The exposed Mule Creek vent deposits record the structure of a volcanic conduit during a hybrid explosive–effusive eruption

Abstract Silicic volcanic eruptions commonly begin with the explosive ejection of pyroclastic material, before transitioning to gentler effusion-dominated activity. Well-exposed dissected silicic systems are scarce and poorly studied, hindering advances in our understanding explosive–effusive transition needed improve interpretations unrest hazard forecasting. The Mule Creek vent (New Mexico, USA) is a conduit that records processes controlling formation evolution, role tuffisites (fractures filled variably welded pyroclasts) play dynamics. Here, we use decimeter-scale photo-mapping lithostratigraphic units thin section analysis differentiate interpret three dominant emplacement styles during evolution. First, there was repeated deposition erosion material at walls, recorded by erosive surfaces breccia agglomerates margins. Second, sub-vertical domains dense melt-dominated magma were emplaced preserved as glass-dominated vitrophyre brecciated vitrophyre, textural hallmarks assembly from welding pyroclasts. Finally, sub-horizontal fracturing previously deposited lithologies produced laterally cross-cutting tuffisites. deposits track widening then narrowing through time reflect progressive insulation generally higher temperatures towards center pyroclasts accumulate. Welding fill vitrophyres lowers deposit porosity effective wall permeability. This drives localized gas pressure increases results gas-driven fracturing, generating tuffisites, which act transient outgassing pathways. structure an transition, constraining evolution aiding interpretation unrest.