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A challenging goal of neural coding is to characterize the neural representations underlying visual perception. To this end, multi-unit activity (MUA) of macaque visual cortex was recorded in a passive fixation task upon presentation of faces and natural images. We analyzed the relationship between MUA and latent representations of state-of-the-art deep generative models, including the conventional and feature-disentangled representations of generative adversarial networks (GANs) (i.e., z- and w-latents of StyleGAN, respectively) and language-contrastive representations of latent diffusion networks (i.e., CLIP-latents of Stable Diffusion). A mass univariate neural encoding analysis of the latent representations showed that feature-disentangled w representations outperform both z and CLIP representations in explaining neural responses. Further, w-latent features were found to be positioned at the higher end of the complexity gradient which indicates that they capture visual information relevant to high-level neural activity. Subsequently, a multivariate neural decoding analysis of the feature-disentangled representations resulted in state-of-the-art spatiotemporal reconstructions of visual perception. Taken together, our results not only highlight the important role of feature-disentanglement in shaping high-level neural representations underlying visual perception but also serve as an important benchmark for the future of neural coding. Author summary: Neural coding seeks to understand how the brain represents the world by modeling the relationship between stimuli and internal neural representations thereof. This field focuses on predicting brain responses to stimuli (neural encoding) and deciphering information about stimuli from brain activity (neural decoding). Recent advances in generative adversarial networks (GANs; a type of machine learning model) have enabled the creation of photorealistic images. Like the brain, GANs also have internal representations of the images they create, referred to as "latents". More recently, a new type of feature-disentangled "w-latent" of GANs has been developed that more effectively separates different image features (e.g., color; shape; texture). In our study, we presented such GAN-generated pictures to a macaque with cortical implants and found that the underlying w-latents were accurate predictors of high-level brain activity. We then used these w-latents to reconstruct the perceived images with high fidelity. The remarkable similarities between our predictions and the actual targets indicate alignment in how w-latents and neural representations represent the same stimulus, even though GANs have never been optimized on neural data. This implies a general principle of shared encoding of visual phenomena, emphasizing the importance of feature disentanglement in deeper visual areas. [ABSTRACT FROM AUTHOR]

Volcano science has been deeply developing during last decades, from a branch of descriptive natural sciences to a highly multi-disciplinary, technologically advanced, quantitative sector of the geosciences. While the progress has been continuous and substantial, the volcanological community still lacks big scientific endeavors comparable in size and objectives to many that characterize other scientific fields. Examples include large infrastructures such as the LHC in Geneva for sub-atomic particle physics or the Hubble telescope for astrophysics, as well as deeply coordinated, highly funded, decadal projects such as the Human Genome Project for life sciences. Here we argue that a similar big science approach will increasingly concern volcano science, and briefly describe three examples of developments in volcanology requiring such an approach, and that we believe will characterize the current decade (2020–2030): the Krafla Magma Testbed initiative; the development of a Global Volcano Simulator; and the emerging relevance of big data in volcano science. [ABSTRACT FROM AUTHOR]

In this work, a partitioned fluid-structure interaction solver is presented. Fluid flow problem is solved with time-discontinuous deforming domain stabilized space-time finite element method. Flow is computed with pressure primitive variables which permit to use the same numerical technique for both compressible and incompressible regimes. Elastic deformation of the structure is modelled in the Lagrangian frame of reference with Saint-Venant Kirchhoff and Neo-Hookean material models - both are non-linear and valid for large deformations. Structure equations are discretized with Galerkin finite element method for space and with generalized-alpha method for the time. Mesh motion is modelled with the elastic deformation method. An implicit algorithm is presented to couple the different solvers. The details are provided on the implementation of the solvers in parallel software. The numerical code is verified and validated on several compressible and incompressible flow benchmarks widely used in the literature. The results demonstrate that the developed solver successfully detects the accurate interaction between fluid and structure. [ABSTRACT FROM AUTHOR]

Object recognition relies on different transformations of the retinal input, carried out by the visual system, that range from local contrast to object shape and category. While some of those transformations are thought to occur at specific stages of the visual hierarchy, the features they represent are correlated (e.g., object shape and identity) and selectivity for the same feature overlaps in many brain regions. This may be explained either by collinearity across representations or may instead reflect the coding of multiple dimensions by the same cortical population. Moreover, orthogonal and shared components may differently impact distinctive stages of the visual hierarchy. We recorded functional MRI activity while participants passively attended to object images and employed a statistical approach that partitioned orthogonal and shared object representations to reveal their relative impact on brain processing. Orthogonal shape representations (silhouette, curvature, and medial axis) independently explained distinct and overlapping clusters of selectivity in the occitotemporal and parietal cortex. Moreover, we show that the relevance of shared representations linearly increases moving from posterior to anterior regions. These results indicate that the visual cortex encodes shared relations between different features in a topographic fashion and that object shape is encoded along different dimensions, each representing orthogonal features. [ABSTRACT FROM AUTHOR]

Detailed characterization of interneuron types in primary visual cortex (V1) has greatly contributed to understanding visual perception, yet the role of chandelier cells (ChCs) in visual processing remains poorly characterized. Using viral tracing we found that V1 ChCs predominantly receive monosynaptic input from local layer 5 pyramidal cells and higher-order cortical regions. Two-photon calcium imaging and convolutional neural network modeling revealed that ChCs are visually responsive but weakly selective for stimulus content. In mice running in a virtual tunnel, ChCs respond strongly to events known to elicit arousal, including locomotion and visuomotor mismatch. Repeated exposure of the mice to the virtual tunnel was accompanied by reduced visual responses of ChCs and structural plasticity of ChC boutons and axon initial segment length. Finally, ChCs only weakly inhibited pyramidal cells. These findings suggest that ChCs provide an arousal-related signal to layer 2/3 pyramidal cells that may modulate their activity and/or gate plasticity of their axon initial segments during behaviorally relevant events. [ABSTRACT FROM AUTHOR]

