Cette étude vise à mieux caractériser les propriétés physico-chimiques de systèmes magmatiques hydratés en contexte subductif. Nous nous intéressons en particulier au comportement d'éléments « traces » modificateurs de réseau (Ni et Zr), ainsi que d'éléments majeurs formateurs de réseau (Ga et Ge) dans ce type de géomatériaux. Le principe de l'étude repose essentiellement sur une approche expérimentale, visant à utiliser des systèmes de haute température et haute pression (cellule à enclumes diamant, presse Paris-Edinburgh) couplés à une méthode d'analyse par spectroscopie d'absorption des rayons X. Pour les différents systèmes chimiques abordés, les résultats obtenus à haute température et/ou haute pression mettent en évidence des comportements très différents pour nickel et pour le zirconium en fonction de la teneur en eau. L'environnement structural local autour du nickel apparaît fortement affecté par la présence d'eau, suggérant une interaction significative du nickel avec la phase aqueuse. En revanche, la structure locale autour du zirconium est reste pratiquement constante. De plus pour les éléments majeurs analogues (Ga et Ge), aucune modification structurale significative n'est mise en évidence en fonction de la température, de la pression ou encore de la teneur en eau ; ce qui tend à suggérer un effet « non-dépolymérisateur » de l'eau sur le réseau silicaté.<br />Des expériences complémentaires nous ont permis de mettre en évidence l'utilité des spectres d'absorption des rayons X pour la détermination in situ des concentrations en nickel, ainsi que de la densité des magmas silicatés hydratés. Les résultats mettent en évidence un coefficient de partage « eau/silicate » très inférieur à 1, suggérant une mobilisation faible, mais néanmoins significative, du nickel par la phase aqueuse lors de la remontée magmatique. Par ailleurs, des mesures de densité apparente de magmas hydratés, à environ 780 °C / 520 MPa, mettent en évidence une valeur proche de 1 g/cm3, suggérant un aspect structural de type « émulsion » particulièrement riche en eau, ainsi qu'une dynamique d'ascension magmatique en écoulement homogène très importante.

Graduation date: 2003 / Presentation date: 2002-06-03

Cette thèse concerne l'étude d'une famille de μ-actionneurs magnétiques en lévitation asservie.<br />Le principe est celui d'un aimant mobile ayant deux positions stables et une position instable. Parmi<br />les différentes applications de cette structure, un μ-positionneur est étudié plus en détails, avec la<br />conception, la modélisation et la réalisation d'une maquette centimétrique de ce μ-positionneur<br />asservi. La conception de μ-positionneur comprend l'étude du capteur capacitif de position et une<br />synthèse du correcteur pour l'asservissement. La modélisation introduit deux méthodes de calcul de la<br />force et du couple magnétostatiques exercés sur l'aimant mobile: méthode de charge équivalente et<br />méthode d'intégration volumique. Les deux méthodes sont validées et puis utilisées pour déterminer<br />la trajectoire de l'aimant mobile comportant 6 degrés de liberté. Une méthode mathématique utilisant<br />les quaternions est mise en oeuvre. La modélisation permet l'analyse du comportement de différents<br />μ-actionneurs magnétiques ainsi que la vérification de la stabilité de l'asservissement. La réalisation<br />de la maquette centimétrique décrit la fabrication d'un prototype ainsi que la réalisation de<br />l'électronique pour capter la position de l'aimant mobile. L'aimant mobile sur la maquette est<br />finalement asservi en lévitation.

