[pt] Na América Latina, a corrupção é elemento constituidor de práticas culturais, sociais e de governo. A partir da Operação Lava Jato, considerado o maior escândalo de corrupção já registrado na região, a pauta ganhou ainda mais centralidade, especialmente por parte da mídia. A visão deste estudo éa de que jornalistas são atores da Comunicação Polí tica fundamentais e que participam ativamente da definição e construção das notícias e, assim, da construção e interpretação da realidade. Nesse sentido, esta pesquisa de jornalismo no âmbito da Comunicação Política identifica e analisa percepções construídas por jornalistas brasileiros sobre a corrupção e a Operação Lava Jato, e o papel do jornalismo e dos jornalistas nessas coberturas. O trabalho realiza um estudo de caso, combinando aplicação e análise temática de entrevistas semiestruturadas a uma análise complementar de enquadramento de conteúdo midiático. A pesquisa mostra que as percepções de jornalistas sobre a corrupção estão ligadas, principalmente, à Política, e que reconhecem a existência de uma aliança entre mídia e força-tarefa durante a Operação, que se constituiu de cumplicidade e instrumentalização. O estudo também detalha percepções acerca do status quo que envolveu e envolve a cobertura de escândalos políticos de grande proporção. Como contribuições, busca trazer pistas sobre as definições de corrupção, Lava Jato e jornalismo político que perpassam arenas de discussão pública no Brasil; e espera auxiliar no uso de métodos qualitativos interpretativos em estudos do Campo na região. / [en] In Latin America, corruption is a constituent element of cultural, social and government practices. After Lava Jato Scandal, considered the biggest corruption scandal ever recorded in the region, the agenda gained even more centrality, especially from the media. The vision of this research is that journalists are fundamental Political Communication actors who actively participate in the definition and construction of news and, thus, in the construction of reality. In this sense, this journalism research in the field of Political Communication identifies and analyzes perceptions constructed by Brazilian journalists about corruption and Lava Jato, and the role of journalism and journalists in this coverage. The work uses a case study research strategy, combining application and thematic analysis of semi-structured interviews with a complementary analysis of media content framing. The research shows that perceptions about corruption are mainly linked to Politics and journalists recognize the existence of an alliance between the media and the task force during the Lava Jato, which was constituted of complicity and instrumentalization. The work also details perceptions about the status quo that involved and involves the coverage of political scandals of great proportion. As contributions, the research seeks to bring clues about the definitions of corruption, Lava Jato and political journalism that pervade public discussion arenas in Brazil; and hopes to assist in the use of qualitative interpretive methods in field studies in the region.

