Geological Society of America

T241 Experimental and Petrologic Investigation of Halogens, Sulfur, and Other Volatile Species in Igneous Systems: In Honor of Jim Webster

Friday, 30 October 2020
10:00 AM - 2:00 PM
Meeting Rooms

THE VOLCANIC EXPLOSIVE-EFFUSIVE TRANSITION EXPLAINED BY COMPETING OUTGASSING MECHANISMS

Paper number: T241-4
Program: Technical Sessions
Time: 10:35 AM – 10:50 AM

Authors

Thomas Herbst Presenting Author
University of Missouri, Columbia, MO
Alan Whittington
The University of Texas at San AntonioGeological Sciences, San Antonio, TX
Alan Whittington
University of Missouri, Columbia, MO
Mattia Pistone
University of Lausanne, Lausanne
Mattia Pistone
University of Georgia, Athens, GA
James Schiffbauer
University of MissouriGeological Sciences, Columbia, MO
James Schiffbauer
University of Missouri, Columbia, MO
Tara Selly
Columbia, MO
Tara Selly
University of Missouri, Columbia, MO

Abstract

Lava dome-forming volcanoes commonly switch between effusive and explosive styles of eruption. Eruptions are driven by gas overpressure, which can be released through development of permeability, yet the least permeable magmas often erupt effusively. We studied gas exsolution and outgassing through experimental vesiculation of hydrous dacite glass samples containing crystal fractions between 0 and 0.8. Outgassing occurs rapidly via fracturing at crystal fractions ≥ 0.7, implying that crystal-rich effusive lavas are likely healed remains of fractured, initially more hydrous magmas. Fracturing and bubble coalescence are both inefficient at crystal fractions of 0.5–0.6, implying eruptive behavior of lava domes can fluctuate in response to minor changes in crystallinity or ascent rate. We delineate a critical permeability-porosity threshold separating effusive magmas from those with explosive potential.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359881

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