Typescript. Includes vita and abstract. Includes bibliographical references (leaves 155-177). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

xvi, 167 p. ; ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Volatiles, particularly H 2 O, play an important role in subduction zone magmatism, from instigating melting of the mantle wedge to influencing the explosivity of eruptions at the surface. To better understand both small-scale eruptive processes and large-scale melt generation processes, concentrations of H 2 O, CO 2 , Cl and S were measured in olivine-hosted melt inclusions from nine monogenetic volcanoes across the Michoacan-Guanajuato Volcanic Field (MGVF) in central Mexico. Melt inclusions, tiny blebs of melt trapped within crystals during growth, record pre-eruptive melt compositions and dissolved volatile contents. Analyses of olivine-hosted melt inclusions from the long-lived (15 years) eruption of Volcan Jorullo illustrate the complexities of cinder cone eruptions. The later-erupted melt inclusions record decreases in crystallization depths, increases in magma storage time, and shallow assimilation of granitic bedrock, suggesting significant evolution of the magma plumbing system over time. Because melt inclusions are trapped at variable depths during magma crystallization, they record progressive degassing of melts during ascent and eruption. Degassing of basaltic melts is variable due to differences in solubility of the volatile components. Estimated volatile solubilities based on variations in melt inclusion data for the MGVF suggest that Cl and S have high solubility, with little to no degassing of these species during ascent and eruption, whereas H 2 O and CO 2 show evidence of substantial degassing. Furthermore, increases in concentrations of incompatible elements in melt inclusions correlate with extents of degassing, suggesting that degassing during ascent drives melt crystallization in many cinder cone eruptions. The volatile contents of mafic arc magmas as revealed by melt inclusions reflect the influx of H 2 O-rich components from the subducted slab to the mantle wedge. Across-arc patterns in volatile and incompatible trace element concentrations for MGVF magmas show that the flux of H 2 O-rich subduction components remains high for large distances across the arc. These data, combined with oxygen isotope analyses of olivine phenocrysts and 2-D thermo-mechanical models of the subduction zone, suggest a complex origin for the H 2 O-rich subduction components, involving dehydration of subducted sediment and storage of volatiles in hydrous minerals in the mantle wedge. This dissertation includes co-authored materials both previously published and submitted for publication. / Adviser: Paul J. Wallace

A Formação Serra Geral é caracterizada por um expressivo volume de derrames básicos de composição toleítica e pela presença muito subordinada de vulcanitos ácidos. Inúmeros corpos intrusivos (soleiras e diques) são correlacionados a esta unidade e juntamente com os depósitos vulcânicos constituem a Província Magmática do Paraná. Este trabalho trata da investigação geológica e petrológica das intrusões básicas-intermediárias da região do Cerro do Coronel, a sudeste da cidade de Pantano Grande, RS. Esses corpos hipabissais estão estratigraficamente vinculados a Formação Serra Geral e formam um trend com orientação NW-SE. Apresentam contatos concordantes com rochas sedimentares das Formações Rio Bonito e Irati. Disjunções colunares são comuns em todas as ocorrências estudadas e são afetadas por forte fraturamento NE e NW. A pequena variação faciológica é caracterizada por termos equigranulares finos a muito finos e raramente porfiríticos. Texturalmente essas rochas apresentam o predomínio da textura intergranular e subofítica ocasional. São constituídos essencialmente por plagioclásio, augita, minerais opacos como minerais primários e material de baixa cristalinidade como etapa final da cristalização. Os dados geoquímicos de elementos maiores e traços permitem classificar as rochas desses corpos hipabissais como andesito-basaltos de afinidade toleítica, cuja evolução deu-se por mecanismos de cristalização fracionada. As características dos elementos maiores, traços e ETR são compatíveis com as apresentadas para magmatismo vinculados a grandes províncias toleíticas continentais. Estas rochas apresentam concentrações de TiO2 inferiores à 2% mostrando uma tendência para o magma-tipo Esmeralda. / The Serra Geral Formation is characterized by a significant volume of basic flows whith tholeiitic composition and the presence of acids volcanites subordinate. Several intrusive bodies (dikes and sills) are correlated to this unit and along with volcanic deposits constitute the Paraná Magmatic Province. This paper deals with the investigation of geological and petrological basic-intermediate intrusions in the region of the Cerro do Coronel, southeast of the city of Pantano Grande, RS. These hypabyssal bodies are stratigraphically linked to the Serra Geral Formation and they make a trend oriented NW-SE. The contacts are concordant with the sedimentary rocks Rio Bonito and Irati Formations. Columnar disjunctions are common in all instances studied and are affected by strong NE and NW fracturing. The few facies variation is characterized by terms equigranular fine and very fine rarely porphyritic. These rocks are the predominant intergranular texture and occasional subophitic texture. They consist essentially of plagioclase, augite, opaque minerals such as primary minerals and crystallization residue such as final stage of crystallization. Geochemical data of major and trace elements allow to classify the rocks of these bodies such as andesite-basalt hypabyssal with tholeiitic affinity, whose evolution occurred by fractional crystallization mechanisms. The characteristics of the major, trace and REE elements are compatible with those presented for magmatism linked to large continental tholeiitic provinces. These rocks have concentrations below the 2% TiO2 showing a tendency to Esmeralda magma-type.

