The purpose of this study was to provide both a detailed geochemical analysis of the lithologies that comprise the Glacier Peak volcanic terrain and to summarize the small amounts of past research which has been completed on this Cascade volcano. A broad and extensive literature search indicates this area was previously unstudied in modern petrochemical terms. This study is a detailed petrochemical description and analysis of the mineral phases and the textures present in the various units in the Glacier Peak area (tephra, lava, breccia, and tuff). A scanning electron microprobe study of the scoriaceous basaltic lapilli of the White Chuck cinder cone, indicates that the contemporaneous basaltic cone is comprised of two or more compositional groups. One group is higher in calcium and iron than the other group. These distinct groups, in the lapilli tephra, may imply that the recent cone was built by a multitude of eruptions which variedslightly in composition over time.Through microprobe techniques and computer point-counting methods, the petrochemistry of the Glacier Peak and Gamma Ridge lava flows and the modal distributions of minerals present were determined. The micropobe data was checked for stochiometry and plotted on triangular variation diagrams. Histograms show the distribution along plagioclase binary, solid-solution series (NaAlS13O8 - CaA1Si208). Standard triangular variation diagrams were used to show the composition of the pyroxenes present in the samples (othopyroxene or clinopyroxene). A bimodal distribution of both the pyroxene and the plagioclase exists.The data and observations made in this thesis study, (1) support the sequence of the Glacier Peak magmatic events (i.e., the late Miocene to Pliocene Gamma Ridge hypersthene-augite dacite flows, the Pleistocene Glacier Peak hypersthene dacite flows, and the recent, basaltic, White Chuck cinder cone tephra eruptions), and (2) suggests changing magmatic conditions which would result in the observed disequilibrium features common throughout the Glacier Peak volcanic series (i.e., resorbed and relict crystals, normal and reverse zoning features, cognate clotting and polymodal distribution of plagioclase compositions).Finally, from these observations made on the sequence of the magmatic events of the Glacier Peak series and the conclusions from the analyzed compositions of these volcanic rocks, which suggest changing magmatic conditions, a generalized magmatic model (introduced by Eichelberger, 1977) has been applied to the Glacier Peak series. This model involves injection of basaltic magma into a more silicic magma chamber and results in a hybridized magma. This would be the Glacier Peak magma and would result in the petrological characteristics which imply disequilibrium conditions.

The northern Lau Basin contains the northeastern-most part of the Tonga arc-basin system. Volcanic rocks associated with the recent-arc have been sampled from Tafahi and Niuatoputapu, and young basalts «1.5Ma) have been dredged from Northern Lau Spreading Centre (NLSC), the northeastern limb of the King's Triple Junction. The 1982 'Kallisto' cruise dredged two ophiolite sections, one containing boninitic, and the other tholeiitic, lavas, from the inner wall of the northern Tonga trench. The magma genesis of these lava suites is related to the structural and geochemical controls imposed during the tectonic evolution of the region. The geochemical controls result from processes related to the mantle dynamics in the northern Lau Basin, and to along-trench variations and the degree of influence of the subduction component. The lavas associated with the Central Lau Spreading Centre are derived from the Lau Basin mantle reservoir, which has Indian MORB mantle (!MM) isotopic characteristics. This reservoir has been present under the region since early-arc magmatism, as indicated by the trace elements and !MM isotopic signatures of the tholeiitic lavas from the eastern ophiolite section, and Eocene lavas from 'Eua. A reservoir with the geochemical characteristics of residual Samoan plume mantle underlies the northern Lau Basin. This mantle has been influxing through the rip in the Pacific plate, at the northern termination of the Tonga trench, since the Lau Basin began to open « 6Ma), as a result of processes relating to subduction roll-back. The north Tongan boninites, the lavas from Tafahi and Niuatoputapu have residual plume mantle sources. However, prior to the opening of the Lau Basin, the proto-Tonga trench formed a barrier to this influx, and therefore, the influence of the plume cannot be detected in lavas associated with the early-arc, such as the tholeiites from one of the ophiolite sections and the Eocene lavas from 'Bua. The variations in the trace element and Pb isotopic compositions of the lavas from the Northern Lau Spreading Centre indicate that mixing has occurred between Lau Basin and residual plume mantle end-members in the central northern Lau Basin. The residual plume mantle sources of the north Tongan boninites and the lavas from Tafahi, Niuatoputapu and the Tofua arc have been enriched by a subduction component, the characteristics of which are enrichment in Lll..E, Ph ± LREE. In the south, the subduction component is made up of fluids derived from subducted Pacific altered oceanic crust and pelagic sediments. However, in the north, it is comprised predominantly of fluids derived from Pacific volcanogenic sediments, with a contribution from altered oceanic crust and possibly subducted plume crust.