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Postglacial activity on the Askja volcanic system, north Iceland, has been dominated by basaltic volcanism. Over 80% of Askja's postglacial basalts fall within a relatively narrow compositional range containing between 4 and 8 wt.% MgO. The 'main series' is further divided into two groups separated by a distinct compositional gap evident in major and trace element concentrations. The most evolved basalts formed by fractional crystallisation within shallow magma reservoirs, followed by the extraction of residual liquid from a semi-rigid, interconnected crystal network. This process is analogous to the formation of melt segregations within single lava flows, and was responsible for generating several small-volume, aphyric basaltic lavas erupted along caldera ring fractures surrounding the Oskjuvatn (Askja lake) caldera in the early 20th century. Further examples of evolved basalt are found throughout Askja's postglacial volcanic record. However, Askja's early postglacial output is dominated by more primitive compositions. Some of the most primitive basalts erupted within the Askja caldera are found in phreatomagmatic tuff cone sequences which crop out in the walls of Oskjuvatn caldera. one such tuff sequence has been dated at between 2.9 and 3.6 ka. This tuff cone shares geochemical source characteristics, such as Nb/La and Nb/Zr, with basaltic tephras erupted during precursory activity to the Plinian-phreatoplinian eruption of 28th-29th March 1875. It may therefore be considered to be compositionally representative of the primitive basaltic magmas supplied to Askja during the postglacial period. The predominance of relatively primitive basalt (6.8 wt.% MgO) within Askia's postglacial lava succession suggests that it did not have a permanent shallow magma chamber during the postglacial period. It is envisaged that the postglacial Askja magmas evolved by a process of polybaric factionation in transient, sill-like magma storage zones located at various levels in the crust. The most primitive magmas erupted directly from deeper reservoirs, while the more evolved magmas experienced longer crustal residence times. The buoyant rise of volatile-enriched melt from these sill-like bodies, without mobilising phenocryst phases, explains the observation that almost all lavas on Askja's eastern and southern lava aprons are essentially aphyric. The 28th-29th March 1975 eruption marked the climax of a volcanotectonic episode on the Askja volanic system lasting from late 1874 to early 1876. Fissure eruptions also occurred at the Sveinagja graben, 45-65 km north of Askja, between February and October 1875, producing the Nyjahraun lava. A strong similarity exists between whole-rock major element concentrations from Myjahraun and the Askja 20th century basalts. This has led to the suggestion that these basalts originated from a common shallow magma reservoir beneath Askja central volcano, with the Nyjahraun eruptions being fed by a lateral dyke extending northwards from Askja. This theory also offers an explanation for the observation that the volume of phyolitic ejecta from 28th-29th March 1875 is significantly less than the volume of Oskjuvatn caldera, which was formed as a result of this eruption. New major and trace element data from whole-rock and glass samples indicated that Nyjahraun and the Askja 20th century basalts did not share a common parental magma. A detailed investigation of historical accounts from explorers and scientists who visited Askja between 1875 and 1932 reveals that Oskjuvatn caldera took over 40 years to reach its current form, and that its size in 1876 was equal to the volume erupted on 28th-29th March 1875. Small injections of magma into an igneous intrusion complex beneath Askja, coupled with background deflation, are sufficient to provide the required accommodation space for continued caldera collapse after 1876. Lateral flow is therefore not required to explain the volume of Oskjuvatn caldera, nor the eruption of evolved basaltic magma on the Askja volcanic system in 1875. It has been conjectured that the Holuhraun lava, located at the southern tip of the Askja volcanic system, was also connected with the 1874-76 Askja volcanotectonic episode. However, major and trace element data from whole-rock samples, glass and melt inclusions receal the Holuhraun is geochemically more similar to basalts erupted on the Bardarbunga-Veidivotn volcanic system than to postglacial basalts from Askja. The division between the 'Askja' and 'Veidivotn' geochemical signatures appears to be linked to east-west-striking lineations in the region south of Askja. This indicates that a particular geochemical signature is not necessarily confined to the tectonic expression of a single volcanic system, and has important implications for the identification and delineation of individual volcanic systems beneath the northwest sector of Vatnajokull.

Geóloga / El flujo de lava asociado al evento eruptivo de 1971 del volcán Villarrica es de composición basáltica y posee características de flujo transicional entre pahoehoe y a a . Su potencia fluctúa entre 13 m y 4 m y alcanza una extensión de 16,5 km la cual, de acuerdo a la literatura, fue alcanzada en apenas 48 horas. En la vereda opuesta se encuentra la colada de lava asociada al cono Navidad. Esta posee un amplio registro sobre su avance elaborado mediante observación durante el mismo evento eruptivo (Naranjo et al., 1992). Se caracteriza por su lento avance, recorriendo 10,2 km desde su fuente en 330 días. Este flujo presenta características transicional entre a a y bloques, y un espesor que aumenta hacia el frente alcanzando casi 50 m. A través de la caracterización petrográfica y morfológica de los depósitos antes mencionados, los cuales poseen grandes diferencias tanto en el estilo eruptivo como en su morfología, se obtuvieron los parámetros eruptivos que caracterizaron estas erupciones. Para ello, se utilizaron modelos basados en una dinámica del flujo de lava controlada por el frente del mismo, y el cual puede ser modelado de acuerdo a una reología de tipo Herschel-Bulkley. Se asume además que el levée más externo que presenta la colada es representativo tanto de la altura máxima que esta alcanzó así como de su reología. Los modelos utilizados son el de velocidad media para un flujo con reología Herschel-Bulkley para el flujo de lava del volcán Villarrica, mientras que para el caso de la colada del cono Navidad se usó el modelo basado en una fuerza de retardo debido al yield strength de la corteza como causante principal de la detención de la colada. Los resultados obtenidos tras la aplicación de estos modelos muestran una gran similitud con los registros históricos. Para el flujo del volcán Villarrica se determinó un tiempo total para su emplazamiento de 42 horas y una tasa eruptiva promedio de 140 m3∙s-1 en comparación a 173 m3∙s-1 de acuerdo a Moreno.,(1993). Para el caso del volcán Navidad, se determinó una duración de 288 días y una tasa eruptiva promedio de 8 m3∙s-1 bastante similar los 11 m3∙s-1 de acuerdo a Moreno y Gardeweg (1989). Del análisis realizado se desprende que flujos con altas tasas eruptivas, de corta existencia y extensos, su avance está dominado por la reología interna de la colada, vale decir, consistencia y yield strength, mientras que flujos con bajas tasas eruptivas, cuyo emplazamiento conlleva un lapso de tiempo considerable, forman una corteza lo suficientemente importante para ser la causante de la dinámica que sigue el flujo durante su avance y finalmente su detención.

