On 2 and 3 May a dense ash plume was visible from the town of Goma rising above Nyiragongo. Continuous ash fall occurred in many villages close to the volcano, and permanent tremor and long-period earthquakes were recorded. During a visit to the volcano during 6 and 7 May scientists saw that the lava pool in the crater was very active, with violent gas outbursts, projection of spatter and surges, and lava splashing the walls of the pit. Occasionally, large (~ 50 m high) flames were hurled from the vents. SO2 emission rates were relatively high during 1-6 May, with the largest emission (~50,000 tons) occurring on 3 May. According to the Toulouse VAAC, a possible ash cloud was visible on satellite imagery on 12 May that remained at a height below 6 km.

Geological Summary. One of Africa's most notable volcanoes, Nyiragongo 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 of a stratovolcano 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 parasitic 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.

Sources: Observatoire Volcanologique de Goma (OVG), Toulouse Volcanic Ash Advisory Centre (VAAC)