Spatial distribution and morphology of satellite cones in the Virunga Volcanic Province (Rwanda, Uganda and Democratic Republic of Congo)

POPPE, S.; GROSSE, P.; SMETS, B.; ALBINO, F.; KERVYN, F.; KERVYN, M.

Praga

Congreso; 26th International Union of Geodesy and Geophysics General Assembly; 2015

Within the western branch of the East-African Rift Valley lies the Virunga Volcanic Province (VVP), shared by DRC, Rwanda and Uganda. While this volcanic province is dominated by eight large polygenetic volcanoes, more than 500 clearly distinguishable eruptive satellite cones lie scattered together with eruptive fissures on the volcanoes? flanks and their surrounding lava fields. Some cones lack any obvious geo-structural link to a specific Virunga volcano.Using recent high-resolution satellite images (SPOT, Pléiades) and a newly-created 5 m resolution digital elevation model (TanDEM-X), we have mapped all satellite cones and eruptive fissures of the VVP. Based upon morphological indicators such as the presence of flank breaches and the presence of multiple or overlapping craters, we propose a grouping of the satellite cones into 4 categories. Using the MORVOLC program a set of morphometric parameters was calculated to highlight systematic spatial variation in size or morphometric ratios of the cones.The eruptive cones display concentrations in clusters and alignments, some of which align with the regional tectonic orientations. Field observations reveal a phreatomagmatic origin for some cones close to Lake Kivu. The Lac Vert tuff complex serves as an example that reveals a stratigraphy that is more complex than expected for ?monogenetic? cones, and radiocarbon dates of intra-cone palaeosols reveal an estimated time gap of 500 to 800 years between separate eruptive episodes that constructed an apparent ?simple? eruptive complex. The Virunga examples demonstrate how small-volume eruptive cones can represent complex eruptive histories that deviate from the classical ?monogenetic? concept, and that need to be constrained through multi-disciplinary studies.