Colombier M., Bernard B., Wright H., Le Pennec Jean-Luc, Caceres F., Cimarelli C., Heap M. J., Samaniego Pablo, Vasseur J., Dingwell D. B. (2022). Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador. Bulletin of Volcanology, 84 (12), 105 [23 p.]. ISSN 0258-8900.
Titre du document
Conduit processes in crystal-rich dacitic magma and implications for eruptive cycles at Guagua Pichincha volcano, Ecuador
Année de publication
2022
Auteurs
Colombier M., Bernard B., Wright H., Le Pennec Jean-Luc, Caceres F., Cimarelli C., Heap M. J., Samaniego Pablo, Vasseur J., Dingwell D. B.
Source
Bulletin of Volcanology, 2022,
84 (12), 105 [23 p.] ISSN 0258-8900
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 similar to 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.
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
Description Géographique
EQUATEUR
Localisation
Fonds IRD [F B010086409]
Identifiant IRD
fdi:010086409
