@article{seropian_higginbotham_kennedy_schaefer_walter_soldati_2023, title={The Effect of Mechanical Shaking on the Rising Velocity of Bubbles in High-Viscosity Shear-Thinning Fluids}, volume={128}, ISSN={["2169-9356"]}, DOI={10.1029/2022JB025741}, abstractNote={The rising velocity of an air bubble in a non‐Newtonian shear‐thinning fluid at low Reynolds numbers is generally similar to the Newtonian case given by Stokes' law. However, when the shear‐thinning fluid is subject to mechanical oscillations, the rising velocity could significantly increase. Here, we present a series of experiments quantifying the rising velocity of single bubbles during shaking in very high‐viscosity (2,000–30,000 Pa·s) shear‐thinning silicone oils. Air bubbles (18–30 mm diameter) were injected in a tank mounted on a shaking table. The tank was horizontally oscillated, at accelerations between 0.4 and 2 g. We observed a small increase in the rising velocity of the shaking cases at our experimental conditions. The increase was larger when bubbles were large and accelerations were high. Larger accelerations experienced the largest observational errors and we emphasize the exploratory nature of our results. We also measured the change in bubble diameter during the oscillations and computed the shear rate at the bubble surface. Maximum shear rates were in the range of 0.04–0.08 s−1. At these shear rates, our analysis indicates that shear thinning behavior of our analog fluids is expected to be small and compete with elastic behavior. This transitional viscous/elastic regime helps explain the small and variable results of our experiments. Our results are relevant to the study of earthquake‐volcano interactions. Most crystal‐free silicate melts would exhibit a purely viscous, shear‐thinning behavior in a natural scenario. Seismically enhanced bubble rise could offer an explanation for the observed increased degassing and unrest following large earthquakes.}, number={5}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH}, author={Seropian, Gilles and Higginbotham, Kaylon and Kennedy, Ben M. and Schaefer, Lauren N. and Walter, Thomas R. and Soldati, Arianna}, year={2023}, month={May} }
 @article{keller_tornos_hanchar_pietruszka_soldati_dingwell_suckale_2022, title={Genetic model of the El Laco magnetite-apatite deposits by extrusion of iron-rich melt}, volume={13}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-022-33302-z}, abstractNote={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. Here, we test the genetic hypothesis that an Fe-rich melt separated from silicate magma and ascended along collapse-related fractures. We complement recent analyses with thermodynamic modelling to corroborate Fe-Si liquid immiscibility evident in melt inclusions at El Laco and present viscometry of Fe- and Si-rich melts to assess the time and length scales of immiscible liquid separation. Using a rock deformation model, we demonstrate that volcano collapse can form failure zones extending towards the edifice flanks along which the ore liquid ascends towards extrusion driven by vapour exsolution despite its high density. Our results support the proposed magmatic genesis for the El Laco deposits. Geochemical and textural similarities indicate magnetite-apatite deposits elsewhere form by similar processes.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Keller, Tobias and Tornos, Fernando and Hanchar, John M. and Pietruszka, Dorota K. and Soldati, Arianna and Dingwell, Donald B. and Suckale, Jenny}, year={2022}, month={Oct} }
 @article{soldati_houghton_dingwell_2021, title={A lower bound on the rheological evolution of magmatic liquids during the 2018 Kilauea eruption}, volume={576}, ISSN={["1872-6836"]}, DOI={10.1016/j.chemgeo.2021.120272}, abstractNote={During the four month-long 2018 Kilauea Lower East Rift Zone (LERZ) eruption, the bulk chemical compositions of magma ranged from basalt to andesite. This compositional variety was reflected in eruptive style, which ranged from Hawaiian fountaining to Strombolian explosions. Here, we quantified the evolution of the melt viscosity of the eruptive products through high-temperature laboratory experiments performed on a representative sample set that was collected in the field immediately after the eruptive series. This suite of 18 samples comprises all major eruptive phases (early phase I, late phase I, phase II, phase III, fissure 17). The results illustrate the significant rheological variability of the eruptive products, and appear to link to variations in eruption dynamics. We propose a new standard for the rheological study of a multi-episode effusive eruption, whereby precise, near-real-time viscosity results are obtained during ongoing eruptions will become a routine component of volcano monitoring during future eruptive events. During the 2018 eruption of Kilauea, emerging magma spanned a wider compositional range than ever previously observed during a single eruption. This compositional diversity was matched by a variety in eruptive styles, which ranged from more persistent fountaining to short-lived explosions. Immediately after the eruption ceased, we collected a representative suite of 18 samples in the field, which comprises all major eruptive phases (early phase I, late phase I, phase II, phase III, fissure 17). We measured the melt viscosity of such samples through high-temperature laboratory experiments. The results illustrate a significant variability in viscosity, which is linked to the highly variable eruption dynamics. Here we propose a new standard for the study of multi-episode effusive eruptions from a viscosity standpoint. We hope and expect that this methodology will become routine practice during future eruption.}, journal={CHEMICAL GEOLOGY}, author={Soldati, A. and Houghton, B. F. and Dingwell, D. B.}, year={2021}, month={Aug} }