A Formação Serra Geral é caracterizada por um expressivo volume de derrames básicos de composição toleítica e pela presença muito subordinada de vulcanitos ácidos. Inúmeros corpos intrusivos (soleiras e diques) são correlacionados a esta unidade e juntamente com os depósitos vulcânicos constituem a Província Magmática do Paraná. Este trabalho trata da investigação geológica e petrológica das intrusões básicas-intermediárias da região do Cerro do Coronel, a sudeste da cidade de Pantano Grande, RS. Esses corpos hipabissais estão estratigraficamente vinculados a Formação Serra Geral e formam um trend com orientação NW-SE. Apresentam contatos concordantes com rochas sedimentares das Formações Rio Bonito e Irati. Disjunções colunares são comuns em todas as ocorrências estudadas e são afetadas por forte fraturamento NE e NW. A pequena variação faciológica é caracterizada por termos equigranulares finos a muito finos e raramente porfiríticos. Texturalmente essas rochas apresentam o predomínio da textura intergranular e subofítica ocasional. São constituídos essencialmente por plagioclásio, augita, minerais opacos como minerais primários e material de baixa cristalinidade como etapa final da cristalização. Os dados geoquímicos de elementos maiores e traços permitem classificar as rochas desses corpos hipabissais como andesito-basaltos de afinidade toleítica, cuja evolução deu-se por mecanismos de cristalização fracionada. As características dos elementos maiores, traços e ETR são compatíveis com as apresentadas para magmatismo vinculados a grandes províncias toleíticas continentais. Estas rochas apresentam concentrações de TiO2 inferiores à 2% mostrando uma tendência para o magma-tipo Esmeralda. / The Serra Geral Formation is characterized by a significant volume of basic flows whith tholeiitic composition and the presence of acids volcanites subordinate. Several intrusive bodies (dikes and sills) are correlated to this unit and along with volcanic deposits constitute the Paraná Magmatic Province. This paper deals with the investigation of geological and petrological basic-intermediate intrusions in the region of the Cerro do Coronel, southeast of the city of Pantano Grande, RS. These hypabyssal bodies are stratigraphically linked to the Serra Geral Formation and they make a trend oriented NW-SE. The contacts are concordant with the sedimentary rocks Rio Bonito and Irati Formations. Columnar disjunctions are common in all instances studied and are affected by strong NE and NW fracturing. The few facies variation is characterized by terms equigranular fine and very fine rarely porphyritic. These rocks are the predominant intergranular texture and occasional subophitic texture. They consist essentially of plagioclase, augite, opaque minerals such as primary minerals and crystallization residue such as final stage of crystallization. Geochemical data of major and trace elements allow to classify the rocks of these bodies such as andesite-basalt hypabyssal with tholeiitic affinity, whose evolution occurred by fractional crystallization mechanisms. The characteristics of the major, trace and REE elements are compatible with those presented for magmatism linked to large continental tholeiitic provinces. These rocks have concentrations below the 2% TiO2 showing a tendency to Esmeralda magma-type.

