Recurrence rate is often used to describe volcanic activity. There are numerous documented ex- amples of non-constant recurrence rate (e.g. Dohrenwend et al., 1984; Condit and Connor, 1996; Cronin et al., 2001; Bebbington and Cronin, 2011; Bevilacqua, 2015), but current techniques for calculating recurrence rate are unable to fully account for temporal changes in recurrence rate. A local–window recurrence rate model, which allows for non-constant recurrence rate, is used to calculate recurrence rate from an age model consisting of estimated ages of volcanic eruption from a Monte Carlo simulation. The Monte Carlo age assignment algorithm utilizes paleomagnetic and stratigraphic information to mask invalid ages from the radiometric date, represented as a Gaussian probability density function. To verify the age assignment algorithm, data from Heizler et al. (1999) for Lathrop Wells is modeled and compared. Synthetic data were compared with expected results and published data were used for cross comparison and verification of recurrence rate and volume flux calculations. The latest recurrence rate fully constrained by the data is reported, based upon data provided in the referenced paper: Cima Volcanic Field, 33 +55/-14 Events per Ma (Dohren- wend et al., 1984), Cerro Negro Volcano, 0.29 Events per Year (Hill et al., 1998), Southern Nevada Volcanic Field, 4.45 +1.84/-0.87 (Connor and Hill, 1995) and Arsia Mons, Mars, 0.09 +0.14/-0.06 Events per Ma (Richardson et al., 2015). The local–window approach is useful for 1) identifying trends in recurrence rate and 2) providing the User the ability to choose the best median recurrence rate and 90% confidence interval with respect to temporal clustering.

La croissance de la phase vésiculée, moteur de l'éruption, est contrôlée par les processus de diffusion qui permettent la migration des gaz (et notamment des gaz rares) dans les bulles. On utilise la haute volatilité des gaz rares comme traceur géochimique de l'évolution d'une phase gazeuse sans interaction chimique. Ainsi, documenter précisément les mécanismes de diffusion des différents gaz rares (He, Ne, Ar) lors de l'éruption (c'est-à-dire en fonction de la chute de température et de pression du système), permet de quantifier les phénomènes de fractionnement de la phase gazeuse. La compréhension des processus de fractionnements cinétiques, permet dès lors de prédire le temps nécessaire pour atteindre une certaine quantité de gaz rares dans une bulle (située au sein d'un système magmatique), lors de l'éjection des laves. Pour cela, la compréhension de l'influence de la température et de la structure du réseau silicaté sur les coefficients de diffusion est nécessaire. Cependant, la compréhension physique des processus de diffusion ainsi que l'évolution des coefficients de diffusion en fonction de la température, n'est pas suffisante pour dériver des temps caractéristiques d'une éruption volcanique de type Plinian. La complexité symptomatique de tels systèmes, nécessite une résolution numérique des équations de diffusion prenant en compte la dépendance des coefficients de diffusion à la température. Plusieurs verres synthétiques et naturels de composition basaltique ont été fabriqués dans le but de déterminer la vitesse de diffusion des gaz rares. Les données de diffusivités expérimentales mesurées sur ces systèmes, depuis l'état vitreux de basse température (T = 423 K) jusqu'à des températures sur-liquidus (T = 1823 K), documentent nos connaissances des processus physiques de diffusion dans ces milieux. Un modèle numérique intègre ces données et permet de suivre en continue la variation des coefficients de diffusion lors de la trempe d'une lave. On a pu ainsi montré : - La relation particulière entre la structure du milieu diffusif et les espèces diffusantes. La quantité de formateurs de réseaux (SiO2) et de modificateurs (CaO - MgO - etc.), joue sur la connectivité des chemins de diffusions de chaque gaz rare, avec un effet antagoniste entre l'ouverture globale du réseau et la connexion des tétraèdres de la structure. - La présence de comportements non-arrheniens des gaz rares proches de la Tg, due à la relaxation du réseau silicate. - L'importance des données expérimentales dans l'étude des mécanismes de dégazage des magmas basaltiques. En effet, les études précédentes utilisent des extrapolations des coefficients de diffusions, mesurés dans le verre pour extrapoler les diffusivités dans le liquide silicaté. Nos données montrent que le fractionnement cinétique des gaz rares pendant le dégazage de lave basaltique, est surestimé par ces extrapolations basées sur les vitesses de diffusions aux basses températures (T << Tg) / Noble gas geochemistry is an important tool for constraining the history of the volatile phase during magmatic eruptions. Degassing processes control the gas flux from liquid to bubble, leading to solubility- or kinetic-control of the fractionation mechanisms. Noble gases have no chemical interactions at magmatic conditions and are therefore well adapted to tracing gas fractionation mechanisms during the evolution of the gas phase. Well constrained diffusion coefficients, and their dependence on temperature, of several noble gases are critical