Water-in-olivine magma ascent chronometry: Every crystal is a clock

The syneruptive decompression rate of basaltic magma in volcanic conduits is thought to be a critical control on eruptive vigor. Recent efforts have constrained decompression rates using models of diffusive water loss from melt embayments, olivine-hosted melt inclusions and clinopyroxene phenocrysts; however, these techniques are difficult to apply because of the rarity of pyroxene crystals or melt embayments suitable for analysis and the complexities associated with modeling water loss from melt inclusions. We have developed a new magma ascent chronometer based on syneruptive diffusive water loss from olivine phenocrysts.