Setúbal e a Primeira Guerra Mundial (1914-1918)

A presente dissertação é circunscrita no espaço e no tempo, tendo como objecto de estudo fundamental o concelho de Setúbal durante a I Guerra Mundial (1914-1918). Enquadrando historicamente os impactos do conflito no contexto nacional, Setúbal é revisitada entre os finais de oitocentos e os primórdios do século XX a fim de retratar política, económica, social e culturalmente um dos maiores centros urbanos portugueses dos finais da Monarquia Constitucional e do início da I República. Numa lógica de impactos políticos e económico-sociais, esta investigação promove o redescobrir das vivências quotidianas de Setúbal durante um dos períodos mais negros da História da Humanidade. Através do estudo dos mecanismos de acção e intervenção municipais, bem como dos resultados eleitorais e dinâmicas políticopartidárias locais, transmite-se como foram vividos acontecimentos marcantes da vida pública de Portugal, nomeadamente o 14 de Maio de 1915 e o coup d’état sidonista, realçando como dimensões operárias anárquicas e sindicalistas conviviam com grupos conservadores, católicos e monárquicos. Num plano de economia de guerra, o mundo agrícola é abordado em diferentes sectores, nomeadamente na laranja, na cortiça e nos vinhos, dando maior atenção às questões relacionadas com a decadência da fruta e à abertura de novos mercados exportadores, como o Brasil, pela Casa José Maria da Fonseca. A indústria de conservas de peixe, que viveu um boom neste período como resultado da intensa procura externa dos países aliados que tinham nas latas de conserva o alimento das tropas nas trincheiras, representa outro foco de análise deste trabalho. Consequentemente aborda-se o papel da estrutura portuária local na resposta às necessidades de consumo britânicas, francesas e italianas. Por fim, os impactos sociais do conflito em Setúbal constituem um dos enunciados desta investigação, compreendendo como o estudo de uma imprensa dividida na questão intervencionismo versus anti-intervencionismo reflectiu um concelho que viveu como poucos a crise de abastecimentos e a carestia de vida. A proliferação de greves, manifestações contra a guerra, as deserções militares e os assaltos colectivos representam o culminar de um vulcão que entrou em erupção e que ainda sofreu as agruras da epidemia da gripe pneumónica até ao final do ano de 1918.

CHARACTERIZING THE FIRST HISTORIC ERUPTION OF NABRO, ERITREA: INSIGHTS FROM THERMAL AND UV REMOTE SENSING

June 2011 saw the first historic eruption of Nabro volcano, one of an ongoing sequence of eruptions in the Afar-Red Sea region since 2005. It halted air travel in northern Africa, contaminated food and water sources, and displaced thousands from their homes. Due to its remote location, little was known about this event in terms of the quantity of erupted products and the timing and mechanisms of their emplacement. Geographic isolation, previous quiescence and regional civil unrest meant that this volcano was effectively unmonitored at the time of eruption, and opportunities for field study are limited. Using free, publicly available satellite data, I examined rates of lava effusion and SO2 emission in order to quantify the amount of erupted products and understand the temporal evolution of the eruption, as well as explore what information can be gleaned about eruption mechanisms using remote sensing data. These data revealed a bimodal eruption, beginning with explosive activity marked by high SO2 emission totalling 1824 - 2299 KT, and extensive ash fall of 270 - 440 km2. This gave way to a period of rapid effusion, producing a ~17 km long lava flow, and a volume of ~22.1 x 106 m3. Mass balance between the SO2 and lava flows reveals no sulfur 'excess', suggesting that nearly all of the degassed magma was extruded. The 2011 eruption of Nabro lasted nearly 6 weeks, and may be considered the second largest historic eruption in Africa. Work such as this highlights the importance of satellite remote sensing for studying and monitoring volcanoes, particularly those in remote regions that may be otherwise inaccessible.