Dois experimentos de fusão por desidratação de quartzo-biotita anfibolito do Complexo Metamórfico Piracaia, Estado de São Paulo, foram efetuados sob condições de 950°C, 900 e 1100 MPa, em aparato pistão-cilindro, tipo end-loaded, Bristol de 200 tons. Em ambos foram utilizadas cápsulas e celas experimentais constituídas por \'Au IND.75\'\'Pd IND.25\' e folha de Pb - NaCl - vidro pirex - grafita - MgO, respectivamente. O tempo total dos experimentos foi superior a 160h e eles simulam condições da crosta inferior (ca. 30 km de profundidade) e crosta inferior profunda (ca. 35-40 km), respectivamente. A amostra de partida apresenta estrutura levemente bandada, migmatítica, textura granoblástica equigranular de granulação média e M\' \'quase igual a\' 50. Localmente apresenta venulações tardias contendo epídoto. Anfibólio cálcico e plagioclásio constituem 90%vol. e ocorrem em proporção próxima a 1:1; em menor proporção aparecem flogopita (5%), quartzo (4%) e os acessórios titanita, apatita, sulfetos, allanita, zircão. A rocha apresenta assinatura geoquímica similar aos E-MORBs, contendo teores mais elevados de K2O e ETRLs em relação a anfibolitos típicos de afinidade MORB. O anfibólio corresponde a pargasita/Mg-hornblenda (0,51 \'<OU=\' mg# \'<OU=\' 0,62), enquanto o plagioclásio é oligoclásio (An20-25); a flogopita apresenta 0,53 mg# \'<OU=\' 0,60. O conteúdo em Al da hornblenda e o equilíbrio hornblenda-plagioclásio indicam pressões e temperaturas de metamorfismo/ migmatização sob 600 (±60) MPa e 660 (±50)°C. Nos dois casos foi obtido 15-20 %vol de fusão de composição monzogranítica, magnesiana, metaluminosa a moderadamente peraluminosa e 80-85 % de fases cristalinas residuais-reequilibradas e/ou neoformadas. Entre estas, predominam o plagioclásio zonado reequilibrado (50% vol, com núcleos de oligoclásio e bordas de andesina) e, como fases neoformadas, ortopiroxênio (Opx) enstatítico (0,67 \'<OU=\' mg# \'<OU=\' 0,85) e clinopiroxênio (Cpx) augítico (0,64 <= mg# <= 0,77), que constituem 19-24% (maior no experimento sob 900 MPa), em uma proporção cpx:opx mais ou menos constante de aproximadamente 10:1. Óxidos neoformados de Fe-Ti correspondem a Ti-magnetita e ilmenita nos experimentos sob 900 e 1100 MPa, respectivamente. Pargasita/Mgedenita (9%) e flogopita residuais/reequilibradas aparecem particularmente nas zonas de borda das cápsulas experimentais; a biotita apenas no experimento de menor pressão. Entre os minerais acessórios, a titanita é a fase mais reativa, aparecendo frequentemente com mantos de óxidos de Fe-Ti. Granada, ao contrário do inicialmente esperado, não aparece entre os produtos do experimento de maior pressão. Os anfibólios apresentam valores mg# algo menores e ocupações de Ca+Na+K maiores no sítio cristalino A quando comparados aos presentes na amostra de partida. As condições de fugacidade de O2 ( fO2) calculadas para o equilíbrio oxired entre Timagnetita e ilmenita do experimento sob 1100 MPa indicam condições relativamente oxidantes, pouco superiores ao buffer Ni-NiO (\'quase igual a\'\'delta\'NNO+0,5). As atividades de H2O (aH2O), estimadas a partir das composições normativas Qz-Ab-Or dos vidros (fusões), sugerem valores abaixo da saturação e pouco menores (0,3 -0,5) para o experimento de maior pressão. Estimativas de P e T independentes, bem como de partição Mg-Fe, embasadas em termômetros e termobarômetros envolvendo os pares opx-fusão, cpxfusão e opx-cpx e partições Mg-Fe entre estas fases [KD(Fe-Mg)Opx-Liq, KD(Fe-Mg)Cpx-liq e KD(Fe-Mg)Opx-Cpx] são perfeitamente compatíveis com as esperadas para as condições de realização dos experimentos e sugerem que ambos alcançaram condições próximas e/ou de equilíbrio mesmo nas zonas centrais das cápsulas. As variações composicionais dos produtos e das texturas associadas reafirmam a ideia de que, em processos de fusão deste tipo, o equilíbrio químico é geralmente alcançado antes