Theoretical and experimental studies of the chemical and physical factors which affect molecular diffusion of dissolved substances from fractures into a tuffaceous rock matrix have been made on rocks from G Tunnel and Yucca Mountain at the Nevada Test Site (NT8). Although a number of physical/chemical processes may cause nonadvective transport of dissolved species from fractures into the tuff matrix, diffusion in these rocks is controlled by the composition of the groundwater through multicomponent effects and several rock properties. The effective molecular diffusion coefficient of a particular species in the tuff can be related to its free aqueous diffusion coefficient by Dₑ = θ(m)(α/τ²)D₀ where bm is matrix porosity, α is the constrictivity, and τ is the tortuosity. The porosities of the samples studied ranged from 0.1 to 0.4. The parameter (α/τ²) ranged from 0.1 to 0.3, and effective matrix dif— fusion coefficients were measured to be between 2 to 17. x 10⁻⁷ cm²/s for sodium halides and sodium pentafluorobenzoate. Total porosity was found to be the principle factor accounting for the variation in effective diffusion coefficients. The constrictivity— tortuosity factor was found to have a fair correlation with the median pore diameters measured by mercury intrusion. Measurements of bulk rock electrical impedance changes with frequency indicate that the constrictivity factor, a, has a maximum value of 0.8 to 1, but may be smaller. If the larger values are correct, then the diffusion paths in tuff are more tortuous than in granular media. The diffusion coefficient matrix computed for various tracers in J-13 well water from the NTS indicates coupling of the diffusion fluxes of all ionic species. Multicomponent diffusion is a second order effect, however, which does not significantly affect experimental results. The results of a bench—scale fracture flow experiment revealed that the transport of ionic tracers (SCN ⁻ and pentafluorobenzoate) was affected by diffusion into the tuff matrix. The transport of a particulate tracer did not appear to be affected by diffusion.

Das Jahr 1816 ist in die Klimatologie als das "Jahr ohne Sommer" eingegangen. Der 1815 erfolgte Ausbruch des Vulkans Tambora auf der indonesischen Insel Sumbawa führte im darauffolgenden Jahr in vielen Teilen der Welt zu katastrophalen Missernten. Während in Nordamerika daran besonders die außerordentlich tiefen Sommertemperaturen Schuld waren, scheinen in Europa dafür sowohl die unter dem Durchschnitt liegenden Temperaturen wie auch die überdurchschnittlichen Regenmengen verantwortlich zu sein. Zeitgenössische Berichte wie auch Niederschlags- und Pegelaufzeichnungen aus verschiedenen Teilen Europas belegen eine besonders hohe Niederschlagstätigkeit im "Erntemonat" Juli des Jahres 1816 und eine hohe Wasserführung der großen europäischen Ströme in den Jahren 1816 und 1817. / The year 1816 is known in climatology as the "Year without Summer". The eruption of the Tambora volcano on the Indonesian island Sumbawa in 1815 led to catastrophic crop failures over many parts of the world in the following year. Whereas in North America those failures originated from extraordinarily low summer temperatures, causes in Europe seem to have been below-normal temperatures as well as above-normal rainfall. Contemporary reports and also precipitation and river gauge measurements from different parts of Europe document enhanced precipitation in July 1816 ("Erntemonat") and high discharges of large European rivers in years 1816 and 1817.