 @article{colombier_vasseur_houghton_caceres_scheu_kueppers_thivet_gurioli_montanaro_soldati_et al._2021, title={Degassing and gas percolation in basaltic magmas}, volume={573}, ISSN={["1385-013X"]}, DOI={10.1016/j.epsl.2021.117134}, abstractNote={Due to their generally low eruptive melt viscosities and concomitant high diffusivities of volatiles, basaltic magmas degas relatively efficiently. This relative efficiency, combined with variations in style, extent, timing and length scales of degassing govern the range of eruptive styles observed at basaltic volcanoes. The result is a surprising complexity of degassing regimes and products in basaltic volcanism. In particular, the transition between closed- and open-system degassing at low pressure at the percolation threshold may strongly affect the type of eruption. Here we aim to better understand degassing and gas percolation processes in basaltic magmas and their implications for eruptive style. Combining new and literature data, we present a database of vesicle metrics in basaltic rocks including vesicularity, vesicle number density, vesicle size distribution (and its polydispersivity), vesicle connectivity and permeability. We combine these textural and petrophysical data with a numerical model of percolation for systems having polydisperse vesicle size distributions. Using this model, we also evaluate different definitions of vesicle connectivity inherent to different measurement techniques. Our results show that polydispersivity exerts a strong control on the percolation threshold of basaltic magmas and consequently on eruptive style. Intermediate to highly polydisperse bubble networks are more typical of Hawaiian activity and are characterized by higher values of percolation threshold. This results in delayed coalescence and an increase in magma vesicularity hindering the formation of large decoupled and buoyant bubbles, which in turn can promote magma acceleration, fragmentation by inertia below the percolation threshold and sustained fountaining activity. Bubble populations with lower polydispersivity, typical of Strombolian eruptions, promote early coalescence prior to fragmentation, which in turn may lead to the formation of large decoupled slugs or gas pockets and/or plugs at the surface via outgassing. Further, we discuss the implications of our findings for Plinian, violent Strombolian, Surtseyan, deep submarine and effusive basaltic eruptions.}, journal={EARTH AND PLANETARY SCIENCE LETTERS}, author={Colombier, Mathieu and Vasseur, Jeremie and Houghton, Bruce F. and Caceres, Francisco and Scheu, Bettina and Kueppers, Ulrich and Thivet, Simon and Gurioli, Lucia and Montanaro, Cristian and Soldati, Arianna and et al.}, year={2021}, month={Nov} }
 @article{soldati_farrell_wysocki_karson_2021, title={Imagining and constraining ferrovolcanic eruptions and landscapes through large-scale experiments}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-021-21582-w}, abstractNote={Abstract Ferrovolcanism, yet to be directly observed, is the most exotic and poorly understood predicted manifestation of planetary volcanism. Large-scale experiments carried out at the Syracuse Lava Project offer insight into the emplacement dynamics of metallic flows as well as coeval metallic and silicate flows. Here, we find that, under the same environmental conditions, higher-density/lower-viscosity metallic lava moves ten times faster than lower-density/higher-viscosity silicate lava. The overall morphology of the silicate flow is not significantly affected by the co-emplacement of a metallic flow. Rather, the metallic flow is largely decoupled from the silicate flow, occurring mainly in braided channels underneath the silicate flow and as low-relief breakouts from the silicate flow front. Turbulent interactions at the metallic-silicate flow interface result in mingling of the two liquids, preserved as erosional surfaces and sharp contacts. The results have important implications for the interpretation of possible ferrovolcanic landscapes across our solar system.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Soldati, A. and Farrell, J. A. and Wysocki, R. and Karson, J. A.}, year={2021}, month={Mar} }
 @article{soldati_houghton_dingwell_2021, title={Subliquidus rheology of basalt from the 2018 Lower East Rift Zone Kilauea eruption: isothermal vs. dynamic expression}, volume={581}, ISSN={["1872-6836"]}, DOI={10.1016/j.chemgeo.2021.120363}, abstractNote={The dynamic effects of temperature and strain rate on rheology of crystal-bearing magma are investigated. We conducted high-temperature rheometry experiments in both isothermal and dynamic crystallization regimes and recovered textural data for the isothermal runs. We propose a framework for the parameterization of magma rheology, via an equation describing how the rheological cutoff temperature (the temperature at which magma stops flowing) varies as a function of cooling rate and strain rate. This equation may be used to inform rapid response in effusive crises. Cooling rate has the larger effect, with higher cooling rates yielding lower cutoff temperatures; higher strain rates yield higher cutoff temperatures. Textural analyses reveal differences in crystal aspect ratios, such that higher cooling rates produce only subequant crystals, whereas lower cooling rates also produce a second, higher aspect ratio crystal population. We identify this textural variation as the physical cause for the dependence of cutoff temperature on cooling rate. As lava cools, it crystallizes. Eventually, this crystallinity becomes so high that the lava can no longer advance. The temperature at which the crystals “lock up” the lava is called the “rheological cutoff temperature.” This depends, in principle, on the crystallization pathway, which is influenced by both the cooling rate and the strain rate of the lava flow. We conducted rheological experiments on 2018 Kilauea lavas along different crystallization pathways. We determined that higher cooling rates (5 °C/min) yield cooler cutoffs (983–1058 °C), and higher strain rates (8 s−1) yield hotter cutoffs (1058–1093 °C). Moreover, the cooling rate affects the cutoff temperature more than the strain rate. Through a complementary set of experiments, we found that the physical cause for the dependence of the cutoff temperature on the cooling rate is crystal aspect ratio (length/width). At any given crystallinity, crystals with a higher aspect ratio interact more, and lock at higher temperatures. Higher cooling rates produce only crystals with an aspect ratio of 1, whereas lower cooling rates produce higher aspect ratio crystals as well. Therefore, lava which has cooled more slowly, which crystallizes higher aspect ratio crystals, has a higher rheological cutoff temperature.}, journal={CHEMICAL GEOLOGY}, author={Soldati, A. and Houghton, B. F. and Dingwell, D. B.}, year={2021}, month={Oct} }