Fakultät für Geowissenschaften - Digitale Hochschulschriften der LMU Archiv

Since the collapse of the Soviet Union and since the start of the economic crisis in Cuba (Periodo Especial), an increase in the variety of ecological problems has been registered concentrating primarily nowadays on the Cuban capital Havana. In conjunction with the aforementioned political and economical situation, Havana became the most important migration centre in Cuba since the beginning of the 90´s. This particular thesis will focus on the analysis of current urban-ecological and landscape-ecological problems in Havana (urban development, water supply and sewage disposal, waste disposal and waste sites, green spaces, agriculture). Solutions proposed by the relevant participants from the sectors planning, environmental politics and local municipality (IPF, DPFF, CITMA, GDIC, TTIB) will be complemented in each case with feasible realistic oriented recommendations made by the author. The primary focus of this thesis addresses the relationship between physical-geographical and social-geographical interacting complexes in the examination area whereby the author has chosen an integrative interdisciplinary approach. Several years of field work research in Havana has served as basis for this research. Within the scope of characterising the physical geographical environment (climate, geology, geomorphology, soil, hydrology, vegetation), the fundamentals associated with ecological degradation were first identified. Havana’s historical urban development and the decisive phases in its historical development (colonialism, republican phase, socialism) were genetically analysed in order to understand the historical background and association with existing problems. In order to understand the approach i.e. possibilities of interventional activities and dealings of Cuban planning authorities in Havana, the author presents new structures respective stakeholders of reorganised urban development, environmental policy and municipal participation. In addressing the issue of urban renewal and problem analysis (infrastructure, foundation of buildings etc.) constructional deficits will be identified focussing on colonial, republican and socialist districts in Havana. A main focus of attention in this thesis is the analysis of Cuban standards (Accesoria, Barrio Insalubre, Bohio, Ciudadela, Cuarteria, Pasaje, Solar) in which an exemplary situation of urban squatters will be depicted (Barrios Insalubres). The negative consequences evolving from the Periodo Especial will be addressed, similarly opportunities resulting from economical transformation (real estate investment, renovation model Habana Vieja etc.). In connection with this, the author assesses the difficulties facing the drinking water supply and waste water disposal in Havana (problems relating to infrastructural supply, water supply, effects on private households, on state owned public waters, on the Gulf of Mexico, surface water and ground water contamination, flooding etc). In respect of waste disposal i.e. waste deposition the main difficulties arise with the safekeeping, treatment and disposal of household waste. These problems pose major health and hygiene risks for the concerned population. With respect to Havana’s “green spaces” problem, characteristically features respective in residential areas, industrial areas and areas at degraded river banks and state initiated (forestation) programmes will be presented. Similarly, the author will propose recommendations aimed at substantial development respective “green spaces planning” (improvement of micro climatic aspects, increase in standard of living, occupational political effects etc.). The conclusion of the problem analysis focuses on the ecological difficulties of the agricultural sector in Havana (sugarcane, pastoral grazing i.e. urban agricultural programmes). Based on representative examples of the most important organisational structures (UBPC, CCS, CPA, Organoponicos, private farmers) these problems will be highlighted (site selection, drainage of contaminated water, soil quality, soil erosion). Programmes of action proposed by the author proposing periphery urban agriculture in Havana mark the conclusion of this chapter wrapping up the complex themes relevant to agriculture (institutions, ecology, economy, social aspects). The conclusion of the thesis focuses on the renaturation of an illegal waste site situated in the west of the Havana city province in which the author and his fellow Cuban colleagues not only developed a renaturation concept for this project but were also involved in all measures associated with it. The ecological problems identified on site mainly concern the inhabitants of the surrounding Barrios Insalubres, whereby the extension of the inner urban protected areas has contributed to an improved social, cultural and economical situation for the population. The author’s intense and close cooperation with relevant Cuban stakeholders from the fields of science, politics, administration, the service sector, planning authorities and local population proved indispensable for the success of the applied oriented approach taken here.

