How to turn off a lava lake? A petrological investigation of the 2018 intra-caldera and submarine eruptions of Ambrym volcano

In December 2018, an unusually large intra- and extra-caldera eruption took place at Ambrym volcano (Vanuatu). The drained the volcano’s five active lava lakes terminated, least momentarily, surface activity that had been ongoing for decades to hundreds of years, sustaining largest recorded persistent degassing on planet. Here, we investigate mechanisms dynamics this major eruption. We use elements volatiles in olivine clinopyroxene-hosted melt inclusions, embayments, crystals matrix glasses together with clinopyroxene geobarometry as well geothermometry diffusion modelling embayments reconstruct chronology timing subsurface processes accompanied find began meeting, mingling limited chemical mixing mostly two magma bodies occupying similar vertical but different horizontal locations crust, one corresponding main plumbing system fed other older, previously cutoff more chemically evolved branch system. Within primitive magma, texturally distinct components—one microlite rich poor—can further be identified. 2018 hence provides a detailed image Ambrym’s complex Our timescales geobarometric estimates coincide closely geophysical observations. They point reconnection magmatic occurring less than 10 h prior intra-caldera period 2 days subsequent > 30-km lateral transport along deeper dike submarine just off SE coast island reaching first followed by mingled containing both compositions. Magma ascent rates are estimated 95 ± 24 m/s last ~ 2.5 km during 80 6 4 Comparison lake draining eruptions reveals striking similarities terms precursory activity, level rising all cases, organization presence peripheral pockets, isolated from can mobilized erupted when met dikes propagating laterally