Precursor-free eruption triggered by edifice rupture at Nyiragongo volcano
Delphine Smittarello, Benoît Smets, Julien Barrière, Caroline Michellier, Adrien Oth, Tara Shreve, Raphaël Grandin, Nicolas Theys, Hugues Brenot, Valérie Cayol, P. Allard, Corentin Caudron, Magdalena Oryaëlle Chevrel, François Darchambeau, Pierre de Buyl, Louise Delhaye, Dominique Derauw, Gaetana Ganci, Halldór Geirsson, Ephrem Kamate Kaleghetso, J. Kambale Makundi, I. Kambale Nguomoja, Célestin Kasereka Mahinda, Matthieu Kervyn, C. Kimanuka Ruriho, Hélène Le Mével, Sander M. Molendijk, Olivier Namur, Sam Poppe, Martin Schmid, Josué Subira, C. Wauthier, M. Yalire, N. d’Oreye, François Kervyn, A. Syavulisembo Muhindo
Abstract
Abstract Classical mechanisms of volcanic eruptions mostly involve pressure buildup and magma ascent towards the surface 1 . Such processes produce geophysical and geochemical signals that may be detected and interpreted as eruption precursors 1–3 . On 22 May 2021, Mount Nyiragongo (Democratic Republic of the Congo), an open-vent volcano with a persistent lava lake perched within its summit crater, shook up this interpretation by producing an approximately six-hour-long flank eruption without apparent precursors, followed—rather than preceded—by lateral magma motion into the crust. Here we show that this reversed sequence was most likely initiated by a rupture of the edifice, producing deadly lava flows and triggering a voluminous 25-km-long dyke intrusion. The dyke propagated southwards at very shallow depth (less than 500 m) underneath the cities of Goma (Democratic Republic of the Congo) and Gisenyi (Rwanda), as well as Lake Kivu. This volcanic crisis raises new questions about the mechanisms controlling such eruptions and the possibility of facing substantially more hazardous events, such as effusions within densely urbanized areas, phreato-magmatism or a limnic eruption from the gas-rich Lake Kivu. It also more generally highlights the challenges faced with open-vent volcanoes for monitoring, early detection and risk management when a significant volume of magma is stored close to the surface.