Report on Nyiragongo (DR Congo) — 23 January-29 January 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 January-29 January 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Nyiragongo (DR Congo). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 23 January-29 January 2002. Smithsonian Institution and US Geological Survey.
1.52°S, 29.25°E; summit elev. 3470 m
All times are local (unless otherwise noted)
During 23-29 January there was no new volcanic activity at Nyiragongo. During 23 to around 25 January many earthquakes occurred in the region around the volcano; the largest earthquake was M 4.7. Many of the earthquakes were felt in towns near the volcano, including Goma, ~10 km S of the volcano. Several buildings were destroyed by the seismicity in towns near Nyiragongo, including Gisenyi, Rwanda. By 28 January seismicity had decreased and earthquakes were not large enough to be felt by the population.
Volcanologists determined that ash observed in Goma on the 23rd originated from the collapse of Nyiragongo's inner crater and not from a new eruption from neighboring Nyamiragira, as was originally stated in several news reports. During a visit to Nyiragongo's main crater on 28 January, the UN Volcano Surveillance Team found that the crater floor had almost completely collapsed more than 600 m. In addition, they saw neither ongoing volcanism nor fumaroles at the bottom of the crater, although they could smell SO2. A few weak steam vents were visible on the inner crater wall and a small gas plume was seen above the crater rim to the NE. On the 28th the volcano was at Alert Level Yellow (second on a four-color scale). The latest information about the Alert Level can be obtained from the Humanitarian Information Center's telephone hotline (084 84901) during the hours of 0800-2200.
Geologic Background. 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. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, 3470-m-high Nyiragongo displays the steep slopes of a stratovolcano. 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.