que o equilíbrio textural. Os resultados obtidos indicam que a fusão por desidratação de pequenas parcelas (15- 20%) de anfibolitos \"enriquecidos\" sob temperaturas de 950°C e pressões na faixa entre 900 e 1100 MPa, pode gerar fusões monzograníticas magnesianas, metaluminosas a marginalmente peraluminosas, com K2O>Na2O, similares aos líquidos precursores do denominado magmatismo de \"tipo-I\", em parte gerados por fusão de rochas meta-ígneas da crosta inferior. A fusão de fontes meta-basálticas deste tipo e a extração dos líquidos insaturados em H2O produzidos deixaria para trás um resíduo de hornblendaclinopiroxênio-granulito máfico, representativos das fácies granulito intermediário, dado pelo equilíbrio entre ortopiroxênio e plagioclásio. A ausência de granada no experimento de maior pressão, bem como as composições monzograníticas obtidas para as fusões, possivelmente estão relacionadas à composição, relativamente \"enriquecida\", do material de partida utilizado quando comparado aos experimentos similares da literatura, efetuados a partir de anfibolitos típicos, que resultam em fusões menos evoluídas, com composições tonalíticas/trondhjemíticas a granodioríticas. / Two dehydration melting experiments of a quartz-biotite amphibolite of the Piracaia Metamorphic Complex (São Paulo, Brazil) were carried out at a temperature of 950°C, and pressure ranges of 900 and 1100 MPa, in an end-loaded, Bristol Type, pistoncylinder apparatus of 200 ton. Both experiments used experimental capsules and cells made of \'Au IND.75\'\'Pd IND.25\' and Pb foil - NaCl - Pyrex glass - Graphite - MgO, respectively. The total time of the two experiments was greater than 160 h and they simulate lower crust (~30 km) and deep lower crust (~35-40 km) conditions, respectively. The starting material employed is characterized by a migmatitic-like banding structure with equigranular granoblastic, medium-grained, texture and M\' (color index) \'quase igual a\' 50. Calcic amphibole and plagioclase are the main minerals (90 wt %) occurring in a 1:1 proportion ratio. Phlogopite (5 %), quartz (4%) and accessory minerals such as titanite, apatite, sulfides, allanite and zircon are also present. The rock has a geochemical signature of E-MORB, with relatively high content of K2O and LREE as compared with typical MORBderived amphibolites. The amphibole is pargasite/Mg-hornblende (0.51 \'<OU=\' mg# \'<OU=\' 0.62), while plagioclase is oligoclase (An20-25) and phlogopite has 0.53 \'<OU=\' mg# \'< OU\'= 0.60. Al-inhornblende and hornblende-plagioclase geothermobarometry point to P-T metamorphic conditions at 600 (± 60) MPa and 660 (± 50)°C. In both cases, it was obtained a 15-20%vol of magnesian monzogranitic melts of metaluminous to moderately slightly peraluminous signatures and 80-85% of newly formed and/or re-equilibrated, residual, crystalline phases. These include re-equilibrated plagioclase with zoned texture (50% vol, from oligoclase cores to andesine rims) and newly formed orthopyroxene (enstatite, 0.67 <= mg# <= 0.85) and clinopyroxene (augite, 0.64 \'< OU=\' mg# \'<OU=\' 0.77) constituting 19-24% (great volume in the 900 MPa experiment) and with a cpx:opx relatively constant proportion of 10:1. Newly grown Fe-Ti oxides are Timagnetite and Ti-magnetite together with ilmenite in the 900 and 1100 MPa experiments, respectively. Residual, re-equilibrated, pargasite/Mg-edenite (9%) and phlogopite appear particularly in capsules border areas; biotite occurs only in the low-pressure experiment. Among the accessory minerals, titanite is the most reactive, with rims of FeTi oxides. Garnet, unlike expected, was not found among the products of the highpressure experiment. Amphiboles have lower mg# and higher Ca+Na+K occupations in the A sites as compared with those of the starting material. Oxygen fugacity (fO2) calculated for redox equilibrium between Ti-magnetite and ilmenite from the