Hydrothermal fluid migration due to interaction with shallow magma: Insights from gravity changes before and after the 2015 eruption of Cotopaxi volcano, Ecuador

On August 14, 2015 Cotopaxi Volcano (Ecuador) erupted with several phreatomagmatic explosions after nearly 135 years of quiescence. Unrest began in April 2015 with an increase in the number of daily seismic events and inflation of the flanks of the volcano. Time-lapse gravity measurements started at...

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Bibliographic Details
Published in:Journal of volcanology and geothermal research 2019-12, Vol.387, p.106667, Article 106667
Main Authors: Calahorrano-Di Patre, Antonina, Williams-Jones, Glyn, Battaglia, Maurizio, Mothes, Patricia, Gaunt, Elizabeth, Zurek, Jeffrey, Ruiz, Mario, Witter, Jeffrey
Format: Article
Language:English
Subjects:
Cotopaxi Volcano
Hydrothermal fluid migration
Time-lapse gravity
Volcanic unrest
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Summary:On August 14, 2015 Cotopaxi Volcano (Ecuador) erupted with several phreatomagmatic explosions after nearly 135 years of quiescence. Unrest began in April 2015 with an increase in the number of daily seismic events and inflation of the flanks of the volcano. Time-lapse gravity measurements started at Cotopaxi volcano in June 2015. Although minor gravity changes were detected prior to eruptive activity, the largest gravity variations at Cotopaxi were measured between October 2015 and March 2016, when other geophysical parameters had reached background levels. Inverse modelling of GPS data suggests a deep intrusion prior to the eruptive activity, while inverse modelling of post-eruptive gravity changes suggests variations in the volcano hydrothermal system. Deformation, seismicity, and gravity changes are consistent with the intrusion of a deep magmatic source between April and August 2015. Part of the magma rose from depth and interacted with the hydrothermal system, causing the phreatomagmatic activity and pushing hydrothermal fluids from a deep aquifer into a shallow perched aquifer. •Gravity changes were detected at Cotopaxi before and after eruptive activity.•Pre-eruptive geophysical changes are consistent with a deep magmatic intrusion.•Post-eruptive gravity changes suggest changes in the volcano's hydrothermal system.•An interaction with a shallow magmatic source likely caused upward fluid migration.
ISSN:0377-0273
1872-6097
DOI:10.1016/j.jvolgeores.2019.106667