Understanding the Changing Dynamics of the 2016-2022 Nevados de Chillán, Chile Eruption through Erupted Volume and Surface Deformation

Improving forecasting of eruptive hazards is a top priority of the volcanological community and can be difficult to do in complex eruptions. From 2016-2022, Nevados de Chillán, Chile, underwent a complex eruption with multiple transitions between effusive and explosive activity, resulting in four domes and eight lava flows. We combine a decade of InSAR time series data with 4.5 years of data at five local GNSS stations to define three distinct periods of co-eruptive surface subsidence and three periods of co-eruptive uplift. We use Markov chain Monte Carlo methods to invert for the source depth and volume change necessary to cause each surface deformation period. We find evidence for the third uplift phase source to be slightly deeper (6.4 ± 0.4 km below ground level) compared to the first two periods of uplift (4.4 ± 0.2 km and 4.8 ± 0.1 km below ground level). We used topographic data from helicopter overflights and Pléiades and Maxar satellites to derive the total erupted volume (~1.1 x 107 m3) between December 2017 and November 2022. We compare these data sets with optical imagery from Planet satellites, thermal time series from Terra’s ASTER instrument, and seismic data. Each effusive phase begins with larger effusion rates that taper off. The episodes of surface uplift coincide with increases in effusion rate and seismicity, indicating a new supply of magma. The combination of ground-based, airborne, and satellite-derived datasets provides dense spatial and temporal information on eruption evolution.