Die fortschreitende Erhöhung des Integrationsgrades moderner elektronischer und optoelektronischer Bauelemente erfordert im zunehmenden Maße eine Funktionalisierung von Systemstrukturen auf Nanometerskala. In diesem Zusammenhang bietet poröses Silizium (PSi) ein heute noch nicht abschätzbares Anwendungspotential, da vor allem seine optischen Eigenschaften auf Quanteneffekten („quantum confinement“) in Kristalliten beruhen, deren Ausdehnung nicht mehr als wenige Nanometern betragen. So sind beispielsweise sehr einfach aufgebaute nanoskalige Punkt- und Linienstrukturen aus porösem Silizium vorstellbar, die ganz bestimmte optische, aber auch elektrische Eigenschaften besitzen. Die vorliegende Arbeit trägt mit ihren Untersuchungen zur Herstellung von integrierten PSi-Emittersensoren für die optische Nahfeldmikroskopie zur Erforschung und Entwicklung solcher nanoskaligen Funktionselemente bei. Dabei mußte weitgehend technologisches Neuland beschritten werden, denn der geforderte Miniaturisierungsgrad für Nahfeldlichtquellen verlangte eine Verfeinerung der Strukturierungsverfahren für poröses Silizium bis zur Größenordnung von 100 nm und darunter. Die speziell zu diesem Zweck entwickelten lokalen PSi-Formierungsverfahren eigenen sich jedoch nicht nur für die definierte und reproduzierbare Formierung nanoskaliger PSi-Regionen an nahfeldoptischen Sensorspitzen. Da sie zu herkömmlichen Siliziumtechnologien kompatibel sind, ermöglichen sie die extrem lokalisierte, monolithische Integration von porösem Silizium in Si-Bauelementen der unterschiedlichsten Strukturformen. Im Ergebnis der Arbeit konnten zwei verschiedene Lösungswege zur Realisierung eines integrierten optischen PSi-Nahfeldsensors aufgezeigt werden. Diese beruhen zum einen auf dem herkömmlichen AFM-Siliziumcantilever und zum anderen auf einem neu entwickelten AFM-Scherkraftsensor. Beide Fertigungskonzepte erlauben eine ökonomisch vertretbare Herstellung des Sensors in einem kostensparenden industriellen Batch-Prozeß, da alle notwendigen technologischen Herstellungsschritte parallelisierbar und in übliche Herstellungsprozesse der Rastersondenfertigung auf Halbleiterbasis implementierbar sind.

Magnetite is a widespread accessory mineral in rocks and soils. As was first shown by Lowenstam (1962), magnetite frequently forms also by biochemical processes, with varying degrees of control of the organisms over the mineralization process. Lowenstam distinguishes between biologically induced (BIM) and biologically controlled mineralization(BCM). The former refers to processes with no biological control, and the later to processes with strict metabolic and genetic control. In this thesis, two examples of biogenic magnetite with eminently different magnetic properties are studied. One is magnetite as found in so-called magnetotactic bacteria; the second example is magnetite as identi¯ed in tissue of pigeon's heads. In the first part of this work, the results of a series of rock magnetic measurements on concentrated samples of pure magnetotactic bacteria will be presented. These bacteria offer a unique opportunity to study the process of biologically controlled mineralization, since these organisms synthesize intracellular particles of magnetite or greigite arranged in chains, that give the bacterium the characteristic property of a swimming compass needle. The magnetic crystals, so-called magnetosomes, are magnetically speaking stable single-domain particles, characterized by a size such that the particles have minimum induced magnetization and maximum permanent magnetic moment (i.e. particle size between 30 and 130 nm). The bacteria studied here have been harvested in sediments from lake Chiemsee. They were extracted from the sediments and concentrated to an extent that enabled a detailed characterization by macroscopic magnetic measurements. The so-called Bacteriodrome was used to concentrate samples of approximately 10E7 cells. Different magnetic criteria, aiming to specifically identify bacterial magnetite in sediments, have been tested, including: (1) acquisition and demagnetization of isothermal remanent magnetization (IRM); (2) acquisition of anhysteretic remanent magnetization and (3) thermal dependence of low temperature saturation IRM, after cooling in zero field (ZFC) or in a 2.5 T field (FC) from 300 to 5 K. The best method turns out to be the so-called delta-delta test (dFC/dZFC), first proposed by Moskowitz et al. (1993), and based on the low temperature variation of the SIRM, measured both in a strong field (FC) and in zero field (ZFC). At the Verwey transition (ca. 120 K) the d-value for each curve is determined and the d-ratio (dFC/dZFC) calculated. Values exceeding 2, are indicators for the presence of chains of stable single-domain particles, which form only under strict biological control. However, it is shown that the suitability of rock magnetic techniques to detect and characterize biogenic magnetite in bulk, natural samples such as lake sediments is still limited, due to diagenetic processes and the occurrence of other non-biogenic magnetic minerals, which blur the distinct magnetic properties of the former. The only certain proof for bacterial magnetite is the optical identification -although time consuming and tedious- by Transmission Electron Microscopy. The magnetite inclusions found in pigeon tissue are very different in their magnetic properties with respect to bacterial magnetite. With their small grain size (between 2 and 10 nm), these particles fall within the superparamagnetic size range and are characterized by a large induced magnetization and no permanent magnetic moment. The pigeon magnetite is concentrated in spherical clusters of approximately 1-3 micrometers in diameter. The response of these clusters to magnetic fields has been simulated by spherules of ferrofluid. Depending on their geometrical arrangement these spherules show peculiar magnetic properties. Based on these properties, three models have been developed experimentally and theoretically with respect to a possible application as biological sensory elements. The magnetic properties of the sensory models are tested in the light of behavioral experiments conducted in the past on homing pigeons and migratory birds. In these experiments, the birds were exposed to defined magnetic fields to specifically affect a magnetite-based magnetoreceptor. As will be seen, most of the responses of the birds observed in the behavioral experiments can be explained by simulating the effects of these magnetic treatment on ferrofluid spherules.

