Report on Nyiragongo (DR Congo) — December 2001
Bulletin of the Global Volcanism Network, vol. 26, no. 12 (December 2001)
Managing Editor: Richard Wunderman
Nyiragongo (DR Congo) Mid-January 2002 lavas bury ~ 4.5 km2 of Goma's city center
Please cite this report as:
Global Volcanism Program, 2001. Report on Nyiragongo (DR Congo). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 26:12. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200112-223030.
1.52°S, 29.25°E; summit elev. 3470 m
All times are local (unless otherwise noted)
An eruption began at Nyiragongo on 17 January 2002 with some lava flows and possibly their feeding fissure vents entering the city of Goma (~18 km S of the volcano, population ~400,000) in the Democratic Republic of Congo (DRC) and threatening refugee camps (figure 10). Encroaching lava spurred massive evacuations of the city. A great deal of conflicting information exists concerning the numbers of people killed or displaced, the amount of property destroyed, the specific paths of the lava flows, etc.
The following is taken primarily from reports by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), the U.S. Agency for International Development - Office of U.S. Foreign Disaster Assistance (USAID/OFDA), and the aid organization Oxfam International.
Numerous dramatic press reports showed multiple lava flows engulfing Goma; city streets became paths for rough-surfaced lava flows, and numerous buildings collapsed, burned, or both. In the end, one of the flows passed completely through Goma to enter Lake Kivu and proceeded to build a lava delta. The lava flows damaged or destroyed agricultural areas around Goma, covered the N part of the runway at the airport, and cut off access to parts of the town. Lava flows destroyed both residential and business districts as well as a cathedral.
Authorities in Goma reported that more than 150,000 people remained there during the peak of the lava flow activity. A report from the UN and USAID/OFDA on 23 January estimated that 147 people were killed because of lava flows and seismically induced building collapses. According to Oxfam International, ~60,000 people lost their homes.
The UN report stated that up to ~250,000 people were displaced as a result of the eruption. These and possibly other displaced people were concentrated in the following places: Goma, DRC (62,500); Sake, DRC (5,000); Rutshuru, DRC (5,000); in camps along the eastern DRC frontier near Gisenyi, Rwanda (6,000-10,000); in Ruhengeri, Rwanda (4,000); in Bukavu, DRC (15,000); in surrounding areas (30,000), in six sites near the NW shore of Lake Kivu (up to 60,000) and in area villages (60,000).
17-21 January 2002 eruption. The start time of the 17 January eruption is uncertain. According to Agence France-Presse, Nyiragongo began to erupt at about 0500. USAID/OFDA reported that the eruption began at about 0930. Most reports stated that three lava flows moved down the E, W, and S flanks. During a 17 January phone conversation with BGVN editors, Richard McDonald, a missionary in the Congo region, noted that his sources had suggested that lava flows traveled to the E, N, and S. Two flows traveled directly S through Goma and divided the city in three. One of these flows continued into Lake Kivu.
MODIS (Moderate Resolution Imaging Spectroradiometer) images from 17 January at 1050 showed a substantial ash plume moving W from Nyiragongo (figure 11).
OCHA stated that at 1100 on 17 January observers flew over the volcano in a helicopter and reported a large lava flow approaching Goma. The lava flow cut the road between Goma and Rutshuru (to the N, figure 10). By 1430, with a small hill slowing its progress, the lava flow had reached 2 km N of the airport and was still progressing southward. The lava flow had reached a width of 2 km, and its velocity was estimated at 2-3 m/minute (0.2 km/hour), a very slow flow rate compared to those reported for the very high velocity 1977 eruption which reached up to 60-100 km/hour (see SEAN 02:03). The smaller of the two lava flows heading toward Goma cut the road leading in from the W (figure 12). OCHA reported that a fourth fissure opened during the afternoon of 17 January. A total of 14 neighboring villages were affected by the lava flows.
|Figure 12. Map of Goma showing lavas from the 17-21 January 2002 eruption of Nyiragongo. Lavas from the eruption ultimately trisected Goma and one branch entered Lake Kivu. Courtesy OCHA Humanitarian Information Center (HIC).|
News reports made much about fires in Goma. Fuel depots exploded and kerosene storage facilities at the airport burned. On 21 January a petrol station exploded killing ten's of people (~50 according to news reports). A UN worker in Goma reported that the air was full of ash and dust during the eruption. News reports also emphasized the fires' smoke and soot.
On 18 January, OCHA reported that tremors occurred every hour, and some were strong enough to damage buildings in Gisenyi (figure 10). Several tremors were felt as far away as at the S end of Lake Kivu in Bukavu (~125 km SE). As of 24 January, earthquakes and tremors up to M 4.7 continued in the vicinity of Nyiragongo.
