Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Science. / Microfiche copy available in Archives and Science. / Bibliography: leaves 132-133. / M.S.

Seamounts, or submarine volcanos, have two distinct phases: the formation phase when the seamount is magmatically active and the passive phase when the seamount is transporting on the seafloor until subduction. Being able to understand various aspects of seamounts both in the formation and passive phase can enhance our understanding of volcanic processes and how seamounts can influence other processes such as crustal deformation, plate subduction, and earthquake generation. The purpose of this thesis is to examine seamounts on the Juan de Fuca plate both in the formation and passive phases. The first three chapters of this thesis focuses on understanding the subsurface properties and volcanic processes of Axial Seamount, an active seamount located on the Juan de Fuca Ridge. The fourth and final chapter focuses on understanding how seamounts influence subduction and the seismogenic properties of the Cascadia Subduction Zone. In chapter 1, I analyze multichannel seismic data to characterize the internal crustal structure of the rift zones of Axial Seamount. The new reflectivity images reveal small and discontinuous crustal magma bodies beneath and in the vicinity of the rift zone lava flows from the three most recent eruptions. We also image wide magma bodies within the overlap regions between the rift zones and neighboring segments of Juan de Fuca Ridge. Collectively the new observations indicate that multiple small crustal magma bodies underlie Axial and likely contribute to rift zone magmatism with implications for interpretations of seismicity patterns and lava flow compositions. In chapters 2 and 3, I process over 7 years of continuous seismic noise at Axial Seamount and use cross-correlation functions to calculate the relative seismic velocity (dv/v) changes beneath the caldera. I find a long-term trend of decreasing velocity during rapid inflation, followed by slight increase in velocities as background seismicity increases and inflation rate decreases. I also observe small short-term increases in dv/v which coincide with short-term deflation events. The observations of changes in dv/v and their correlation with other geophysical data provide insights into how the top ~1 km of the crust at Axial Seamount changes in response to subsurface magma movement and capture the transition from a period of rapid reinflation to a period where the caldera wall faults become critically stressed and must rupture to accommodate further inflation. From the relative seismic velocity variations, I also observe a strong annual pattern constrained within the 0.1-0.2Hz filter band. This annual pattern correlates well with timing and location of storm activity within the Pacific Ocean. Through the comparison of annual variation with ocean data, we determine that the annual pattern observed is likely an apparent velocity change due to changes in the seismic noise source. Lastly, in chapter 4, I utilize multichannel seismic data and high-resolution P-wave velocity (Vp) models of the CASIE21 expedition to calculate residual Vp models to examine properties of the sediments relative to seamounts on the incoming plate. At one of the larger seamounts located within 25km of the deformation front, I show evidence consistent with predicted stress effects of buried topography where there is an increase in normal stresses landward and a stress shadow seaward of the seamount, which can alter and impact rupture patterns along the margin. I also show evidence for signatures of enhanced hydrothermal circulation at seamounts near the deformation front which show that seamounts can be potential carriers of additional fluid into the margin when subducted. In additional to looking at the sediments relative to the seamounts, I also evaluate properties of a high Vp basal layer that is prevalent on all of the lines which can provide insights into the earthquake rupture and tsunami potential for the area.

xviii, 179 p. : ill. (some col.). Includes 3 video files. / Mafic arc volcanoes have eruption styles that range from explosive to effusive. In a broad sense, eruption style is controlled by the rate of magma supply to the vent. In this dissertation I examine relationships between eruption rate and style in two separate studies: (1) an investigation of ongoing activity at NW Rota-1, a submarine volcano in the Mariana arc, and (2) a morphologic study of the Collier Cone lava flow field in the Central Oregon Cascades. The eruptions of NW Rota-1 range from effusive to moderately explosive; eruptions are effusive when mass eruption rate (MER) is low and explosive when MER increases. The explosivity of submarine eruptions is suppressed by seawater because of increased hydrostatic pressure, rapid cooling, and the high viscosity of water relative to air (which limits expansion). The combination of seawater and relatively low MERs limit pyroclast deposition to within meters to tens of meters of the vent. In fact, many pyroclasts fall back into the vent and are recycled. Evidence for recycling includes microcrystalline inclusions within erupted pyroclasts and elevated Cl and Na concentrations in matrix glass. Enrichment of Cl and Na suggests that seawater assimilation provides a geochemical signature of recycling. Recycling is limited to low MER explosive eruptions and is not observed in either effusive lava or deposits from high MER explosions. Direct observations of eruptions allow measurements of eruption rate. However, it is more challenging to estimate MERs of eruptions that were not observed. To address this problem, I develop and test methods of constraining the eruption rate (and duration) of the c. 1600 year old Collier Cone lava flow using the flow morphology. To quantify flow morphology I combine field observations with GIS analysis of Lidar-derived digital topography. Channel dimensions constrain emplacement rates; dominant wavelengths and amplitudes of surface folds constrain spatial and temporal changes in flow rheology. Three videos of eruption activity accompany this dissertation as supplemental files. This dissertation includes both previously published and unpublished co-authored material. / Committee in charge: Dr. Katharine V. Cashman, Chair; Dr. Joshua J. Roering, Member; Dr. Paul J. Wallace, Member; Dr. Patricia F. McDowell, Outside Member; Dr. William W. Chadwick, Outside Member