This thesis describes volcanic records from the Andean southern volcanic zone, based on the collection of field data between Calbuco and Puyuhuapi volcanic centres, with a particular focus on the Hualaihue peninsula, combined with existing records from the region as a whole. These data, extending the understanding of the volcanic history of southern Chile, are examined for evidence of spatial or temporal variability, which may be used to explore underlying controls on volcanic processes. All three volcanoes on the Hualaihue peninsula have been active in the Holocene. A large mafic scoria unit from Apagado is unusually primitive, providing a potential window into primary magma generation in the arc. Dynamically similar eruptions occurred at Hornopirén and widely along the regional scale Liquiñe-Ofqui fault zone (LOFZ). Although the Hualaihue centres are closely related, petrological evidence indicates a complex magmatic storage system. Effusive activity is predominant at Yate and Hornopirén, and the tephrostratigraphy of the Hualaihue area is dominated by units from Calbuco volcano, to the north. The 2008 eruption of Chaitén provided an analogue for past large explosive eruptions in the region, with tephra deposition reflecting variable eruption intensity in a changing wind field. The regional tectonic setting and the LOFZ influence dyke ascent, volcano morphology and, as demonstrated at Yate, edifice stability, determining the orientation of collapse. Explosive eruption records over the post-glacial period also indicate a limited response of volcanism to deglaciation, suggesting a control on magma storage arising from changing crustal stress regimes, both at the arc front and along the LOFZ. On short timescales, large earthquakes are shown to influence eruption rate across the arc, implying a triggering role for dynamic seismic stresses. This work demonstrates the existence of a range of external forces affecting Chilean arc volcanism, but the degree to which these are quantifiable is strongly constrained by the quality of the available data.

Air pollution has adverse effects on human health. The respiratory system is the most exposed and short-term changes in air pollution levels have been associated with worsening of asthma symptoms and increased rates of heart attacks and stroke. Air pollution in cities due to traffic is the major concern, as many people are exposed. However, natural sources of air pollution such as natural dust storms and ash from volcanic eruptions can also compromise human health. Exposure to volcanic eruptions and other natural hazards can also threaten mental health. Air pollution has not been extensively studied in Iceland, in spite of the presence of several natural pollution sources and a sizeable car fleet in the capital area. The aim of this thesis was to determine if there was a measurable effect on health which could be attributed to air pollution in Iceland. This aim was pursued along two paths; time series studies using register data aimed to determine the short-term association between daily variation in air pollution and on one hand daily dispensing of anti-asthma medication or the daily number of emergency room visits and emergency admissions for cardiopulmonary causes and stroke. The other method was to investigate if exposure to the Eyjafjallajökull volcanic eruption was associated with adverse health outcomes, either at the end of the eruption, or 6 months later. In paper I time series regression was used to investigate the association between the daily number of individuals who were dispensed anti-asthma medication and levels of the air pollutants particle matter with an aerodynamic diameter less than 10 μm (PM10), nitrogen dioxide (NO2), ozone (O3), and hydrogen sulfide (H2S) during the preceding days. For the study period 2006-9, there were significant associations between the daily mean of PM10 and H2S and the sales of anti-asthma medication 3 to 5 days later. Giving the exposure as the highest daily one-hour mean gave more significant results. Air pollution negatively affected the respiratory health of asthma medication users, prompting them to refill their prescriptions before they had originally intended to. In paper II the main outcome was the number of individuals seeking help at Landspitali University Hospital emergency room for cardiopulmonary disease or stroke. Time series regression was used to identify the lag that gave the best predictive power, and models were run for data for 2003-9 pollutants PM10, NO2, and O3. O3 was significantly associated with the number of emergency hospital visits the same day and two days