DOING MORE WITH SHORT PERIOD DATA: DETERMINING MAGNITUDES FROM CLIPPED AND OVER-RUN SEISMIC DATA AT MOUNT ST. HELENS

How can we calculate earthquake magnitudes when the signal is clipped and over-run? When a volcano is very active, the seismic record may saturate (i.e., the full amplitude of the signal is not recorded) or be over-run (i.e., the end of one event is covered by the start of a new event). The duration, and sometimes the amplitude, of an earthquake signal are necessary for determining event magnitudes; thus, it may be impossible to calculate earthquake magnitudes when a volcano is very active. This problem is most likely to occur at volcanoes with limited networks of short period seismometers. This study outlines two methods for calculating earthquake magnitudes when events are clipped and over-run. The first method entails modeling the shape of earthquake codas as a power law function and extrapolating duration from the decay of the function. The second method draws relations between clipped duration (i.e., the length of time a signal is clipped) and the full duration. These methods allow for magnitudes to be determined within 0.2 to 0.4 units of magnitude. This error is within the range of analyst hand-picks and is within the acceptable limits of uncertainty when quickly quantifying volcanic energy release during volcanic crises. Most importantly, these estimates can be made when data are clipped or over-run. These methods were developed with data from the initial stages of the 2004-2008 eruption at Mount St. Helens. Mount St. Helens is a well-studied volcano with many instruments placed at varying distances from the vent. This fact makes the 2004-2008 eruption a good place to calibrate and refine methodologies that can be applied to volcanoes with limited networks.

Volcanic processes and human exposure as elements to build a risk model for Volcan de Fuego, Guatemala

The activity of Fuego volcano during the 1999 - 2013 eruptive episode is studied through field, remote sensing and observatory records. Mapping of the deposits allows quantifying the erupted volumes and areas affected by the largest eruptions during this period. A wide range of volcanic processes results in a diversity of products and associated deposits, including minor airfall tephra, rockfall avalanches, lava flows, and pyroclastic flows. The activity can be characterized by long term, low level background activity, and sporadic larger explosive eruptions. Although the background activity erupts lava and ash at a low rate (~ 0.1 m3/s), the persistence of such activity over time results in a significant contribution (~ 30%) to the eruption budget during the studied period. Larger eruptions produced the majority of the volume of products during the studied period, mainly during three large events (May 21, 1999, June 29, 2003, and September 13, 2012), mostly in the form of pyroclastic flows. A total volume of ~ 1.4 x 108 m3 was estimated from the mapped deposits and the estimated background eruption rate. Posterior remobilization of pyroclastic flow material by stream erosion in the highly confined Barranca channels leads to lahar generation, either by normal rainfall, or by extreme rainfall events. A reassessment of the types of products and volumes erupted during the decade of 1970's allows comparing the activity happening since 1999 with the older activity, and suggests that many of the eruptive phenomena at Fuego may have similar mechanisms, despite the differences in scale between. The deposits of large pyroclastic flows erupted during the 1970's are remarkably similar in appearance to the deposit of pyroclastic flows from the 1999 - 2013 period, despite their much larger volume; this is also the case for prehistoric eruptions. Radiocarbon dating of pyroclastic flow deposits suggests that Fuego has produced large eruptions many times during the last ~ 2 ka, including larger eruptions during the last 500 years, which has important hazard implications. A survey was conducted among the local residents living near to the volcano, about their expectations of possible future crises. The results show that people are aware of the risk they could face in case of a large eruption, and therefore they are willing to evacuate in such case. However, their decision to evacuate may also be influenced by the conditions in which the evacuation could take place. If the evacuation represents a potential loss of their livelihood or property they will be more hesitant to leave their villages during a large eruption. The prospect of facing hardship conditions during the evacuation and in the shelters may further cause reluctance to evacuate. A short discussion on some of the issues regarding risk assessment and management through an early warning system is presented in the last chapter.

VALIDATION OF A 'DISPLACEMENT TOMOGRAPHY' INVERSION METHOD FOR MODELING SHEET INTRUSIONS

The study of volcano deformation data can provide information on magma processes and help assess the potential for future eruptions. In employing inverse deformation modeling on these data, we attempt to characterize the geometry, location and volume/pressure change of a deformation source. Techniques currently used to model sheet intrusions (e.g., dikes and sills) often require significant a priori assumptions about source geometry and can require testing a large number of parameters. Moreover, surface deformations are a non-linear function of the source geometry and location. This requires the use of Monte Carlo inversion techniques which leads to long computation times. Recently, ‘displacement tomography’ models have been used to characterize magma reservoirs by inverting source deformation data for volume changes using a grid of point sources in the subsurface. The computations involved in these models are less intensive as no assumptions are made on the source geometry and location, and the relationship between the point sources and the surface deformation is linear. In this project, seeking a less computationally intensive technique for fracture sources, we tested if this displacement tomography method for reservoirs could be used for sheet intrusions. We began by simulating the opening of three synthetic dikes of known geometry and location using an established deformation model for fracture sources. We then sought to reproduce the displacements and volume changes undergone by the fractures using the sources employed in the tomography methodology. Results of this validation indicate the volumetric point sources are not appropriate for locating fracture sources, however they may provide useful qualitative information on volume changes occurring in the surrounding rock, and therefore indirectly indicate the source location.

