Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 173-197).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: David B. Goldstein and Philip L. Varghese. Vita. Includes bibliographical references.

No description available.

Eruption dynamics are sensitive to ash aggregation, and ash aggregates (e.g. accretionary lapilli) are commonly found in eruptive deposits, yet few experiments have been conducted on aggregation phenomena using natural materials. Experiments were developed to produce a probabilistic relationship for the efficiency of ash aggregation with respect to particle size, collision kinetic energy and atmospheric water vapor. The laboratory experiments were carried out in an enclosed tank designed to allow for the control of atmospheric water vapor. A synthetic ash proxy, ballotini, and ash from the 2006 eruption of Tungurahua, in Ecuador, were examined for their aggregation potential. Image data was recorded with a high speed camera and post-processed to determine the number of collisions, energy of collisions and probability of aggregation. Aggregation efficiency was dominantly controlled by collision kinetic energy and little to no dependence on atmospheric water vapor was seen in the range of relative humidity conditions tested, 20 to 80%. Equations governing the relationships between aggregation efficiency and collision kinetic energy and the related particle Stokes number, respectively, were determined for implementation into large scale numerical volcanic models.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "May 2007." Includes bibliographical references (p. 239-253). Also available via the World Wide Web.

Volcanic eruptions pose hazards to life and insfrastructure, and contribute to the resurfacing of earth and other planetary bodies. Lavas and magmas are multi-phase suspensions of silicate melts (liquids), solid crystals, and vapor bubbles, and solidify into glass and rock upon cooling. The interactions between phases place important controls on the dynamics and timescales of magma and lava transport and emplacement. The purpose of this thesis is to explore the role of multiphase interactions in controlling eruption dynamics and inform conceptual and numerical models for hazard prediction. In Chapters 1 and 2, centimeter to meter scale analog experiments are used to explore the multi-phase rheological properties and flow behaviors of bubble- and particle-bearing suspensions. Optical imaging of dam-break experiments presented in Chapter 1 expand existing experimental parameter ranges for lava analogs to higher bubble concentrations than existing datasets (up to 82% by volume bubbles and 37% by volume particles). I develop a constitutive relationship for threephase relative viscosity, and demonstrate that at the low strain-rate conditions relevant to many natural lava flows, accounting for the rheological effect of bubbles can result in the prediction of slower runout speeds. Chapter 2 expands upon the work of Chapter 1 using different analog materials observed using nuclear magnetic resonance imaging (MRI) phase-contrast velocimetry (PCV) to measure velocity in the flow interior of three-phase dam-break experiments. I find that for high-aspect ratio particles (sesame seeds), phase segregation into shear bands readily occurs, even at low particle fraction (20%) and results in strain localization. I suggest that the presence of shear bands can lead to faster flow runout than predicted using assumptions of bulk rheology. Chapter 3 analyzes thermal infrared (IR) time-lapse photography and videography of Hawaiian to Strombolian explosive activity during the 2021 eruption of Cumbre Vieja volcano, La Palma, Canary Islands, Spain. Images are analyzed to find time series of apparent plume radius, velocity, and apparent volume flux of high-temperature gas and lava. I compare with other measures of eruptive activity, including remote observations of plume height, SO₂ flux, effusive flux, tremor, and events at the volcano edifice including edifice collapses and the opening of new vents. I find correlations between tremor and explosive flux, but no correlation with SO2 flux or effusive flux, which I interpret as evidence of bubble segregation, highlighting the role of phase segregation and temporal variability in material properties in natural systems. Finally, in Chapter 4, I develop a novel finite element model to explore the interaction between a viscous flow with a solidified crust, and the effect of these interactions on lava flow and lava dome emplacement. I develop a model that couples a temperature-dependent viscous interior with an elastic shell flowing into air, water, or dense atmospheres. The model expands upon existing numerical simulations used in volcanology to have direct applications to lava flows and domes on the sea floor, which accounts for a large portion of the volcanism on Earth, and volcanism on other planetary bodies. Additionally, the formation of levees or solidified flow fronts that fracture and lead to a restart of flow. These lava flow breakouts pose a significant hazard, but there are currently no volcanological community codes capable of using a physics-based approach to predict the timing or location of breakouts. The model in Chapter 4 is the first to allow for assessment of the likelihood of failure at the scale of a flow lobe. Chapter 4 describes the model formulation and verification, and validation against centimeter-scale molten basalt experiments. The dissertation as a whole integrates work using a variety of methods including analog experiments, observations of natural eruptions, and numerical simulations to contribute to our understanding of the effects of multi-phase interactions on volcanic eruptions.