Neuronal activity in the primary visual cortex (V1) is driven by feedforward input from within the neurons' receptive fields (RFs) and modulated by contextual information in regions surrounding the RF. The effect of contextual information on spiking activity occurs rapidly and is therefore challenging to dissociate from feedforward input. To address this challenge, we recorded the spiking activity of V1 neurons in monkeys viewing either natural scenes or scenes where the information in the RF was occluded, effectively removing the feedforward input. We found that V1 neurons responded rapidly and selectively to occluded scenes. V1 responses elicited by occluded stimuli could be used to decode individual scenes and could be predicted from those elicited by non-occluded images, indicating that there is an overlap between visually driven and contextual responses. We used representational similarity analysis to show that the structure of V1 representations of occluded scenes measured with electrophysiology in monkeys correlates strongly with the representations of the same scenes in humans measured with functional magnetic resonance imaging (fMRI). Our results reveal that contextual influences rapidly alter V1 spiking activity in monkeys over distances of several degrees in the visual field, carry information about individual scenes, and resemble those in human V1. [Display omitted] • We recorded from V1 neurons in monkeys viewing natural or partially occluded scenes • V1 neurons with receptive fields on occluded image regions encode scene information • Individual scenes could be decoded from V1 activity elicited by the occluder • Monkey V1 representations resemble those in human V1 as measured with fMRI Papale et al. record the spiking activity of V1 neurons in monkeys viewing natural scenes and scenes with an occluder covering the receptive field. They show that V1 neurons rapidly and reliably encode scenes, even with no information in their receptive field, providing new insights into the selectivity of feedback influences in the visual cortex. [ABSTRACT FROM AUTHOR]

• The large-scale brain architecture develops even in the absence of visual experience. • The sensory-deprived brain maintains a lifelong sensitivity to environmental inputs. • The functional 'fate' of V1 in congenitally blind people is still disputed. • V1 may retain most of its intrinsic functioning also in congenitally blind individuals. [ABSTRACT FROM AUTHOR]

Many volcanic eruptions are shortly preceded by injection of new magma into a pre-existing, shallow (<10 km) magma chamber, causing convection and mixing between the incoming and resident magmas. These processes may trigger dyke propagation and further magma rise, inducing long-term (days to months) volcano deformation, seismic swarms, gravity anomalies, and changes in the composition of volcanic plumes and fumaroles, eventually culminating in an eruption. Although new magma injection into shallow magma chambers can lead to hazardous event, such injection is still not systematically detected and recognized. Here, we present the results of numerical simulations of magma convection and mixing in geometrically complex magmatic systems, and describe the multiparametric dynamics associated with buoyant magma injection. Our results reveal unexpected pressure trends and pressure oscillations in the Ultra-Long-Period (ULP) range of minutes, related to the generation of discrete plumes of rising magma. Very long pressure oscillation wavelengths translate into comparably ULP ground displacements with amplitudes of order 10-10 m. Thus, new magma injection into magma chambers beneath volcanoes can be revealed by ULP ground displacement measured at the surface. [ABSTRACT FROM AUTHOR]

Abstract: Determining consistent sets of vent conditions for next expected eruptions at Vesuvius is crucial for the simulation of the sub-aerial processes originating the volcanic hazard and the eruption impact. Here we refer to the expected eruptive scales and conditions defined in the frame of the EC Exploris project, and simulate the dynamics of magma ascent along the volcanic conduit for sub-steady phases of next eruptions characterized by intensities of the Violent Strombolian (VS), Sub-Plinian 2 (SP2), and Sub-Plinian 1 (SP1) scale. Sets of conditions for the simulations are determined on the basis of the bulk of knowledge on the past history of Vesuvius [Cioni, R., Bertagnini, A., Santacroce, R., Andronico, D., Explosive activity and eruption scenarios at Somma–Vesuvius (Italy): towards a new classification scheme. Journal of Volcanology and Geothermal Research, this issue.]. Volatile contents (H2O and CO2) are parameterized in order to account for the uncertainty in their expected amounts for a next eruption. In all cases the flow in the conduit is found to be choked, with velocities at the conduit exit or vent corresponding to the sonic velocity in the two-phase non-equilibrium magmatic mixture. Conduit diameters and vent mixture densities are found to display minimum overlapping between the different eruptive scales, while exit gas and particle velocities, as well as vent pressures, largely overlap. Vent diameters vary from as low as about 5 m for VS eruptions, to 35–55 m for the most violent SP1 eruption scale. Vent pressures can be as low as less than 1 MPa for the lowest volatile content employed of 2 wt.% H2O and no CO2, to 7–8 MPa for highest volatile contents of 5 wt.% H2O and 2 wt.% CO2 and large eruptive scales. Gas and particle velocities at the vent range from 100–250 m/s, with a tendency to decrease, and to increase the mechanical decoupling between the phases, with increasing eruptive scale. Except for velocities, all relevant vent quantities are more sensitive to the volatile content of the discharged magma for the highest eruptive scales considered. [Copyright &y& Elsevier]