This study examines the impact mountain gorillas has on the sustainable and developmental life of the Volcanoes National Park (VNP) in Rwanda. The study is equally based on the on psychosocial perspectives as it concerns the behavior of the population. It emphases on how ecotourism works and how it affects the mountain gorillas on the nature reserve. The study also investigates the impact of ecotourism with regards to the locals, society and the country using research that has been previously carried out.   The study's findings show that the revenue-sharing system from mountain gorilla tourism activities has changed local communities view on ecotourism both positively and negatively through opportunities and weaknesses in sustainable development. In addition, the study shows the government's ongoing commitment to improving and maintaining the eco-tourism sector by diversifying its activities. It shows that the government of Rwanda has included conferences, ceremonies, and tours in its ecotourism efforts that further provides variation for visitors so that tourism develops throughout the country. / Denna studie undersöker bergsgorillornas påverkan utifrån ett hållbarhets- och utvecklingsperspektiv i Volcanoes National Park (VNP) i Rwanda. Studien utgår från ett psykosociolaperspektiv, hur ekoturismen fungerar och påverkar bergsgorillorna i VNP. Studien undersöker även med hjälp av tidigare forskning; vilka konsekvenser som tillkommer med ekoturism med avseende på lokalbefolkning, samhället och landet. Studiens resultat visar att intäktsdelningsystemet från bergsgorillaturismen har förändrat lokala samhällen både positivt och negativt genom möjligheter och svagheter i hållbarutveckling. Studien visar regeringens ständiga åtaganden att förbättra och upprätthålla ekoturismsektorn genom att diversifiera verksamheten. Rwanda har inkluderat konferenser, ceremonier och turer i sin ekoturism som ytterligare ger variation för besökarna så att turismen utvecklas i hela landet.

The transport and emplacement mechanisms of the highly energetic pyroclastic density current (PDC) generated in the blast style eruption of Soufriere Hills Volcano, Montserrat, on 26 December 1997 are examined through detailed lithological mapping and sedimentological analysis of the deposits. The PDC formed deposits which range in grain size from coarse breccias to fine ash, with distinctive bipartite layering and well-developed grading and stratification. On a large scale the PDC was highly erosive, sculpting large bedforms and depositing relatively thin deposits. However, locally, centimetre scale topographic protuberances were responsible for significant variations in deposit thickness, grain size, and the development of dune bedforms. The strong lateral and vertical lithofacies variations are attributed to well-developed density stratification, which formed during explosive expansion of the dome prior to PDC formation. Experimental modelling of stratified inertial gravity currents was carried out to investigate the effects of density stratification prior to release of the current. The degree of stratification governs the rate of mixing in the current, which in turn influences the velocity. Well·stratified currents initially move faster than homogenous currents but are slower in the latter stages of current propagation. The results have important implications for deposition from particle-laden flows, which may become stratified with coarser material concentrated at the base of the current. The role of PDCs jn the formation of unit US2-B, emplaced during the Upper Scoriae 2 eruption (79± 8 ka) on Santorini, Greece, was investigated through sedimentological analysis and mapping. Proximally, the unit exhibits features characteristic of emplacement from a flow, such as thickening into palaeochannels and erosive basal contacts. Distally, the unit is of uniform thickness and grain size parameters suggest the deposit is more characteristic of exnplacement from a fallout mechanism. Discrete lenses of fine-grained material within US2-B, and a gradational upper contact with PDC deposits suggest that there may have been contemporaneous deposition resulting the development of a hybrid deposit.

The Petroglyph National Monument Rapid Ethnographic Assessment Project had two primary goals. One was the identification of those American Indian Tribes, Pueblos, and Spanish heritage groups who wanted to participate in a long -term consultation process with the National Park Service about the management of the new Petroglyph National Monument located outside of Albuquerque, New Mexico. The second goal was to document the cultural resource concerns of the Native Americans and the Spanish heritage people, so that protection of these cultural resources could be incorporated into the General Management Plan that the National Park Service is developing for the Petroglyph National Monument.

This report presents the results of ethnographic fieldwork conducted at Timber Mountain Caldera (TMC) on the NTS. Volcanic in origin, the caldera is a geologic feature that was formed when a large volcano collapse thousands of years ago producing the large circular crater that exists today. Since that event, the caldera has experienced other volcanic eruptions making a complex topographic landscape. The ethnographic fieldwork (conducted in 2005) that forms the foundation of this report included official tribal representatives from the Owens Valley Paiute, Western Shoshone, and Southern Paiute ethnic groups. This report presents the findings of the tribal representatives’ visits to several sites in the TMC and the cultural value associated with it. These research findings are based upon interviews conducted with tribal representatives selected by the American Indian Writers Subgroup of the culturally affiliated Consolidated Group of Tribes and Organizations (CGTO).

No description available.