later in all models, and both for men, women and the elderly. Only emergency hospital visits of the elderly were associated with NO2, and there were no associations with PM10. In paper III the aim was to investigate if the health effects of PM10 were affected by the addition of volcanic ash from the 2010 eruption of Eyjafjallajökull and 2011 eruption of Grímsvötn to PM10 in the capital area. Time series regression of emergency hospital visits and PM10 before and after the Eyjafjallajökull eruption showed that the effect tended to be higher after the eruption, but the results were not significant. Analysis with a binary indicator for high levels of PM10 from volcanic ash and other sources showed that volcanic ash was associated with increased emergency hospital visits. There were no associations with high levels of PM10 from other sources. In paper IV, the health of the population exposed to the ongoing eruption of Eyjafjallajökull in 2010 was investigated thoroughly. Lung function in adults was better than in a reference group from the capital area, though many reported sensory organ irritation symptoms and symptoms of stress and mental unhealth, especially those with underlying diseases. Paper V report the results from a questionnaire study which was carried out six months after the Eyjafjallajökull eruption. The study population comprised a cohort of south Icelanders exposed to the eruption to varying degrees and a reference group from north Iceland. Respiratory and eye symptoms were much more common in south Icelanders than in the reference group, after adjusting for demographic characteristics. Mental unhealth rates had declined considerably. In the studies, we found that urban air pollution and natural particles have short-term effects on anti-asthma medication dispensing and emergency room visits and hospital admissions. Exposure to natural particles in the form of volcanic dust was associated with increased respiratory symptoms in a very exposed population. There were indications that volcanic ash particles were associated with increased emergency hospital visits in the following days. / <p>Statement of collaboration</p><p>This thesis and the work in it have been produced in collaboration between University of Iceland and Umeå University. The thesis was issued and defended at both institutions. Responsible</p>

Reconnaissance work and high-density sampling of volcanic rocks at the Quaternary Tatara-San Pedro complex (TSPC) in the Southern Volcanic Zone (SVZ) of Chile has yielded one of the most complete eruptive chrono-stratigraphies and comprehensive geochemical datasets of any arc volcano on Earth. The TSPC is a large frontal arc stratovolcano within the SVZ that exhibits a wide compositional diversity of lavas from basalt to rhyolite, covering most of the ranges in major and trace element contents across the SVZ. The TSPC occupies a pivotal position within the SVZ, where it is "intermediate" in terms of geophysical and geochemical characteristics between northern and southern SVZ volcanoes. The large TSPC dataset and stratigraphic control provides a unique opportunity to elucidate magma source heterogeneity and distinguish between contributions from upper mantle, subducted slab, and crust in a volcanic complex overlying relatively thick continental crust. Furthermore, the results of this investigation provide important constraints about the role of various recycled materials in generating the SVZ mantle and implications for along-arc magmatism and geochemical variability. TSPC magmas least impacted by crustal contamination (evolved lavas are filtered out on the basis of > 56 wt.% SiO2 and Rb/Y >1.75) have compositions bounded by three chemically and isotopically distinct mantle-derived end-members. The `prevalent TSPC mantle' end-member, which includes the largest number of analyzed lavas, is interpreted to represent melts of the upper mantle below TSPC that has been modified by long-term subduction. A second end-member shows extreme depletions in incompatible high field strength elements (HFSE) and the lowest concentrations of fluid-immobile incompatible elements, but has the highest aqueous fluid-mobile/immobile element ratios at the volcano (e.g., Sr/Nd and Pb/Ce). The source of these `low HFSE' magmas is `prevalent TSPC mantle' that experienced previous melt extraction, followed by more recent melting due to infiltration of solute-rich fluid from the subducting basaltic Nazca oceanic crust. A third end-member is enriched in incompatible elements and has the lowest Nd-Hf and highest Sr isotope ratios. This `TE enriched' end-member has common chemical characteristics