Diverse patterns of ascent,degassing, and eruption of rhyolite magma during the 1.8 ka Taupo eruption,New Zealand: Evidence from clast vesicularity |
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| Authors: | Bruce F Houghton Rebecca J Carey Katharine V Cashman Colin JN Wilson Barbara J Hobden Julia E Hammer |
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| Institution: | 1. Department of Geology and Geophysics, University of Hawai''i, 1680 East-West Road, Honolulu, HI 96822, USA;2. Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA;3. School of Geography, Environment and Earth Sciences, Victoria University, Wellington 6140, New Zealand;4. Department of Earth Sciences, University of Waikato, Hamilton, New Zealand |
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| Abstract: | The 22 km3 (DRE) 1.8 ka Taupo eruption ejected chemically uniform rhyolite in a wide range of eruptive styles and intensities. The 7 eruptive units include the ‘type examples’ of phreatoplinian (units 3 and 4) and ultraplinian fall (unit 5) deposits, and low-aspect-ratio ignimbrite (unit 6). Contrasts in bulk vesicularity, vesicle (and microlite) number densities and the size distributions of bubbles (and crystals) in the Taupo ejecta can be linked to the influence of shallow conduit processes on volatile exsolution and gas escape, before and during eruption, rather than changes in pre-eruptive chemistry. Existing work has modeled the individual phases of this complex eruption but not fully explained the abrupt shifts in style/intensity that occur between phases. We link these rapid transitions to changes in vent position, which permitted contrasts in storage, conduit geometry, and magma ascent history. |
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| Keywords: | explosive volcanism vesiculation conduit process Plinian Taupo eruption |
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