Mit der Einführung eines fallpauschalierten Vergütungssystems für die Finanzierung von Krankenhausleistungen, den German-Diagnosis Related Groups (G-DRGs), sollen Wirtschaftlichkeitsreserven sowie Qualitätsverbesserungen erreicht werden. Im Gegensatz zum bisherigen Finanzierungssystem, bei dem die Höhe der Vergütung nach der Anzahl der Behandlungstage berechnet wurde und bei dem die individuellen Kostenstrukturen der einzelnen Krankenhäuser zum Tragen kamen, beruhen die G-DRGs auf der medizinisch orientierten Gruppierung von Fallgruppen mit einem ähnlichen Ressourcenverbrauch. Diese Durchschnittspreise bewirken eine Umverteilung der Geldströme von den vergleichsweise ineffizienten zu den besonders effizienten Krankenhäusern. Das Funktionieren des G-DRG-Systems hängt entscheidend von der Gestaltungsfreiheit ab, die den Krankenhäusern und den Krankenkassen bei der zukünftigen Gestaltung und Verteilung der notwendigen Krankenhausleistungen zugestanden wird. Dem steht derzeit die Krankenhausplanung der Bundesländer diametral entgegen, weil diese üblicherweise als angebotsorientierte Kapazitätsplanung ausgestaltet ist, bei der für festgelegte Standorte der Umfang und die Fachrichtung der vorzuhaltenden Betten vorgegeben wird. Ein Festhalten an dieser Kapazitätsplanung würde die Ziele der G-DRGs unterlaufen. Trotzdem verbleibt bei den Bundesländern die Aufgabe, für eine flächendeckende und wohnortnahe Versorgung der Bevölkerung mit Krankenhausleistungen zu sorgen. Als zentrales Instrument dafür ist vorgesehen, dass die Bundesländer abweichend von den Vereinbarungen zwischen Krankenhäusern und Krankenkassen bei Gefährdung der Versorgung einzelnen Krankenhäuser einen Sicherstellungszuschlag zugestehen können. Für die Sicherstellung der stationären Notfallversorgung ist ein entgegengesetzter Anreizmechanismus vorgesehen. Hier müssen diejenigen Krankenhäuser eine finanzielle Einbuße hinnehmen, die aus dieser Versorgung ausscheiden. Damit wird die Aufrechterhaltung der stationären Notfallversorgung auch eine betriebswirtschaftliche Abwägung, ob die Vorhaltung bestimmter Einrichtungen teurer ist als die Inkaufnahme eines Abschlages pro erbrachter Leistung. Schließlich kann die Vorgabe von Mindestmengen, von der die weitere Erbringung der entsprechende Leistungen abhängig gemacht wird, deutliche Einschränkungen für die regionale Verfügbarkeit stationärer Leistungen bewirken. Derzeit stehen den Bundesländern keine geeigneten Instrumente zur Verfügung, um die aktuelle Versorgungssituation zu erheben und zu bewerten und ggf. abzuwägen, ob Planungseingriffe notwendig sind. Im Rahmen dieser Untersuchung werden mit sog. Angebots- und Nachfrageprofilen GIS-basierte Instrumente vorgestellt, mit denen zentrale Planungsparameter abgebildet werden können: Entfernung zur Bevölkerung, Kapazitäten sowie Umfang der potentiell zu versorgenden Bevölkerung. Durch die exemplarische Umsetzung im Untersuchungsgebiet konnte die grundsätzliche Eignung dieser Instrumente bei der Bearbeitung der zukünftigen Planungsfragen gezeigt werden. Gleichzeitig bilden diese Instrumente einen Ausgangspunkt für die Entwicklung eines umfassenden GIS-basierten Monitoringkonzeptes für die Krankenhausplanung, mit dem über die Integration und Verknüpfung unterschiedlicher und voneinander unabhängiger Daten sowohl kurzfristige Analysen von Versorgungssituationen als auch mittelfristige Bedarfsprognosen sowie Simulationsmodelle umgesetzt werden können.

