Conduit dynamics of highly explosive basaltic eruptions: The 1085 CE Sunset Crater sub-Plinian events

G. La Spina, Amanda Clarke, M. de' Michieli Vitturi, M. Burton, C. M. Allison, K. Roggensack, F. Alfano

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Basaltic volcanoes produce a range of eruptive styles, from Strombolian to low-intensity fire fountaining to, much more rarely, highly explosive Plinian eruptions. Although the hazards posed by highly explosive eruptions are considerable, controlling mechanisms remain unclear, and thus improving our understanding of such mechanisms is an important research objective. To elucidate these mechanisms, we investigate the magma ascent dynamics of basaltic systems using a 1D numerical conduit model. We find that variations in magmatic pressure at depth play a key role in controlling modelled eruption characteristics. Our most significant result is that a decrease in pressure at depth, consistent with the emptying of a magma chamber, results in enhanced volatile exsolution and in deepening fragmentation depth. The corresponding decrease in conduit pressure ultimately produces a collapse of the conduit walls. This type of collapse may be a key mechanism responsible for the cessation of individual explosive eruptions, a notion previously explored for silicic eruptions, but never before for basaltic systems. Using previously published field and sample analysis to constrain model parameters, we simulate scenarios consistent with sub-Plinian eruptions, similar to those at Sunset Crater volcano in ~1085 CE in terms of mass eruption rates and duration. By combining these analyses with a chamber-emptying model, we constrain the size of the magma chamber at Sunset Crater to be on the order of tens of km3. During the 1085 CE Sunset Crater eruption, there were three main sub-Plinian events that erupted between 0.12 and 0.33 km3 of tephra (non-DRE), indicating that ~1% of the total chamber volume was erupted during each sub-Plinian pulse.

Original languageEnglish (US)
Article number106658
JournalJournal of Volcanology and Geothermal Research
Volume387
DOIs
StatePublished - Dec 1 2019

Keywords

  • Basalt
  • Conduit model
  • Explosive eruption
  • Magma ascent
  • Magma chamber
  • Sunset Crater

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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