Pore connectivity is a measure of the fraction pore space (vesicles, voids or cracks) in material that interconnected on system length scale. fundamentally related to permeability, which has been shown control magma outgassing and explosive potential during ascent shallowest part crust. Here, we compile database porosity from published sources supplement this with additional measurements, using natural volcanic rocks produced broad range eruptive styles bulk composition. The comprises 2715...

[1] Sintering and densification are ubiquitous processes influencing the emplacement of both effusive explosive products volcanic eruptions. Here we sinter ash-size fragments a synthetic National Institute Standards Technology viscosity standard glass at temperatures which resultant melt has ∼108-109 Pa.s 1bar to assess sintering dynamics under near-surface conditions. We track strength recovery via uniaxial compressive tests. observe that ash is dominantly time dependent, temperature grain...

Abstract Elastic waves are generated when brittle materials subjected to increasing strain. Their number and energy increase non-linearly, ending in a system-sized catastrophic failure event. Accelerating rates of geophysical signals ( e.g. , seismicity deformation) preceding large-scale dynamic can serve as proxies for damage accumulation the Failure Forecast Method (FFM). Here we test hypothesis that style mechanisms deformation accuracy FFM, both tightly controlled by degree...

In sedimentary basins and volcanic edifices, granular materials undergo densification that results in a decrease of porosity permeability.Understanding the link between permeability is central to predicting fluid migration crust during outgassing.Sedimentary diagenesis welding both involve transition an initially material non-granular (porous dense) rock.Scaling laws for prediction such remain contested.Here, based on collated literature data range rocks which initial state was granular, we...

Abstract Volcanic ash is often deposited in a hot state. containing glass, above the glass transition interval, has potential to sinter viscously both itself (particle‐particle) and exposed surfaces. Here we constrain kinetics of this process experimentally under nonisothermal conditions using standard glasses. In absence external load, dominantly driven by surface relaxation. such cases sintering rate limited melt viscosity, size particles melt‐vapor interfacial tension. We propose...

Geothermal projects in the Upper Rhine Graben aim to harness thermal anomalies that have arisen due hydrothermal circulation within granitic basement and overlying Permo-Triassic sedimentary units. We present here a systematic microstructural, mineralogical, petrophysical characterisation of lowermost unit this succession—the Buntsandstein—sampled from exploration well EPS-1 at Soultz-sous-Forêts geothermal site (France). Twelve depths were sampled (from 1008 1414 m) cylindrical cores...

Tuffisites are veins of variably sintered, pyroclastic particles that form in conduits and lava domes as a result localized fragmentation events during gas-and-ash explosions. Those observed in-situ on the active 2012 dome Volcán de Colima range from voids with intra-clasts showing little movement interpreted to be failure-nuclei, sub-parallel lenses sintered granular aggregate horizons, through infilled fractures evidence viscous remobilization. All tuffisites show sintering. Further...

We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders spherical glass beads are heated above their transition temperature, causing them densify under surface tension. determine evolving volume bead pack at high spatial and temporal resolution. use these data test a range existing models. extend models account for time-dependent droplet viscosity that results from non-isothermal conditions, non-zero final porosity. also present method...

Abstract Degassing dynamics play a crucial role in controlling the explosivity of magma at erupting volcanoes. magmatic water typically involves bubble nucleation and growth, which drive ascent. Crystals suspended may influence both growth bubbles. Micron- to centimeter-sized crystals can cause heterogeneous facilitate coalescence. Nanometer-scale crystalline phases, so-called “nanolites”, are an underreported phenomenon could exert primary control on eruptive style silicic Yet nanolites...

Silicic volcanic activity has long been framed as either violently explosive or gently effusive. However, recent observations demonstrate that and effusive behavior can occur simultaneously. Here, we propose rhyolitic magma feeding subaerial eruptions generally fragments during ascent through the upper crust result from conduit blockage sintering of pyroclastic products deeper cryptic fragmentation. Our proposal is supported by (i) lavas are volatile depleted; (ii) textural evidence supports...

The fusion dynamics of volcanic ash strongly impacts deposition in hot parts jet engines. In this study, we investigate the sintering behavior using natural intermediate composition, erupted 2012 at Santiaguito Volcano, Guatemala. A material science procedure was followed which monitored geometrical evolution cylindrical-shaped compact upon heating from 50 to 1400°C a microscope. Combined morphological, mineralogical, and rheological analyses helped define during constrain their sticking...

The 2010 eruption of Eyjafjallajökull (Iceland) and the 2011 eruptions Grimsvötn (Iceland), Cordon Caulle (Chile) Nabro (Ethiopia) have drastically heightened level awareness in general population how volcanic activity can affect everyday life by disrupting air travel. ingestion airborne matter into jet turbines may cause harm (1) abrasion engine parts, (2) destabilisation fuel/air mix its dynamics (3) melting sintering ash onto parts. To investigate behaviour upon reheating, we performed...

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

Columnar joints form by cracking during cooling-induced contraction of lava, allowing hydrothermal fluid circulation. A lack direct observations their formation has led to ambiguity about the temperature window jointing and its impact on flow. Here we develop a novel thermo-mechanical experiment disclose columnar in lavas. Using basalts from Eyjafjallajökull volcano (Iceland) show that cooling induces stress build-up below solidus (980 °C), resulting localised macroscopic failure between 890...

Abstract The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability lava domes and shallow conduits. Lava generally consist a porous outer carapace surrounding denser core with internal shear zones variable porosity. Here we examine densification using uniaxial compression experiments on variably crystalline rhyolitic dome lavas from Taupo Volcanic Zone. Experiments were conducted 900°C an applied stress 3 MPa to 60% strain, while...

Abstract Surtseyan eruptions are shallow to emergent subaqueous explosive that owe much of their characteristic behavior the interaction magma with water. The difference in thermal properties between water and air affects cooling postfragmentation vesiculation processes erupted into column. Here we study during 2009 2014–2015 Hunga Tonga‐Hunga Ha'apai volcano by combining 2‐D 3‐D vesicle‐scale analyses lapilli bombs numerical modeling. Most show gradual textural variations from rim core....

A major hazard to jet engines posed by volcanic ash is linked the wetting and spreading of molten droplets on engine component surfaces. Here, using sessile drop method, we study evolution wettability ash. We employ rapid temperature changes up 1040-1450 °C, replicate heating conditions experienced entering an operating engine. In this scenario, samples densify as particles coalesce under surface tension until they form a large system-sized droplet (containing remnant gas bubbles crystals),...

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

Abstract Taupō volcano, New Zealand, is a large caldera volcano that has been highly active through the Holocene. It most recently erupted ∼1,800 years ago but there have multiple periods of historic volcanic unrest. We use seismological and geodetic analysis to show in 2019 underwent period unrest characterized by increased seismic activity swarms was accompanied ground deformation within caldera. The earthquakes, which include non‐double‐couple events, serve outline an aseismic zone...