Enhanced knowledge of pre- and syn-eruptive processes is vital to deal with the increasing threat imposed to population and infrastructure by volcanoes that have been active historically and may potentially erupt in future. For many years, most of this knowledge was received from experiments on analogue materials and/or numerical models. In order to increase their significance and applicability for the “real” case, the natural complexity may not be oversimplified and the input parameters must be reliable and realistic. In the light of this, a close connection of field and laboratory work is essential. Volcanic eruptions may be phreatic, phreatomagmatic or magmatic, the latter scenario of which was addressed in this study. Rising magma is subject to decreasing lithostatic pressure. As a direct consequence, volatiles become increasingly oversaturated and bubbles will nucleate and grow depending on initial volatile content and melt viscosity. Both factors directly influence the diffusivity that limits the rate of bubble growth. Increasing amounts of bubbles increase the buoyancy difference to the surrounding rocks and lead to an acceleration of the rising melt-bubble mixture. Beside these limiting factors, the overpressure in the gas bubbles greatly depends on the magma’s ascent speed as it controls the residence time to conditions favourable to degassing (a combination of lithostatic pressure and magma temperature) and the time of overpressure reduction due to degassing. Volcanic eruptions occur when the bubbly melt can no longer withstand the exerted stress that derives from the overlying weight (lithostatic pressure), the expanding gas bubbles (internal gas overpressure) and different ascent velocities in the conduit (velocity profile). The melt will be fragmented and the gas-pyroclast mixture will be erupted. This study has combined close investigation of the deposits of the 1990-1995 eruption of Unzen volcano, Japan and detailed laboratory investigations on samples of this eruption and other volcanoes. The field work intended to reveal the density distribution of samples from within the eruptive products. Although all samples already underwent one eruption, their physical state (e.g. crystallinity, porosity) mostly remained close to sub-surface pre-eruption conditions due to their high viscosity and accordingly allowed their usage for the analysis of the fragmentation behaviour. In that purpose, rapid decompression experiments that simulate volcanic eruptions triggered by internal gas overpressure have been performed at 850 °C to evaluate fragmentation threshold and fragmentation efficiency. Laboratory investigations of that kind are one approach to bridge the gap between observational field volcanology and risk assessment as they reveal information on what can not be investigated closely but what is essential to know for realistic eruption models and the adjacent hazard mitigation. Changing the experimental conditions and close investigation of the artificial products reveals the influence of physical properties on the fragmentation behaviour. The density distribution inside a dome and the upper part of the conduit is crucial to the eruptive style of an explosive volcano. This information cannot be collected during an ongoing eruption but is important for future hazard assessment via modelling conduit flow and dome collapse/explosion behaviour. Therefore, the percentage of the mass fractions of all rock types in the primary and secondary volcanic deposits must be evaluated. For this purpose and at the lowest logistic effort, field-based density measurements have been performed on Unzen volcano, Japan. The resultant density distribution was found to be generally bimodal at constant peak values but changing peak ratios. The most abundant rock types at Unzen exhibited an open porosity of 8 and 20 vol.%, respectively. The porosity was found to be arranged in layers of cm- to dm-scale that were oriented subparallel to flow direction, i.e. subvertical within the conduit and flank-parallel within the dome lobes. The achieved results allowed for an internal picture of the dome during the last eruption of Unzen volcano. The evaluated picture of the density distribution within the uppermost parts of the conduit and the dome itself allowed for insights into and a better understanding of magma ascent and degassing conditions at Unzen volcano during its last eruption. Knowledge of the density distribution is additionally required to draw conclusions from the results of laboratory investigations on the fragmentation behaviour to the monitored behaviour of Unzen volcano during its last eruption. In the laboratory, the fragmentation behaviour upon rapid decompression has been investigated in a modified fragmentation bomb (Spieler et al., 2004). At 850 °C, initial overpressure conditions as high as 50 MPa have been applied to sample cylinders (25 mm diameter, 60 mm length) drilled from natural samples. In a first step, the minimum overpressure required to cause complete sample fragmentation (= fragmentation threshold, ΔPfr) has been evaluated. Results from samples of several volcanoes (Unzen, Montserrat, Stromboli, and Mt. St. Helens) showed that ΔPfr mainly depended on open porosity and permeability of the specific sample as these parameters were controlling pressure build-up and loss. The experiments further revealed that sample fragmentation was not the result of a single process but the result of a combination of simultaneously occurring processes as indicated by Alidibirov et al. (2000). The degree of influence of a single process to the fragmentation behaviour was found to be porosity-dependent. Further experiments at initial pressure conditions above ΔPfr and close investigation of the artificially generated pyroclasts allowed evaluating the fragmentation efficiency upon changing physical properties of the used samples. The efficiency of sample size reduction was investigated by grain-size analysis (dry sieving for particles bigger than 0.25 mm and wet laser refraction for particles smaller than 0.25 mm) and surface area measurements (by Argon adsorption). Results of experiments with samples of different porosities at different initial pressure values showed that the efficiency of fragmentation increased with increasing energy. The energy available for fragmentation was estimated from the open porosity and the applied pressure. A series of abrasion experiments was performed to shed light on the grain size reduction due to particle-particle interaction during mass movements. The degree of abrasion was found to be primarily depending on porosity and experimental duration. The results showed that abrasion may change the density distribution of block-and-ash flows (BAF) by preferentially abrading porous clasts. However, during the short drying interval prior to the analysis of the experimental pyroclasts, abrasion-induced grain-size reduction only played a minor role and was assumed to be negligible.

