Ricerc@Sapienza

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.