Magma interactions, crystal mush formation, timescales, and unrest during caldera collapse and lateral eruption at ocean island basaltic volcanoes (Piton de la Fournaise, La Réunion)

A study of Piton de la Fournaise volcano reveals that magma interactions and crystal mush formation during caldera collapse and lateral eruptions differ significantly from other mafic ocean island volcanoes. The research, using olivine crystal compositions and melt inclusions, shows that the 2007 eruption was driven by rapid magma crystallization at shallow depths without significant magma mixing. Geophysical data indicated that magma intrusion began approximately a month before the eruption, migrating from ~3 km below sea level to about 1 km above sea level. The chemical zoning of olivine crystals suggests lateral movement of crystal mush towards the surface within days to months. Post-caldera samples also showed significant hydrogen loss due to depressurization. These findings contrast with other volcanoes like Kilauea and Etna, where magma mixing is more common, and are attributed to variations in magma supply rates from depth.

Albert, H., Costa, F., Di Muro, A., Herrin, J., Métrich, N., & Deloule, E. (2019). Magma interactions, crystal mush formation, timescales, and unrest during caldera collapse and lateral eruption at ocean island basaltic volcanoes (Piton de la Fournaise, La Réunion). Earth and Planetary Science Letters, 515, 187–199. https://doi.org/10.1016/j.epsl.2019.02.035