Microstructure linking external forcing to supereruption

Large rhyolitic eruptions with ejecta of transcontinental scale have catastrophic effects on the environment. Despite its importance in volcanic hazard assessment and potentially influencing climate, the triggering of supervolcanoes remains enigmatic. Many valid mechanisms for mobilizing an eruptible magma reservoir exist, however, the fundamental question of how to initially form the magma reservoir responsible for a supereruption is unknown. Here we show that the deformation microstructure of partially molten rock could accelerate melt extraction and assemble a large eruptible magma reservoir. By modeling observed shape and orientation of melt pockets in deformed samples, we predict that deformation microstructure forms a melt network that enhances melt flux by up to 30 times. Our results suggest that compressing a crystal-rich magmatic mush in volcanic arcs or under glacial loading can assemble a large crystal-poor magma reservoir in a few thousand years, a timescale in consistent with petrological evidence of rapid assembly. Because external stress is common to most magmatic systems, deformation microstructure could be a ubiquitous catalyst for magmatic activities including supereruptions.