium eruption). The initial velocities (m/s) range from 50 (1903 eruption) to as high as 300 (Millennium eruption). The input parameters have constructed three scenarios (1903, 1668–1702, and Millennium eruptions) following the recent volcanic history of Baekdusan volcano. These eruptions embrace all the possibly explosive eruptive scenarios that can occur at Baekdusan volcano in the future. The 1903 type scenario has been performed; according to the vent location, the flow moves in diverse directions (NE, SE) with a thickness of 3 m, and if the vent is the center of the caldera the flow fills the caldera with a thickness of 5 m. The emplacement of the 1668–1702 AD scenarios will involve at least two populated cities nearest to Baekdusan volcano. The scenario of the Millennium eruption will be much more severe and it will hit all the cities and towns within a range of 80 km. The impact will be from regional to global. This, however, is an underestimation of the runout for the diluted pyroclastic density currents.
Since the 1970s, multiple reconstruction techniques have been proposed and are currently used, to extrapolate and quantify eruptive parameters from sampled tephra fall deposit datasets. Atmospheric transport and deposition processes strongly control the spatial distribution of tephra deposit; therefore, a large uncertainty affects mass derived estimations especially for fall layer that are not well exposed. This paper has two main aims: the first is to analyse the sensitivity to the deposit sampling strategy of reconstruction techniques. The second is to assess whether there are differences between the modelled values for emitted mass and grainsize, versus values estimated from the deposits. We find significant differences and propose a new correction strategy. A numerical approach is demonstrated by simulating with a dispersal code a mild explosive event occurring at Mt. Etna on 24 November 2006. Eruptive parameters are reconstructed by an inversion information collected after the eruption. A full synthetic deposit is created by integrating the deposited mass computed by the model over the computational domain (i.e., an area of 7.5x10^4 km 2). A statistical analysis based on 2000 sampling tests of 50 sampling points shows a large variability, up to 50% for all the reconstruction techniques. Moreover, for some test examples Power Law errors are larger than estimated uncertainty. A similar analysis, on simulated grain-size classes, shows how spatial sampling limitations strongly reduce the utility of available information on the total grain size distribution. For example, information on particles coarser than ϕ(−4) is completely lost when sampling at 1.5 km from the vent for all columns with heights less than 2000 m above the vent. To correct for this effect an optimal sampling strategy and a new reconstruction method are presented. A sensitivity study shows that our method can be extended to a wide range of eruptive scenarios including those in which aggregation processes are important. The new correction method allows an estimate of the deficiency for each simulated class in calculated mass deposited, providing reliable estimation of uncertainties in the reconstructed total (whole deposit) grainsize distribution.
Fragmentation processes in eruptions are commonly contrasted as phreatomagmatic or magmatic; the latter requires only fragmentation of magma without external intervention, but often carries the connotation of disruption by bubbles of magmatic gas. Phreatomagmatic fragmentation involves vaporization and expansion of water as steam with rapid cooling and/or quenching of the magma. It is common to assess whether a pyroclast formed by magmatic or phreatomagmatic fragmentation using particle vesicularity, shape of particles, and degree of quenching. It is widely known that none of these criteria is entirely diagnostic, so deposit features are also considered; welding and/or agglomeration, particle aggregation, lithic fragment abundance, and proportion of fines. Magmatic fragmentation yields from rhyolite pumice to obsidian to basaltic achneliths or carbonatitic globules, making direct argument for magmatic fragmentation difficult, so many have taken an alternative approach. They have tested for phreatomagmatism using the fingerprints listed above, and if the fingerprint is lacking, magmatic fragmentation is considered proven. We argue that this approach is invalid, and that the criteria used are typically incorrect or incorrectly applied. Instead, we must consider the balance of probabilities based on positive evidence only, and accept that for many deposits it may not be possible with present knowledge to make a conclusive determination.
Strong ground motions induce large dynamic stress changes that may disturb the magma chamber of a volcano, thus accelerating the volcanic activity. An underground nuclear explosion test near an active volcano constitutes a direct treat to the volcano. This study examined the dynamic stress changes of the magma chamber of Baekdusan (Changbaishan) that can be induced by hypothetical North Korean nuclear explosions. Seismic waveforms for hypothetical underground nuclear explosions at North Korean test site were calculated by using an empirical Green’s function approach based on a source-spectral model of a nuclear explosion; such a technique is efficient for regions containing poorly constrained velocity structures. The peak ground motions around the volcano were estimated from empirical strong-motion attenuation curves. A hypothetical M7.0 North Korean underground nuclear explosion may produce peak ground accelerations of 0.1684 m/s2 in the horizontal direction and 0.0917 m/s2 in the vertical direction around the volcano, inducing peak dynamic stress change of 67 kPa on the volcano surface and ~120 kPa in the spherical magma chamber. North Korean underground nuclear explosions with magnitudes of 5.0–7.6 may induce overpressure in the magma chamber of several tens to hundreds of kilopascals.
Well water level changes associated with magmatic unrest can be interpreted as a~result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use Finite Element Analysis to demonstrate the response of aquifers to volumetric strain induced by pressurised magma reservoirs.