with behind-the-arc basalts, indicating derivation from trace element-enriched behind-the-arc South American mantle that has been advected trenchward into the convecting mantle wedge. Determining the composition and relative input of slab-derived components to the SVZ mantle wedge has remained elusive for the last 2+ decades because of inadequate datasets and the controversial role of crustal contamination within the thick Andean continental crust. The `prevalent TSPC mantle' magmas, which best represent melts of the subduction-modified mantle wedge composition beneath the TSPC, provide important constraints on both the composition of the "pre-subduction" mantle and geochemical modifications by way of subduction. Mass-balance modeling suggests that the source of `prevalent TSPC mantle' magmas has been generated by a two-stage, three component mixing process. Isotopic and trace element evidence indicate that ~7-11% bulk subducted Chilean trench sediment has been added to an `E-MORB-like' pre-subduction mantle composition. This mantle mixture is further infiltrated by ~4% solute-rich fluid derived from the subducted Nazca basaltic oceanic crust. Trace element patterns of end-member `prevalent TSPC mantle' magmas are best fit by a two-stage partial melting model whereby the residual mantle, after a small degree melt extraction (F = 0.1%), undergoes F = 22% partial melting. The high melt fraction appears to potentially correspond with large volumes of solute-rich fluid released from the subducted Mocha Fracture Zone (MFZ). Although geochemical attributes of mafic TSPC magmas suggest that they are all derived from the same general mantle framework operating below the complex, one lava sequence appears to deviate. The mantle origins of the Upper Placeta San Pedro Sequence (UPSPS) have remained elusive since first being studied. It is a well-characterized basaltic lava series that erupted over a short interval at ~235-240 ka with highly variable incompatible element abundances and a large xenocrystic cargo. The new comprehensive chemical and radiogenic isotope (Sr-Nd-Pb-Hf) dataset, along with stratigraphic control and understanding of the larger-scale geochemical variability at the TSPC, provides fresh perspectives about the mantle sources and evolution of UPSPS magmas. While the UPSPS magmas are derived from the same sources as other TSPC magmas, they have undergone a unique petrogenetic evolution. This is evident from decoupled trace element-isotopic trends that are difficult to reconcile with other mafic TSPC magmas. Based on the Nd-Hf isotope ratios and trace element ratios, the two UPSPS unit magmas are derived from depleted-`TE enriched' and `prevalent TSPC mantle' sources. High ratios of aqueous fluid-mobile/immobile elements, such as high Pb/Ce and Sr/Nd, as well distinctive Sr and Pb isotope ratios, indicate that the UPSPS magmas were generated through fluxing of the mantle wedge, already depleted by melt removal by an solute-rich fluid derived from the subducted Pacific oceanic crust as well as the overlying trench sediment, which caused it to melt.

O Complexo Vulcânico Yate (CVY) está localizado na Zona Vulcânica Sul dos Andes, Chile. É constituído pelos vulcões Yate, Hornopirén e Gualaihué, além de um conjunto de cones monogênicos conhecido como Centros Eruptivos Cordón Cabrera; aflora em uma área de aproximadamente 400 km2, representado por uma sequência vulcânica de mais de 2.000 metros de sessão vertical contínua. O Vulcão Yate é o maior dos vulcões do complexo, correspondendo a um tipo combinado constituído por cinco unidades litoestratigráficas que se estendem no tempo desde o Pleistoceno Superior (c. 122 ka) até o Holoceno. O Vulcão Hornopirén corresponde a um vulcão estromboliano com registro de atividade eruptiva mais antiga, no Pleistoceno Inferior-Médio (c. 1,4-0,26 Ma), estendendo-se até Holoceno. Por fim, o Vulcão Gualaihué corresponde a um vulcão tipo escudo com atividades efusiva, restrita ao Pleistoceno Médio (c. 440 ka), e freatomagmática no Holoceno. A assinatura geoquímica diversificada das rochas do CVY levou à individualização de quatro tipos de basaltos e andesitos basálticos (BABs) com associações mineralógicas particulares: (i) de alto alumínio e baixo magnésio (BAB-A), com olivina-clinopiroxênio-plagioclásio; (ii) de baixo alumínio e alto magnésio (BAB-AM), com olivina-plagioclásio; (iii) de alto magnésio (BO), com olivina; e (iv) de alto potássio (BAB-K), com coexistência de duas associações mineralógicas incongruentes, olivinaplagioclásio e plagioclásio-clinopiroxênio-orotopiroxênio. A assinatura isotópica desses BABs diferenciase apenas