R-3 Repository :: Browsing by Author "Gonnermann, Helge M."

Browsing by Author "Gonnermann, Helge M."

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Biochar particle size, shape, and porosity act together to influence soil water properties
(Public Library of Science, 2017) Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A.; Gonnermann, Helge M.
Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar’s effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar’s intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles’ elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils.
Effect of freeze-thaw cycling on grain size of biochar
(Public Library of Science, 2018) Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A.; Wahab, Leila M.; Gonnermann, Helge M.; Nittrouer, Jeffrey A.
Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle.
Evolution of Glacially Derived Freshwater and Overpressure in the Massachusetts Shelf: An Integration of Geophysical and Numerical Methods
(2013-10-24) Siegel, Jacob; Dugan, Brandon; Gonnermann, Helge M.; Anderson, John B.; Bedient, Philip B.
The continental shelf offshore Massachusetts, USA experienced repeated glaciations throughout the late Pleistocene that emplaced freshwater and generated overpressure in the shelf sediments that still remains offshore. To show this, I processed and interpreted high-resolution, multi-channel seismic data that was collected offshore Massachusetts to infer the glacial history and to incorporate the glacial history into numerical modeling. Interpretations of the seismic data reveal the shelf stratigraphy and the location of a late Pleistocene (Marine Oxygen Isotope Stage 12) ice sheet. The ice sheet extended 100 km farther onto the shelf compared to the Laurentide ice sheet during the Last Glacial Maximum (LGM). It also contained an ice stream that was likely sourced from the Gulf of Maine. I show that the late Pleistocene ice sheet influenced the shelf hydrogeology by generating overpressure and emplacing freshwater into the shelf sediments. Overpressure is modeled in 1D from high-resolution, full-waveform inversion p-wave velocities obtained from the seismic data and from a finite-difference fluid flow model that accounts for sedimentation and ice sheet loading. The results demonstrate how loading from the late Pleistocene ice sheet caused focused fluid flow that created localized zones of overpressure nearly 1-2 MPa in offshore sediments. Freshwater emplacement into shelf sediments is estimated with a finite-element, variable-density model of fluid flow and heat and solute transport that accounts for ice-sheet loading and sea-level change. The model helps explain how the late Pleistocene ice sheet emplaced nearly 100 km3 of freshwater into the sediments. Our results thus integrate seismic interpretations of ice sheet history with numerical techniques of fluid flow modeling to show how the past glacial history influenced the present freshwater distribution.
Identifying rheological regimes within pyroclastic density currents
(Springer Nature, 2024) Jones, Thomas J.; Shetty, Abhishek; Chalk, Caitlin; Dufek, Josef; Gonnermann, Helge M.
Pyroclastic density currents (PDCs) are the most lethal of all volcanic hazards. An ongoing challenge is to accurately forecast their run-out distance such that effective mitigation strategies can be implemented. Central to this goal is an understanding of the flow mobility—a quantitative rheological model detailing how the high temperature gas-pyroclast mixtures propagate. This is currently unknown, yet critical to accurately forecast the run-out distance. Here, we use a laboratory apparatus to perform rheological measurements on real gas-pyroclast mixtures at dynamic conditions found in concentrated to intermediate pumice-rich PDCs. We find their rheology to be non-Newtonian featuring (i) a yield stress where deposition occurs; (ii) shear-thinning behavior that promotes channel formation and local increases in velocity and (iii) shear-thickening behavior that promotes decoupling and potential co-PDC plume formation. We provide a universal regime diagram delineating these behaviors and illustrating how flow can transition between them during transport.
