Basaltic Plinian eruptions at Las Sierras-Masaya volcano driven by cool storage of crystal-rich magmas

Abstract Although rare, basaltic Plinian eruptions represent a considerable volcanic hazard. The low viscosity of crystal-poor magma inhibits fragmentation; however, Las Sierras-Masaya volcano, Nicaragua, has produced multiple eruptions. Here, we quantify the geochemistry and volatile concentrations melt inclusions in samples Fontana Lapilli Masaya Triple Layer to constrain pre-eruptive conditions. Combining thermometry geochemical modelling, show that cooled ~1000 °C prior eruption, crystallising mush was erupted preserved scoriae. We use these data numerical conduit model, which finds conditions most conducive are temperature <1100 total crystal content >30 vol.%. Cooling, crystal-rich, large-volume bodies may be hazardous due their potential erupt with magnitude. Rapid ascent rates mean there only some minutes between eruption triggering activity at Masaya.