Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador

Mathieu Colombier; Benjamin Bernard; Heather M. Wright; Jean-Luc Le Pennec; Francisco Caceres; Corrado Cimarelli; Michael J. Heap; Pablo Samaniego; Jeremie Vasseur; Donald B. Dingwell

doi:10.1007/s00445-022-01612-1

Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador

Bulletin of Volcanology

By: Mathieu Colombier, Benjamin Bernard, Heather M. Wright, Jean-Luc Le Pennec, Francisco Caceres, Corrado Cimarelli, Michael J. Heap, Pablo Samaniego, Jeremie Vasseur, and Donald B. Dingwell

https://doi.org/10.1007/s00445-022-01612-1

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Abstract

Stratovolcanoes are commonly characterised by cyclic eruptive activity marked by transitions between dome-forming, Vulcanian, Subplinian and Plinian eruptions. Guagua Pichincha volcano (Ecuador) has been a location of such cyclicity for the past ~ 2000 years, with Plinian eruptions in the first and tenth centuries AD (Anno Domini/after Christ), and CE (Common Era) 1660, which were separated by dome-forming to Subplinian eruptions, such as the recent 1999–2001 eruption. These cycles are therefore a prominent example of effusive-explosive transitions at varying timescales. Here, we investigate the reasons for such shifts in activity by focusing on degassing and outgassing processes within the conduit. We have coupled a petrophysical and textural analysis of dacites from the CE 1660 Plinian eruption and the 1999–2001 dome-forming/Vulcanian eruption, with different percolation models in order to better understand the role of degassing on eruptive style. We demonstrate that the transition from dome-forming to Plinian activity is correlated with differences in phenocryst content and consequently in bulk viscosity. A lower initial phenocryst content and viscosity is inferred for the Plinian case, which promotes faster ascent, closed-system degassing, fragmentation and explosive activity. In contrast, dome-forming phases are promoted by a higher magma viscosity due to higher phenocryst content, with slower ascent enhancing gas escape and microlite crystallization, decreasing explosivity and yielding effusive activity.

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Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador
Series title	Bulletin of Volcanology
DOI	10.1007/s00445-022-01612-1
Volume	84
Year Published	2022
Language	English
Publisher	Springer
Contributing office(s)	Volcano Science Center
Description	105, 23 p.
Country	Ecuador
Other Geospatial	Guagua Pichincha volcano
Google Analytic Metrics	Metrics page