Volcanic eruptions are one of the most spectacular and dangerous natural phenomena. Volcanic activity can either be effusive, dominated by quiescent emission of lava or explosive, dominated by the eruption of pyroclastic material. A rapid transition between these two regimes is possible. possible. On a broad scale, a clear distinction of the eruption style can be drawn by magma composition. Large-scale basaltic eruptions are mostly effusive, whereas large-scale silicic eruptions are mostly explosive. Thus silicic volcanism possesses a severe hazard potential and can have devastating effects on human population. This work comprises experimental investigations of the fragmentation behavior of porous magma as well as of the propagation of elastic waves within this material. The analyses were conducted on samples from Unzen Volcano, Japan as well as samples from Soufrière Hills Volcano, Montserrat, West Indies. The elastic wave velocities of differently porous Unzen dacite samples were investigated with the use of a cubic multi-anvil press. The main results of this study show that porosity (density) and texture affect the elastic properties of samples at a given temperature. In particular, it can be stated: (1) Seismic velocities increase with pressure due to compaction and closing of microcracks. The Vp anisotropy decreases with pressure for the same reason. (2) Increasing the temperature also leads to higher elastic wave velocities and lower anisotropies. This must be highlighted as the inverse behavior is documented for the majority of rocks. The effect may be linked to reduction of pore volume and further closing of microcracks due to reduction of cooling tensions. At 600 °C mean Vp values of 4.31 - 5.64 km/s and mean Vs* values of 2.20 - 3. 32 km/s could be determined. (3) The velocity anisotropy can be linked to the texture of the samples: Those with a high anisotropy show a pronounced shape-preferred orientation of phenocrysts and microcrystals, sometimes in addition to layering within the groundmass of the sample. Since the crystals are typically aligned parallel to walls of volcanic conduits, the velocity normal to the walls is likely to be reduced. The data allows better estimates of the properties of silicic volcanic rocks at shallow depths within volcanoes, e.g. at conduit walls. These estimates are vital for computation of conduit models as well as the modelling of volcano seismic data, and may lead to an improved analysis of precursor phenomena in volcanic areas. The physical properties of magma within volcanic conduits and domes are crucial for modelling eruptions. This study comprises a detailed investigation of the fragmentation behavior (threshold and propagation speed) of differently porous sets of dacitic and andesitic samples derived from Unzen Volcano, Japan and Soufrière Hills Volcano, Montserrat, West Indies. The experiments were performed with a shock-tube based fragmentation apparatus and pertain to the brittle fragmentation process. The results show a strong influence of the open porosity and the initial pressure on the fragmentation behavior. The speed of fragmentation follows a logarithmic relationship with the pressure difference, the fragmentation threshold an inversely proportional power-law relationship with increasing porosity. In this study fragmentation speed values ranging from 15 - 150 m/s were observed for applied pressure differences of up to 40 MPa and open porosities from 2.5 - 67.1 %. The expansion of the pressurized gas in the vesicles largely provides the energy driving the fragmentation process. The fragmentation speed results of all analyzed samples show a close relationship to the energy density (fragmentation energy standardized to volume). A logarithmical increase of the propagation speed was observed with the energy density as soon as the energy threshold of 2.0 x 0.5 J/m³ was exceeded. The fragmentation speed is independent from the origin and composition of the samples, proving the governing role of the energy to the initiation a propagation of fragmentation process. Different fragmentation mechanisms were discussed and the layer-by-layer fragmentation due to vesicle bursting is concluded to be the main process responsible for the disintegration of vesicular rocks. The increased importance of fracturing due to the passing of the unloading wave after a rapid decompression could be proved for low porous samples. Further the influence of the sample’s permeability on the fragmentation behavior was evaluated. It could be shown that a high permeability hinders the initiation of a fragmentation and reduces the propagation speed of this process at a certain energy density. The fragmentation results were applied to the dome collapse events and Vulcanian events of the 1990-1995 Unzen eruption and the 1997 Vulcanian events at Montserrat. Large blocks with layers of various porosity were observed at the block-and-ash flow deposits of Unzen Volcano and support the model that a dome and dome lobes consist of areas of differing porosity. In addition, the samples gained from Montserrat, allow to postulate a porosity gradient within a volcanic conduit, with low porous magma close to the conduit walls. A layered