Magma accumulation at depths of prior rhyolite storage beneath Yellowstone Caldera

Seismic tomography has provided key insight into Yellowstone’s crustal magmatic system that includes attempts to understand the melt distribution in the subsurface and the current stage of the volcano’s life cycle. We present new tomographic images of the shear wave speed of the Yellowstone magmatic system based on full waveform inversion of ambient noise correlations, which illuminates shear wave speed reductions of greater than 30% associated with Yellowstone’s silicic magma reservoir. The slowest seismic wave speeds (shear wave speed less than 2.3 kilometers per second) are present at depths between 3 and 8 kilometers, overlapping with petrological estimates of the assembly depth of erupted rhyolite bodies. Assuming that Yellowstone’s magmatic system is a crystal mush with broadly distributed melt, we estimate a partial melt fraction of 16 to 20%. Description Picturing Yellowstone’s plumbing Yellowstone is an active supervolcano that will cause mass destruction when it next erupts. Maguire et al. use full waveform seismic imaging to map the location and amount of melt under the volcano (see the Perspective by Cooper). They find the largest amount of melt is roughly in the depth range where previous eruptions were sourced. However, the amount of melt is much lower than required for a massive eruption anytime in the near future. Continued monitoring of the subsurface should provide a clear picture if the situation begins to dramatically change. —BG Seismic imaging shows a melt fraction of up to 20% in the depth range that supplied prior Yellowstone eruptions.