Abstract: The volatile saturation surface in H2O–CO2–silicate melt systems is modeled by applying thermodynamic equilibrium between gaseous and liquid volatile components. The whole database of existing saturation data in the C–O–H–silicate liquid systems has allowed us to re-calibrate a previously developed fully multicomponent H2O–CO2 saturation model [Papale, P., 1999. Modeling of the solubility of a two-component H2O+CO2 fluid in silicate liquid. Am. Mineral., 84, 477–492]. The new database nearly doubles the previous one, greatly improving the performances of the whole model, which now adopts a significantly lower number of model parameters with respect to the previous calibration. The multicomponent H2O+CO2 saturation model is fully non-ideal, the only assumption being that the excess Gibbs free energy of the silicate mixture can be represented by an expansion of first-order symmetric interaction terms. No a-priori assumption is made on the P–T dependence of the volatile–oxide interaction terms, meaning that no assumption is made on the partial molar volume and enthalpy of the dissolved volatiles. The whole treatment is evaluated by restrictive statistical algorithms, which confirm the model validity on an extended database. The model allows to investigate extensively the dependence of the complex volatile saturation surface on composition. In order to explore the non-linear behaviors implicit in the physics of the dissolution process, the model is employed in a series of calculations aimed at illustrating some of the compositional features of the volatile saturation surface in both one-component and two-component volatile conditions. The results show compositional-dependent minima and maxima, some of which are known from the experiments. Non-ideal behavior is enhanced in two-component fluid phase conditions and pressures above a few hundreds MPa, where calculated isobaric H2O–CO2 saturation curves reveal the possible existence of a maximum in CO2 saturation at non-zero H2O contents. Due to the compositional dependence of the volatile saturation surface, it is outlined the important role played by redox conditions, especially in iron-rich melt systems like basalts. [Copyright &y& Elsevier]

Abstract: The equilibrium between a 4-component H2O–CO2–SO2–H2S gas phase and a 13-component silicate liquid made of 10 major oxides plus dissolved H2O, CO2, and S, is investigated by means of calculations involving homogeneous reactions in the gas phase and heterogeneous gas–liquid saturation modeling based on classical Gibbs thermodynamics and Toop–Samis polymeric approach. Sulfur is assumed to be present in two different oxidation states in the gas (sulfur dioxide and hydrogen sulfide) and liquid (sulfide and sulfate ions) phase, implying a dependence of the equilibrium conditions on the redox state of the system. Sulfur-bearing solid phases and Fe–O–S immiscible liquid are not accounted for in the modeling. The thermodynamic model is an extension of the one presented in Moretti et al. [Moretti R., Papale P. and Ottonello, G., 2003. A model for the saturation of C–H–O–S fluids in silicate melts. In: Oppenheimer C., Pyle D.M., Barclay J. (eds.) Volcanic Degassing, Geol. Soc. London Spec. Publ., 213, 81–101.] to account for iron speciation at high pressure and dissolved water contents. The consequences on the equilibrium conditions of different assumptions concerning the effective redox buffer in magma are examined through calculations made on two different liquids of shoshonitic and rhyolitic composition, determining the equilibrium conditions on the basis of (i) constant ferric to ferrous mass ratio, (ii) constant hydrogen sulfide to sulfur dioxide fugacity ratio, and (iii) constant oxygen fugacity relative to a solid–gas buffer (ΔNNO±0.5). Following Giggenbach [Giggenbach, W.F., 1996. Chemical composition of volcanic gases. In: Scarpa R., Tilling R.I. (eds.) Monitoring and Mitigation of Volcano Hazards, Springer-Berlin, 202–226.], the first two buffers are expected to be effective in basaltic and rhyolitic magmas, respectively, according to the most abundant reservoir of redox couples represented by iron in basalts, and sulfur in rhyolite. The model results show strongly nonlinear dependence of the equilibrium compositions in the gas and liquid phases, as well as of the oxidation state of the system, on the assumed redox buffer. Furthermore, for each assumed redox buffer, the pressure dependence of phase composition and oxidation state of the system also shows strongly nonlinear trends. The largest compositional differences are shown by sulfur species; however, the concentrations of water and carbon dioxide in the two phases at equilibrium also show nonnegligible dependence on the redox conditions. For each assumed redox buffer, sulfur dioxide in the gas phase, and sulfate ions in the liquid phase, are found to be present in appreciable quantities or represent the dominating sulfur species even at the largest employed pressures approaching 500 MPa. The more reliable redox buffers represented by constant ferric to ferrous mass ratio for shoshonite, and constant hydrogen sulfide to sulfur dioxide fugacity ratio for rhyolite, show that oxygen fugacity paths during magma depressurization strongly deviate from those parallel to NNO. Therefore, the characterization of the oxidation state in depressurizing magmas on the basis of deviations from solid buffers (usually NNO or QFM) may not be appropriate. [Copyright &y& Elsevier]

We have performed a parametric study on the dynamics of trachytic (alkaline) versus rhyolitic (calc-alkaline) eruptions by employing a steady, isothermal, multiphase non-equilibrium model of conduit flow and fragmentation. The employed compositions correspond to a typical rhyolite and to trachytic liquids from Phlegrean Fields eruptions, for which detailed viscosity measurements have been performed. The investigated conditions include conduit diameters in the range 30–90 m and total water contents from 2 to 6 wt%, corresponding to mass flow rates in the range 106–108 kg/s. The numerical results show that rhyolites fragment deep in the conduit and at a gas volume fraction ranging from 0.64 to 0.76, while for trachytes fragmentation is found to occur at much shallower levels and higher vesicularities (0.81–0.85). An unexpected result is that low-viscosity trachytes can be associated with lower mass flow rates with respect to more viscous rhyolites. This is due to the non-linear combined effects of viscosity and water solubility affecting the whole eruption dynamics. The lower viscosity of trachytes, together with higher water solubility, results in delayed fragmentation, or in a longer bubbly flow region within the conduit where viscous forces are dominant. Therefore, the total dissipation due to viscous forces can be higher for the less viscous trachytic magma, depending on the specific conditions and trachytic composition employed. The fragmentation conditions determined through the simulations agree with measured vesicularities in natural pumice clasts of both magma compositions. In fact, vesicularities average 0.80 in pumice from alkaline eruptions at Phlegrean Fields, while they tend to be lower in most calc-alkaline pumices. The results of numerical simulations suggest that higher vesicularities in alkaline products are related to delayed fragmentation of magmas with this composition. Despite large differences in the distribution of flow variables which occur in the deep conduit region and at fragmentation, the flow dynamics of rhyolites and trachytes in the upper conduit and at the vent can be very similar, at equal conduit size and total water content. This is consistent with similar phenomenologies of eruptions associated with the two magma types. [Copyright &y& Elsevier]

