Oxide nanolitisation-induced melt iron extraction causes viscosity jumps and enhanced explosivity in silicic magma.

Explosivity in erupting volcanoes is controlled by the degassing dynamics and the viscosity of the ascending magma in the conduit. Magma crystallisation enhances both heterogeneous bubble nucleation and increases in magma bulk viscosity. Nanolite crystallisation has been suggested to enhance such processes too, but in a noticeably higher extent.

Nanoscale silicate melt textures determine volcanic ash surface chemistry.

Explosive volcanic eruptions produce vast quantities of silicate ash, whose surfaces are subsequently altered during atmospheric transit. These altered surfaces mediate environmental interactions, including atmospheric ice nucleation, and toxic effects in biota. A lack of knowledge of the initial, pre-altered ash surface has required previous studies to assume that the ash surface composition created during magmatic fragmentation is equivalent to the bulk particle assemblage.

The porosity of felsic pyroclasts: laboratory validation of field-based approaches.

Unlabelled: Volcanic eruptions are driven by magma rising through Earth's crust. The style of an eruption depends on intrinsic and extrinsic parameters and is commonly a dynamic process. Thorough and holistic investigation of the related products is key to understanding eruptive phenomena and assessment of volcano-specific hazards.

Glass transition temperatures and crystallization kinetics of a synthetic, anhydrous, amorphous calcium-magnesium carbonate.

We report the first calorimetric observations of glass transition temperatures and crystallization rates of anhydrous, amorphous calcium-magnesium carbonate using fast scanning differential scanning calorimetry. Hydrous amorphous CaMgCO · 0.5HO (ACMC) solid was precipitated from a MgCl-NaHCO buffered solution, separated from the supernatant, and freeze-dried.

Effect of water on the glass transition of a potassium-magnesium carbonate melt.

Calorimetric measurements of the glass transition temperatures () of hydrous carbonate melts are reported on a near-eutectic composition of 55 mol% KCO - 45 mol% MgCO with up to 42 mol% bulk HO dissolved in the carbonate melt. Hydrous melts were quenched from 750°C to transparent and crystal-free glasses and were subsequently analysed for water content before and after measuring by high-sensitivity differential scanning calorimetry. The glass transition and limited fictive temperatures as a function of the water content were determined at 10 K/min cooling/heating rates resulting in ranging from 245°C at nominally anhydrous conditions to 83°C in the presence of 42 mol% HO in the glass.

Experimental generation of fulgurite under realistic lightning discharge conditions.

Fulgurites have been documented in geological deposits from throughout Earth's history. They have also been assigned a potential role in prebiotic chemistry as a source of reactants. Fulgurites are generated in nature by cloud-to-ground lightning strikes.

The physics of dancing peanuts in beer.

In Argentina, some people add peanuts to their beer. Once immersed, the peanuts initially sink part way down into the beer before bubbles nucleate and grow on the peanut surfaces and remain attached. The peanuts move up and down within the beer glass in many repeating cycles.

Molten-Volcanic-Ash-Phobic Thermal Barrier Coating based on Biomimetic Structure.

Volcanic ash is a major threat to aviation safety. The softening/melting temperatures of volcanic ash lie far below typical aero-engine operating temperatures. Thus, molten ash can accelerate the failure of thermal barrier coatings (TBCs).

Bubble rise in molten glasses and silicate melts during heating and cooling cycles.

The Hadamard-Rybczynski equation describes the steady-state buoyant rise velocity of an unconfined spherical bubble in a viscous liquid. This solution has been experimentally validated for the case where the liquid viscosity is held constant. Here, we extend this result for non-isothermal conditions, by developing a solution for bubble position in which we account for the time-dependent liquid viscosity, liquid and gas densities, and bubble radius.

Genetic model of the El Laco magnetite-apatite deposits by extrusion of iron-rich melt.

Magnetite-apatite deposits are important sources of iron and other metals. A prominent example are the magnetite lavas at the El Laco volcano, Northern Chile. Their formation processes remain debated.

Complex geometry of volcanic vents and asymmetric particle ejection: experimental insights.

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.

Interparticle and Brownian forces controlling particle aggregation and rheology of silicate melts containing platinum-group element particles.

We study the rheology of silicate melts containing platinum-group element (PGE) particles. They exhibit a shear-thinning behaviour, an intense aggregation tendency, and an anomalously high apparent viscosity in the low shear rate limit, even at very low particle volume fraction. Using a compilation of published experimental data, we analyse these effects in three steps.

Inflated pyroclasts in proximal fallout deposits reveal abrupt transitions in eruption behaviour.

During explosive eruption of low viscosity magmas, pyroclasts are cooled predominantly by forced convection. Depending on the cooling efficiency relative to other timescales, a spectrum of deposits can be formed. Deposition of hot clasts, above their glass transition temperature, can form spatter mounds, ramparts and clastogenic lava flows.

Universal scaling for the permeability of random packs of overlapping and nonoverlapping particles.

Constraining fluid permeability in porous media is central to a wide range of theoretical, industrial, and natural processes. In this Letter, we validate a scaling for fluid permeability in random and lattice packs of spheres and show that the permeability of packs of both hard and overlapping spheres of any sphere size or size distribution collapse to a universal curve across all porosity ϕ in the range of ϕ_{c}<ϕ<1, where ϕ_{c} is the percolation threshold. We use this universality to demonstrate that permeability can be predicted using percolation theory at ϕ_{c}<ϕ≲0.