for estimating the timescale of a plinian eruption, for example. During the quench phase of the lava ejected in the plume, atmospheric noble gases will diffuse through the liquid/glass shell surrounding gas bubbles. Diffusion of these atmospheric gases determine the gas content measured in the eruption products, which are therefore a function of the timescale of the eruption, the initial and final temperatures, the glass/liquid shell thickness and the cooling rate of the magma. Therefore, it should be possible to calculate plinian eruption timescales from noble gas fractionation patterns trapped in pumice. However, in order to perform the diffusion calculations, it is first necessary to model the diffusive system: a numerical resolution of the diffusion equations for hollow sphere geometry is required as there are no analytical solutions (for complex thermal histories such as for a plinian ash column). In order to constrain the diffusion mechanisms (He, Ne and Ar) in silicate glasses and liquids, several synthetic basaltic glasses were produced. Diffusion coefficients were measured from low temperatures (423 K) to the Tg (glass transition temperature) of the system (1005 K). These experiments allowed us to investigate the physical processes that limit diffusion in glassy media: He, Ne and Ar diffusion in silicate glasses show non-Arrhenian behavior as the Tg is approached thought to be due to structural relaxation of the silicate network itself. Complementary diffusion experiments (on He and Ar) at super-liquidus conditions (1673 K and 1823 K) provide important information on the temperature dependency of He/Ar fractionation in silicate liquids. These diffusion measurements required that a new experimental protocol was developed in order to investigate noble gas diffusivities in silicate melts. The results show that relative He and Ar diffusion (i.e. DHe/DAr) decreases with temperature, from 165 at temperatures close to the Tg to 3.2 at high (>1823K) temperature. The measured coefficient diffusions are incorporated to a numerical model of the diffusion equations for a hollow sphere geometry that were developed as a MatLab code as part of this thesis work. This enabled us to determine the likely timescales of plinian eruptions from existing noble gas measurements. These results also have important implications for mechanisms of degassing in basaltic magmas: previous work used diffusivities measured on glasses in order to extrapolate to noble gas diffusivities at magmatic temperatures. Our measurements show that kinetic fractionation of noble gases during degassing of basaltic magmas has likely been overstated because noble gas diffusion in the glass cannot be extrapolated to the liquid state

On June 15, 1991, Mount Pinatubo, Philippines, ejected 20 million tonnes of sulfur dioxide into the atmosphere, significantly impacting global climate and stratospheric ozone. Recharging basaltic magma mixed into the 50 km³ dacitic magma reservoir 6 to 11 km beneath Mount Pinatubo, and triggered the 1991 eruption. The result of the magma mixing was a hybrid andesite with quenched basalt inclusions that erupted as a dome between June 7 and June 12. On June 15, approximately 5 km³ of anhydrite-bearing magma was erupted from the main phenocryst-rich, dacitic reservoir. This study will utilize this extraordinary framework of the 1991 Pinatubo eruption to investigate the systematics of sulfur uptake by apatite in order to further develop apatite as a monitor for magmatic sulfur. In the dacite and hybrid andesite, apatite occurs as individual phenocrysts (up to ~200 μm diameter) or included within anhydrite, hornblende, and plagioclase phenocrysts. In the basaltic magmatic inclusions, apatite is found as acicular microphenocrysts. Electron microprobe data collected on apatite yield low- (0.7 wt.% SO₃) apatites in all juvenile products, and show that two distinct populations of apatites exist: "silicic" apatites (hosted in dacite and andesite) and basalt apatites. Apatites crystallizing from silicic melt have predominantly low- to medium-sulfur contents, but high-sulfur apatites with as much as 1.2-1.7 wt.% SO₃ occur sporadically as inclusions in plagioclase, hornblende, Fe-Ti oxide, and anhydrite. These concentrations are much higher than what could be achieved through equilibrium crystal-melt partitioning at pre-eruption conditions (760±20°C, 220MPa, NNO+1.7, 77 ppm S in melt inclusions) and a partition coefficient of 13. Apatite in the basalt is always sulfur-rich with compositions forming a continuous array between 0.7 to 2.6 wt.% SO₃. The population of apatite that crystallized from silicic melt has elevated cerium, fluorine, and chlorine and lower magnesium concentrations (average dacite values in wt.%: 0.21 Ce₂O₃, 1.4 F, 1.1 Cl, & 0.14 MgO) relative to the population of apatite from the basalt (average basalt values in wt.%: 0.05 Ce₂O₃, 1.0 F, 0.78 Cl, & 0.22 MgO). LA-ICP-MS trace element data also show distinct apatite populations between silicic and basalt apatites. Silicic apatites have elevated REE concentrations (La avg. = 750 ppm), lower Sr (avg.