The AD 79 eruption of Vesuvius is certainly one of the most investigated explosive eruptions in the world. This makes it particularly suitable for the application of numerical models since we can be quite confident about input data, and the model predictions can be compared with field-based reconstruction of the eruption dynamics. Magma ascent along the volcanic conduit and the dispersal of pyroclasts in the atmosphere were simulated. The conduit and atmospheric domain were coupled through the flow conditions computed at the conduit exit. We simulated two different peak phases of the eruption which correspond to the emplacement of the white and gray magma types that produced Plinian fallout deposits with interlayered pyroclastic flow units during the gray phase. The input data, independently constrained and representative of each of the two eruptive phases, consist of liquid magma composition, crystal and water content, mass flow rate, and pressure–temperature–depth of the magma at the conduit entrance. A parametric study was performed on the less constrained variables such as microlite content of magma, pressure at the conduit entrance, and particle size representative of the eruptive mixture. Numerical results are substantially consistent with the reconstructed eruptive dynamics. In particular, the white eruption phase is found to lead to a fully buoyant eruption plume in all cases investigated, whereas the gray phase shows a more transitional character, i.e. the simultaneous production of a buoyant convective plume and pyroclastic surges, with a significant influence of the microlite content of magma in determining the partition of pyroclast mass between convective plumes and pyroclastic flows. [Copyright &y& Elsevier]

Open conduit volcanoes erupt with the highest frequency on Earth. Their activity is characterized by an outgassing flux that largely exceeds the gas that could be released by the erupted magma; and by frequent small explosions intercalated by larger events that pose a significant risk to locals, tourists, and scientists. Thus, identifying the signs of an impending larger explosion is of utmost importance for the mitigation of volcanic hazard. Larger explosive events have been associated with the sudden ascent of volatile rich magmas, however, where and why magma accumulates within the plumbing system remains unclear. Here we show that the interaction between CO2‐rich fluids and magma spontaneously leads to the accumulation of volatile‐rich, low density and gravitationally unstable magma at depth, without the requirement of permeability barriers. CO2‐flushing forces the exsolution of water and the increase of magma viscosity, which proceeds from the bottom of the magma column upward. This rheological configuration unavoidably leads to the progressive thickening of a gas‐rich and low density (i.e., gravitationally unstable) layer at the bottom of the feeding system. Our calculations account for observations, gas monitoring and petrological data; moreover, they provide a basis to trace the approach to deeply triggered large or paroxysmal eruptions and estimate their size from monitoring data. Our model is finally applied to Stromboli volcano, an emblematic example of open conduit volcano, but can be applied to any other open conduit volcano globally and offers a framework to anticipate the occurrence of unexpectedly large eruptions. Plain Language Summary: Open conduit volcanoes erupt with the highest frequency on Earth and release significantly more gas than magma. Their activity is characterized by almost continuous and small explosions that are intercalated by significantly larger explosive events. The relatively continuous explosive activity makes these volcanoes attractive both for scientific research and tourism, however, unexpectedly large explosions pose a significant risk to scientists and tourists. The excess gas these volcanoes release is CO2‐rich and its interaction with magma leads to the accumulation of gas‐rich and low‐density magma at depth, below higher density magma. We suggest that the gravitational destabilization of this deep and gas rich magma is ultimately responsible for the large explosions that punctuate the activity of open conduit volcanoes. The approach to this larger events can be traced with continuous gas monitoring, which therefore provides a unique opportunity to anticipate this otherwise unexpected explosions. Key Points: Continuous CO2 flushing can prime basaltic volcanic systems toward more energetic eruptionsAccumulation of gas‐rich and low‐density magma at depth results from CO2 flushing alone and no ad‐hoc physical barrier is requiredBuild‐up to larger explosions can be monitored through continuous gas monitoring at the surface [ABSTRACT FROM AUTHOR]

Discusses volcanic eruptions and presents a model in which a fragmentation criterion based on a rate-limited crossing of the glass transition, is incorporated into a multiphase fluid-dynamic description of magma ascent. How the numerical results of this model demonstrate the feasibility of strain-induced brittle fragmentation of magma in volcanic eruptions, and reconcile experimental with theoretical studies as well as with the observed volcanic products of large explosive eruptions.

Presents information on a study which modeled the solubility of a two-component, water + carbon dioxide fluid in silicate liquids. Description of the model; Re-derivation of the carbon dioxide-related model parameters; Results of the study.

Presents a thermodynamic model of the solubility of water and carbon dioxide in natural silicate liquids. Comparison between the solubility model and the speciation of water and carbon dioxide in silicate liquids; Impact of the model on volcanic-relevant conditions.

The article examines the need for international resilience plans for volcanic eruptions. It discusses how risk-mitigation strategies based on evacuations are not sufficient responses in the event of cataclysmic volcanic eruptions that include impacts beyond direct exposure. Particular attention is given to recordings on the Volcanic Explosivity Index (VEI).