'Natural' disasters have traditionally been viewed as the result of an extreme physical environment. A radical backlash against this dominant view, in the nineteen seventies and eighties, moved the debate to the opposite extreme and in doing so replaced physical with social determinism. Vulnerability analysis is proposed as a methodology that bridges these extremes. It takes into account individual decision making, social milieu and physical hazard when describing human habitation in areas of volcanic activity. It is argued that vulnerability should be defined in terms of universal human needs in order to avoid it simply being a measure of the chance of death and injury or losing its meaning in the uncertainty of cultural relativism. Once vulnerability is identified it is important to explore why it has come to exist. A contextual theory of vulnerability change is presented. Vulnerability to volcanic activity was explored in the area around Mt. Etna in Sicily (Italy) and Furnas volcano San Miguel in the Azores (Portugal) using a case study methodology. This included: collecting data through interviews (semistructured and structured) and field surveying, utilising census and other secondary data sources, and examining historical documents and texts. The volcanic hazard on Mt. Etna is related to regular (4-7 years) effusive lava flows which threaten property and land rather than people. Living in a European state, it is likely that a victim of Mt. Etna will have their basic needs provided for in the long-term and therefore they are not vulnerable. In contrast the irregular explosive eruptions of Furnas, last eruption 1630, not only damage property and land but also endanger lives. The limited ability of individuals to protect themselves in the event of an eruption and organisations to aid them in this means that, in spite of state insurance, many around Furnas are vulnerable. The production of vulnerability around Etna and Furnas is strongly related to the socio-economic nature of the region and wider European and global contexts. Opportunities and constraints that exist across socio-physical space encourage behaviour and forms of life which, in tum, produce various levels of vulnerability. Individuals seem to cognitively diminish their perceptions of this threat within a context of social representations of low risk. They, and society as a whole, rarely seem to engage directly with the risk itself.

Nous étudions dans un premier temps l'intérêt de l'utilisation de la "multichannel singular spectrum analysis" (M-SSA) sur des séries temporelles de positionnements GPS. Cette méthode permet de simultanément analyser un ensemble de séries temporelles et d'en extraire des modes de variabilités communs sans utiliser d'information a priori sur les structures spatiales et temporelles des champs géophysiques. Ces modes correspondent à des tendances non linéaires, des oscillations ou du bruit. Nous l'appliquons à des données enregistrées sur le volcan Akutan en Alaska. Nous y extrayons deux types de signaux. L'un correspondant à des déformations dites saisonnières, l'autre représentant deux cycles d'inflations et de déflations successifs du volcan Akutan. Les inflations sont rapides et courtes et suivies de déflations plus lentes et plus longues. Dans une seconde partie nous tirons parti de la M-SSA pour analyser des séries temporelles enregistrées sur plusieurs volcans. Les volcans Okmok et Shishaldin en Alaska et le Piton de la Fournaise à la Réunion possèdent une partie de leurs histoires de déformations qui est similaire à celle d'Akutan. Le caractère oscillatoire de ces cycles de déformations est comparé au régime oscillatoire d'un simple oscillateur non linéaire. Les données pétrologiques, géochimiques et géophysiques disponibles pour Okmok et le Piton de la Fournaise combinées aux contraintes sur la dynamique apportées par l'oscillateur non linéaire permet de proposer un modèle physique. Deux réservoirs superficiels sont connectés par un conduit cylindrique dans lequel le magma possède une viscosité qui dépend de la température. Un tel système se comporte de manière similaire à l'oscillateur non linéaire étudié précédemment. Lorsque que le gradient de température vertical présent dans le fluide est suffisamment important et que le flux de magma entrant dans le système de réservoirs est compris entre deux valeurs déterminées analytiquement un régime oscillatoire se met en place. / We study the use of the "multichannel singular spectrum analysis" on GPS time series. This method allows to simultaneously analyze a set of time series in order to extract from it common modes of variability without using any a priori on the temporal or the spatial structure of geophysical fields. The extracted modes correspond either to nonlinear trends, oscillations or noise. The method is applied on a set of GPS time series recorded at Akutan, a volcano located in Aleutian arc in Alaska. Two types of signals are extracted from it. The first one corresponds to seasonal deformations and the other represents two successive cycles of inflation and subsidence of Akutan volcano. The inflations are fast and short and are followed by deflations that are slower and longer. In the second part we take benefit of the M-SSA to analyze GPS time series recorded at several volcanoes. Okmok and Shishaldin in Alaska and Piton de la Fournaise in La Réunion possess a part of their deformation history that is similar to Akutan volcano. The cyclic nature of the observed deformations leads us to make an analogy between the oscillatory regime of a simple nonlinear oscillator and the deformation cycles of these volcanoes. Geochemical, petrological and geophysical data available for Okmok and Piton de la Fournaise combined with the constraint on the qualitative dynamics bring by the nonlinear oscillator allow to propose a physical model. Two shallow reservoirs are connected by a cylindrical conduit in which the magma have a viscosity that depends on the temperature. Such system behaves like the nonlinear oscillator mentioned above. When the temperature gradient inside theconduit is large enough and the flux of magma entering the shallow system is bounded by values that are determined analytically anonlinear oscillatory regime arises.