The Magmatic System Under Hunga Volcano Before and After the 15 January 2022 Eruption

Publication

http://www.science.org/doi/10.1126/sciadv.adh3156(external link) 

One of the largest explosive eruptions instrumentally recorded occurred at Hunga volcano on January 15, 2022. The magma plumbing system under this volcano is unexplored due to inherent difficulties caused by its submarine setting. We use marine gravity data derived from satellite altimetry combined with multibeam bathymetry to model the architecture and dynamics of the magmatic system before and after the January 2022 eruption. We provide geophysical evidence for significant melt accumulation in three reservoirs at shallow depths (2 to 10 km) under the volcano. We estimate that less than ~30% of the existing melt was evacuated by the main eruptive phases, enough to trigger caldera collapse. The eruption and associated caldera collapse reorganized magma storage resulting in an increased connectivity between the two spatially distinct reservoirs. These estimates of magma storage volume and depth will improve future volcanic hazard assessment at Hunga and other submarine volcanoes.

Presentation:

https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1245310(external link)

One of the largest explosive eruptions instrumentally recorded occurred at Hunga volcano on January 15, 2022. The magma plumbing system under this volcano is unexplored due to inherent difficulties caused by its submarine setting.

We use marine gravity data derived from satellite altimetry combined with multibeam bathymetry to model the architecture and dynamics of the magmatic system before and after the January 2022 eruption. To isolate the anomalies due to underground density variations we model and remove the gravity effect of the bathymetry interface using two independent high-resolution multibeam bathymetry data sets acquired before and after the eruption, in 2016 and May 2022, respectively. We then model the pre-, co-, and post-eruptive residual Bouguer anomaly grids using a gradient-based mixed norm inversion method to determine the subsurface density distribution and its temporal evolution.

We provide geophysical evidence for significant melt accumulation in three reservoirs at shallow depths (2 to 10 km) under the volcano. We estimate that less than ~30% of the existing melt was evacuated by the main eruptive phases, enough to trigger caldera collapse. The eruption and associated caldera collapse reorganized magma storage resulting in an increased connectivity between the two spatially distinct reservoirs. Understanding the conditions and configuration of melt storage under Hunga – depth and volume – is crucial to better assess volcanic hazards in the Tonga archipelago and will eventually help provide a more accurate forecast of the size and likelihood of future eruptions.