Biological vision relies on representations of the physical world at different levels of complexity. Relevant features span from simple low-level properties, as contrast and spatial frequencies, to object-based attributes, as shape and category. However, how these features are integrated into coherent percepts is still debated. Moreover, these dimensions often share common biases: for instance, stimuli from the same category (e.g., tools) may have similar shapes. Here, using magnetoencephalography, we revealed the temporal dynamics of feature processing in human subjects attending to objects from six semantic categories. By employing Relative Weights Analysis, we mitigated collinearity between model-based descriptions of stimuli and showed that low-level properties (contrast and spatial frequencies), shape (medial-axis) and category are represented within the same spatial locations early in time: 100–150 ms after stimulus onset. This fast and overlapping processing may result from independent parallel computations, with categorical representation emerging later than the onset of low-level feature processing, yet before shape coding. Categorical information is represented both before and after shape, suggesting a role for this feature in the refinement of categorical matching. [ABSTRACT FROM AUTHOR]

Magmas discharged during individual volcanic eruptions commonly display compositional variations interpreted as new arrivals at shallow depth of more primitive, hotter, volatile-rich magma batches mixing with resident, colder, partially degassed magma. Heterogeneities in eruption products are often interpreted as evidence of short times of order tens of hours from new magma arrival to eruption, raising concerns for emergency planning. We show here, through numerical simulations, that magma convection and mixing in a shallow magma chamber can result in long-lived, dynamically stable configurations with coexistence of magmas from nearly pure to variably mixed end-member compositions. Short mixing time scales may therefore relate to sin-eruptive processes, as heterogeneities found in the eruptive products are not necessarily the fingerprint of new magma arrival shortly preceding or triggering the eruption. [ABSTRACT FROM AUTHOR]

Explosive eruptions are the final result of complex dynamics occurring within the volcanic plumbing system and involving domains such as one or more magma chambers, their connecting dykes, and the conduit or dyke connecting magma with the surface. We present here a 1D quasi-steady numerical modeling approach that allows the interplay between magmatic reservoirs located at different depths to be taken into account in the analysis of the eruption dynamics. We simulate a set up, common to a large number of real eruption cases, where a shallow, relatively small magma chamber hosting partially degassed, chemically more evolved magma is connected through a dyke to a deeper, much larger, gas-rich, less differentiated magmatic body. The numerical results describe two separate regimes controlled by either the shallow or the deep magma reservoir. While the shallow-controlled regime shows a general increase of eruption magnitude with increasing volume of magma stored at shallow depth, the deep-controlled regime, that we associate to the potential occurrence of a large caldera collapse, lacks such a relationship, resulting in eruption magnitudes that are substantially independent from the volume of the shallow magma reservoir. The efficiency of the deep interconnections between magmatic reservoirs, exemplified in our simulations by the width of the interconnecting dyke, is found to be a major factor controlling the shift from one regime to the other. [ABSTRACT FROM AUTHOR]

Eruption products of individual volcanic eruptions commonly display heterogeneities that are often interpreted as evidence of short times from new magma arrival to eruption. The time evolution of magma mixing and the degree of homogenization are still not well understood. We present the results of a parametric study through numerical simulations of andesite-dacite buoyancy driven magma mixing, by varying viscosity and volatile contents. The results show that highly efficient buoyancy-driven mixing is followed by a phase where stable convective layers develop, and mixing becomes progressively less efficient. Low viscosity and more volatiles favor mixing and achievement of a higher level of homogenization. On the contrary, high viscosity and lower volatiles give rise to long lived heterogeneities, in some cases preserving the end member compositions. Analysis of the results suggest that during the early transient phase of efficient magma mixing, crystal dissolution dominates; however, for cases where the transient phase takes longer, growth and resorption can act together, likely resulting in multiple resorption surfaces and zoning patterns before stable conditions are reached and euhedral crystal growth takes place. Crystals initially in equilibrium with magma can display a range of textural evolutions depending on their initial composition and individual paths during one single event of magma recharge, convection and mixing. Overall, the numerical simulations suggest that complex patterns of growth and dissolution followed by euhedral rims of various composition can be associated with single recharging events; and that short reaction times do not necessarily reflect comparably short times from recharge to eruption. [ABSTRACT FROM AUTHOR]

The recent development and analysis of global databases of continental volcanic eruptions is increasingly providing new understanding of their global time-size distribution and of the global rates of volcanism on Earth. We now know that volcanic eruptions are globally Poissonian (memoryless) events, implying that previously widespread concepts such as that of retarding or "overdue" events are actually meaningless when referred to volcanic eruptions; and we have discovered a power law relationships between the size of explosive volcanic eruptions (VEI = Volcanic Explosivity Index equal or larger than 3) and their frequency, possibly placing a theoretical limit to our capability to anticipate the occurrence of a volcanic eruption of a given size, e.g., the occurrence of a cataclysmic super-eruption. Maximum likelihood estimates of rate parameters associated with exponentially-distributed inter-event eruption times allow global volcanic hazard and global rates of continental volcanism to be quantified over different time windows. Here I present the results of a Monte Carlo simulation showing the distribution of the global rates of continental volcanism over different time windows from 1 to 100,000 years. The new estimates presented here can be used as robust constraints for geodynamic models, e.g., models of plume dynamics and mantle-crust interaction, as well as for atmospheric evolution and climate change models. [ABSTRACT FROM AUTHOR]

This paper presents the numerical results of compressible and incompressible flow problems through a unified approach based on a stabilized space–time finite element method. The numerical approach is continuous in space and discontinuous in time. The proposed method starts by the use of a stabilized space–time variational formulation, which allows the use of the same order interpolation functions for all solution variables. The numerical technique is tested through comparison with standard compressible and incompressible flow benchmarks. Compressible flow cases include 1D and 2D shock problems. Incompressible flow cases include lid-driven cavity flow and flow over a backward-facing step computed over a range of R e numbers. The results demonstrate high stability and accuracy of the numerical technique over a wide range of flow regimes, suggesting straightforward extension to many flow cases not yet investigated. [ABSTRACT FROM AUTHOR]

