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Conduit evolution during explosive activity at an andesitic stratovolcano, an example from Taranaki Mounga, New Zealand

Henry Hoult\1, Ben Kennedy1, Alexander R. L. Nichols1, Shane Cronin2, Leighton Watson3, Jonathan B. Hanson4

  • Affiliations: 1School of Earth and Environment, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand 2School of Environment, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand 3School of Mathematics and Statistics, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand 4GNS Science Te Pū Ao, 1 Fairway Drive, Avalon 5010, PO Box 30-368, Lower Hutt 5040

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 213

  • Programme No: 3.2.36

  • Theme 3 > Session 2

Abstract

**Presenting author * Volcanic conduits play an important role in modulating eruption dynamics by influencing outgassing of ascending magma and the density of eruption plumes. Inhibiting outgassing of magma during ascent promotes explosivity. Increasing the density of plumes through conduit wall erosion increases the likelihood of plume collapse and pyroclastic density current generation. Here, we combine textural and physical property analysis with componentry and field data to provide an overview of conduit establishment, evolution, and closure at Taranaki Mounga, New Zealand. The dominant lithic types across explosive eruptions from both Taranaki's andesitic summit vent and basaltic-andesitic parasitic vent represent material from the shallow conduit and vent. Variable alteration, fracturing and sintering of lithic clasts indicate both juvenile and remnant material comprised a lined shallow conduit system whose permeability and strength evolved across eruptive periods. Componentry analysis and field data from the AD 1655 sub-Plinian Burrell eruption reveals shallow juvenile linings build concentrically inwards and are then removed across different phases of the same eruption. Lining accumulation and destruction in this way correlates with transitions in eruption style. Pumice and lithic textures show the juvenile-lithic transition can occur on intra-eruption timescales, meaning future studies should incorporate characteristics and abundances of the pumice-lithic spectrum to build a full picture of conduit wall evolution both between and during eruptions. This is important for risk assessments based on trends in recent activity as repeated effusive activity may sequentially increase the likelihood for explosivity, and vice versa, at global stratovolcanoes.