We present an integrated petrological study of the 2021 Tajogaite eruption, La Palma, examining magmatic processes that initiated, sustained, and terminated surface volcanic activity. High temporal resolution sampling of near-continuously erupted alkali-basalt lava and tephra over the 85-day event reveals magma plumbing system dynamics from compositional trends. Initial deposits were mineralogically varied, reflecting mobilisation of shallow, evolved mush perturbed by fresh deep, primitive magma influx (Stage 1 - initiation). Transition to more primitive, uniform compositions recorded progressively deeper tapping of pre-existing magmatic zonation (Stage 2 - evacuation). The final stage (Stage 3 - waning) was characterised by more evolved magma compositions on the same fractionation trend as Stage 2, with tephra glass compositions suggesting a proportionately larger role of mush interstitial melts. We suggest this reflects shutdown of mantle-derived magma supply, a key process in eruption waning and termination, and compression-driven melt extraction of less mobile melts. Correlation with geophysical monitoring data demonstrates how near-real-time petrological monitoring could improve understanding of when an eruption may end.
