Easter Island and Sala y Gomez are part of the Sala y Gomez Ridge, a broad band of high topography and scattered seamounts extending ESE from the East Pacific Rise. It has been proposed that the Sala y Gomez Ridge results from the movement of the Nazca Plate over a fixed melting spot in the mantle. To test this hypothesis volcanic rocks from Easter Island and Sala y Gomez were analyzed for their K-Ar ages and major element abundances. Subaerial Easter Island was constructed in three distinct episodes, occurring at 2.5 m.y., 0.9 m.y., and 0.4 m.y. ago. The youngest rocks on the island are the Roiho olivine basalts, and are probably less than 50,000 years old. Eruptive activity on Sala y Gomez was essentially contemporaneous with the early volcanism on Easter Island. No migration of volcanism with time is apparent along the Sala y Gomez Ridge, thus a major criterion of the melting spot hypothesis is not fulfilled. Volcanic rocks from Easter Island constitute a tholeiitic differentiation series; they are chemically similar to those from other islands situated near mid-ocean rise crests. The wide compositional spectrum is most likely the result of fractional crystallization from a basaltic parent liquid, though the data is ambiguous for the highly silicic differentiates. The youngest basalts possess more alkaline affinities which are probably not related to fractional crystallization from the earlier basalts. The alkaline nature of these rocks may be the result of a downward migration of the fusion zone with time, as the island moved eastward over a progressively thickening lithosphere. Volcanic rocks from Sala y Gomez belong to an alkali olivine basalt series. The fundamental chemical differences between the Easter Island and Sala y Gomez suites suggest that the two islands were not derived from a common source, as predicted by the melting spot hypothesis. The evidence does not support a melting spot origin for Easter Island, Sala y Gomez, and the Sala y Gomez Ridge. An alternative model involving diapiric intrusion and decompression melting of asthenosphere material along a major fracture in the Nazca Plate provides a better explanation for the data. Synchronous volcanism along the eastern extension of the Easter Island transform fault has given rise to the islands and seamounts on the Sala y Gomez Ridge. / Graduation date: 1975

Graduation date: 1999

Thesis (M.A.)--University of Texas at Austin, 1990. / Vita. Includes bibliographical references (leaves 96-101).

Risks posed by geohazards to urban centres are constantly increasing, due to the continuous increase in population and associated infrastructure. A major risk to North Island urban centres is impacts from volcanic ashfall. This study analyses the vulnerabilities of selected New Zealand lifelines infrastructure to volcanic ash, to better understand and mitigate these risks. Telecommunications and wastewater networks are assessed, as is the vulnerability of Auckland Airport and grounded aircraft. The ability of vehicles to drive on ash covered roads is also tested, to determine the extent to which emergency services, utility providers and the public will be able to travel during and immediately after ashfall. Finally, air-conditioners have been identified as a significant vulnerability during ashfall, due to the high dependence on cooling for infrastructure and lifelines providers. These are examined to quantify the effects of ashfall on their performance. Each of the selected infrastructure types is assessed through a review of past impacts of ashfall, and experimentation either in the field or under laboratory conditions. Where appropriate, mitigation options that reduce identified vulnerabilities are considered. In most cases these options are operational rather than physical engineering solutions, and indicate pre-planning and response requirements. Key recommended mitigation options include the acquirement or strategic relocation of resources prior to ashfall, regular cleaning and maintenance of essential air conditioners during ashfall to enable their continued use, access to appropriate vehicles for utility providers to reach infrastructure, and discharge of untreated wastewater into Waitemata harbour at Orakei during ashfall on Auckland, to preserve the ability to continue treating wastewater at the Mangere treatment plant

Risks posed by geohazards to urban centres are constantly increasing, due to the continuous increase in population and associated infrastructure. A major risk to North Island urban centres is impacts from volcanic ashfall. This study analyses the vulnerabilities of selected New Zealand lifelines infrastructure to volcanic ash, to better understand and mitigate these risks. Telecommunications and wastewater networks are assessed, as is the vulnerability of Auckland Airport and grounded aircraft. The ability of vehicles to drive on ash covered roads is also tested, to determine the extent to which emergency services, utility providers and the public will be able to travel during and immediately after ashfall. Finally, air-conditioners have been identified as a significant vulnerability during ashfall, due to the high dependence on cooling for infrastructure and lifelines providers. These are examined to quantify the effects of ashfall on their performance. Each of the selected infrastructure types is assessed through a review of past impacts of ashfall, and experimentation either in the field or under laboratory conditions. Where appropriate, mitigation options that reduce identified vulnerabilities are considered. In most cases these options are operational rather than physical engineering solutions, and indicate pre-planning and response requirements. Key recommended mitigation options include the acquirement or strategic relocation of resources prior to ashfall, regular cleaning and maintenance of essential air conditioners during ashfall to enable their continued use, access to appropriate vehicles for utility providers to reach infrastructure, and discharge of untreated wastewater into Waitemata harbour at Orakei during ashfall on Auckland, to preserve the ability to continue treating wastewater at the Mangere treatment plant

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona, 1985. / Includes bibliographical references (leaves 182-187).

Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 200-207).

Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 248-255).

Thesis (M.S.)--Oregon State University, 1992. / Includes map in pocket. Typescript (photocopy). Includes bibliographical references (leaves. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1990. / Typescript (photocopy). Includes mounted photographs. Includes folded plates in pocket. Includes bibliographical references (leaves 377-396). Also available via the World Wide Web.