NanoSIMS results from olivine-hosted melt embayments: Magma ascent rate during explosive basaltic eruptions
(Elsevier, 2014) Lloyd, Alexander S.; Ruprecht, Philipp; Hauri, Erik H.; Rose, William; Gonnermann, Helge M.; Plank, Terry
The explosivity of volcanic eruptions is governed in part by the rate at which magma ascends and degasses. Because the time scales of eruptive processes can be exceptionally fast relative to standard geochronometers, magma ascent rate remains difficult to quantify. Here we use as a chronometer concentration gradients of volatile species along open melt embayments within olivine crystals. Continuous degassing of the external melt during magma ascent results in diffusion of volatile species from embayment interiors to the bubble located at their outlets. The novel aspect of this study is the measurement of concentration gradients in five volatile elements (CO2, H2O, S, Cl, F) at fine-scale (5–10 μm) using the NanoSIMS. The wide range in diffusivity and solubility of these different volatiles provides multiple constraints on ascent timescales over a range of depths. We focus on four 100–200 μm, olivine-hosted embayments erupted on October 17, 1974 during the sub-Plinian eruption of Volcán de Fuego. H2O, CO2, and S all decrease toward the embayment outlet bubble, while F and Cl increase or remain roughly constant. Compared to an extensive melt inclusion suite from the same day of the eruption, the embayments have lost both H2O and CO2 throughout the entire length of the embayment. We fit the profiles with a 1-D numerical diffusion model that allows varying diffusivities and external melt concentrations as a function of pressure. Assuming a constant decompression rate from the magma storage region at approximately 220 MPa to the surface, H2O, CO2 and S profiles for all embayments can be fit with a relatively narrow range in decompression rates of 0.3–0.5 MPa/s, equivalent to 11–17 m/s ascent velocity and an 8 to 12 minute duration of magma ascent from ~ 10 km depth. A two stage decompression model takes advantage of the different depth ranges over which CO2 and H2O degas, and produces good fits given an initial stage of slow decompression (0.05–0.3 MPa/s) at high pressure (> 145 MPa), with similar decompression rates to the single-stage model for the shallower stage. The magma ascent rates reported here are among the first for explosive basaltic eruptions and demonstrate the potential of the embayment method for quantifying magmatic timescales associated with eruptions of different vigor.
Outgassing through magmatic fractures enables effusive eruption of silicic magma
(Elsevier, 2022) Crozier, Josh; Tramontano, Samantha; Forte, Pablo; Oliva, Sarah Jaye C.; Gonnermann, Helge M.; Lev, Einat; Manga, Michael; Myers, Madison; Rader, Erika; Ruprecht, Philipp; Tuffen, Hugh; Paisley, Rebecca; Houghton, Bruce F.; Shea, Thomas; Schipper, C. Ian; Castro, Jonathan M.
Several mechanisms have been proposed to allow highly viscous silicic magma to outgas efficiently enough to erupt effusively. There is increasing evidence that challenges the classic foam-collapse model in which gas escapes through permeable bubble networks, and instead suggests that magmatic fracturing and/or accompanying localized fragmentation and welding within the conduit play an important role in outgassing. The 2011–2012 eruption at Cordón Caulle volcano, Chile, provides direct observations of the role of magmatic fractures. This eruption exhibited a months-long hybrid phase, in which rhyolitic lava extrusion was accompanied by vigorous gas-and-tephra venting through fractures in the lava dome surface. Some of these fractures were preserved as tuffisites (tephra-filled veins) in erupted lava and bombs. We integrate constraints from petrologic analyses of erupted products and video analyses of gas-and-tephra venting to construct a model for magma ascent in a conduit. The one-dimensional, two-phase, steady-state model considers outgassing through deforming permeable bubble networks, magmatic fractures, and adjacent wall rock. Simulations for a range of plausible magma ascent conditions indicate that the eruption of low-porosity lava observed at Cordón Caulle volcano occurs because of significant gas flux through fracture networks in the upper conduit. This modeling emphasizes the important role that outgassing through magmatic fractures plays in sustaining effusive or hybrid eruptions of silicic magma and in facilitating explosive-effusive transitions.
Permeability During Magma Expansion and Compaction
(Wiley, 2017) Gonnermann, Helge M.; Giachetti, Thomas; Fliedner, Céline; Nguyen, Chinh T.; Houghton, Bruce F.; Crozier, Joshua A.; Carey, Rebecca J.
