HotStuff - Are all lavas a sintered byproduct of explosive eruptions? - Fabian Wadsworth

We are pleased to announce a HotStuff seminar by Fabian Wadsworth on the topic of: Are all lavas a sintered byproduct of explosive eruptions?

Abstract:

We typically think of lavas as representing relatively gentle effusive eruptions. However, silicic lavas are intimately linked to explosive eruptions and true effusion may not exist on Earth. Direct observations of the 2011-12 eruption of Cordón Caulle (Chile) demonstrated that an initially explosive eruption will give way to lava production, but only after a substantial period of hybrid - or mixed - behaviour where lava is produced continuously but where the explosive eruption continues. This raises the critical question: how can vigorous sustained explosive activity occur at the same vent location as far slower lava effusion? The only tenable explanation is that the explosive eruption produces the lava itself. It is easy to imagine that as hot pyroclasts accelerate toward the surface, a fraction of them can become stuck to volcanic conduit walls, building up volumes of sintering and densifying melt blebs. If that process occurs, then the densified mass of accumulating deforming pyroclasts is the lava itself such that the onset of lava effusion occurs when the vent region becomes fully clogged up with sintering pyroclasts. In this conception of effusive volcanism, hybrid behaviour occurs when the vent is clogged with lava, but continued explosive fragmentation beneath causes volcanic-fracking of the lava and country rock, intermittently tapping the underlying gas-and-ash region, and recorded in tuffisites. In this talk, Fabian will survey the implications of this model for geophysics, geochemistry, petrology, and our understanding of eruption timescales, as well as exploring the extent to which this model could be extended to intermediate dome-forming eruptions.