Article révisé par les pairs
Résumé : Nyiragongo is one of the rare volcanoes on Earth hosting a lava lake. However, the understandingof its plumbing and lava lake systems remains limited, with, until recently, only sporadic or time-limitedhistorical observations and measurements. Combining dense accurate lava lake and crater floor levelmeasurements based on 1,703 satellite radar images and topographic reconstructions using photogrammetry,we obtain the first reliable picture and time evolution of intra-crater erupted lava volumes between the two lastflank eruptions in January 2002 and May 2021. The filling of the crater by lava, initiated in 2002 and continuedup to May 2021, is seen as an evidence of a long-term pressure build up of the magmatic system. This fillingoccurs through irregular pulsatory episodes of rising lava lake level, some of which overflow and solidify onthe surrounding crater floor. Pauses of stable molten lava lake level and sudden numerous level drops alsomarked the summit's eruptive activity. The joint analysis with seismic records available since 2015 revealedthat the largest lava lake drops are synchronous with seismic swarms associated with deep magma intrusions,generally preceded by an increase of extrusion rate within the crater. The appearance of a spatter cone in thesummit crater in 2016, most likely superficially branched to the lava lake, was a clear marker of the change ineruption dynamics. This first long-term time series of Nyiragongo's crater topography between two hazardousflank eruptions might further help to better decipher Nyiragongo's past and future behavior using multi-parameter observations.

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