composition of a dome and dome lobes, respectively, may lead to the fragmentation of single layers, followed by the collapse of the overlaying sections. These events could catalyze gravitationally induced dome collapse events leading to vigorous pyroclastic flows and / or trigger a sector collapse followed by an Vulcanian event. A porosity gradient at the magma in the conduit leads to a concave shape of the fragmentation surface and facilitates lateral fragmentation of dense magma close to the conduit walls. Conduit implosion may to occur during most explosive eruptions and is likely to influence the cessation or pulsation of the eruption. The slow magma ascent and extrusion rate at Unzen resulted in relatively dense extruded magma, as the magma could almost completely degas during the ascent. The low porosity of this magma causes a high fragmentation threshold of most material, which is too high for unassisted fragmentation. Therefore dome collapse events were the most abundant events of the 1990-1995 activity of Unzen Volcano, leading to numerous block-and-ash flows. Also the fragmentation-amplified collapse of dome lobes or parts of the dome are reasonable. This accounts especially for the long lasting collapse events with vigorous pyroclastic flows at the early stage of the eruption in June 1991, which were followed by minor Vulcanian events. Nevertheless a larger explosive event would have been possible, triggered by a landslide or a sector collapse of the dome. Similarly to Unzen, the first phase of activity of the recent eruption of Montserrat is characterized by numerous dome collapse events leading to violent pyroclastic flows. As the magma extrusion rate was quite high during this phase, the extruded magma was higher vesiculated compared to the Unzen magma and thus a more violent evolution of the eruption activity took place. Large dome collapse events frequently caused Vulcanian events, and even two cycles of Vulcanian activity from August to September 1997 occurred. The calculations of the fragmentation depth, reached by this explosions yielded about 1500 m, based on the laboratory gained fragmentation speeds, which is in good agreement numerical models and observations. In silicic volcanic systems the conduit seems not to be sharply defined. The conduit walls are more to be seen as a kind of transition zone between a hot, ductile and vesicular magma within the conduit and the host rock. The rocks forming this transition zone are assumed to be quite hot, but presumably below glass transition and react therefore solely brittle. Furthermore these rocks should be quite dense, compared to magma in the conduit, and heavily fractured due to the high shear strains this zone is presumably exposed to. The transition zone is less likely affected by a fragmentation event. Their rocks (magma as well as host rocks) are too dense to fragment due to pore pressure. The needed pressure difference is unrealistically high, for example an overpressure of 18 MPa would be needed to initiate the fragmentation of rocks with a porosity of 7.5 %. Nevertheless this material may be found in the deposits of explosive events, due to processes like conduit wall erosion or as remnant of dense lenses within more porous areas. Indeed, also fragmentation may take place, the most likely process fragmenting even this dense material is by lateral fragmentation, which may occur from a certain depth on behind a fast propagating fragmentation of highly vesicular magma at the center of the conduit. The style and progression of an eruption is depending on the properties of this vesicular magma. If its fragmentation threshold can be exceeded, an explosive event may take place. Otherwise the magma is extruded quiescent in a dome forming eruption. The transition zone bears important implications on the one hand for the explosive event as a lateral fragmentation of a certain area may cause cessation or pulsation of the event, on the other hand for the propagation of seismic signals related to the eruption. Within this transition zone as well as the nearby host rock a decisive change of temperature and porosity can be supposed. This leads to a significant shift of the elastic wave velocities within this zone, sometimes resulting in trapped waves within this zone as observed for Montserrat. Especially the abnormal velocity increase with increasing temperatures has to be mentioned. Thus implications for an overall view of a volcanic system are provided in this study, with the transition zone as the common link. The properties of the elastic wave velocities account for the for host rock as well as the transition zone and bear vital constraints for the interpretation and modelling of volcano seismic data. The results of the fragmentation experiments are applicable for dome rocks, the vesicular interior of a conduit as well as the transition zone and contain important implications for the modelling of conduit processes. Together the results of this study may contribute to a refined understanding of processes typical for silicic volcanism. This may allow an improved analysis of precursor phenomena in volcanic areas and consequently provide important constraints to the hazard and risk management.