Representatives from OCHA reported on 20 January that a new crater had opened on the NW side of Nyiragongo, and the temperature of some parts of Lake Kivu reached up to 40°C.
By 21 January, the rapid advance of new lava flows appeared to be over, but residual molten lava still slowly seeped into Lake Kivu, where it formed a ~100-m-wide delta. Although no new lava flows threatened the city, some scientists feared that lava entering the lake or seismic activity could disturb the lake sufficiently to release significant amounts of carbon dioxide and methane gas lying at the lake bottom. News and other scientific sources suggested a gas release was unlikely.
OCHA reported that a 22 January a flight over the volcano confirmed a lack of new activity, including the crater where only a few fumaroles were present. A system of fractures was visible along the southern slope of the volcano, starting from the eastern flank of Shaheru crater (close to the main Nyiragongo cone) and propagating down close to the outskirts of Goma. The fractures were generally meters wide, and during the eruption lava poured out from different locations and altitudes along the fracture system. The lowest lava emission point in this fracture system, as estimated from the helicopter, was at least ~2 km from Goma.
According to OCHA, volcanologists determined that ash observed in Goma on 23 January originated from the collapse of Nyiragongo's inner crater and not from a Nyamuragira eruption, as was originally (incorrectly) 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 collapsed more than 600 m. In addition, they reported no ongoing volcanism nor any 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 28 January the volcano was at Alert Level Yellow (second on a four-color scale).
Regional seismicity. On 4 January 2002, an M 4.8 earthquake occurred near Nyiragongo. Local volcanologists had planned to visit Nyiragongo on 19 January to observe its activity, but the volcano erupted before the visit.
According to Bruce W. Presgrave of the USGS National Earthquake Information Center (NEIC), there was an unusual number of tectonic earthquakes in the Goma-Nyiragongo region starting ~9 hours after Nyiragongo's alleged initial lavas at 0500. The sequence included ~100 earthquakes M 3.5 or larger. Tectonic swarms of this size occasionally appear in conjunction with volcanism. For example, seismologists noted intense protracted swarms during Miyake-jima's intrusions and eruptions during the year 2000 (BGVN 25:05, 25:07, and 25:09).
The largest earthquake to date in the sequence was M 5; it struck at 0214 on 20 January at 1.76°S, 29.08°E. The second largest, M 4.8, struck at 2201 on 17 January at 1.74°S, 29.08°E, about 17 hours after the estimated onset of the lava flows according to news reports. Though imprecisely fixed, these estimated epicenter locations are just a few ten's of kilometers WSW of Goma; and the probable uncertainty could place them closer to Goma and Nyiragongo.
In addition to registering at the two closest stations in Mbarara, Uganda (MBAR, 0.602°S, 30.738°E) and Kilima Mbogo, Kenya (KMBO, 1.127°S, 37.252°E), the earthquakes also left clear signatures on instruments at great distances, for example in China and at the South Pole, Antarctica. The earthquakes contained sharp P- and S-wave arrivals. Also, as would be expected of tectonic events at teleseismic distances, the associated signals at even the closest stations MBAR and KMBO lacked tremor. The signals were not the sort that could be expected to arise from surficial processes like sudden mass wasting, fuel explosions, building collapses, etc. First motion or minimal tensor results are not yet available.
Comparatively few news accounts discussed the seismic activity or seismically induced damage, perhaps because residents were concerned with more pressing aspects of Nyiragongo's eruption. However, NEIC has received email messages indicating that numerous earthquakes were felt near Kigali, Rwanda (~100 km E of Nyiragongo, table 2).
Table 2. Summary of earthquakes felt near Kigali, Rwanda (~ 100 km E of Nyiragongo) during 10-22 January 2002. The earthquakes were all recorded instrumentally as well. Courtesy Bruce Presgrave (NEIC) and Fr. Stephen Yavorsky, S.J.[Skip text table]
Date Local Estimated Magnitude Comment (2002) Time Location ~10 Jan ~1530-1600 -- 4.0 17 Jan 2201 1.75°S, 29.07°E, 4.8 15 km depth ~115 km W of Kigali 18 Jan 1008 -- 4.0 18 Jan 2309 -- 4.0 19 Jan ~1606 -- ~4.0 19 Jan ~2233 -- ~4.0 19 Jan ~1912 -- ~4.0 20 Jan 0214 1.76°S, 29.08°E 5.0 21 Jan ~0130-0530 -- ~4.0 Numerous tremors felt during 4-hour period 21 Jan 0640 -- ~4.7 21 Jan 1553 -- ~4.0 21 Jan 1630 -- ~4.0 22 Jan 1732 1.72°S, 20.10°W, 4.9 ~15 km WSW of Gisenyi 22 Jan 1822 -- 4.4-4.7
As a result of the seismicity, many buildings collapsed in Goma. At least 25 buildings in Gisenyi were also destroyed. By 28 January seismicity had decreased and earthquakes were not large enough to be felt by the population.