= 594 ppm), and a pronounced negative Eu anomaly (avg. Eu/Eu* = 0.57) relative to basalt apatites (avg. values: 217 ppm La, 975 ppm Sr, and Eu/Eu* = 1.16). The correlation of EMP sulfur data and LA-ICP-MS trace element data show no difference between high-S and low-S silicic apatites. These compositional systematics rule out the possibility that sulfur-rich apatite from dacite are inherited from mafic magma. Sulfur element maps of apatites show no evidence of S-diffusion from anhydrite hosts. Areas of high-S concentrations show complicated patterns that suggest multiple periods of sulfur enrichment. High-S silicic apatites are likely the product of "fluid-enhanced crystallization" from early enrichment of a SO₂ rich fluid phase from the underplating basalt, which occurred prior to or at anhydrite saturation. This fluid phase is the only possible sufficient source of sulfur for generating high-S apatites in a cool, "wet", dacitic melt. The dynamics of apatite sulfur enrichment via "fluid-enhanced crystallization" is yet unclear and requires further experimental laboratory investigation.

No description available.

In this dissertation, we introduce three projects in machine learning and reliability applications after the general introductions in Chapter 1. The first project concentrates on the multivariate sensory data, the second project is related to the bivariate recurrent process, and the third project introduces thermal index (TI) estimation in accelerated destructive degradation test (ADDT) data, in which an R package is developed. All three projects are related to and can be used to solve certain reliability problems. Specifically, in Chapter 2, we introduce a clustering method for multivariate functional data. In order to cluster the customized events extracted from multivariate functional data, we apply the functional principal component analysis (FPCA), and use a model based clustering method on a transformed matrix. A penalty term is imposed on the likelihood so that variable selection is performed automatically. In Chapter 3, we propose a covariate-adjusted model to predict next event in a bivariate recurrent event system. Inspired by geyser eruptions in Yellowstone National Park, we consider two event types and model their event gap time relationship. External systematic conditions are taken account into the model with covariates. The proposed covariate adjusted recurrent process (CARP) model is applied to the Yellowstone National Park geyser data. In Chapter 4, we compare estimation methods for TI. In ADDT, TI is an important index indicating the reliability of materials, when the accelerating variable is temperature. Three methods are introduced in TI estimations, which are least-squares method, parametric model and semi-parametric model. An R package is implemented for all three methods. Applications of R functions are introduced in Chapter 5 with publicly available ADDT datasets. Chapter 6 includes conclusions and areas for future works. / Doctor of Philosophy / This dissertation focuses on three projects that are all related to machine learning and reliability. Specifically, in the first project, we propose a clustering method designated for events extracted from multivariate sensory data. When the customized event is corresponding to reliability issues, such as aging procedures, clustering results can help us learn different event characteristics by examining events belonging to the same group. Applications include diving behavior segmentation based on vehicle sensory data, where multiple sensors are measuring vehicle conditions simultaneously and events are defined as vehicle stoppages. In our project, we also proposed to conduct sensor selection by three different penalizations including individual, variable and group. Our method can be applied for multi-dimensional sensory data clustering, when optimal sensor design is also an objective. The second project introduces a covariate-adjusted model accommodated to a bivariate recurrent event process system. In such systems, events can occur repeatedly and event occurrences for each type can affect each other with certain dependence. Events in the system can be mechanical failures which is related to reliability, while next event time and type predictions are usually of interest. Precise predictions on the next event time and type can essentially prevent serious safety and economy consequences following the upcoming event. We propose two CARP models with marginal behaviors as well as the dependence structure characterized in the bivariate system. We innovate to incorporate external information to the model so that model results are enhanced. The proposed model is evaluated in simulation studies, while geyser data from Yellowstone National Park is applied. In the third project, we comprehensively discuss three estimation methods for thermal index. They are the least-square method, parametric model and semi-parametric model. When temperature is the accelerating variable, thermal index indicates the temperature at which our materials can hold up to a certain time. In reality, estimating the thermal index precisely can prolong lifetime of certain product by choosing the right usage temperature. Methods evaluations are conducted by simulation study, while applications are applied to public available datasets.