Life Cycle of Deccan Trap Magma Chambers: A Crystal Scale Elemental and Strontium Isotopic Investigation

The Deccan Trap basalts are the remnants of a massive series of lava flows that erupted at the K/T boundary and covered 1-2 million km2 of west-central India. This eruptive event is of global interest because of its possible link to the major mass extinction event, and there is much debate about the duration of this massive volcanic event. In contrast to isotopic or paleomagnetic dating methods, I explore an alternative approach to determine the lifecycle of the magma chambers that supplied the lavas, and extend the concept to obtain a tighter constraint on Deccan’s duration. My method relies on extracting time information from elemental and isotopic diffusion across zone boundary in an individual crystal. I determined elemental and Sr-isotopic variations across abnormally large (2-5 cm) plagioclase crystals from the Thalghat and Kashele “Giant Plagioclase Basalts” from the lowermost Jawhar and Igatpuri Formations respectively in the thickest Western Ghats section near Mumbai. I also obtained bulk rock major, trace and rare earth element chemistry of each lava flow from the two formations. Thalghat flows contain only 12% zoned crystals, with 87Sr/86Sr ratios of 0.7096 in the core and 0.7106 in the rim, separated by a sharp boundary. In contrast, all Kashele crystals have a wider range of 87Sr/86Sr values, with multiple zones. Geochemical modeling of the data suggests that the two types of crystals grew in distinct magmatic environments. Modeling intracrystalline diffusive equilibration between the core and rim of Thalghat crystals led me to obtain a crystal growth rate of 2.03x10-10 cm/s and a residence time of 780 years for the crystals in the magma chamber(s). Employing some assumptions based on field and geochronologic evidence, I extrapolated this residence time to the entire Western Ghats and obtained an estimate of 25,000 – 35,000 years for the duration of Western Ghats volcanism. This gave an eruptive rate of 30 – 40 km3/yr, which is much higher than any presently erupting volcano. This result will remain speculative until a similarly detailed analytical-modeling study is performed for the rest of the Western Ghats formations.

Determining magmatic processes from analysis of phenocrysts and gabbroic xenoliths contained in Calbuco andesites

Calbuco Volcano, in Southern Chile, has eruptive products of predominantly andesitic hornblende-bearing lava. A purpose of this work is to understand magmatic processes and how Calbuco magma chemistry is related to the explosive volcanic character. Calbuco lava has a mineral assemblage of plagioclase, hornblende, orthopyroxene, clinopyroxene, olivine, and magnetite and entrained gabbroic xenoliths with the same mineral assemblage. The presence of hornblende is evidence for dissolved water in the magma. Detailed petrographic/textural analysis has been done using petrographic microscopy and back-scattered electron imaging (BSE); geochemical analysis by electron microprobe (EPMA). Major findings include 1) that hornblende and hornblende-bearing gabbroic cumulates crystallize from Calbuco magma, 2) that plagioclase grains are compositionally zoned, recording evidence of temperature, chemical, and water content fluctuations in the magma, and 3) that hornblende is unstable under upper magma chamber conditions at Calbuco, and is breaking down into plagioclase, olivine, orthopyroxene, clinopyroxene, and magnetite in the magma.

