This work explores the use of both a geographical information system (GIS) and a global database for reconciling pyroclastic density current field data with conceptual and computational analogs. This study has four parts: 1) The suitability and use of different PDC mobility metrics is investigated by developing FlowDat, a global database of mass flows. This work reexamines the use of mobility metrics for characterizing PDC mobility and the frequency-magnitude relationships of PDCs, and shows how such data might be used for producing event trees. The work also tests the use of measurable deposit parameters as inputs for geophysical mass flow models, and shows that [delta]H/L (height-dropped/runout) values can be used as an estimate for the basal friction input parameter for TITAN2D; that the constant retarding stress parameter for VolcFlow can be estimated from field measurements, but not predicted; and that the calculation of the LAHARZ coefficients for the planimetric- and cross-sectional area-volume relationships using statistical analysis of data is problematic for forward modeling of PDCs. 2) The relative effectiveness of three popular computational models to simulate PDCs is explored by comparing both best-fit and FlowDat-derived model simulations to all mapped PDCs from the eruption of Soufrière Hills Volcano (SHV), Montserrat. This work expands upon single-deposit comparisons of models, and is instead able to compare models over a range of volumes and emplacement environments. Results show that TITAN2D and VolcFlow are both able to replicate smaller-volume flows better than larger-volume flows, probably due to the increasing complexity in source characteristics and unsteadiness and non-uniformity of PDCs of larger volumes. LAHARZ is capable of reproducing mapped deposits, but its use for forward modeling is questioned. 3) The role of topography in the detachment of ash-cloud surges is derived from both field and GIS measurements of SHV deposits and digital elevation models (DEMs). The cross-sectional area of the channel is identified as a trigger of ash-cloud surge detachment, and a critical volume-specific cross-sectional area is determined. The results indicate that surge mobility and detachment are a complex product of flow mass flux, energy or granular temperature, and topography and that future efforts to model dense-dilute coupled flows will need to account for and integrate several mechanisms acting on different parts of the flow. 4) The relationships between surge detachment and topography mean that careful attention must be paid to the ways in which topography changes through time. Rapid topographic changes during an ongoing eruptive crisis can have important hazard implications, as in-filled valleys are less able to contain subsequent flows and steeper average drainage slopes can increase flow mobility. This work explores how topography has changed through time at SHV, Montserrat, and how these changes may impact future hazards in the Belham Valley. The Belham Valley, which is of paramount importance for hazard assessment on Montserrat, has steepened, lost cross-sectional area due to deposition, and the main channel has shifted toward the northern banks. Together, these changes increase the risks to populated areas from PDCs and lahars in the future. Each of these components contributes to our understanding of the mobility and behavior of PDCs, especially in relation to topographical effects. An important contribution is highlighting the differences between small-volume flows, which are better characterized by models and metrics, and larger-volume flows which are more complex and less well-characterized by models and metrics, which essentially average out aspects of these highly unsteady flows in both space and time. This presents important limits to the scalability of small-scale experiments and models developed in the context of these experiments. This work also seeks to use digital representations of deposits and topography to extract added value from already completed field investigations using a GIS. Field campaigns can be expensive, impractical, and even dangerous, and the work presented herein devises new ways to leverage existing data for further investigation.

During some explosive volcanic eruptions, multiple pyroclastic density currents have been produced within a short time span of each other and flowed through the same area. This creates the potential for the currents to interact, specifically in a way where a leading current is produced, and then a similar trailing current is produced a short time later and possibly flows into the leading current. The leading current, having changed the ambient surroundings from normal air, may then have an effect on the dynamics and behavior of the trailing current. To examine this effect, we designed scaled experiments to produce an analogue leading current and a trailing current that flows into it. The experiments took place in both an air medium and a water medium. The results of the experiments showed that the behavior of the trailing current may change as a result of interacting with the leading current. After certain intervals of time between currents, the trailing current had a longer final runout distance compared to the leading current it flowed through. This is caused by the presence of a plume created by the leading current when it reverses buoyancy. At intermediate heights above the bed, after moderate amounts of time between currents, the leading plume is less dense than the newly created trailing plume, and the trailing current cannot rise, and the momentum stays in the body of the trailing current. This accelerates the trailing current, which decreases sedimentation rate, and allows the current to runout to a greater distance before lifting off. At low heights and great heights above the bed, the leading plume is denser than the trailing plume, and the trailing plume can then rise without impediment. In natural pyroclastic density currents, the magnitude by which the leading current affects the trailing current depends on the rise time of the leading plume.