The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understanding of magmatic processes and formation of the earliest continental crust. Particularly significant is magma-crust interaction that can modify the composition of magma and the dynamics of volcanism. This thesis investigates silicic magma genesis on different scales in two ocean island settings. First, volcanic products from a series of voluminous Neogene silicic centres in northeast Iceland are investigated using rock and mineral geochemistry, U-Pb geochronology, and oxygen isotope analysis. Second, interfacial processes of magma-crust interaction are investigated using geochemistry and 3D X-ray computed microtomography on crustal xenoliths from the 2011-12 El Hierro eruption, Canary Islands. The results from northeast Iceland constrain a rapid outburst of silicic magmatism driven by a flare of the Iceland plume and/or by formation of a new rift zone, causing large volume injection of basaltic magma into hydrated basaltic crust. This promoted crustal recycling by partial melting of the hydrothermally altered Icelandic crust, thereby producing mixed-origin silicic melt pockets that reflect the heterogeneous nature of the crustal protolith with respect to oxygen isotopes. In particular, a previously unrecognised high-δ18O end-member on Iceland was documented, which implies potentially complex multi-component assimilation histories for magmas ascending through the Icelandic crust. Common geochemical traits between Icelandic and Hadean zircon populations strengthen the concept of Iceland as an analogue for early Earth, implying that crustal recycling in emergent rifts was pivotal in generating Earth’s earliest continental silicic crust. Crustal xenoliths from the El Hierro 2011-2012 eruption underline the role of partial melting and assimilation of pre-island sedimentary layers in the early shield-building phase of ocean islands. This phenomenon may contribute to the formation of evolved magmas, and importantly, the release of volatiles from the xenoliths may be sufficient to increase the volatile load of the magma and temporarily alter the character and intensity of an eruption. This thesis sheds new light on the generation of silicic magma in basalt-dominated oceanic settings and emphasises the relevance of magma-crust interaction for magma evolution, silicic crust formation, and eruption style from early Earth to present.

Currently, many developing countries are experiencing rising prevalences of caries associated with changes in lifestyle and living conditions. Objectives: To describe the hygiene, eating habits, and oral health status of Nepalese children. Materials and Methods: A stratifiedsample of 231 children 5–7, 11–13, and 15–16 years of age (53% boys, 47% girls) who attended public high schools in the rural area of the Lalitpur District, Nepal was selected. The study was a field study combining a clinical examination (plaque, gingivitis, calculus, and caries) and a questionnaire. The questions concerned sanitary conditions, health support, personal hygiene, tooth cleaning, and eating habits. Results: During the school day, half of the children ate nothing at all. General personal hygiene was associated with tooth-cleaning frequency.Four out of five children in the entire sample cleaned their teeth once/day or more, using their own toothbrush. The use of fluoride toothpaste was rare.More frequent tooth cleaning and lower plaque indices were seen among girls and older children. More plaque was found on the occlusal surfaces of erupting permanent molars than on fully occluded permanent molars. Most children had a low prevalence of manifest caries in the primary and the permanent dentitions. However, every fifth 5–7-yr-old had manifest caries in three or more primary teeth. The occlusal surfaces of molars accounted for almost all registered caries in both dentitions. Conclusion: Although the prevalence of manifest caries was low, the low level of preventive activities may cause an increase in the prevalence of caries, as in other developing countries. The presumed risk scenario needs to be met by comprehensive and systematic health promotion and preventive measures. / Sammanfattning: I många utvecklingsländer sker förändringar av livsstil och levnadsförhållanden med samtidig ökad förekomst av karies. Mål: Att beskriva hygien, matvanor och munhälsa hos nepalesiska barn. Material och Metod: Ett stratifierat urval av 231 barn, som i åldrarna 5-7, 11-13 och 15-16 år (53% pojkar, 47% flickor), elever i statliga grundskolor på landsbygden, Lalitpur distriktet Nepal, användes. Studien utformades som en fältstudie med klinisk undersökning (plack, gingivit, tandsten och karies) kombinerad med en enkätstudie. Frågorna rörde sanitära förhållanden, hälsostöd från hemmet, personlig hygien, tandrengörings- och matvanor. Resultat: Under skoldagen åt hälften av barnen ingenting alls. Allmän personlig hygien var associerad med tandrengörings frekvens. Av alla barn, som användande sin egen tandborste, borstade