The first part of this thesis investigates the mixing of ambient fluid into axisymmetric high Reynolds number gravity currents. A series of laboratory experiments were conducted in which small scale gravity currents travelled along a wedge shaped channel with an increasing width in the downstream direction. The channel was filled with fresh water and the current was generated using saline solution introduced either by a rapid release of a known finite volume from behind a lock gate or by pumping at a constant rate into the apex of the channel. The distribution and evolution of the density of the flow with distance downstream was measured using a light attenuation technique. Additional experiments were performed by injecting parcels of dye in different regions of the flow in order to visualise the motion of fluid in and surrounding the gravity current. Unlike currents introduced by the release of a finite volume of fluid, where most mixing occurs in the head of the flow, currents produced from a steady source develop a steady tail region behind the front which is also found to entrain a significant amount of ambient fluid. In both types of current, we estimate the fraction of displaced ambient fluid that is entrained into the flow. We then derive a new class of self-similar solutions for gravity currents produced from a finite volume release of fluid. The second part of this thesis develops the experimental method of measuring mixing using light attenuation to investigate the mixing of liquid in a vertical conduit which results from a continuous stream of high Reynolds number gas bubbles. The experiments identify that the mixing in the wake of the bubbles leads to a net dispersive transport along the conduit. The process provides an explanation for the heat transfer within a volcanic conduit in the case of a gas-slug flow regime as occurs in the near surface region of volcanic conduits connected to surface lava lakes. We derive a theoretical model to estimate the heat flux associated with such a system using the empirical law for the dispersive mixing. The predicted heat flux associated with the bubbles is found to be comparable to the heat loss at the surface of lava lakes associated with radiative and convective heat loss. Given values for the gas flux, the lake area and the temperature at the surface of the lake, the model enables new predictions for the size of the volcanic conduit.

The purpose of this research is to better understand how residents of communities located on the flanks of Kilauea, Hawai'i view the hazards associated with volcanic events taking into account hazard proximity, cultural beliefs, municipal trust, and evacuation planning. The study was conducted in the lower Puna district, an area with a rapidly growing population but limited infrastructure. Data were collected though a questionnaire survey undertaken at venues throughout the district, including grocery markets, bakeries, farmers markets, the public pool, and other gathering places. Overall, the results indicated that people understand the natural hazards of the place but are generally not concerned about the potential impacts of these hazards on their livelihoods; few could determine whether or not they lived in a lava zone, the impacts on health, and the need for evacuation planning. Cultural considerations appear to play major role and many residents believe that Madam Pele, Goddess of Fire, has a stake in the events of Kilauea. Both hazard understanding and cultural belief systems varied by gender, age, income, and education. When compared to findings from earlier studies within the lower Puna district, it was noted that opinions have shifted over time and that belief in Pele had strengthened. This study demonstrated that understanding the opinions and patterns of belief within communities must be ongoing and municipal planning must be altered over time to accommodate evolving needs and beliefs of a community to obtain optimum community support.