em termos da razão 87Sr/86Sr, em parte acompanhada pelas razões 06Pb/204Pb; as razões 143Nd/144Nd, no entanto, são pouco variáveis. Quando comparados, os BAB-A são as rochas mais radiogênicas, sendo que as razões isotópicas de Sr (> 0,70440) não se correlacionam com a razão Rb/La, sugerindo que o enriquecimento isotópico não teria relação com contaminação crustal. A modelagem quantitativa sugere que esses BABs poderiam ser produto de graus variáveis de fusão parcial de um manto peridotítico, na presença de água (c. 1%). Modelo petrogenético semelhante é proposto para os BAB-AM e BO, todavia com volume de água menor. Já os BAB-K apresentam claras evidências de desequilíbrio mineral, sugerindo a atuação de ambos assimilação e mistura de magmas na sua gênese.Com respeito às rochas mais evoluídas (ABSiO2, andesitos e dacitos), presentes exclusivamente no Vulcão Yate, as características texturais e químicas são pouco conclusivas, sendo as tendências geoquímicas divergentes daquelas típicas de cristalização fracionada. O comportamento geoquímico, endossado pelas texturas de desequilíbrio mineral comuns a esses magmas, mostra mistura (mixing ou mingling) de magmas como um mecanismo importante em suas histórias petrogenéticas. Por fim, a gênese dos riolitos (com anfibólio) parece sugerir fusão parcial de uma crosta anfibolítica ou cristalização fracionada a partir de um magma andesítico, a ~12 km de profundidade. A evolução magmática no CVY, desde o Pleistoceno Inferior-Médio até o Holoceno, incluiria atividade eruptiva de magmas básicos (BABs), ao longo de estruturas N-S (Vulcão Hornopirén) e NE-SW (Vulcão Gualaihué), os quais também devem ter interagido com uma câmara magmática em evolução (Vulcão Yate, c. 10 km de profundidade), provavelmente disposta na junção destas estruturas. Essa interação teria produzido graus variáveis de mistura, cristalização fracionada e assimilação crustal de seus produtos. / The Yate Volcanic Complex (CVY) is located in the Southern Volcanic Zone of the Chilean Andes, at 42°30S, comprising the Yate, Gualaihué and Hornopirén volcanoes. The Yate volcano is a major compound type in which effusive activity occurred since Upper Pleistocene (c. 122 ka) until Holocene. Hornopirén and Gualaihué are minor, and represent strombilian- and shield-type volcanoes, respectively. Effusive activity in Hornopirén extended since Lower to Middle Pleistocene (c. 1,4 Ma to 260 ka), and in Gualaihué was around Middle Pleistocene (c. 440 ka), with subordinate phreatomagmatic eruptions during Holocene. Four types of basalt and basalt andesite associations (BABs) were recognized in YVC: (i) a high-Al and low-Mg group (BAB-A), with olivine-clinopyroxene-plagioclase phenocrystal assembly; (ii) a high-Mg and low-Al group (BAB-AM), with olivine-plagioclase; (iii) a high-Mg group (BO), with olivine and, (iv) a K-rich group (BAB-K) including two incongruent mineral assemblies, olivineplagioclase and clinopyroxene-orthopyroxene. Sr (and Pb) isotopic ratios show different patterns for BABs. When compared together, BAB-A is the most radiogenic group, with 87Sr/86Sr ratios higher than 0.70440 showing no correlation with Rb/La ratios. This suggests that isotopic (and incompatible element) enrichment may not be exactly related to crustal contamination. Quantitative modeling points to partial melting, in c. 1% water (slab-derived fluids), of an enriched peridotite as a possible mechanism involved in the genesis of BAB-A magmas. Similar petrogenetic model is envisaged for BAB-AM and BO; however, minor water contents during melting should be required for. Striking features of mineral disequilibrium suggest each (K-rich) crust assimilation and magma mixing influenced compositional signature of the BAB-K magmas. Magma mixing and mingling seems to be also an important petrogenetic mechanism in genesis of the evolved magmas (silica-rich basalt andesites, andesites, dacites) from the YVC, as shown by petrographic (olivine-clinopyroxene [Mg# 0,8], coexisting with clinopyroxene-orthopyroxene [Mg# 0,76-0,63]) and geochemical features. Genesis of amph-riolites, however, can be explained to each partial melting of amphibolite crust or ~12 km-deep fractional crystallization from an andesitic magma. In summary, the magmatic evolution of YVC, from the Middle Pleistocene to Holocene, is dominated by geochemically distinct basic magmas emplaced along NS- and SW-trending structures. Chemical and mechanical interaction between these magmas occurred into the magma chamber, located at the junction of those structures. In addition, partial melting of the crust produced the most evolved magmas of the complex.