This work aims to develop a numerical wave tank for viscous and inviscid flows. The Navier-Stokes equations are solved by time-discontinuous stabilized space-time finite element method. The numerical scheme tracks the free surface location using fluid velocity. A segregated algorithm is proposed to iteratively couple the fluid flow and mesh deformation problems. The numerical scheme and the developed computer code are validated over three free surface problems: solitary wave propagation, the collision between two counter moving waves, and wave damping in a viscous fluid. The benchmark tests demonstrate that the numerical approach is effective and an attractive tool for simulating viscous and inviscid free surface flows. [ABSTRACT FROM AUTHOR]

Numerical simulations of volcanic processes play a fundamental role in understanding the dynamics of magma storage, ascent, and eruption. The recent extraordinary progress in computer performance and improvements in numerical modeling techniques allow simulating multiphase systems in mechanical and thermodynamical disequilibrium. Nonetheless, the growing complexity of these simulations requires the development of flexible computational tools that can easily switch between sub-models and solution techniques. In this work we present MagmaFOAM, a library based on the open-source computational fluid dynamics software OpenFOAM that incorporates models for solving the dynamics of multiphase, multicomponent magmatic systems. Retaining the modular structure of OpenFOAM, MagmaFOAM allows runtime selection of the solution technique depending on the physics of the specific process and sets a solid framework for in-house and community model development, testing, and comparison. MagmaFOAM models thermomechanical nonequilibrium phase coupling and phase change, and it implements state-of-the-art multiple volatile saturation models and constitutive equations with composition-dependent and space–time local computation of thermodynamic and transport properties. Code testing is performed using different multiphase modeling approaches for processes relevant to magmatic systems: Rayleigh–Taylor instability for buoyancy-driven magmatic processes, multiphase shock tube simulations propaedeutical to conduit dynamics studies, and bubble growth and breakage in basaltic melts. Benchmark simulations illustrate the capabilities and potential of MagmaFOAM to account for the variety of nonlinear physical and thermodynamical processes characterizing the dynamics of volcanic systems. [ABSTRACT FROM AUTHOR]

Short-term interaction of magma with crustal carbonates can affect a volcano's eruptive style and drive even low-viscosity magmas toward large explosive eruptions. Only a few studies have focused on short-term magma-carbonate interaction under controlled laboratory conditions and the physical processes behind the experimental observations are still poorly understood. In this work, we present the first numerical modelling study of short-term magma-carbonate interaction and provide an interpretative framework for experimental and field observations. We developed thermodynamic and dynamic models for carbonate dissolution and mixing and mingling between contaminated magma pockets and host magma. We find that mixing and mingling can play a central role in modulating the efficiency of volatile exsolution. The increasing viscosity of the host melt slows down melt mingling and hence the mixing process, limiting volatile exsolution. Less efficient mixing and mingling could allow the fingerprints of short-term magma-carbonate interaction to be preserved in volcanic and intrusive rocks. Finally, we highlight that the mechanism and timescale of magma-carbonate interaction open a key question about the anomalous high mobility of CaO during carbonate dissolution. • Modelling of magma-carbonate interaction to interpret experimental observations. • Anomalous high mobility of calcium during carbonate dissolution. • Mixing and mingling can modulate volatile exsolution. [ABSTRACT FROM AUTHOR]

Mt. Cameroon is one of the most active effusive volcanoes in Africa. About 500,000 people living or working around its fertile flanks are subject to significant threat from lava flow inundation. Lava flow hazard and risk were assessed by simulating probable lava flow paths using the DOWNFLOW code. The vent opening probability density function and lava flow length distribution were determined on the basis of available data from past eruptions at Mt. Cameroon volcano. Code calibration was performed through comparison with real lava flow paths. The topographic basis for simulations was the 90-m resolution SRTM DEM. Simulated lava flows from about 80,000 possible vents were used to produce a detailed lava flow hazard map. The lava flow risk in the area was mapped by combining the hazard map with digitized infrastructures (i.e., human settlements and roads). Results show that the risk of lava flow inundation is greatest in the most inhabited coastal areas comprising the town of Limbe, which constitutes the center of Cameroon's oil industry and an important commercial port. Buea, the second most important town in the area, has a much lower risk although it is significantly closer to the summit of the volcano. Non-negligible risk characterizes many villages and most roads in the area surrounding the volcano. In addition to the conventional risk mapping described above, we also present (1) two reversed risk maps (one for buildings and one for roads), where each point on the volcano is classified according to the total damage expected as a consequence of vent opening at that point; (2) maps of the lava catchments for the two main towns of Limbe and Buea, illustrating the expected damage upon venting at any point in the catchment basin. The hazard and risk maps provided here represent valuable tools for both medium/long-term land-use planning and real-time volcanic risk management and decision making. [ABSTRACT FROM AUTHOR]

Sophisticated models of volcanic scenarios are increasingly sensitive to the accuracy of their input parameters and constitutive equations for magma properties. Viscosity is certainly one of the most important magma properties, but only recently systematic investigations on silicate liquids with natural compositions have started. We investigated the Newtonian viscosity of dry and hydrous phonolitic and trachytic melts from Vesuvius and Phlegrean Fields volcanic complexes, respectively. The analysed samples come from the deposits of the AD 1631 (Vesuvius) and ca. 4400 BP Agnano Monte Spina (AMS) (Phlegrean Fields) eruptions that are commonly taken as reference events for the most hazardous scenarios in case of reactivation of the two volcanoes. Samples were hydrated via piston cylinder synthesis at P=10 kbar and T=1600 °C. The dry high temperature and dry or hydrous low temperature viscosities were measured by a combination of micropenetration and concentric cylinder techniques, covering a total temperature range from about 400 to 1500 °C, water content range from virtually dry to 3.8 wt.%, and viscosity range from 102 to 1012 Pa s. The viscosity data for each composition were fitted by a modified Tamman–Vogel–Fulcher equation, allowing viscosity calculations at eruption temperatures and for dissolved water contents in the range of those examined. The viscosity data and model calculations were used for a comparison with other natural or synthetic phonolitic and trachytic melts, as well as with rhyolitic melts, for which viscosities had been measured. At water contents less than 1 wt.%, a trend of increasing viscosity from phonolitic to trachytic to rhyolitic melts is found. At water contents larger than 1 wt.%, the viscosity of trachytic melts is close to that of rhyolitic melts, while the viscosity of phonolitic melts is one to two orders of magnitude lower. A compositional parameter given by the (Na+K+H)/(Si+Al) molar ratio is found to be linearly related to the low-T hydrous viscosity of the trachytic and phonolitic melts considered, either analysed in this work or taken from literature. Differently, the rhyolitic melt shows significant variations from the trend found for phonolitic and trachytic melts. [Copyright &y& Elsevier]

