Observatoire Volcanologique de Goma (OVG) reported that the sulfur dioxide (SO2) flux at Nyiragongo decreased slightly but remained at moderate levels during 18-23 March. The Munigi station measured a small increase in carbon dioxide (CO2) concentrations from fractures in the S area. Additionally, CO2 concentrations in the “mazuku”, or lowland areas located in the W area of the city of Goma, remained lethal. The Alert Level remained at Yellow.

Geological Summary. The Nyiragongo stratovolcano contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Source: Observatoire Volcanologique de Goma (OVG)