fyra av fem, en gång om dagen eller mer. Äldre barn och flickor rengjorde tänderna oftare och hade ett lägre plackindex. Mer plack fanns på erupterande molarers occlusalytor jämfört med molarer i full ocklusion. De flesta barnen hade en låg frekvens manifest karies i primära och permanenta bettet. Dock hade en femtedel av 5-7 åringarna tre eller fler manifesta kariesangrepp i primära bettet. Ocklusal karies på molarerna utgjorde nästan all registrerad karies i båda dentitionerna. Slutsats: Låg frekvens av manifest karies, men en låg grad av förebyggande aktiviteter, kan medföra en ökad kariesfrekvens liknande den i andra utvecklingsländer. Den förmodande risken måste bemötas med behovsinriktade och systematiska hälsobefrämjande och preventiva åtgärder. / <p>ISBN 91-7997-151-2</p>

After 1815's eruption of Mount Tambora, the following period was named the "Year without a Summer" and experienced irregularly cold weather, failed crops, rampant disease, and riots. In the summer of 1816, Lord Byron, Percy Bysshe Shelley, and Mary Wollstonecraft Shelley met in the Alps and wrote "Darkness," "Mont Blanc," and Frankenstein respectively. This thesis focuses on these works' depictions of nature in light of how these features may have been impacted by the climate. It argues in Chapter One that the volcanic eruption caused global climate changes that affected these writers. In Chapter Two, it illustrates differences in nature's representation between first generation and second generation Romantic works. The conclusion synthesizes the arguments made in Chapters One and Two, suggesting that 1816's climate affected these writers in such a way as to produce an environment from which science fiction could emerge in Frankenstein. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Mosses are some of the first colonizers to disturbed sites, yet their roles in early plant community structuring are not well understood. The primary succession zones of volcanoes provide opportunities to conduct natural experiments into how mosses contribute to early plant community formation, as well as how the unique environments found in such zones affect plant traits, particularly those associated with stress tolerance. Though plant community changes have been well-documented since Mount St. Helens (MSH) volcano erupted in 1980, the volcano's moss assemblages, their influence on other plants, and their potential roles in chemical-mediated competition and biogeochemical cycling have garnered little attention. Using a natural stress gradient from primary to secondary succession zones on MSH, and in control and nutrient manipulated test plots, I sought to elucidate how populations of three dominant moss species, Polytrichum juniperinum, Ceratodon purpureus, and Racomitrium canescens, respond to abiotic stress, as well as to provide life history and interaction data on establishment stages of these stress tolerant taxa. I first analyzed possible tradeoffs in survival strategies of four moss communities in test plots along an abiotic stress gradient. In P. juniperinum, seta specific density (mg/mm) increased significantly in response to nitrogen (N) addition. Differences in both vegetative and sexual reproductive morphological measurements were dependent on site and did not correlate with abiotic stress. In C. purpureus, the percentage of total spores germinated increased with N addition. Site dependent responses in nutrient allocation to vegetative and reproductive structures may be a result of phenotypic plasticity alone or may be a result of local adaptation. In mosses adapted to environmental stress, the allocation of nitrogen must be balanced between growth and survival. Efficient nitrogen uptake confers a competitive advantage if allocated to the higher dispersal of quickly germinating spores. Second, my results show the moss R. canescens may be able to inhibit the germination rate of co-occurring moss spores when spores were germinated in moss gametophyte infusions. R. canescens may also inhibit the germination of the co-occurring vascular plant Lupinus lepidus when seeds are germinated within intact moss patches. By uncovering chemical-mediated interactions between mosses on the germination and initial growth of neighboring mosses and vascular plants we can gain a better understanding of the mechanisms stress tolerant plants may use to limit resource competition. Such advantages offer insight into how mosses effectively colonize and affect primary succession landscapes.

This master's thesis deals with the issue of volcanic ash as a complex and its impact on aviation, including the volcanic activity itself (conditions for its existence, for existence of eruptions and their basic products). In addition, the thesis also deals with effect of volcanic ash on aircraft and airports, possibilities of its detection or monitoring as well as mechanism of its spreading in airspace. The emphasis is laid mainly on air incidents related to volcanic ash and on danger it poses to the airspace of the Czech Republic.