Soputan volcano is one of the few basaltic volcanoes among 127 active volcanoes in Indonesia. It is part of the Sempu-Soputan volcanic complex located south of Tondano Caldera, North Sulawesi and commonly produces both explosive eruptions with VEI 2-3 and effusive lava dome and flow eruptions. Over the last two decades, Soputan had thirteen eruptions, the most recent in 2016. Most eruptions started explosively, followed by dome growth and in some cases pyroclastic flows. Our study focuses on understanding the magmatic system of Soputan and what processes are responsible for its highly explosive eruptions, which are typically uncommon for a basaltic magma composition. Our study includes tephra samples predating the 1911 eruptions, lava flow samples from the 2015 eruption, and ash from a 2015 fallout deposit. Our whole rock major and trace element composition are virtually identical to lava flow and select pyroclastic deposit compositions of Kushendratno et al. (2012) for the 1911-1912 and 1991-2007 eruptions. Bulk rocks contain 49 to 51 wt.% SiO2, whereas 2015 ash samples are slightly more silicic with 53 wt.% SiO2, consistent with segregation of groundmass from phenocrysts in the eruption cloud. Mantle normalized incompatible trace elements indicate strongly depleted HFSE (High Field Strength Elements) and REE (Rare Earth Elements) signatures but with spikes at Pb and Sr and mild enrichment of Rb and Ba. In comparison of data of this study with what was reported by Kushendratno et al. (2012), Fo68-79 olivine-hosted melt inclusions range from basaltic (48-52 wt.% SiO2) to basaltic andesite (54-55 wt.%) as compared to 54 - 65 wt.% SiO2 glass in Fo68-74 olivines. The compositional range of melt inclusions is consistent with 50% fractionation of multiple minerals including observed phenocrysts of olivine, plagioclase, pyroxene and oxides. Compositional trends with an inflection point likely reflect a change in the crystallizing assemblage, where early crystallization includes clinopyroxene and plagioclase, while later crystallization is dominated by plagioclase. New volatile concentration data from melt inclusions (S max. 0.35 wt.%, Cl max. 0.17%, H2O max. 5.2 wt.% from FTIR analyses) are higher than previously reported from younger samples (S max. ~0.07 wt.%, Cl max. 0.2%, H2O max. ~1 wt.%). H2O is relatively constant (~1-4 wt.%) for individual tephra samples (data by FTIR and water by difference method). Our inclusion data suggest that more volatile-rich magmas exist at depth and this is consistent with a model whereby recharge of deep, volatile-rich magmas into a more degassed and crystal-rich magma initiates a new, highly explosive eruption.

Deuterium ratios (δD) of hydrated volcanic glass have been used to reconstruct paleoenvironments, although the reliability and proper sample preparation protocol have been debated. In this study, hydrated volcanic ash samples from the lee of the Cascades were prepared using two separate methods. Method 1 involves sonicating and rinsing samples with hydrochloric acid (HCl) followed by hand-selection of glass shards (125-212µm). Method 2 requires hydrochloric acid (HCl) and hydrofluoric acid (HF) abrasion as well as heavy liquid separation of shards (70-150µm). Method 2 produced more consistent results with decreased intra-replicate variability in both water content (-0.92 wt. %) and deuterium values (-2.5‰ δD). Method 2 δD values of ≥99% isotropic glass were also 2.5-10 % more negative relative to Method 1 values, with an increasing discrepancy with age (3.68-32.66 Ma). Method 2 results suggest volcanic glass did not re-equilibrate with modern water, based on 1) < 2‰ discrepancies between samples of the same ash flow taken from unique sample localities and 2) a ~20‰ difference between samples of different ages (~8 Ma apart) from the same locality. These results support the specified use of HF abrasion and heavy liquid separation on 70-150 µm glass shards to minimize the impact of contaminants on reconstructed paleowater δD values.

