1 10 1 https://theses.otagogeology.org.nz/files/original/9b2e4d651d320427e3c84a79c0d427df.pdf 24e712f6349f496fb1f8727dc4a5563d Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Geology theses OU Geology thesis Thesis or dissertation completed by University of Otago Geology students Author last name Last name of the Author Schipper Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? PhD Advisers Who supervised/advised this student White. J.D.L. Abstract The Abstract for this thesis Even though the vast majority of volcanism on Earth occurs under water, very little is known about submarine volcanoes and their eruptions. The hydrostatic pressure at submarine vents was long thought to preclude submarine explosive eruptions, until recent exploration with submersibles revealed that widespread volcaniclastic deposits bearing striking similarity to the products of subaerial explosive eruptions are found to great depths in all the world's oceans. This has inspired the current investigation into the relative roles of magmatic degassing and magma-water interaction that permit submarine basalt explosivity in the deep sea. Lo'ihi Seamount is the youngest and southernmost active volcano in the HawaiianEmperor Volcanic Chain. Its~ 1 km deep summit plateau is home to many different volcaniclastic and pyroclastic deposits. A sampling-focused submersible dive series to Lo 'ihi in 2006 provided the material for this study, which is divided into three parts, covering: Poseidic scoria cones, primary pyroclastic deposit L8, and limu o Pele. The "Poseidic" name is introduced for an end-member style of submarine basalt explosivity identified by measurable features ofpyroclasts from two scoria cones on Lo'ihi's summit plateau. Vesicle textures in lapilli, dissolved volatiles in matrix glasses and olivine hosted glass inclusions, and fine ash morphology, are used to constrain this uniquely submarine, cone-forming style of eruption. The Poseidic eruption style involves cooperative processes of strongly volatile-coupled degassing and hydromagmatic fragmentation, that challenge traditional assumptions about depth limitations to these processes. A bedded, primary pyroclastic deposit ("L8"), exposed in a fault scarp on Lo'ihi's summit plateau allowed a series of samples to be collected upward through a volcaniclastic sequence. The bedding characteristics, clast vesicularities, microtextures, and geochemistry through the stratigraphy of this deposit indicate that the magma experienced variable ascent rates, and complex cooling regimes in the conduit. Deep-sea limu o Pele, shards of basaltic glass commonly described as "bubble walls," were found concentrated in ash lenses interbedded with thin lava sheets, and separated from an overlying volcaniclastic sequence by a discontinuity. Different theories have been presented about how these enigmatic particles form, either by hydrovolcanic volcanism, when submarine lava flows entrap and vaporise seawater, or by Strombolian-like explosive eruptions. The geometry and geochemistry of the Lo'ihi deposit provides compelling evidence for a hydrovolcanic, sheet-flow related origin. Theoretical considerations are presented to demonstrate that this process is viable even below the critical depth of seawater, where limu formation is driven by supercritical water, rather than water vapour. Submarine explosive eruptions are usually described by analogy to classical subaerial eruption styles, and many key eruption style-determining processes have previously only been treated theoretically. The robust samples collected for this study, and the detailed treatment of them, shows: (1) that submarine explosive eruptions are different from subaerial ones in almost all ways; (2) that many classical theories about what is and what is not possible at submarine volcanoes need constant reevaluation as new data become available; and (3) that the textures and chemistry of submarine pyroclasts can be used to rigorously determine eruption styles. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Lo'ihi seamount Hawai'i Thesis description Number of pages, maps, CDs, etc. ix, 218, 47 p. : ill. (some col.) ; 30 cm. + 1 CD-ROM. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Identifier An unambiguous reference to the resource within a given context 2010Schipper Creator An entity primarily responsible for making the resource Schipper, C. Ian. (Christopher Ian) Date A point or period of time associated with an event in the lifecycle of the resource 2010 Title A name given to the resource Explosive submarine volcanism at Lo`ihi Seamount, Hawai`i Subject The topic of the resource Volcanology Lo'ihi seamount. Hawahi'I Submarine explosive eruptions.