Thesis (Ph. D.)--Oregon State University, 1992. / Includes mounted photographs. Typescript (photocopy). Includes bibliographical references (leaves 181-198). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 272-295).

Thesis (Ph. D.)--California Institute of Technology, 1983. UM No. 83-12,057. / Some maps on folded sheets in pocket. Advisor names found in the Acknowledgments pages of the thesis. Title from home page (viewed 04/28/2010). Includes bibliographical references.

xvi, 182 p. : col. ill. / Volatile components (H 2 O, CO 2 , S, Cl) dissolved in magmas influence all aspects of volcanic activity from magma formation to eruption explosivity. Understanding the behavior of volatiles is critical for both mitigating volcanic hazards and attaining a deeper understanding of large-scale geodynamic processes. This work relates the dissolved volatile contents in olivine-hosted melt inclusions from young volcanics in the Central Oregon and Northern California Cascades to inferred magmatic processes at depth and subsequent eruptive activity at the surface. Cinder cone eruptions are the dominant form of Holocene volcanism in the Central Oregon segment of the High Cascades. Detailed field study of deposits from three cinder cones in Central Oregon reveals physical and compositional similarities to explosive historic eruptions characterized as violent strombolian. This work has important implications for future hazard assessments in the region. Based on melt inclusion data, pre-eruptive volatile contents for seven calc-alkaline cinder cones vary from 1.7-3.6 wt.% H 2 O, 1200-2100 ppm S, and 500-1200 ppm Cl. Subarc mantle temperatures inferred from H 2 O and trace elements are similar to or slightly warmer than temperatures in other arcs, consistent with a young and hot incoming plate. High-magnesium andesites (HMA) are relatively rare but potentially important in the formation of continental crust. Melt inclusions from a well-studied example of HMA from near Mt. Shasta, CA were examined because petrographic evidence for magma mixing has stimulated a recent debate over the origin of HMA magmas. High volatile contents (3.5-5.6 wt.% H 2 O, 830-2900 ppm S, 1590-2580 ppm Cl), primitive host crystals, and compositional similarities with experiments suggest that these inclusions represent mantle-derived magmas. The Cascades arc is the global end member, warm-slab subduction zone. Primitive magma compositions from the Cascades are compared to data for arcs spanning the global range in slab thermal state to examine systematic differences in slab-derived components added to the mantle wedge. H 2 O/Ce, Cl/Nb, and Ba/La ratios negatively correlate with inferred slab surface temperatures predicted by geodynamic models. Slab components become increasingly solute-rich as slab surface temperatures increase from ∼550 to 950°C at 120 km depth. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Dr. Paul J. Wallace, Chair and Advisor; Dr. Katharine Cashman, Member; Dr. Ilya Bindeman, Member; Dr. Richard Taylor, Outside Member

Typescript (photocopy) / xiv, 220 leaves, [11] leaves of plates : ill., charts, maps ; 30 cm. + 2 fold. col. maps in end pocket / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology, 1982

Master of Science / Department of Geology / Matthew E. Brueseke / The Jarbidge Rhyolite of Elko County, Nevada, is approximately 26 mapped bodies of porphyritic rhyolite. Several of the bodies are truncated by the Idaho or Utah border, and extend into the states for an unknown distance. This study focuses on five bodies, the Mahoganies, two near Wild Horse Reservoir, the outcrop enclosing the Jarbidge Mountains, and one outcrop south of Wells. The study’s focus is providing field, petrography, geochemistry, oxygen isotope, and geochronology information about the five previously mentioned bodies. Physical volcanology encountered during this study indicates the sampled Jarbidge Rhyolite are effusive lava flows and domes that coalesced over the life of the volcanic system. First order approximations indicate that erupted products cover ~1,289 km2 and erupted material totals ~509 km3. Petrography indicates primary anhydrous mineral assemblages, assimilation of granitoid, possible assimilation of metamorphic rock and magma mixing of mafic and silicic bodies. Collectively, the Jarbidge Rhyolite lava flows sampled are compositionally restricted from rhyolite to high silica rhyolite and all samples demonstrate A-type magma characteristics. Compositions from different bodies overlap on Harker diagrams, and trace element ratios distinguish few flows from the other samples. Rare earth element patterns mimic one another, and incompatible trace element ratios overlap between bodies, likely indicating the presence of one large magma body. Oxygen isotope values for selected samples range 6.61-8.95%oVSMOW are coincident with normal igneous values. New 40Ar/39Ar geochronology indicates Jarbidge Rhyolite volcanism initiated ca. 16.7 Ma near Wild Horse Reservoir and was active at Bear Creek Summit ca.15.8 Ma. Local Steens Basalt, geochemistry, and Au-Ag mineralization indicate Jarbidge Rhyolite is similar to Middle Miocene silicic volcanics (e.g. Santa Rosa-Calico volcanic field) further west in the Oregon-Idaho-Nevada tristate region.