North Crater occupies the north-western quadrant of the Tongariro Volcanic Centre and represents one of at least eleven vents which have been active on Tongariro since the last glacial maximum. The most recent cone-forming activity at North Crater is thought to have occurred between 14-12 ka ago to produce the distinct, wide, flattopped andesite cone. This project focused mainly on the cone-building eruptions at North Crater, including stratigraphic correlations with distal tephra, interpreting eruptive processes, and establishing the sequence of events during cone construction. Detailed field work identified key stratigraphic sections and facies in the proximal, medial and distal environments. These sections allowed stratigraphic correlations to be made between proximal cone-building facies and distal sheet-forming facies at North Crater, and established a complete North Crater eruption stratigraphy. In the proximal environment, welded and non to poorly welded facies formed from fallout of a lava-fountain, pyroclastic flow or as fallout from a convecting plume. In the medial and distal environment, the lithofacies consist of fallout from a convecting plume and minor pyroclastic flow. Convective fall and non to poorly welded pyroclastic flow deposits dominate the lower eruption stratigraphy suggesting explosive eruptions involving a gas-rich magma. A change to welded deposits produced from lava-fountaining occurs later in the cone-building sequence and suggest a change to lower explosively and eruption of gas-poor magma. Grain size, componentry data, density, petrography and SEM analysis were carried out on representative samples to characterise the different facies, and reveal information about eruption processes. The non to poorly welded deposits are typically made up of vesicular pumice, scoria and mingled clasts of sub-rounded bombs and lapilli. The welded facies are relatively dense and clast outlines are often difficult to distinguish. The eruptives are porphyritic with abundant plagioclase gt clinopyroxene gt orthopyroxene gt opaques. Quartzofeldspathic crustal xenoliths are common and indicate crustal assimilation. Mingled clasts of light and dark glass were found to have microlites present in the dark glass, but were absent in the light glass. Electron microprobe analyses found that the dark and light glass components in a single clast had similar compositions, showing that the contrasting physical appearance of the glass is not due to a different chemical composition. Forty three whole rock XRF analyses showed that the magmas ranged from basaltic andesite to andesite, and Harker variation plots display linear trends typical of magma mixing. Magma mixing as the most important magmatic process is supported by disequilibrium of phenocryst compositions and phenocryst textures. Magma viscosity, bulk density and temperature was determined using MAGMA (Kware), and indicate that they fall into the range of typical andesites. Eruptive activity involved vigorous lava-fountaining, minor convecting eruption plumes and dominant collapsing eruption plumes. This activity has produced welded and non-welded pyroclastic flow and fall deposits to form the large cone seen today. There are significant volcanic hazards associated with this style of activity at North Crater, characterised by lava-fountaining, eruption plume fallout, and widespread pyroclastic flows and lahars extending beyond the ring plain. These could all be potentially devastating to the central North Island of New Zealand.

Tectonic windows are faulted escarpments that expose extensive sections of <em>in situ</em> oceanic crust, providing valuable opportunities to examine upper crustal architecture from a perspective unmatched by other approaches. Recent investigations of tectonic windows by submersible (<em>Alvin, Nautile</em>) and remotely-operated vehicle (<em>Jason II</em>) have recovered an unprecedented suite of dikes and lavas. We focus on compositions of dikes and lavas from intermediate- and super-fast rate crust exposed, respectively, in the Western Blanco Transform (BT) fault and the Pito Deep Rift (PD), to better understand accretionary processes at mid-ocean ridges. In the BT, the upper lavas are generally more primitive than the lower lavas, supporting geophysical and geological studies that suggest off-axis volcanism plays an important role in constructing the upper crust at intermediate-rate spreading centers. The wide range in lava compositions exposed along the BT scarp also lends caution to studies that rely on surface lavas to determine the evolution of sub-axial magmatic conditions.The PD suite allows us to examine accretionary processes over an impressive temporal range, including long-term (millions of years) changes in mantle composition and medium-rate (100s of ka) changes in magmatic regime. Compositions of adjacent dikes reveal that the ocean crust is heterogeneous on short time (<10>ka) and spatial (meters) scales, reflecting along-axis transport of magma from chemically heterogeneous portions of the melt lens. High compositional variability was also observed in adjacent dikes from Hess Deep (HD), a tectonic window into fast-rate crust, suggesting that lateral dike intrusion occurs at all mid-ocean ridges. PD lavas are offset to lower density compositions compared to dikes, an observation previously made in HD, but made here for the first time in other dike-lava populations, suggesting that buoyancy plays a major role in partitioning magma between dikes and lavas. A model for intrusion of a single dike shows that crustal density, magma pressure, and tectonic stress affect the intensity of density-based magma partitioning in a systematic way that can be related to compositions of dike-lava populations. / Dissertation

Diese Arbeit beschäftigt sich mit dem zeitlichen Verlauf und den Gründen des Wechsels zwischen zwei magmatischen Regimen während der Hebung der Zentralen Anden. Das ältere vulkanische Regime wird durch miozäne Schildvulkane repräsentiert, die voluminöse Lavaströme hinterließen. Das zweite Regime besteht aus differenzierteren, steilen Stratovulkanen, mit einem weitaus geringeren Eruptionsvolumen.