Stratigraphic reconstruction of the Víti breccia at Krafla volcano (Iceland): insights into pre-eruptive conditions priming explosive eruptions in geothermal areas.

Unlabelled: Krafla central volcano in Iceland has experienced numerous basaltic fissure eruptions through its history, the most recent examples being the Mývatn (1724‒1729) and Krafla Fires (1975-1984). The Mývatn Fires opened with a steam-driven eruption that produced the Víti crater. A magmatic intrusion has been inferred as the trigger perturbing the geothermal field hosting Víti, but the cause(s) of the explosive response remain uncertain.

Linking gas and particle ejection dynamics to boundary conditions in scaled shock-tube experiments.

Unlabelled: Predicting the onset, style and duration of explosive volcanic eruptions remains a great challenge. While the fundamental underlying processes are thought to be known, a clear correlation between eruptive features observable above Earth's surface and conditions and properties in the immediate subsurface is far from complete. Furthermore, the highly dynamic nature and inaccessibility of explosive events means that progress in the field investigation of such events remains slow.

Permeability of packs of polydisperse hard spheres.

The permeability of packs of spheres is important in a wide range of physical scenarios. Here, we create numerically generated random periodic domains of spheres that are polydisperse in size and use lattice-Boltzmann simulations of fluid flow to determine the permeability of the pore phase interstitial to the spheres. We control the polydispersivity of the sphere size distribution and the porosity across the full range from high porosity to a close packing of spheres.

India-Asia collision as a driver of atmospheric CO in the Cenozoic.

Deep Earth degassing is a critical forcing factor for atmospheric CO variations and palaeoclimate changes in Earth's history. For the Cenozoic, the key driving mechanism of atmospheric CO variations remains controversial. Here we analyse three stages of collision-related magmatism in Tibet, which correspond temporally with the three major stages of atmospheric CO variations in the Cenozoic and explore the possibility of a causal link between these phenomena.

Release characteristics of overpressurised gas from complex vents: implications for volcanic hazards.

Many explosive volcanic eruptions produce underexpanded starting gas-particle jets. The dynamics of the accompanying pyroclast ejection can be affected by several parameters, including magma texture, gas overpressure, erupted volume and geometry. With respect to the latter, volcanic craters and vents are often highly asymmetrical.

Assessment of the potential for in-plume sulphur dioxide gas-ash interactions to influence the respiratory toxicity of volcanic ash.

Background: Volcanic plumes are complex environments composed of gases and ash particles, where chemical and physical processes occur at different temperature and compositional regimes. Commonly, soluble sulphate- and chloride-bearing salts are formed on ash as gases interact with ash surfaces. Exposure to respirable volcanic ash following an eruption is potentially a significant health concern.

Heated gas bubbles enrich, crystallize, dry, phosphorylate and encapsulate prebiotic molecules.

Non-equilibrium conditions must have been crucial for the assembly of the first informational polymers of early life, by supporting their formation and continuous enrichment in a long-lasting environment. Here, we explore how gas bubbles in water subjected to a thermal gradient, a likely scenario within crustal mafic rocks on the early Earth, drive a complex, continuous enrichment of prebiotic molecules. RNA precursors, monomers, active ribozymes, oligonucleotides and lipids are shown to (1) cycle between dry and wet states, enabling the central step of RNA phosphorylation, (2) accumulate at the gas-water interface to drastically increase ribozymatic activity, (3) condense into hydrogels, (4) form pure crystals and (5) encapsulate into protecting vesicle aggregates that subsequently undergo fission.

Combined effusive-explosive silicic volcanism straddles the multiphase viscous-to-brittle transition.

Magma is a viscoelastic fluid that can support fracture propagation when local shear stresses are high, or relax and flow when shear stresses are low. Here we present experiments to confirm this using synthetic and natural magmatic liquids across eruptive conditions and use Maxwell's linear viscoelasticity to parameterize our results and predict the maximum stresses that can be supported during flow. This model proves universal across a large range of liquid compositions, temperatures, crystallinity and rates of strain relevant to shallow crustal magma ascent.

Aggregation in particle rich environments: a textural study of examples from volcanic eruptions, meteorite impacts, and fluidized bed processing.

Aggregation is a common process occurring in many diverse particulate gas mixtures (e.g. those derived from explosive volcanic eruptions, meteorite impact events, and fluid bed processing).

Volcanic Ash Activates the NLRP3 Inflammasome in Murine and Human Macrophages.

Volcanic ash is a heterogeneous mineral dust that is typically composed of a mixture of amorphous (glass) and crystalline (mineral) fragments. It commonly contains an abundance of the crystalline silica (SiO) polymorph cristobalite. Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome, a cytosolic receptor complex that plays a critical role in driving inflammatory immune responses.

Topological inversions in coalescing granular media control fluid-flow regimes.

Sintering-or coalescence-of viscous droplets is an essential process in many natural and industrial scenarios. Current physical models of the dynamics of sintering are limited by the lack of an explicit account of the evolution of microstructural geometry. Here, we use high-speed time-resolved x-ray tomography to image the evolving geometry of a sintering system of viscous droplets, and use lattice Boltzmann simulations of creeping fluid flow through the reconstructed pore space to determine its permeability.