Humanitarian crisis. According to OCHA and various news reports, refugees began to return to Goma just a few days after the eruption, despite the dangers that still existed in the area. USAID/OFDA reported that on the morning of 20 January, more than 15,000 people per hour were returning to Goma from points E of the city, while simultaneously 3,000 people per hour were fleeing the city to locations W. Aid workers reported that the refugees would rather return to Goma and risk another eruption than stay in displacement camps in Rwanda, which they perceived to be a hostile country. On 21 January, continuing seismic activity caused buildings to collapse, resulting in more deaths.
Poor access to people in affected parts of Goma was a problem for relief efforts. Several humanitarian groups, along with news agencies, reported that aid workers, along with returning refugees, crossed freshly crusted lava flows to access certain areas. On 18 January two out of three water pumping stations were not working.
Eye irritation and breathing difficulties were reported as a result of the ash and fumes in Goma. Health care centers were provided with medication, and all health care has been free thus far. A few suspected cases of cholera have been reported, but OCHA reported that relief agencies felt prepared for possible disease outbreaks.
According to Oxfam International, the major problems facing the people of Goma were water supply and sanitation facilities, shelter, food, medical care, and damage to schools. A qualitative helicopter assessment on 23 January indicated that ~30% of Goma was destroyed by the lava flows and that up to 50,000-60,000 people in the E of the town lost their homes. On the other hand, the 27 January map-based assessment illustrated by figure 12 concluded that lava flows had affected 4.5 km2 of the city's 35 km2 populated area. Thus, this analysis suggested that ~13% of Goma had been affected.
Figure 12 shows that the E portion of Goma had been cut off from the rest of the town by lava. During the first four days of the eruption, speedboats transported relief workers between the E and W parts of Goma.
On 23 January, 11 sites (in Goma and Sake) operated by the World Food Program began to distribute food and non-food items to refugees (several of these sites appear on figure 12). Other NGO's had collaborated to purchase food locally to provide food for refugees prior to this distribution, but many people had not received food since the eruption began.
A report from OCHA on 25 January confirmed that two access roads into Goma had been cut through the hardened lava and that a third would soon be completed. They reported that 50% of the water network in Goma was operational and that aid agencies had positioned bladders in areas not served by the network. Agencies planned to have the entire water network operational by 4 February. On 25 January, Oxfam reported that the operational portion of the water network still mainly serviced the western part of Goma, and that in the eastern part an estimated 100,000 people remained in dire need of drinking water. Water from Lake Kivu was determined to be potable for adults if filtered. About 22 water purification points were established for residents withdrawing lakewater.
The Goma airport reopened to small aircraft on 25 January. However, the tower was considered inoperable due to the risk of gas explosion.
As of 25 January, seismic activity continued, and monitoring in Goma suggested that some epicenters were at shallow depth beneath the city. OCHA warned that further eruptions were still possible near Goma and Lower Gisenyi. Several humanitarian efforts continued to help the people in Goma through the ongoing crisis. Further information will be forthcoming in future Bulletin reports, including more technical information from volcanologists on the scene.
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: United Nations Office for the Coordination of Humanitarian Affairs (OCHA), United Nations, New York, NY 10017 USA (URL: http://www.reliefweb.int); Oxfam International, Suite 20, 266 Banbury Road, Oxford, OX2 7DL, United Kingdom (URL: http://www.oxfaminternational.org); Richard McDonald, c/o Independent Missionaries, Box 42, Cyangugu, Rwanda; U.S. Agency for International Development (USAID)/Office of U.S. Foreign Disaster Assistance (OFDA), Ronald Reagan Building, Washington, DC 20523-1000, USA (URL: http://www.usaid.gov); Bruce Presgrave, USGS National Earthquake Information Center (NEIC), MS 967, Denver Federal Center, Box 25046, Denver, CO 802225, USA (Email: CARACARA@neis.cr.usgs.gov); Fr. Stephen Yavorsky, S.J., Maison Régionale Jésuite, B.P. 6039, Kigali, Rwanda; National Aeronautics and Space Administration (NASA), Washington, DC 20456-0001, USA (URL: http://www.nasa.gov).