Plinian lapilli from the 1060 Common Era Glass Mountain rhyolitic eruption of Medicine Lake Volcano, California, were collected and analyzed for vesicularity and permeability. A subset of the samples were deformed at a temperature of 975°, under shear and normal stress, and postdeformation porosities and permeabilities were measured. Almost all undeformed samples fall within a narrow range of vesicularity (0.7–0.9), encompassing permeabilities between approximately 10−15 m2 and 10−10 m2. A percolation threshold of approximately 0.7 is required to fit the data by a power law, whereas a percolation threshold of approximately 0.5 is estimated by fitting connected and total vesicularity using percolation modeling. The Glass Mountain samples completely overlap with a range of explosively erupted silicic samples, and it remains unclear whether the erupting magmas became permeable at porosities of approximately 0.7 or at lower values. Sample deformation resulted in compaction and vesicle connectivity either increased or decreased. At small strains permeability of some samples increased, but at higher strains permeability decreased. Samples remain permeable down to vesicularities of less than 0.2, consistent with a potential hysteresis in permeability‐porosity between expansion (vesiculation) and compaction (outgassing). We attribute this to retention of vesicle interconnectivity, albeit at reduced vesicle size, as well as bubble coalescence during shear deformation. We provide an equation that approximates the change in permeability during compaction. Based on a comparison with data from effusively erupted silicic samples, we propose that this equation can be used to model the change in permeability during compaction of effusively erupting magmas.
Reconciling bubble nucleation in explosive eruptions with geospeedometers
(Springer Nature, 2021) Hajimirza, Sahand; Gonnermann, Helge M.; Gardner, James E.
Magma from Plinian volcanic eruptions contains an extraordinarily large numbers of bubbles. Nucleation of those bubbles occurs because pressure decreases as magma rises to the surface. As a consequence, dissolved magmatic volatiles, such as water, become supersaturated and cause bubbles to nucleate. At the same time, diffusion of volatiles into existing bubbles reduces supersaturation, resulting in a dynamical feedback between rates of nucleation due to magma decompression and volatile diffusion. Because nucleation rate increases with supersaturation, bubble number density (BND) provides a proxy record of decompression rate, and hence the intensity of eruption dynamics. Using numerical modeling of bubble nucleation, we reconcile a long-standing discrepancy in decompression rate estimated from BND and independent geospeedometers. We demonstrate that BND provides a record of the time-averaged decompression rate that is consistent with independent geospeedometers, if bubble nucleation is heterogeneous and facilitated by magnetite crystals.
Relating vesicle shapes in pyroclasts to eruption styles
(Springer-Verlag, 2013) Moitra, Pranabendu; Gonnermann, Helge M.; Houghton, Bruce F.; Giachetti, Thomas
Vesicles in pyroclasts provide a direct record of conduit conditions during explosive volcanic eruptions. Although their numbers and sizes are used routinely to infer aspects of eruption dynamics, vesicle shape remains an underutilized parameter. We have quantified vesicle shapes in pyroclasts from fall deposits of seven explosive eruptions of different styles, using the dimensionless shape factor , a measure of the degree of complexity of the bounding surface of an object. For each of the seven eruptions, we have also estimated the capillary number, Ca, from the magma expansion velocity through coupled diffusive bubble growth and conduit flow modeling. We find that Ω is smaller for eruptions with Ca 1 than for eruptions with Ca 1. Consistent with previous studies, we interpret these results as an expression of the relative importance of structural changes during magma decompression and bubble growth, such as coalescence and shape relaxation of bubbles by capillary stresses. Among the samples analyzed, Strombolian and Hawaiian fire-fountain eruptions have Ca 1, in contrast to Vulcanian, Plinian, and ultraplinian eruptions. Interestingly, the basaltic Plinian eruptions of Tarawera volcano, New Zealand in 1886 and Mt. Etna, Italy in 122 BC, for which the cause of intense explosive activity has been controversial, are also characterized by Ca 1 and larger values of Ω than Strombolian and Hawaiian style (fire fountain) eruptions. We interpret this to be the consequence of syn-eruptive magma crystallization, resulting in high magma viscosity and reduced rates of bubble growth. Our model results indicate that during these basaltic Plinian eruptions, buildup of bubble overpressure resulted in brittle magma fragmentation.
The origin and evolution of the deep lithosphere beneath continental arcs: constraints from lower crustal and mantle xenoliths from the Sierra Nevada, California
(2013-11-18) Chin, Emily; Lee, Cin-Ty A.; Dasgupta, Rajdeep; Whitmire, Kenton H.; Gonnermann, Helge M.
