Show simple item record  

dc.contributor.authorKrippner, Janine Barbaraen_NZ
dc.date.accessioned2009-02-19T12:01:18Z
dc.date.available2009-07-30T09:33:40Z
dc.date.issued2009en_NZ
dc.identifier.citationKrippner, J. B. (2009). Ngauruhoe inner crater volcanic processes of the 1954-1955 and 1974-1975 eruptions (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/2760en
dc.identifier.urihttps://hdl.handle.net/10289/2760
dc.description.abstractNgauruhoe is an active basaltic andesite to andesite composite cone volcano at the southern end of the Tongariro volcanic complex, and most recently erupted in 1954-55 and 1974-75. These eruptions constructed the inner crater of Ngauruhoe, largely composed of 1954-55 deposits, which are the basis of this study. The inner crater stratigraphy, exposed on the southern wall, is divided into seven lithostratigraphic units (A to G), while the northern stratigraphy is obscured by the inward collapse of the crater rim. The units are, from oldest to youngest: Unit A, (17.5 m thick), a densely agglutinated spatter deposit with sharp clast outlines; Unit B, (11.2 m) a thick scoria lapilli deposit with local agglutination and scattered spatter bombs up to 1 m in length; Unit C, (6.4 m thick) a clastogenic lava deposit with lateral variations in agglutination; and Unit D, (10 m thick) a scoria lapilli with varying local agglutination. The overlying Unit E (15 cm thick) is a fine ash fallout bed that represents the final vulcanian phase of the 1954-55 eruption. Unit F is a series of six lapilli and ash beds that represent the early vulcanian episode of the 1974-75 eruption. The uppermost Unit G (averaging 10 m thick) is a densely agglutinated spatter deposit that represents the later strombolian phase of the 1974-75 eruption. Units A-D juvenile clasts are porphyritic, with phenocrysts of plagioclase, orthopyroxene, clinopyroxene, minor olivine, within a microlitic glassy groundmass. Quartzose and greywacke xenoliths are common in most units, and are derived from the underlying basement. The 1954-55 and 1974-75 eruptions are a product of a short-lived, continental arc medium-K calc-alkaline magma. The magma originated from the mantle, then filtered through the crust, undergoing assimilation and fractionation, and evolving to basaltic andesite and andesite compositions. The magma body stagnated in shallow reservoirs where it underwent further crustal assimilation and fractionation of plagioclase and olivine, and homogenisation through magma mixing. Prior to the 1954-55 eruption a more primitive magma body was incorporated into the melt. The melt homogenised and fed both the 1954-55 and 1974-75 eruptions, with a residence time of at least 20 years. The 1954-55 eruption produced alternating basaltic andesite and andesite strombolian activity and more intense fire fountaining, erupting scoria and spatter that built up the bulk of the inner crater. A period of relative quiescence allowed the formation of a cooled, solid cap rock that resulted in the accumulation of pressure due to volatile exsolution and bubble coalescence. The fracturing of the cap rock then resulted in a vulcanian eruption, depositing a thin layer of fine ash and ballistic blocks. The 1974-75 eruption commenced with the rupturing of the near-solid cap rock from the 1954-55 eruption in an explosive vulcanian blast, the result of decompressional volatile exsolution and bubble coalescence, and possible magma-water interaction. The eruption later changed to strombolian style, producing a clastogenic lava that partially flowed back into the crater.en_NZ
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherThe University of Waikatoen_NZ
dc.rightsAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectvolcanoen_NZ
dc.subjectNgauruhoeen_NZ
dc.subjecteruptionen_NZ
dc.subjectstrombolianen_NZ
dc.subjectvulcanianen_NZ
dc.subjectfire fountainen_NZ
dc.subjectcomposite coneen_NZ
dc.subjectTongariroen_NZ
dc.subjectTVZen_NZ
dc.subjectTgVCen_NZ
dc.subjectvolcanicen_NZ
dc.subjectvolcanologyen_NZ
dc.subjectTaupo Volcanic Zoneen_NZ
dc.subjectstratovolcanoen_NZ
dc.subjectbasaltic andesiteen_NZ
dc.subjectandesiteen_NZ
dc.titleNgauruhoe inner crater volcanic processes of the 1954-1955 and 1974-1975 eruptionsen_NZ
dc.typeThesisen_NZ
thesis.degree.disciplineScience and Engineeringen_NZ
thesis.degree.grantorUniversity of Waikatoen_NZ
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (MSc)en_NZ
uow.date.accession2009-02-19T12:01:18Zen_NZ
uow.date.available2009-07-30T09:33:40Zen_NZ
uow.identifier.adthttp://adt.waikato.ac.nz/public/adt-uow20090219.120118en_NZ
pubs.elements-id55727
pubs.place-of-publicationHamilton, New Zealanden_NZ


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record