"Pyroclastic currents are the deadliest hazard associated with explosive volcanic eruptions. These gravity-driven currents consist of volcanic gases and solid particles that range in size from fine ash to boulders. The dangers associated with pyroclastic currents stem from their unpredictability and ability to travel extremely long distances, sometimes in excess of 100 km. To mitigate the risk to populations and infrastructure, we must understand the processes that control the runout distance of pyroclastic currents. The runout distance depends on the complex interplay of processes related to sediment transport, erosion, and deposition. Historically, studies focused on understanding sediment transport and deposition, but studies within the last 15 years demonstrate the important effect of erosional processes on the behavior of pyroclastic currents. This dissertation research builds on recent studies to investigate how pyroclastic currents interact with the bed via erosion and mixing processes. I seek to answer questions related to the mechanisms by which erosion occurs, how the properties of the bed affect erosion and mixing processes, and how interactions between the flow and the bed affect flow behavior and runout distance. To address these questions, I combine detailed field studies of pyroclastic current deposits with analogue laboratory experiments that simulate pyroclastic currents in a controlled environment. Synthesizing these two approaches, field and experimental, allows for even greater insight into basal processes than either approach could provide on its own. Ultimately, I show that erosion occurs via a fluid-like mixing process as a result of granular shear instabilities formed at the flow-bed interface. The mixing process generates wave-like structures at the contact between the flow and the bed, and the structures can be preserved in the deposits of both natural and experimental flows. The dimensions of the structures recorded in the deposits directly relate to flow parameters, such as velocity and thickness, at the time the structures formed. I apply scaling relationships derived from experimental data to sedimentary structures observed in the deposits of the pyroclastic currents produced during the May. 18, 1980 eruption of Mount St Helens. This approach produces quantitative estimates of the flow velocity and thickness, important flow parameters that were unconstrained prior to this study. Additionally, the experiments suggest that the erosion and mixing processes decrease the runout distance of pyroclastic currents relative to non-erosive flows, which has important implications for hazard mitigation. Finally, the datasets produced both from the field and experimental studies can be used to test and refine numerical models of pyroclastic currents with the ultimate goal of improving the accuracy of risk assessments for these hazardous flows. While this dissertation research improves our understanding of the erosion and mixing processes that occur at the flow-bed interface in pyroclastic currents, the final conclusions also beget new questions. Future studies should investigate other mechanisms by which erosion occurs because the mechanism discussed here is not likely to be the single way in which pyroclastic currents entrain bed material. Continued work to synthesize experimental and field studies has the potential to produce additional methods to derive quantitative information from natural pyroclastic deposits. Finally, the next major goal moving forward in the study of pyroclastic currents must be to obtain in situ measurements of flows in real time. Such a dataset will provide the means to test many of the hypotheses set forth regarding the internal processes that govern the behavior of these dangerous volcanic phenomena."--Boise State University ScholarWorks.

An impressive collection of 62 technical papers recounting the eruption of Mo Pinatubo in 1991 and its aftermath. The contributors reflect the internatio cooperation exhibited during the eruption (ten times larger than Mount St. Helens) and explore the precursors, processes, and products of the eru

"The science of informatics in the broadest sense has been several thousands of years in the making. With the recent emergence of large storage devices and high-speed processing of data, it has become possible to organize vast amounts of data as digital products with ontologic tags and concepts for smart queries. Coupling this computational capability with earth science data defines the emerging field of geoinformatics. Since the science of geology was established several centuries ago, observations led to conclusions that were integrative in concept and clearly had profound implications for the birth of geology. As disciplinary information about Earth becomes more voluminous, the use of geoinformatics will lead to integrative, science-based discoveries of new knowledge about planetary systems. Twenty one research papers, co-authored by 96 researchers from both earth and computer sciences, provide the first-ever organized presentation of the science of informatics as it relates to geology. Readers will readily recognize the vast intellectual content represented by these papers as they seek to address the core research goals of geoinformatics."--Publisher's website.

This publication provides information on detailed methodologies and examples in the application of volcanic hazard assessment to site evaluation for nuclear installations, thereby addressing the recommendations in IAEA Safety Standards Series No. SSG-21, Volcanic Hazards in Site Evaluation for Nuclear Installations. It demonstrates the practicability of evaluating the recommendations through a systematic volcanic hazard assessment and examples from Member States. The results of this hazard assessment can be used to derive the appropriate design bases and operational considerations for specific nuclear installations.