Report on Nyamuragira (DR Congo) — April 2004
Bulletin of the Global Volcanism Network, vol. 29, no. 4 (April 2004)
Managing Editor: Edward Venzke.
Nyamuragira (DR Congo) New eruption on 8 May spawns cones, lava lake, fountains, and lava flows
Please cite this report as:
Global Volcanism Program, 2004. Report on Nyamuragira (DR Congo) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 29:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200404-223020.
1.408°S, 29.2°E; summit elev. 3058 m
All times are local (unless otherwise noted)
The Observatoire Volcanologique de Goma (Goma Volcano Observatory, GVO) reported that a new eruption at Nyamuragira began at 0548 on 8 May 2004. Activity started in the summit caldera and later propagated to the N flank. Since July 2003 Nyamuragira had shown abnormal behavior, having an average of 3 distinct seismic swarms per month (see Bulletin, v. 28, no. 9, 10, and 12). The last of these swarms occurred during 4-6 May 2004. The eruption was also preceded by an important high frequency (HF) earthquake felt in the Virunga area at 0144 on 8 May, localized below the N part of Lake Kivu. This event was followed at 0315 on 8 May by a high-amplitude long-period earthquake located N of Virunga. Unusual and significant fumarolic activity from the Nyamuragira caldera was seen from Goma (~ 40 km S) on 2 May 2004.
On its overpass of Nyamuragira at 1056 on 8 May 2004, the Earth Probe Total Ozone Mapping Spectrometer (EP TOMS) detected large SO2 clouds released by the current eruption of Nyamuragira. However, the situation was complicated by the fact that EP TOMS has recorded SO2 emissions from Nyiragongo (~ 15 km SSE of Nyamuragira) since October 2002, and therefore some SO2 from Nyiragongo was also likely to be present. Daily SO2 amounts observed at Nyiragongo over the past month have been in the range of ~ 5-30 kilotons (kt). An SO2 cloud was detected extending in several directions from Nyamuragira, containing ~ 30 kt of SO2. A data gap over eastern Democratic Republic of Congo (DRC) prevented measurements on 9 May, although there was evidence for some SO2 drifting over northern Tanzania, ~ 720 km from Nyamuragira.
On 10 May at 1055 a broad SO2 cloud extended up to ~ 180 km W, ~ 360 km S, and ~ 260 km ESE of the volcano, completely covering Rwanda and Burundi, with the highest SO2 concentrations detected in a zone directed SSE across Rwanda. This cloud contained ~ 190 kt of SO2. Another data gap on 11 May prevented measurements directly over eastern DRC, but a large SO2 mass (~ 116 kt) was present W of the data gap, ~ 560 km S of Nyamuragira at its maximum extent. No ash was detected in the volcanic clouds by EP TOMS as of 12 May, and the maximum altitude reached by the SO2 was unclear. A number of anomalous pixels indicating a hot spot just N of Nyamuragira were observed at 1030 on 9 May from the MODIS (Moderate Resolution Imaging Spectroradiometer) thermal satellite imagery (URL: http://modis.higp.hawaii.edu/).
Overflights attempted by GVO on 8 May failed because of the rainy season's bad weather, but the quick glimpse suggested a significant lava flow descending the N slope. On 9 and 12 May GVO plane overflights and a field mission in the area located to the volcano's N revealed that one active lava lake appeared an unstated distance NNE of the Nyamuragira caldera. This lake, ~ 300 m in diameter, was located in a pit ~ 15 m deep and fed by 4 strong lava fountains. Activity was much reduced by 12 May. The surface was a solid crust with three vents open through it. All vents displayed Strombolian activity with spatter splashing and short lava overflows; accumulation of spatter tends to build low cones.
An eruptive fracture, ~ 2 km long, was found on the N-NW flank of the volcano. Several lava fountains were very active all along the fracture and 4 main cones were building up to heights estimated as 30-50 m. Lava poured from many vents and turned into a main flow directed towards the N-NW, always within the Virunga National Park boundaries. Flows made an intricate delta below the lower cone, turning onto a very wide lava flow that covered an area with a total length estimated to be ~ 12 km. Although this flow continued to move, it failed to threaten any populated areas. Ashfalls were observed in several villages on the W and N sides of the volcano. The activity remained quite strong and apparently stable in comparison with other documented Nyamuragira eruptions.
Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.
Information Contacts: Kasereka Mahinda and Jacques Durieux, Observatoire Volcanologique de Goma (Goma Volcano Observatory), Department de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; Simon Carn, TOMS Volcanic Emissions Group, University of Maryland, 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/).