The eruptions of Nyamulagira volcano have direct consequences on the surrounding environment.
1) Ash and gas plume
Each eruption of Nyamulagira produces a huge volcanic plume that seriously affects the surrounding area.
At the early stage of the eruptions, the plume contains ash, scoriae, bombs and pelee’s hairs. Scoriae and bombs usually fall down maximum 2-3 km far from the eruptive vent while ash and pelee’s hairs can be found tens of kilometers away from the eruptive vent(s). Eruptions generally take place within the National Park, but those pyroclastic deposits can cause problems to the local population leaving outside of the park, mainly by affecting crops and livestock.
Each volcanic plume of Nyamulagira also contains large amounts of gases, especially CO2, SO2 and other acid gases. According to the measurements of the Total Ozone Mapping Spectrometer (TOMS) reported by Bluth and Carn (2008), Nyamulagira has been the world’s largest source of volcanogenic SO2 released to the atmosphere since 1979, accounting for a cumulated emission of ~25 Mt of SO2 between 1979 and 2005. These volcanic gas plumes are at the origin of sometimes-important acid rains. In the close vicinity of the active vent(s), SO2 and acid gases seriously affect the vegetation and pollute river waters.
2) Lava flows
The lava flow field of Nyamulagira covers more than 1100 km2 and is mainly located inside the Virunga National Park (VNP), an endangered UNESCO World Heritage.
Nyamulagira flank eruptions always affect the VNP by burning several hundreds hectares of the protected forest. Since the 1938-40 eruption, flank eruptions have dominated the Nyamulagira activity. As vegetation takes time to colonize fresh lavas, the lava flows of these eruptions have progressively reduced the area occupied by the dense forest during the last 70 years. When distal eruptions* occur, the lava flows can reach roads, crops and urban areas. These lava flows mainly cause material damages and are usually not a lethal hazard for the population.
* We call here a “distal eruption” an eruptive event that occurs more than 9 km away from the Nyamulagira main edifice.
Bluth G.J.S., Carn S.A. (2008) – Exceptional sulphur degassing from Nyamuragira volcano, 1979-2005. Int. J. Remote Sensing 29 (22), 6667-6685.