The organization of semantic information in the brain has been mainly explored through category-based models, on the assumption that categories broadly reflect the organization of conceptual knowledge. However, the analysis of concepts as individual entities, rather than as items belonging to distinct superordinate categories, may represent a significant advancement in the comprehension of how conceptual knowledge is encoded in the human brain. Here, we studied the individual representation of thirty concrete nouns from six different categories, across different sensory modalities (i.e., auditory and visual) and groups (i.e., sighted and congenitally blind individuals) in a core hub of the semantic network, the left angular gyrus, and in its neighboring regions within the lateral parietal cortex. Four models based on either perceptual or semantic features at different levels of complexity (i.e., low- or high-level) were used to predict fMRI brain activity using representational similarity encoding analysis. When controlling for the superordinate component, high-level models based on semantic and shape information led to significant encoding accuracies in the intraparietal sulcus only. This region is involved in feature binding and combination of concepts across multiple sensory modalities, suggesting its role in high-level representation of conceptual knowledge. Moreover, when the information regarding superordinate categories is retained, a large extent of parietal cortex is engaged. This result indicates the need to control for the coarse-level categorial organization when performing studies on higher-level processes related to the retrieval of semantic information. [ABSTRACT FROM AUTHOR]

On December 29, 2013, an isolated vulcanian-type eruption occurred at Chaparrastique volcano (El Salvador) after 12 years of inactivity. The eruption was classified as VEI 2 and produced an ash plume with a maximum height of ~ 9 km. Textural and compositional data from phenocrysts from the erupted products have been integrated with geochemical and isotopic information from bulk rocks to elucidate the magmatic processes responsible for the reawakening of volcanic activity. Phenocrysts consist of Fo-rich poikilitic olivines hosting high-Mg titanomagnetites, and Fo-poor olivines coexisting with low-Mg titanomagnetites. Mineral-melt equilibria suggest an origin for the distinct phenocryst populations by mixing between a high- T (~ 1130–1150 °C), basaltic magma with f O 2 (NNO buffer) typical of the lower crust in arc systems and a low- T (~ 1060–1080 °C), basaltic andesitic magma with f O 2 (NNO + 1 buffer) commonly encountered in shallower, more oxidized crustal reservoirs. Thermobarometry based on Fe-Mg exchange between orthopyroxene and clinopyroxene constrains the crystallization before eruption at relative low- P (~ 150–250 MPa) and low- T (~ 1000–1050 °C). Mixing between two chemically distinct magmas is also evidenced by the occurrence of reverse zoned plagioclase phenocrysts with resorbed sodic cores and re-growth of sieve-textured calcic mantles. Conversely, plagioclase rims exhibit disequilibrium compositions addressed to decompression kinetics (~ 10 − 3 MPa/s) driven by rapid magma ascent to the surface (~ 0.03 m/s). Major and trace element modelling excludes fractional crystallization as the primary mechanism controlling the bulk rock variability, whereas geochemical data align along a mixing trend between two end-members representative of the primitive basalt and the differentiated basaltic andesite. Trace element and isotope data indicate that the primary source of magmatism is an enriched MORB-like mantle with the contribution of fluxes of metasomatic fluids and/or melts produced by the subducted slab. The role played by slab-fluid inputs of carbonate origin and slab-melts from the hemipelagic sediments seems to be minimal. Assimilation/contamination processes of magmas by crustal rocks are also negligible. In contrast, the geochemical signature of magmas is greatly influenced by slab-derived aqueous fluids produced prevalently by progressive dehydration of marine sediments and altered basaltic crust. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editors discuss the announcement of media and information company Thomson Reuters to include the journal in their ISI listings and acknowledge the Copernicus Publications and the authors who contributed to the success of the journal.

The article focuses on the announcement of the information service company Thomson Reuters that they will include the journal "Solid Earth" to its ISI listings. Topics discussed include the scientific research papers published in "Solid Earth" since February 2010, the journal's synergy and publications with Copernicus Publications, and the announcement of the Impact Factor of Thomson for the journal's issue on June 2013.

The article offers the author's insights on the journal "Solid Earth Discussions" which is included in the ISI listings of multinational media and information firm Thomson Reuters. The author states that being included in the ISI listings is an excellent news for the journal and reflects the efforts of the editorial board. He adds that Thomson Reuters will be backdating the listing to the journal's first issue.

The article reports that information service company Thomson Reuters Corp. announced the inclusion of the "Solid Earth" (SE) journal in the science citation index. It states that the announcement was made after the assessment of quality, numbers, characteristics of papers published in the journal since February 2010. It adds that the first impact factor of all the issues of the journal will be announced in June 2013.

The article focuses on the announcement of Thomson Reuters regarding the inclusion of the journal "Solid Earth" (ESD) in their Institute of Science (ISI) listings after completing the quality assessment of the papers published in the journal since February 2010. It says that the move reflects the effort of the editorial board and the trust of the scientific community in the journal. It mentions that the company will backdate the first issue of the journal.