highpressure experiment indicates oxidizing conditions somewhat above the Ni-NiO \'quase igual a\' \'\'delta\' NNO+0.5) buffer. Water activities (aH2O) estimates from the Qz-Ab-Or normative compositions of the formed glasses suggest under-saturated water environments, with values somewhat lower (0,3 -0,5) for the low-pressure experiment. Independent pressure and temperature estimates as well as Fe-Mg partitioning coefficients, based on opx-melts, cpx-melts and opx-cpx pairs thermometry and thermobarometry and Fe-Mg partitioning coefficients [KD(Fe-Mg)Opx-melt,KD(Fe-Mg)Cpx-melt and KD(Fe-Mg)Opx-Cpx], are compatible with the expected results under the selected conditions for both experiments and suggests that equilibrium or near-equilibrium conditions were reached in the central area of the capsules. Compositional variations in the final products and associated textures reaffirm the idea that, in melting experiments of the conducted type, chemical equilibria is reached before textural equilibria. Experimental results indicate that dehydration melting in relatively small fractions (15- 20% melt volumes) of \"enriched\" amphibolites under a temperature of 950°C and pressures between 900 and 1100 MPa could generate magnesian monzogranitic melts with a metaluminous to moderately peraluminous character and K2O>Na2O, like precursor liquids of the so-called I-type magmatism, partly generated by partial melting of meta-igneous rocks constituting the lower crust. The partial melting of such meta-basaltic sources and extraction of the waterundersaturated liquids would leave behind a hornblende-clinopyroxene bearing mafic granulite residue representative of the intermediate granulite facies given by the orthopyroxene and plagioclase equilibria. The absence of garnet in the higher-pressure experiment as well as the monzogranitic compositions obtained are related to a relative \"enriched\" nature of the starting material as compared to other experimental results, starting from typical amphibolites, which result in less evolved melts, with tonalitictrondhjemitic to granodioritic compositions.

The Bingham porphyry Cu-Au-Mo deposit, Utah, may only be world-class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc-alkaline system. Volcanic mafic alkaline rocks in the district are enriched in Cr, Ni, and Ba as well as ore-related constituents of Cu, Au, platinum group elements (PGE) and S. The bulk of the volcanic section that is comagmatic with ore-related porphyries is dacitic to trachytic in composition, but has inherited the geochemical signature of high Cr, Ni, and Ba from magma mixing with the mafic alkaline rocks. The volcanic section that most closely correlates in time with ore-related porphyries is very heterogeneous containing clasts of scoriaceous latite, latitic minette and flows of melanephelinite, shoshonite and olivine latite in addition to the volumetrically dominant dacite/trachyte. Bingham ore-related porphyries show ample evidence of prior mixing with mafic alkaline magmas. Intrusive porphyries that have not been previously studied well have several chemical and mineralogical indications of magma mixing. These "mixed" lithologies include the hybrid quartz monzonite porphyry, biotite porphyry, and minette dikes. Even some of the more silicic latite and monzonite porphyries retain high Cr and Ba contents indicative of mixing and contain trace amounts of sapphire ( Magma mixing calculations suggest about 10% of the monzonitic/latitic ore-related magma may have been derived from mafic alkaline magma similar to the melanephelinite. If the original S content of the mafic magma was about 2000-4000 ppm, comparable to similar magmas, then the mafic magma may have been responsible for contributing more than half of the S and a significant portion of the Cu, Au, and PGE in the Bingham deposit.

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.