This research involves a study of a 2 km thick volcanic succession which accumulated during the opening stages of the precursor of the Reykjanes-Langjökull axial rift zone in W-Iceland, between 6-3 m.y. Following the initial accumulation of olivine tholeiite lavas, which lie unconformably on an older crustal basement 10-13 m.y.), a central volcano developed in the Hafnarfjall-Skarðsheiði area. It was active for some 1.5 m.y. and consists of four volcanic phases: I. The Brekkufjall phase is characterized by basaltic volcanism followed by voluminous and copious extrusions of differentiated rocks culminating in a sudden caldera collapse (c.5 km wide) in Brekkufjall. II. During the Hafnarfjall phase a thick extrusive sequence of basaltic to rhyolitic compositions accumulated, mainly fed by ENE fissures. During the gradual subsidence of the Hafnarfjall caldera (7 by 5 km) a marked decrease occurred in lava accumulation rate outside the caldera. Epicentres of three cone sheet swarms coincide in time and space with three basinal structures of this caldera. III. The Skarðsheiði phase is characterized by N-S fissuring and a marked bimodal basalt-rhyolite lava accumulation. IV. Remnants of the Heioarhorn phase include compositions ranging from basalts to rhyolites. The western boundary of the axial rift zone is marked by large intrusives, basalt flexuring, a sheet swarm and the disappearance of dyke swarms. The lenticular unit was later buried by lavas of the Hvalfjörður lenticular unit. Rocks of the central volcano follow the Þingrmúli trend, but is discontinuous in the basal tic andesite range. Basalts (frequently porphyritic) with relatively monotonous compositions and low LIL abundancies predominate during episodes of low extrusion rate whereas high elemental dispersion characterizes basalts of high extrusion rate episodes. The basalt compositions are believed to be controlled more by partial melting processes rather than by episodes of low-pressure fractionation. The differentiated rocks are considered to have predominantly formed by partial melting of the lower crust.

Determining the eruption temperature of Io's dominant silicate lavas would constrain Io's present interior state and composition. We have examined how eruption temperature can be estimated at lava tube skylights through synthesis of thermal emission from the incandescent lava flowing within the lava tube. Lava tube skylights should be present along Io's long-lived lava flow fields, and are attractive targets because of their temporal stability and the narrow range of near -eruption temperatures revealed through them. We conclude that these skylights are suitable and desirable targets (perhaps the very best targets) for the purposes of constraining eruption temperature, with a 0.9:0.7-mu m radiant flux ratio <= 63 being diagnostic of ultramafic lava temperatures. Because the target skylights may be small - perhaps only a few m or 10 s of m across - such observations will require a future Io-dedicated mission that will obtain high spatial resolution (<100 mipixel), unsaturated observations of Io's surface at multiple wavelengths in the visible and near-infrared, ideally at night. In contrast to observations of lava fountains or roiling lava lakes, where accurate determination of surface temperature distribution requires simultaneous or near simultaneous (<0.1 s) observations at different wavelengths, skylight thermal emission data are superior for the purposes of temperature derivation, as emission is stable on much longer time scales (minutes, or longer), so long as viewing geometry does not greatly change during that time. (C) 2016 Elsevier Inc. All rights reserved.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Monowai is an active submarine volcanic center in the Kermadec Arc, Southwest Pacific Ocean. We show, using cross-correlation and time-difference-of-arrival techniques, that low-frequency underwater sound waves from the volcano travel in the Sound Fixing and Ranging (SOFAR) channel and can be detected by bottom-moored hydrophone arrays of the International Monitoring System (IMS), a global sensor network maintained by the Comprehensive Nuclear-Test-Ban Treaty Organization. Hydroacoustic phases associated with the May 2011 eruption at Monowai are identified in the record of the IMS station at Ascension Island, Equatorial Atlantic Ocean. The source-receiver distance of ~15,800 km is the furthest documented range of any naturally occurring underwater signal ever observed. Our observations are consistent with results from transmission loss modeling, which suggest that acoustic propagation at southern latitudes is facilitated by the anomalous temperature regime of the Antarctic Circumpolar Current. Subsequently, we examine the 3.5-year record of the IMS hydrophone station near Juan Fernández Islands, Southeast Pacific Ocean, for volcanic activity at Monowai. Density-based clustering of arrivals during the time periods when data is available, i.e. from July 2003 to March 2004, and between April 2014 and January 2017, reveals 82 discrete episodes that are spaced days to weeks apart, typically ranging from a few hours to days in length. The resolution of the hydrophone data for seismic events at the volcano is estimated at 2.2 m_b and exceeds regional broadband networks by one order of magnitude. Considering the results and techniques developed in the study of Monowai, we investigate the 2014 submarine eruption of Ahyi volcano in the Northern Mariana Islands. Acoustic phases of the 15-day episode are identified in the record of an IMS hydrophone array located at Wake Island in the northwestern Pacific Ocean. Explosive volcanic activity occurred in two bursts, accompanied by a decrease in low-frequency arrivals that is interpreted as a shift in signal source parameters. Acoustic energy released during the event is on the order of 9.7 10¹³ J.