Trace elements (elements that constitute less than 0.1 wt.% of the analyzed sample) are important tracers for a great variety of processes in many research areas, such as biochemistry, medicine, semi-conductor and nano-technology, environmental science and geosciences (e.g., Anita et al. [2002]; Becker et al. [2004]; Barbante et al. [2004]; Tibi and Heumann [2003]). Accordingly, much scientific effort and financial resources are raised to develop new high-performance analytical techniques and methods for trace element analysis. In geosciences, the capabilities of trace elements analytics have not been used to its full potential because of the complex matrix of the analyzed samples (rocks) and the time consuming procedure to obtain high-quality trace element data by isotope dilution. Accordingly, the aim of this study is to develop of a new, easy-to-use and fast ID-method for the simultaneous determination of many trace elements in geological materials. In addition, the application of this new technique to the analysis of ocean island basalts (OIB) revealed that evolution of geochemical mantle heterogeneities (HIMU, EM-1, EM-2) is far more complex than perviously thought. In the first part of this thesis, a multi-element technique for the simultaneous determination of 12 trace element concentrations in geological materials by combined isotope dilution (ID) sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) following simple sample digestion is presented. The concentrations of additional 14 other trace elements have been obtained using the ID determined elements as internal standards. This method combines the advantages of ID (high precision and accuracy) with those of SF-ICP-MS (multi-element capability, fast sample processing without element separation) and overcomes the most prevailing drawbacks of ICP-MS (matrix effects and drift in sensitivity). Trace element concentration data for the geological reference material BHVO-1 (n = 5) reproduce to within 1-3% RSD with an accuracy of 1-2% relative to respective literature data for ID values and 2-3% for all other values. To test the overall performance of the method the technique has been applied to the analysis of 17 well-characterized geological reference materials from the United States Geological Survey (USGS), the Geological Survey of Japan (GSJ) and the International Association of Geoanalysts (IAG). The sample set also includes the new USGS reference glasses BCR-2G, BHVO-2G, and BIR-1G, as well as the MPI-DING reference glasses KL2-G and ML3B-G and the National Institute of Standards and Technology (NIST) SRM 612. Most data agree within 3-4% with respective literature data. The concentration data of USGS reference glasses agree in most cases with respective data of the original rock powder within the combined standard uncertainty of the method (2-3%), except the U concentration of BIR-1G, which shows a three times higher concentration compared to BIR-1. In the second part of this thesis, this new method is used to determine the trace element concentrations of basaltic samples form the ocean islands St. Helena, Gough and Tristan da Cunha. The results are used to test the validity of established models concerning the trace element systematics of mantle heterogeneities. Since the early 1990's, recycling of altered oceanic crust together with small amounts of 'pelagic' and 'terrigeneous' sediments has become somewhat of a paradigm for explaining the geochemical and isotopic systematics in global OIB. The vastly increased number of data in the literature, in addition to new high-precision trace element data on samples from St. Helena, Gough, and Tristan da Cunha presented here (altogether more than 300 analyses from basalts from 15 key islands), reveals that the trace element systematics in enriched mantle (EM)-type OIB are far more complex than previously thought. In contrast to EM basalts, HIMU (high μ; μ = 238U/204Pb) basalts have remarkably uniform trace element characteristics (systematic depletion in Cs, Rb, Ba, Th, U, Pb, Sr, and enrichment of Nb, Ta relative to La), which are adequately explained by being derived from sources containing subduction-modified oceanic crust. EM-type basalts have La/Th, Rb/Ba, and Rb/K ratios similar to those in HIMU-type OIB, but at the same time, also share some common characteristics that distinguish them from HIMU basalts (e.g., high Rb/La, Ba/La, Th/U, Rb/Sr, low Nb/La, U/Pb, Th/Pb). EM-type OIB also have far more variable very incompatible elements contents (Cs, Rb, Ba, Th, U, Nb, Ta, La) and are less depleted in Pb and Sr than HIMU-type OIB. In addition, each suite of EM-type basalts carries its own specific trace element signature that must ultimately reflect different source compositions. Consequently, although the compositional similarities between HIMU and EM-type basalts suggest that their sources share a common precursor (subducted oceanic crust), their compositional differences can only be explained if EM sources have a more complex evolution and/or contain an additional component compared to HIMU sources. This additional component in EM basalts is likely to originate from a common, although to some degree compositionally heterogeneous, reservoir. Possible candidates are marine sediments; but they do not, at the same time, provide a plausible explanation of the isotopic bimodality in EM-type basalts (EM-1 and EM-2) because the parent/daughter ratios in marine sediments are unimodally distributed. Similar to the bimodal isotopic compositions in EM basalts, the continental crust is composed of two broadly compositionally different parts: the upper and lower continental crust. Relative to the upper continental crust, the lower continental crust is similarly enriched in very incompatible elements, but has systematically lower Rb/Sr, U/Pb, Th/Pb, and higher Th/U ratios. Thus, over time, the upper and lower continental crust evolve along distinct isotopic evolution paths but retain their complex trace element characteristics, similar to what is observed in EM-type basalts worldwide. It is therefore propose here that recycling of oceanic crust together with variable proportions of lower continental crust (scrapped off from the overlying continental crust during subduction at erosive plate margins) and upper continental crust (either in the form of sediments or eroded continental crust) provides a possible explanation for the trace element and isotope systematics in EM-type ocean island basalts.

