Speaker
Description
Eruptions at continental basaltic volcanoes, the dominant mode of volcanism on Earth, can take and combine various forms, including lava lake, lava flows and fountaining, explosions or structural collapses. Aside from a few well-instrumented cases, accurately reconstructing their precise processes and chronology is hampered by the lack of detailed visual observations in space and time. However, because they emit infrasounds, any changing and potentially hazardous eruptive activity can be inferred with specialised microphones. At Nyiragongo volcano (D.R. Congo), its flank eruption in 2021 was accompanied by the drainage of the world’s largest lava lake modifying the acoustic resonance of the summit pit crater. Too low to be perceived by human ears, the excitation of resonance frequencies were recorded from local distance (0-20 km) up to Kenya (~800 km) and are interpreted in terms of the time-varying pit-crater geometry using acoustic numerical modelling. We also tracked lava fountaining and flows on Nyiragongo’s flank by means of the emitted infrasound to get a consistent scenario of lava movements between crater and flank. This remarkable acoustic signature thus encoded the underlying mechanisms of a rare flank eruption, which could help to anticipate the next one.
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