Conceptualization and definitions of pre-eruptive storage and extraction pressures after Gualda et al. (2019b). Interstitial melt is physically separated from a magma mush (‘extraction’) to form a crystal-free magma. The extracted melt may stay in contact with the mush, or it may move to a separate, shallower, magma body. Crystals grow in the extracted magma over the time referred to as ‘pre-eruptive storage’. During a very rapid eruption, the melt is quenched to glass and the crystals are preserved as phenocrysts. In a slower eruption, there may be syn-eruptive crystallization. In either eruption style, the pressure that the whole-rock composition equilibrated with the mush mineral assemblage is the ‘extraction pressure’. The pressure that rapidly cooled glass was in equilibrium with the phenocryst mineral assemblage is the ‘pre-eruptive storage pressure’.