Report on Nyiragongo (DR Congo) — October 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 10 (October 1982)
Managing Editor: Lindsay McClelland
Nyiragongo (DR Congo) Lava lake level high, but growing at slower rate
Please cite this report as:
Global Volcanism Program, 1982. Report on Nyiragongo (DR Congo). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 7:10. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198210-223030.
1.52°S, 29.25°E; summit elev. 3470 m
All times are local (unless otherwise noted)
By 23 July, lava from several vents had formed a lake about 300 m deep with an estimated volume of 36 x 106 m3. By mid-September, the volume of the lava lake had approximately doubled, but the eruption rate was declining slowly (table 1).
Table 1. Daily eruption rates at Nyiragongo over various time periods between 21 June and 15 September 1982. Calculated by M. Krafft.[Skip text table]
DATES (1982) ERUPTION RATE (x 106 m3/day) June 21-26 0.2 27-30 0.6 July 01-07 2.5 08-21 1.0 21-31 0.5 August 01- September 15 0.4
Geologists climbed to the crater rim on 31 July, 4 and 17 August, and 3 and 15 September. Between 24 and 31 July, the level of the lake surface rose about 20 m. On 4 August, however, the domical upwellings of lava that had marked the location of the 2 vents beneath the NW part of the lake on 23 July were not active. The entire surface of the lake was chilled and no glow was visible. On 17 August, an area of upwelling about 100 m in diameter and 10 m high was again active over one of the vents. A geologist descended to the surface of the lava lake 3 September and took samples. In hand specimen, these appeared to have a composition very similar to the melilite nephelinite of the 1928-1977 lake. A glowing red fissure that averaged about 30 cm wide and 20 cm deep ringed the lake ~2 m from its edge, emitting gases.
Between late July and 15 September, the lava lake continued to grow, raising its surface an additional 100 m to about 400 m below the highest point on the crater rim. The lake's average diameter on 15 September was 700 m, its depth was 400 m, and it contained ~70 x 106 m3 of lava. The zone of upwelling over the active vent was 250 m across and lava fountains reached a maximum height of 70 m. At the time of the 1977 eruption, the lava lake volume was ~20 x 106 m3 and the surface stood about 200 m from the crater rim. The surface of the more voluminous 1982 lava lake was roughly 200 m lower than that of the 1977 lake because morphological changes associated with the 1977 eruption considerably increased the volume of the crater.
Further References. Krafft, M. and Krafft, K., 1983, Le reapparition du lac de lave dans le cratère du volcan Nyiragongo de Juin a Septembre 1982 (Kivu-Zaire), histoire, dynamisme, debits et risques volcaniques: C.R. Acad. Sci. Paris, serie II, v. 296, p. 797-802.
Tazieff, H., 1984, Mt. Nyiragongo: Renewed activity of the lava lake: JVGR, v. 20, p. 267-280.
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.
Information Contacts: M. Krafft, Cernay.