Two different aquifers are invoked -- an unconsolidated pyroclastic deposit and a~vesicular lava flow -- and embedded in an impermeable crust, overlying a~magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurisation and the resulting hydraulic head changes as well as flow through the porous aquifer, i.e. porous flow. The simulated strain leads to centimetres (pyroclastic aquifer) to meters (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system.
Well level changes are particularly sensitive to chamber volume, shape and pressurisation strength, followed by aquifer permeability and the phase of the pore fluid. The depths of chamber and aquifer, as well as the aquifer's Young's Modulus also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time.
We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to strain-induced well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a~pore fluid and its flow have a~significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do mirror volumetric strain and wells are therefore a valuable addition to monitoring systems that could provide important insights into pre-eruptive dynamics.
Merapi Volcano eruption in 2010 caused a lot of damage to infrastructure. The damage caused by disasters such as volcanic primary heat clouds and volcanic ash rain , and secondary disasters such as lahar. This study aims to analyze process / lahar formation mechanism based on a study of the retention of surface water by the surface material on instantaneous rainfall (storm rainfall). The method used is the calculation of water retention with SCS-CN method (Soil Conservation Service-Curve Number). The calculation of the value of CN (Curve Number) based on multitemporal image data combined with field surveys and in-depth interviews with residents around the area affected is then analyzed using a geographic information system (GIS). The analysis showed that the retention value actually increased after the eruption , however, based on interviews discharge in the river after a rain Opaque becomes larger because of the lahar flood. This is a lahar flood events that occurred since the first time about 80 years. Based on the analysis conducted , it is known that the ability of the material from the eruption (new) for meresapakan water high enough , but at the bottom there is the old coating with lower porosity. This causes the surface layer of soil in the study experienced saturation and trigger the movement that then formed due to gravitational flow of lahar flood. Abstrak Erupsi Gunungapi Merapi tahun 2010 menyebabkan banyak kerusakan infrastruktur. Kerusakan ditimbulkan oleh bencana primer gunungapi seperti awan panas dan hujan abu gunungapi, serta bencana sekunder yang berupa banjir lahar. Penelitian ini bertujuan menganalisis proses/mekanisme pembentukkan lahar berdasarkan pada kajian retensi air permukaan oleh material permukaan pada kejadian hujan sesaat (storm rainfall). Metode yang digunakan adalah perhitungan retensi air dengan metode SCS-CN (Soil Conservation Service-Curve Number). Perhitungan nilai CN (Curve Number) didasarkan pada data citra multitemporal yang dikombinasikan dengan survei lapangan dan wawancara mendalam dengan penduduk di sekitar wilayah terdampak yang kemudian dianalisis dengan menggunakan sistem informasi geografis (SIG). Hasil analisis menunjukkan bahwa nilai retensi justru meningkat setelah terjadi erupsi, namun demikian berdasarkan hasil wawancara debit di Sungai Opak setelah terjadi hujan menjadi semakin besar karena adanya banjir lahar. Banjir lahar ini merupakan kejadian yang pertama kali terjadi sejak sekitar 80 tahun terakhir. Berdasarkan analisis yang dilakukan, diketahui bahwa kemampuan material hasil erupsi (baru) untuk meresapakan air cukup tinggi, namun pada bagian bawahnya terdapat lapisan lama dengan porositas yang lebih rendah. Hal ini menyebabkan lapisan atas permukaan tanah di lokasi kajian mengalami kejenuhan dan memicu gerakan akibat gravitasi yang kemudian membentuk aliran banjir lahar.
This review article provides an overview of dry granular flows and particle fluid mixtures, including experimental and numerical modeling at the laboratory scale, large scale hydrodynamics approaches and field observations
Well water level changes associated with magmatic unrest can be interpreted as a result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use Finite Element Analysis to demonstrate the response of aquifers to volumetric strain induced by pressurised magma reservoirs.
Two different aquifers are invoked – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurisation and the resulting hydraulic head changes as well as porous flow in the aquifer. The simulated deformational strain leads to centimetres (pyroclastic aquifer) to meters (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system.
Well level changes are particularly sensitive to chamber volume and shape, followed by chamber depth and the phase of the pore fluid. The Young's Modulus and permeability of the aquifer, as well as the strength of pressurisation also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time.
We investigated a period of pre-eruptive head changes recorded at Usu volcano, Japan, where well data were interpreted using an analytical deformation model. We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a pore fluid and its flow have a significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do mirror volumetric strain and wells can therefore serve as comparatively cheap strain meters that could provide important insights into pre-eruptive dynamics.