Three volcanic domes and related volcanic rocks of Tertiary age are located near Etna, Utah, in Box Elder County. The domes follow a north-south trend and are fault controlled. Flow structure indicates a change from a less viscous, flow-forming lava which produced an exogenous dome to a more viscous lava which formed endogenous domes. Associated pyroclastic deposits are negligible. The volcanic rocks are composed of porphyritic rhyolite and rhyolitic vitrophyre having phenocrysts of quartz, sanidine, plagioclase and biotite with minor amounts of Fe-Ti oxides, hypersthene, allanite and calcic amphibole. Quartz and sanidine phenocrysts are generally embayed whereas plagioclase phenocrysts are euhedral and extensively zoned. Average whole-rock chemical analyses yield: SiO2, 77.13; TiO2, 0.12; Al2O3, 11.01; Fe2O3, 0.9; FeO, 0.35; MnO, 0.02; MgO, 0.19; CaO, 0.82; Na2O, 2.93; K2O, 4.99; P2O5, 0.03; H2O+, 1.17; H2O-, 0.22; total, 99.94 weight percent. Coexisting Fe-Ti oxide microphenocrysts yield equilibration temperatures ranging from 872° to 684°C while respective log f0 2 values range from -13.5 to -19.5. These temperatures are comparable to temperatures obtained using the plagioclase-glass geothermometer at a water pressure of 1 kb. Mineral buffer reactions yield water fugacities with corresponding water pressures up to 4.9 kb. Assuming water pressure equals total pressure, calculated depths of approximately 18 km are obtained indicating an origin within the crust. High silica values and high alkali to calcium ratios indicate that ix the lavas are chemically similar to bimodal rhyolite-basalt assemblages located in other areas of the western United States. Small outcrops of basalt, located west of the Etna area, also suggest a bimodal assemblage. Viscosity values (log n) for the south dome range from 7.05 to 10.35 suggesting that there was a change from a less viscous to a more viscous lava. Comparisons between hydrous and dry calculations indicate that falling water content as well as decreasing temperature were responsible for the change in viscosity and resulting structural changes.

The aim of this thesis is to examine the resilience and vulnerability of Taranaki communities to volcanic hazards, and to propose a strategy to ensure the safety and longevity of Taranaki residents in the event of an eruption. Mt Taranaki is a dormant volcano that is surrounded by a ring plain populated by over 100,000 people. The volcano has had an average eruptive cycle of 330 years, with the last eruption dated at ~1755 AD. Hazards include ash fall, lahars, debris avalanches and pyroclastic density currents. Inglewood, Stratford and Opunake are the largest population centres located in moderate to high hazard zones, and for this reason were chosen as the study communities. Resilience is defined as the capacity to respond to a hazard event by physically and psychologically recovering, adapting to, or changing to similar or better conditions than those experienced before the event. Vulnerability is defined to be people�s incapacity to cope with a hazardous event as a result of their personal characteristics. A person�s vulnerability and resilience is influenced by demographic variables, socio-cognitive variables and preparedness. Inglewood, Stratford and Opunake adults have good self-efficacy and action-coping use, fair risk perceptions, outcome expectancy and response efficacy, but poor understanding of event timing relative to eruption probability, critical awareness, preparedness and information-seeking intentions and preparedness levels. Preparedness is found to be influenced by residents� intentions to prepare, which in turn are influenced by critical awareness, action-coping and outcome expectancy. Taranaki students have a fair awareness of hazard and knowledge of correct response behaviours to various hazards. Preparedness, in terms of preparedness measures undertaken, emergency plans made and emergency practices in place, is low. Students who have participated in hazard-education programmes have a better knowledge of response behaviours, lower levels of hazard-related fear, and reported higher level of preparedness. Spatial analyses, carried out to determine the geographic distribution of at-risk groups within the study communities, showed that the areas most at-risk tend to be those with the highest population densities. The spatial analysis was not as beneficial as expected, due to small data sets, but did provide some results to be considered as a basis for further research. Effective public education can be achieved when delivered to a set of guidelines, such as providing information regularly through multiple media and sources, ensuring consistent messages, targeting information to at-risk groups and monitoring programme effectiveness. Community capacity building projects decrease aspects of vulnerability and build resilience by working at a local scale and targeting at-risk groups. Psychological preparedness education helps citizens to mentally prepare for an event and should be a component of all projects. The proposed strategy calls for (a) forming partnerships with relevant stakeholders to assist with public education, research, and funding, (b) further research into the characteristics of Taranaki communities and effective public education campaigns, (c) the development and implementation of a public education schedule and projects that build community capacity, and d) long-term planning, periodic revision of programmes and consistent public engagement.