AVALANCHAS EN LA SIERRA VOLCANICA CENTRAL. EL CASO DE RIO CIRUELAS

El dia 20 de julio de 1988, en la tarde, se produjo una avalancha considerable en el rio Ciruelas, localizado en la ladera suroeste del volcán Barva, Heredia, Costa Rica, causando daños enormes en la población de San Bosco de Santa Bárbara.  El área afectada se dividió en tres grandes sectores, descritos a continuación: I.        SECTOR SUPERIOR (DESLIZAMIENTOS)Comprendido entre las cotas de 2.600m y 2.800 m, o sea cerca de la cima del Barva, caracterizado por desprendimientos de materiales poco consolidados (cenizas gruesas) con un ancho de aproximadamente 30m-40m y una profundidad de aproximadamente 4m-5m en casi todos los afluentes del rio Ciruelas. II.      SECTOR INTERMEDIO (TRANSITO)Comprendido entre las cotas de 2.600m y 1.600m, caracterizado por profundización erosiva del cauce en areas de materiales poco resistentes y por la ocurrencia de pequeños deslizamientos secundarios causados por la profundización del cauce. III.    SECTOR BAJO ( SEDIMENTACION)De 1.600m hasta 950m, caracterizado por la sedimentación en los primeros kilómetros de material grueso(bloques mayores de 2m). El pueblo de San Bosco esta situado sobre un abanico aluvial de materiales de eventos similares. En lo9s siguientes kilómetros se presenta la sedimentación de materiales mas finos.  La causa de esta desastre es únicamente la presencia de lluvias de alta intensidad provocadas por un frente de brisa, que en este dia ocurrieron en el sector I, provocando los deslizamientos y por ende las avalanchas de rocas y lodo que llegaron a los lugares mas bajos. Por estar el sector superior totalmente y el sector intermedio parcialmente en la selva virgen del Parque Nacional Braulio Carrillo se puede excluir definitivamente algún impacto humano que haya causado la desestabilización de las laderas. Por los vestigios de eventos antiguos de este tipo( acumulaciones cerca de San Bosco) se puede derivar que estos fenómenos también ocurrieron en tiempos pasados , sin embargo, se estima la probabilidad de una repetición pronta como muy baja. SUMMARYA big avalanche  that occurred the 20 th of july in the afternoon in the (rio ciruelas) watershed situated on the sowthwestern slope of the Volcano Barva, Costa Rica, caused big losses in the village of San Bosco de Santa Barbarbara. Based on field observations we distinguished three sectors analysed below: I.                    SUPERIOR SECTOR (LAND SLIDES)Localed in altitude between 2.600m and 2.800m near the peak of the volcano, characterized by landslides of poorly consolidated ashes, with a  width of between 30m-40m and a depth of about 4m to 5m, found in nearly and all of the affluents of the (Rio Ciruelas). II.                  MEDIUM SECTOR (TRANSIT)Between 2.600m and 1.600m, characterized by deep erosion in area of materials of low resistivity and by secondary(small) landslides provoked by the destruction of the support. III.                LOWER SECTOR ( SEDIMENTATION)Between 1.600m and 950m, characterized by sedimentation, in the first kilometers of coarse material (sometimes<2m).The village of San Bosco was constructed exactly above the detrictic cone of anterior events. In the subsequent kilometers we found the sedimentation of fine materials. As the cause of this desastre we analysed high intensity rainfalls provoked by a local front in the zone of the firt sector, causing landslides and then avalanches in the lower part of the primary forest of the national park <<Braulio Carrillo>>.The sediments of older events(the San Bosco cone) prove that avalanches ocurr in this area with a certain frecuency, but with relatively long recurrence intervals.   

DESLIZAMIENTOS EN LA CUENCA MEDIA Y SUPERIOR DEL RIO REVENTADO, CARTAGO, COSTA RICA

La cuenca del río Reventado, situada en la vertiente sur del Volcán Irazú, Costa Rica, presenta actualmente un riesgo para la ciudad de Cartago (aproximadamente 30.000 habitantes), especialmente para algunos asentamientos cercanos al río mismo.  Este riesgo consiste, en primer lugar, en un deslizamiento con grandes extensiones en la parte inferior de la cuenca media, el deslizamiento llamado San Blas. Este deslizamiento está formado por la antigua terraza de Banderilla de material de avalanchas holocenas y que fue activado en el comienzo de la década de los setenta por la destrucción de su sostén por la explotación de materiales en tajos. Anteriormente, la última vez en los años 63-65, el riesgo era diferente:Erupciones del Irazú con grandes cantidades de cenizas originaron un cambio violento del régimen hidrológico, intensas lluvias causaron crecidas y avalanchas, profundizando en la cuenca superior los cauces y provocando así deslizamientos. En la cuenca baja estas avalanchas provocan inundaciones y acumulaciones de los abanicos diferentes. Los deslizamientos activados por estos eventos actualmente muestran poca o ninguna actividad, pero el riesgo de repeticiones de estos eventos persiste. SUMMARYThe Rio Reventado watershed, situated in the southern slope of the Irazú volcano, Costa Rica, presents a risk for the town of Cartago (30.000 inhabitants) and specially for some settlements near the river.  In first place, this risk consists of a huge landslide in the lower part of the watershed, the<<San Blas- landslide, which is formed by the labaric material of a Holocene terrace of the Reventado, called <<Banderilla- terrace>>. At the beginning of the seventies this terrace was activated due the explotation of its materials in two quarries.  The risks existing before in this watershed were of an other nature, an example give the events of years 1963-65:A violent hydrologic change in the upper part of the Reventado watershed due to the ashfall of an eruption of the Irazú caused big mudflows whish depend the river beds and thus provoked landslides.  These mud flows caused inundations and accumulations in the lower watershed. Today, the land slides activated in the sixties are stable or semistable, but the risk of repetitions still persists.