Thesis (Ph. D.)--University of Canterbury, 2007. / Title from PDF title page (viewed on Feb. 23, 2008). Includes bibliographical references (p. 239-253).

Volcanogenic lightning has a long documented history in the scientific field, though its origins are still poorly understood. The interactions leading to electrification of ash plumes is essentially a function of the microphysics controlling and affecting ash particle collisions. This thesis presents measurements made on charged particle interactions in a fluidized bed, with large-scale applications to the phenomenon of volcanogenic lightning and charged particle dynamics in volcanic plumes. Using a fluidized bed of ash samples taken from Ecuador's Volcán Tungurahua, particles are introduced to a collisional environment, where they acquire an associated polarity. A charged copper plate is used to collect particles of a given polarity, and particle size distributions are obtained for different weight fractions of the ash. It is observed that relatively smaller particles acquire a net negative charge, while larger particles in the sample charge positively. This is a well-documented occurrence with perfectly spherical, chemically identical samples, but this work represents one of the first applications of the principle to volcanic ash. Image analysis is preformed to determine the size distribution associated with specific polarities, and the associated minimum charge on each particle is calculated based on the plate collection height and particle size. We also present results that demonstrate the relationship between particle collisions and the amount of charge exchanged. Using techniques developed to examine the collision rate within a flow, combined with the charging rates determined from this experiment, we determine a maximum charge exchange rate of 1.28±0.23 electrons transferred per collision.

This research involves a study of a 2 km thick volcanic succession which accumulated during the opening stages of the precursor of the Reykjanes-Langjökull axial rift zone in W-Iceland, between 6-3 m.y. Following the initial accumulation of olivine tholeiite lavas, which lie unconformably on an older crustal basement 10-13 m.y.), a central volcano developed in the Hafnarfjall-Skarðsheiði area. It was active for some 1.5 m.y. and consists of four volcanic phases: I. The Brekkufjall phase is characterized by basaltic volcanism followed by voluminous and copious extrusions of differentiated rocks culminating in a sudden caldera collapse (c.5 km wide) in Brekkufjall. II. During the Hafnarfjall phase a thick extrusive sequence of basaltic to rhyolitic compositions accumulated, mainly fed by ENE fissures. During the gradual subsidence of the Hafnarfjall caldera (7 by 5 km) a marked decrease occurred in lava accumulation rate outside the caldera. Epicentres of three cone sheet swarms coincide in time and space with three basinal structures of this caldera. III. The Skarðsheiði phase is characterized by N-S fissuring and a marked bimodal basalt-rhyolite lava accumulation. IV. Remnants of the Heioarhorn phase include compositions ranging from basalts to rhyolites. The western boundary of the axial rift zone is marked by large intrusives, basalt flexuring, a sheet swarm and the disappearance of dyke swarms. The lenticular unit was later buried by lavas of the Hvalfjörður lenticular unit. Rocks of the central volcano follow the Þingrmúli trend, but is discontinuous in the basal tic andesite range. Basalts (frequently porphyritic) with relatively monotonous compositions and low LIL abundancies predominate during episodes of low extrusion rate whereas high elemental dispersion characterizes basalts of high extrusion rate episodes. The basalt compositions are believed to be controlled more by partial melting processes rather than by episodes of low-pressure fractionation. The differentiated rocks are considered to have predominantly formed by partial melting of the lower crust.

No description available.