Abstract: Persistent degassing of closed-conduit explosive volcanoes may be used to inspect and monitor magmatic processes. After interaction with shallow hydrothermal fluids, volcanic gases collected at surface can differ substantially from those exsolved from magma. We report here on an innovative approach to identify and separate the contribution of variable magmatic components from fumarolic gases, by processing the 30-year-long geochemical dataset from the Campi Flegrei caldera, Southern Italy. The geochemical record shows periodic variations, which are well correlated with geophysical signals. Such variations are interpreted as due to the time-varying interplay of two magma degassing sources, each differing in size, depth, composition, and cooling/crystallization histories. Similar multiple degassing sources are common at explosive volcanoes, with frequent ascent and intrusion of small magma batches. Our innovative method permits the identification of those magma batches, which contributes to the interpretation of unrest signals, forecasting and assessment of volcanic hazards. [Copyright &y& Elsevier]

Abstract: The recent eruption of Stromboli in February–April 2007 offered a unique chance to test our current understanding of processes driving the transition from ordinary (persistent Strombolian) to effusive activity, and the ability of instrumental geophysical and geochemical networks to interpret and predict these events. Here, we report on the results of two years of in-situ sensing of the CO2/SO2 ratio in Stromboli''s volcanic gas plume, in the attempt to put constraints on the trigger mechanisms and dynamics of the eruption. We show that large variations of the plume CO2/SO2 ratio (range, 0.9–26) preceded the onset of the eruption (since December 2007), interrupting a period of relatively-steady and low ratios (time-averaged ratio, 4.3) lasting from at least May to November 2006. By contrasting our observations with numerical simulations of volcanic degassing at Stromboli, derived by use of an equilibrium saturation model, we suggest that the pre-eruptive increase of the ratio reflected an enhanced supply of deeply-derived CO2-rich gas bubbles to the shallow-plumbing system. This larger-than-normal ascent of gas bubbles was likely sourced by a 1–3 km deep gas–melt separation region (probably a magma storage zone), and caused faster convective overturning of magmas in the shallow conduit; an increase in the explosive rate and in seismic tremor, and finally the collapse of the la Sciara del Fuoco sector triggering the effusive phase. The high CO2/SO2 ratios (up to 21) observed during the effusive phase, and particularly in the days and hours before a paroxysmal explosion on March 15, 2007, indicate the persistence of the same gas source; and suggest that de-pressurization of the same 1–3 km deep magma storage zone could have been the trigger mechanism for the paroxysm itself. [Copyright &y& Elsevier]

Abstract: The eruptive dynamics of volcanic systems are largely controlled by the viscosity of deforming magma. Here we report the results of a series of high-temperature, high-pressure experiments at conditions relevant for volcanic conduits (250 MPa confining pressure and temperature between 500 °C and 900 °C) that were undertaken to investigate the rheology of magma with crystal fractions varying between 0.5 and 0.8 (50 to 80 wt.%) at different strain-rate conditions. The experiments demonstrate that the presence of crystals increases the relative viscosity (ratio between the viscosity of the mixture and the viscosity of the melt phase) of magmas and additionally induces a decrease of the relative viscosity with increasing strain-rate (shear thinning, non-Newtonian behavior). The experimental results, combined with existing data at low crystal fractions (0–0.3), were used to develop a semi-empirical parameterization that describes the variations of relative viscosity for crystal fractions between 0 and 0.8 and accounts for the complex non-Newtonian rheology of crystal-bearing magmas. The new parameterization, included into numerical models simulating the magma ascent dynamics, reveals that strain-rate-dependent rheology significantly modifies the dynamic behavior inside volcanic conduits, particularly affecting the magma fragmentation conditions. [Copyright &y& Elsevier]

It is generally accepted, but not experimentally proven, that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data. By discussing the results of two years of real-time observation of H2O, CO2, and SO2 in volcanic gases from Mount Etna volcano, we unambiguously demonstrate that increasing CO2/SO2 ratios can allow detection of the pre-eruptive degassing of rising magmas. Quantitative modeling by the use of a saturation model allows us to relate the pre-eruptive increases of the CO2/SO2 ratio to the refilling of Etna's shallow conduits with CO2-rich deep-reservoir magmas, leading to pressurization and triggering of eruption. The advent of real-time observations of H2O, CO2, and SO2, combined with well-constrained models of degassing, represents a step forward in eruption forecasting. [ABSTRACT FROM AUTHOR]

Abstract: Viscosity of hydrous trachytes from the Agnano Monte Spina eruption (Phlegrean Fields, Italy) has been determined at 1.0 GPa and temperatures between 1200 and 1400 °C using the falling sphere method in a piston cylinder apparatus. The H2O content in the melts ranged from 0.18 to 5.81 wt.%. These high-temperature hydrous viscosities, along with previous ones determined at low-temperature (anhydrous and hydrous) and at high-temperature (anhydrous), at 1 atm on the same melt composition, represent the only complete viscosity data set available for K-trachytic melts, from magmatic to volcanic conditions. Viscosity decreases with increasing temperature and water content in the melt. At constant temperature, viscosity appears to significantly decrease when the first wt.% of H2O is added. At H2O content higher than 3 wt.% the effect of temperature on viscosity is slight. Moreover, the deviation from Arrhenian behaviour towards greater “fragility” occurs with increasing water content. We combined low- and high-temperature viscosities (also from literature) and parameterized them by the use of a modified Vogel–Fulcher–Tamman equation, which accommodates the non-Arrhenian temperature dependence of melt viscosity. Moreover, in order to explore the extent to which the improved knowledge of Agnano Monte Spina trachyte viscosity may affect simulation of volcanic eruption at Phlegrean Fields, we included our viscosity models in numerical simulations of magma flow and fragmentation along volcanic conduits. These simulations show that the new parameterizations (and hence the new equations) give stronger predictions in the temperature interval relevant for magmatic and eruptive processes. [Copyright &y& Elsevier]