Quantifying degassing-driven crystal growth in basaltic lavas

As magma ascends and decompresses, volatile exsolution not only produces bubbles, but increases the liquidus temperature of the residual melt, resulting in an undercooling that can trigger crystallisation. In volcanic systems of intermediate composition, late-stage crystallisation and vesiculation in the shallow conduit have been shown to exert a strong control on eruptive style. These processes may be similarly important during subsurface and surface transport of basaltic melts. In recent experiments we demonstrated that the lag between degassing and crystallisation is sufficiently short that crystallisation as a consequence of degassing can be expected to occur in the conduit, depending on ascent rates. Up to 35% volume crystals were observed to grow as a result of the degassing of