Publications

d'Oreye, N.,  Derauw, D.,  Geirsson, H.,  Smets, B.,  Samsonov, S.,  Barrière, J.,  Oth, A.,  Theys, N.,  Kasereka, C.,  Libert, L.,  Nobile, A. & Kervyn, F. 2017. ‘Recent activity in Nyiragongo active crater, Democratic Republic of Congo – remote sensing and in-situ measurements’. IAVCEI Scientific Assembly 2017. Book of abstracts.

Résumé de colloque

Nyiragongo volcano in the Virunga Volcanic Province is one of the rare volcanoes that host a semi-permanent lava lake. Being ~220 m wide, the lava lake nested in 1.2 km wide crater is the largest on Earth. Recurrent lava overflows inundate the crater floor, which after solidification make the floor to rise up to several dozens of meters per year. After its drainage during the last eruption in 2002, the crater filled up on ~400 m thickness until 2008. Since then, the activity reduced and was mostly characterized by lava level fluctuations of various amplitude and time scales within the pit hosting the lake (Smets et al., this meeting). Incidentally, at the time of a large volume eruption in 2011-2012 at neighboring Nyamulagira volcano located 13 km away, the level of the lava lake progressively lowered, reaching ~70 m below the crater floor. It remained at that low level until the end of 2015. Early in 2016 a new vent opened within the crater, at the contact point between the crater floor and the sub vertical rim. Such an activity, still visible at the time of writing, has never been observed since the discovery of the volcano in the late 19th Century. The intermittent activity at the vent emits an important volume of degassed lava that now blankets the crater and flows back into the lava lake. Here we analyze the rise of the crater floor and the lava lake level fluctuations measured from the module of hundreds of SAR images (ENVISAT, RADARSAT, TERRASAR, COSMOSKYMED, SENTIEL 1) and digital elevation models obtained from SplitBand Radar Interferometry. We compare these measurements with other parameters: seismicity (Oth et al., this meeting), gas emission (Barrière et al., this meeting), ground deformation (Geirsson et al., this meeting) and visual observations. We will discuss possible interactions between that crater activity and tectonic and volcanic activity at neighboring Nyamulagira volcano. Advanced InSAR time series method as well as photogrammetry-derived DEM models (see Smets et al, this meeting) also show a near-field, meter-scale deformation signal affecting the crater floor and bordered by ring-fractures. We will compare and contrast plausible models of processes contributing to this near-field deformation, including thermal contraction, elastic response, block rotation, structural weaknesses, and subsurface shape of the lava lake.