Integrated petrological, geochemical, and geophysical constraints on pre- and syn-eruptive magma dynamics during the 2021 Tajogaite monogenetic eruption (La Palma, Canary Islands)

The 2021 Tajogaite eruption on La Palma (Canary Islands) offers an exceptional opportunity to investigate magma dynamics in an actively monitored monogenetic volcanic system. We present an interdisciplinary study integrating petrological, geochemical, and geophysical datasets to reconstruct the pre- and syn-eruptive evolution of the magmatic plumbing system and its implications for eruption forecasting. Our dataset includes whole-rock and mineral chemistry, olivine diffusion chronometry, gas geochemistry, GNSS and InSAR ground deformation measurements, seismicity, and eruptive column height monitoring.

This integrated approach allows us to constrain magma storage conditions, ascent timescales, and the temporal evolution of the magmatic plumbing system. The results reveal a multi-stage pre-eruptive history involving at least three magmatic intrusions (2017–2018, 2020, and weeks prior to the 2021 eruption) that progressively reactivated the system. Olivine diffusion modeling indicates that the eruption was triggered by a late-stage intrusion in early September 2021, with magma ascent times of approximately 10–30 days.

During the eruption, recurrent injections of deeper magma were detected through systematic changes in crystal chemistry, ground deformation, and eruptive behavior. The earliest erupted products were relatively evolved and contained olivine crystals with oscillatory zoning, reflecting rapid ascent and conduit opening. In contrast, the second half of the eruption was marked by the development of a transient crystal mush zone in the upper crust, where magma accumulated without immediate eruption. This transition is supported by longer olivine residence times and a consistent ∼5-day lag between deformation maxima and peak eruptive column heights.

These observations demonstrate the dynamic nature of magma storage in monogenetic systems and highlight the value of integrating petrological data, including timescales, with real-time geophysical and geochemical monitoring. Such multi-parameter approaches are essential for improving the interpretation of unrest signals, constraining the formation and role of transient upper-crustal magma storage zones controlling eruption dynamics, and enhancing eruption forecasting during future monogenetic eruptions.

 

This research was funded by the following projects: DYNAMICS (PID2023-151693NA-I00 funded by MCIN/AEI/10.13039/501100011033 and by ‘ERDF A way of making Europe’), PROMEDED (PID2019-104624RB-I00; Ministerio de Ciencia, Innovación y Universidades), and LAJIAL (PGC2018-101027-B-I00, MCIU/AEI/FEDER, EU), MESVOL (SD RD 1078/2021 LA PALMA).