Eruptive process documented from the last eruption of Ubinas volcano – July 2019

Abstract

The Ubinas stratovolcano, located in the CVZ segment of the central Andes, is one of the 10 most active volcanoes in Peru, with more than 26 eruptive episodes of low to moderate magnitudes (VEI 1-3), ranging from 2 to 7 eruptions per century. After 2 years of calm, a new eruptive stage began on July 19, 2019. Unlike previous eruptions, this eruptive process was monitored with continuous multiparametric instrumental monitoring, which allowed for the documentation and identification of the first signs of volcanic unrest. Three stages have been documented: (1) Unrest Period, where very energetic and high-frequency seismic signals are identified, associated with a change in the dynamics of the volcano, (2) Precursor Activity, a stage in which variations in deformation and periods of deflation of -12±6 cm and inflation of 75±15mm are detected, along with low seismic activity, while on June 18, small VT seismicity swarms are recorded, characterizing a magmatic transition stage with intrusions in the superficial regions of Ubinas, (3) Eruptive Period, characterized by a gradual increase in low-frequency seismicity (LP), with SO2 values increasing from moderate to high levels, pressurizing the volcanic conduit system and leading to the eruption on July 19, which released a seismic energy of 336 MJ and a recalculated volume of 4.6x10^6 m^3 of volcanic products. The magnitude of the eruption was classified with a VEI of 2. Permanent multiparameter instrumental monitoring allowed for the recording of relevant data for understanding the internal processes in the Ubinas volcanic system and documented signals associated with the movement of magmas.