L’hydrovolcanologie profonde s’intéresse au rôle joué par la molécule d’eau (sous forme hydroxylée ou moléculaire) dans l’individualisation des magmas par fusion partielle au sein du manteau et/ou de la croûte terrestre, leur remontée dans la plomberie magmatique, jusqu’à l’exsolution‑fragmentation grande responsable des dynamismes éruptifs explosifs. L’hydrovolcanologie superficielle couvre le champ des phénomènes paravolcaniques pré et postéruptifs : solfatares, fumerolles, sources chaudes, flux géothermiques, qui représentent un indicateur important en terme de prévisions volcanologiques. Elle permet de mieux comprendre la dynamique des lacs de cratère et des lacs de rift, souvent sursaturés en CO2 d’origine volcanique, susceptibles d’éruptions limniques. L’hydrovolcanologie présente une perspective nouvelle au sein des sciences hydrotechniques où l’eau est à la fois l’élément déclencheur, voire le catalyseur, d’éruptions explosives majeures, mais aussi un indicateur précieux en matière de prévision et de gestion du risque.
Our knowledge of the physics of how volcanoes work has expended enormously over the past 20 years,
as have our methods of studying volcanic processes. In seeking to understand volcanic behavior, volcanologists call on a diversity of physics subdisciplines, including fluid dynamics, thermodynamics, solid mechanics, hydrovolcanology, ballistics and acoustics, to name a few. Deep hydrovolcanology describes the water involvement in magma generation and segregation through partial melting into the Earth’s crust and/or mantle, magma upward migration in the volcanic plumbing system and exsolution‑fragmentation in the subsurface. As the magma rises towards the surface the confining pressure decreases, the volatiles gradually exsolve from the magma forming the gas bubbles which are distributed throughout the liquid. It is the connecting together of a network of these bubbles that ultimately causes the continuous body of liquid to break apart or fragment into a spray of droplets or clots suspended in the gas. In magmas, typically 95‑99% of the ‘mass’ of material erupted is liquid rock – at most the gas accounts for only a few percent of the weight; but that small amount of gas represents a very large ‘volume’ as it expands to atmospheric pressure, and is fundamentally important in producing explosive eruptions. Continued rise of the magma leads to further exsolution of gas and growth of gas bubbles through diffusion, decompression and bubble coalescence. The relative importance of each process depends on the amount of volatiles (gas ‑ mostly water) present in the magma, the magma composition and the magma rise speed. Surface hydrovolcanology is involved in pre and post‑eruptive paravolcanic activity such as solfataras, fumaroles, hydrothermal heat and water fluxes. It also focuses on limnic eruptions, otherwise referred to as a lake overturns, a type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep volcanic lakes, suffocating wildlife,
livestock and humans. Hydrovolcanology presents a new perspective within hydrotechnical sciences where water is a trigger in magma generation and segregation, magma rising and eruption style. Water appears to be a most valuable indicator for volcanic hazard assessment and mitigation, short‑term eruption prediction, and volcanic risk management.
Understanding the physical behavior of volcanoes is critical for assessing the hazards posed to the ever‑increasing populations living in close proximity to active volcanoes, and thus for mitigating the risk posed by those hazards.
A workshop entitled "Tracking and understanding volcanic emissions through cross-disciplinary integration: a textural working group" was held at the Université Blaise Pascal (Clermont-Ferrand, France) on the 6–7 November 2012. This workshop was supported by the European Science Foundation (ESF). The main objective of the workshop was to establish an initial advisory group to begin to define measurements, methods, formats and standards to be applied in the integration of geophysical, physical and textural data collected during volcanic eruptions. This would homogenize procedures to be applied and integrated during both past and ongoing events. The workshop comprised a total of 35 scientists from six countries (France, Italy, Great Britain, Germany, Switzerland and Iceland). The four main aims were to discuss and define: standards, precision and measurement protocols for textural analysis; identification of textural, field deposit, chemistry and geophysical parameters that can best be measured and combined; the best delivery formats so that data can be shared between and easily used by different groups; and multi-disciplinary sampling and measurement routines currently used and measurement standards applied, by each community. The group agreed that community-wide, cross-disciplinary integration, centred on defining those measurements and formats that can be best combined, is an attainable and key global focus. Consequently, we prepared this paper to present our initial conclusions and recommendations, along with a review of the current state of the art in this field that supported our discussions.
Volcanic plumes can be hazardous to aircraft. A correlation between plume height and ground deformation during an eruption of Grímsvötn Volcano, Iceland, allows us to peer into the properties of the magma chamber and may improve eruption forecasts.
Explosive eruptions can severely disturb landscapes downwind or downstream of volcanoes by damaging vegetation and depositing large volumes of erodible fragmental material. As a result fluxes of water and sediment in affected drainage basins can increase dramatically. System-disturbing processes associated with explosive eruptions include tephra fall, pyroclastic density currents, debris avalanches, and lahars—processes having greater impacts on water and sediment discharges than lava-flow emplacement. Geomorphic responses to such disturbances can extend far downstream, persist for decades, and be hazardous. The severity of disturbances to a drainage basin is a function of the specific volcanic process acting, as well as distance from the volcano and magnitude of the eruption. Post-disturbance unit-area sediment yields are among the world’s highest; such yields commonly result in abundant redeposition of sand and gravel in distal river reaches, which causes severe channel aggradation and instability. Response to volcanic disturbance can result in socioeconomic consequences more damaging than the direct impacts of the eruption itself.
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