This thesis is a palaeoenviromnental investigation into possible non-climatic effects on the environment from volcanic ash fall and toxic emissions outside the blast zone of a volcanic eruption. These effects are determined from palynological and geochemical changes following tephra fall at a range of sites across the North Island of New Zealand which were located at increasing distances from the main volcanic source, the Taupo Volcanic Zone. These sites collectively covered a wide variety of habitats existing under different climatic regimes. The first site is a peat bog at a warm temperate, comparatively unstable coastal location, Matakana Island. The peat profile extends to 1000 yrs BP and contains the Kaharoa Tephra layer, erupted around the time of early human settlement in New Zealand. The second study site is Kaipo peat bog which, in contrast to Matakana Island, is an upland sub-alpine site existing under a harsher climatic regime with cool temperatures, strong winds and heavy rainfall. The Kaipo record covers the Holocene period up to recent times. Lake Rotoroa is the third site which is located inland, sheltered within the Waikato valley, an area of rich fertile soils and mild temperate climate. The Lake Rotoroa record extends to approximately 15,000 yrs BP including the end of the last glacial period and the Holocene. The final site investigated, Kohuora bog, is situated in an extinct late Quaternary volcanic crater within Auckland urban area, a region of warm temperate climate. This record extends from the last glacial period to the present. Fine resolution sampling methods were employed above tephra layers preserved at each of these sites to examine the immediate short-term palaeoenvironmental impacts from volcanic tephra deposition. The methods used included pollen analysis, and the relatively new technique of Energy Dispersive X-ray Micro Analysis (EDMA) which investigated changes in sediment geochemistry to provide further information on local environmental change following tephra impact. The use of pollen analysis together with EDMA proved beneficial in assessing overall short term environmental impacts from tephra fell. Results revealed that thicker tephra layers did not always cause extensive environmental damage, as impacts seen above the 0.5 cm thick Egmont 15 Tephra at Lake Rotoroa were among the most significant recorded at this site. Instead, the contributing factors of prevailing climate and local site factors (e.g. drainage, soils, vegetation cover and shelter) at the time of an eruption, together with local forest diversity and species sensitivity to tephra deposition, proved more important in determining the degree of tephra impact. Taxa found to be particularly sensitive to tephra deposition included Halocarpus, with inconsistent impacts from tephra fell on Dacrydium and Metrosideros. Duration of tephra impacts varied between sites, but broad estimates from the results showed the time taken for recovery of forest vegetation following an eruption was >100 years, with environmental stability returning after a minimum period of 50 years. The results from Matakana Island revealed that any possible tephra impacts from deposition of the Kaharoa Tephra were obscured owing to large-scale deforestation following Polynesian settlement on the island around the time of the Kaharoa eruption. This study indicates the importance of investigating distal volcanic impacts prior to human settlement to eliminate ambiguity in interpretation of palaeoenvironmental data.

The term “blue-sky eruption” (BSE) can be used to describe eruptions which are unexpected or have no detected precursory activity. Case study analyses indicate that they have a diverse range of characteristics and magnitudes, providing both direct and indirect hazards and occur in both under-developed and developed countries. BSEs can be a result of physical triggers (e.g. the lack of physically detectable precursors or a lack of understanding of the eruption model of the volcano), social triggers (such as an inadequate monitoring network), or a combination of the two. As the science of eruption forecasting is still relatively young, and the variations between individual volcanoes and individual eruptions are so great, there is no effective general model and none should be applied in the absence of a site-specific model. Similarly, as methods vary between monitoring agencies, there are no monitoring benchmarks for effective BSE forecasting. However a combination of seismic and gas emission monitoring may be the most effective. The United States began a hazard and monitoring review of their volcanoes in 2005. While the general principles of their review would be beneficial in a monitoring review of New Zealand’s volcanoes, differences in styles of volcanism, geographic setting and activity levels mean changes would need to be review to fully appreciate the risk posed by New Zealand’s volcanoes. Similarly, the monitoring benchmarks provided in the U.S. review may not be fully applicable in New Zealand. While advances in technology may ultimately allow the effective forecasting of some BSEs, the immediate threat posed by unexpected eruptions means that effective management and mitigation measures may be the only tools currently at our disposal to reduce the risks from BSEs.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 122-128).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 115-118).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 129-132).

Thesis (Ph. D.)--University of New South Wales, 2003. / Also available online.

Thesis (M.Sc. Earth and Ocean Science)--University of Waikato, 2008. / Title from PDF cover (viewed August 26, 2008) Includes bibliographical references (p. 169-177)

Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains xi, 221 p. : ill. (some col.), maps. Includes bibliographical references.