Lower crustal and upper mantle xenoliths from the Sierra Nevada continental arc in California, USA reveal a complex P-T-X-t (pressure-temperature-composition-time) evolution of the deep lithosphere. Metasedimentary xenoliths, despite high quartz contents, preserve granulite-facies equilibration conditions, necessitating transport from the surface into the lower crust. U-Pb and Hf isotope data on detrital zircon in the metasediments support continental underthrusting coeval with the peak of arc magmatism. Mantle xenoliths, represented by spinel and garnet-bearing spinel peridotites, indicate that shallow (spinel-facies), high-degree melt residues underwent thickening, cooling, and metamorphism into refertilized garnet peridotites that equilibrated below 800 °C and ca. 3 GPa. The source of refertilizing melts appears to be the mantle wedge itself, rather than the subducting slab based on mass-balance models and oxygen isotopes. Textural disequilibria, particularly Al-depletion haloes between orthopyroxene and exsolved garnet in peridotites, are diagnostic features related to cooling and increasing pressure. Diffusion modeling indicate that such disequilibria formed within 6 to 8 Ma. Coupled Lu-Hf and Sm-Nd age data on garnet pyroxenites show a significant lag between closure of the two chronometers in a lower crustal pyroxenite, but negligible difference in the deepest websterites. As a whole, the Sierran xenolith data provide insights into the origin and evolution of a mature continental arc, particularly highlighting the importance of thickening in both the crust and mantle lithosphere.
Transport of Surfactant and Foam in Porous Media for Enhanced Oil Recovery Processes
(2013-09-16) Ma, Kun; Hirasaki, George J.; Biswal, Sibani Lisa; Miller, Clarence A.; Gonnermann, Helge M.
The use of foam-forming surfactants offers promise to improve sweep efficiency and mobility control for enhanced oil recovery (EOR). This thesis provides an in depth understanding of transport of surfactant and foam through porous media using a combination of laboratory experiments and numerical simulations. In particular, there are several issues in foam EOR processes that are examined. These include screening of surfactant adsorption onto representative rock surfaces, modeling of foam flow through porous media, and studying the effects of surface wettability and porous media heterogeneity. Surfactant adsorption onto rock surfaces is a main cause of foam chromatographic retardation as well as increased process cost. Successful foam application requires low surfactant adsorption on reservoir rock. The focus of this thesis is natural carbonate rock surfaces, such as dolomite. Surfactant adsorption was found to be highly dependent on electrostatic interactions between surfactants and rock surface. For example, the nonionic surfactant Tergitol 15-S-30 exhibits low adsorption on dolomite under alkaline conditions. In contrast, high adsorption of cationic surfactants was observed on some natural carbonate surfaces. XPS analysis reveals silicon and aluminum impurities exist in natural carbonates, but not in synthetic calcite. The high adsorption is due to the strong electrostatic interactions between the cationic surfactants and negative binding sites in silica and/or clay. There are a number of commercial foam simulators, but an approach to estimate foam modeling parameters from laboratory experiments is needed to simulate foam transport. A one-dimensional foam simulator is developed to simulate foam flow. Chromatographic retardation of surfactants caused by adsorption and by partition between phases is investigated. The parameters in the foam model are estimated with an approach utilizing both steady-state and transient experiments. By superimposing contour plots of the transition foam quality and the foam apparent viscosity, one can estimate the reference mobility reduction factor (fmmob) and the critical water saturation (fmdry) using the STARS foam model. The parameter epdry, which regulates the abruptness of the foam dry-out effect, can be estimated by a transient foam experiment in which 100% gas displaces surfactant solution at 100% water saturation. Micromodel experiments allow for pore-level visualization of foam transport. We have developed model porous media systems using polydimethylsiloxane. We developed a simple method to tune and pattern the wettability of polydimethylsiloxane (PDMS) to generate porous media models with specific structure and wettability. The effect of wettability on flow patterns is observed in gas-liquid flow. The use of foam to divert flow from high permeable to low permeable regions is demonstrated in a heterogeneous porous micromodel. Compared with 100% gas injection, surfactant-stabilized foam effectively improves the sweep of the aqueous fluid in both high and low permeability regions of the micromodel. The best performance of foam on fluid diversion is observed in the lamella-separated foam regime, where the presence of foam can enhance gas saturation in the low permeable region up to 45.1% at the time of gas breakthrough. In conclusion, this thesis provides new findings in surfactant adsorption onto mineral surfaces, in the methodology of estimating foam parameters for reservoir simulation, and in micromodel observations of foam flow through porous media. These findings will be useful to design foam flooding in EOR processes.

Browsing by Author "Gonnermann, Helge M."

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