The explosive engine of the 2022 Hunga submarine eruption

Ryo Okuwaki , Wenyuan Fan, Osamu Sandanbata , Diana C. Roman, Yuri Fialko 

The 2022 submarine eruption of Hunga volcano, Tonga, was among the largest volcanic eruptions in the modern era, yet the processes controlling its explosive sequence remain poorly understood. Here we present the first detailed insight into the internal mechanics of an explosive cycle from teleseismic waveforms. Four eruptive episodes repeat an implosion-explosion cycle, separated by a 3-minute pause dominated by shear deformation. The cycles reveal an explosive engine driven by a hydraulically isolated, conduit-scale volume that is orders of magnitude smaller than the reservoir and re-pressurized between failures through seawater-driven phreatomagmatic inflow. Because recurrence is set by the repressurization rate of the sealed volume, the pace of an explosive sequence reflects the scale of its driving system, from minutes at conduit scale to days at reservoir scale.