Black Point – Pyroclasts of a Surtseyan eruption show no change during edifice growth to the surface from 100 m water depth

Surtseyan eruptions have long been studied from their edifice deposits, emplaced subaqueously or subaerially. Here we characterize a Surtseyan eruption from both edifice and ash-sheet deposits using a combination of techniques. The volcano studied is Black Point, which erupted into Lake Russell about 13,000 years ago from a water depth of 105 m, producing a total of ~0.8 km³ of tephra. The techniques, applied to samples acquired by targeted sampling based on geological observations in the field, include geochemical characterization of the eruption products, grain-size analysis of the ash-size fraction at proximal and medial sites, three-dimensional characterization of vesicles in lapilli, and particle-shape analysis for ash grains using the recently introduced freeware PARTISAN