The Antarctic Peninsula forms part of a magmatic arc at least since Jurassic times. Magmatic dykes are essential elements of such arcs and intrude along zones of instability. In contrast to other hypabyssal intrusions and the effusive products of arc activity, dykes do not only reflect the geochemical characteristics of their magma source but also the tectonic parameters at the time of their emplacement. The South Shetland Islands form an archipelago located at the northern tip of the Antarctic Peninsula and belong to this arc. Areas of up to 100,000 m2 have been mapped at several locations of these islands, mainly on King George and Livingston Island. A structural analysis of the dykes and the host rocks was carried out, and about 250 dykes were sampled for further studies. As deduced from field relationships, on Livingston Island six different intrusive events could be distinguished, on King George Island up to seven. This subdivision into different intrusive events is also well reflected by the geochemical data. Analysis of the structural data of the dykes and their host rocks shows, that the tectonic stress field was not only very similar throughout the archipelago, but that moreover only minor changes of this stress field occurred during the time of dyke emplacement. This holds for all investigated areas in the South Shetland Islands. The geochemical data (ICP-MS) reveal, that most dykes of the South Shetland Islands belong to a calc-alkaline, arc-related suite, ranging from basalts to highly differentiated rhyolites. However, especially during early stages of intrusive activity in the respective areas, also tholeiites occur. Isotopic data (Sr, Nd, Pb) prove a strong crustal component during initial stages of magmatic activity, especially on Hurd Peninsula (Livingston Island). This crustal component decreased with time, accompanied by an increase of sedimentary input into the subduction zone. The high amount of crustal contamination during the initial stages was probably due to a still unstretched continental crust. Besides the continental crust underlying the South Shetland Islands, partial melts from the subducted sediments, fluids derived from the subducting plate and a depleted, heterogeneous mantle wedge contributed to arc magma genesis. According to Ar-Ar datings on plagioclase separates and K-Ar (WR) age determinations, dyke intrusion was restricted to the Paleocene and Eocene. The dykes started to intrude around the Cretaceous/Paleogene boundary at Livingston Island. Only around the Thanetian/Ypresian boundary, dyke intrusion commenced also further NE at Nelson and King George Island, culminating during the Lutetian at 47-45 Ma in all investigated areas. Dyke intrusion then ceased in the latter areas but still continued at Livingston Island until the Priabonian. Combining the information given by the tectonic and geochemical datasets, the time interval covered by the dykes obviously marks a period of geodynamic stability. This includes a stable geometry of the subduction zone and the corresponding parameters (subduction direction and velocity) during that time, as well as stable magma sources. The contribution of the respective sources (sediments, slab, mantle, crust) varied, but the sources themselves remained the same. Very primitive, olivine tholeiitic dykes sampled on Penguin Island as a by-product of this work yielded an unexpectedly high Ar-Ar age (Tortonian), thus questioning the onset of rifting in Bransfield Strait during the Pliocene, as believed so far.

Der von häufigen Befeuchtungs- und Trocknungszyklen hervorgerufene physikalische Prozess des Quellens und Schwindens wird gegenwärtig als Hauptschadensursache für die Verwitterung von tonmineralreichen Sandsteinen angesehen. Hauptziel der Arbeit war deshalb die Messung des bei Befeuchtung entstehenden Druckes und der Vergleich der erhaltenen Quelldruck Werte mit den Festigkeitskennwerten der untersuchten Sandsteine.

The physical determination of the hydraulics of the vadose zone in sediments and porous building-materials is the basis of the calculation and modelling of fluid, pollutant and heat transport. Here the pore size distribution and the heterogeneous structure of the pore space play a decisive role as an input parameter. Parameters of the hydraulics and unsaturated flow of sediment bodies were obtained by desorption and tank experiments and represented in two-dimensional visualizations. The experimental setup contained a two-dimensional measurement of the hydraulic potential and the distribution of the electrical conductivity during different stationary and dynamic flow processes. These experiments, along with the application of visual methods by means of tomography and image analysis, allowed for new approaches for the detection of the pore space properties and its heterogeneities: The hydraulic laboratory experiments identified a variation of the flow parameters in homogeneous sediment bodies. Optical methods demonstrated through the non-destructive process of the tomography a future practical strategy for undisturbed probes since great development potentials of the optical resolution are still physically possible opposite the used x-ray scanner. By contrast, the image analysis of scanned polished sections is connected to a sample treatment, but stands out due to a high degree of automation and low costs. The application of the different methods could represent the correlation of pore space structure and hydraulic properties. Due to the visual methods the complex structural properties are received quickly andversatilely. So the pore size distribution and the sum of the grain surfaces could be detected among other things. From this, a numeric model approach could be developed for the hydraulic properties and the moisture transport of porous media.