Report on Nyamuragira (DR Congo) — March 2014
Bulletin of the Global Volcanism Network, vol. 39, no. 3 (March 2014)
Managing Editor: Richard Wunderman.
Nyamuragira (DR Congo) Eruption during 6 November 2011 to April 2012; pit crater morphology changes
Please cite this report as:
Global Volcanism Program, 2014. Report on Nyamuragira (DR Congo). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 39:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201403-223020.
1.408°S, 29.2°E; summit elev. 3058 m
All times are local (unless otherwise noted)
Our last report (BGVN 35:08) described a flank eruption at Nyamuragira during 2-27 January 2010 that produced a new cone and 12-km-long lava flows. The final report of the GORISK Scientific Network (Kervyn and others, 2010) stated that this eruption ended by 27 January 2010. At this stage we lack reporting from the field on Nyamuragira's behavior during February 2010 through early November 2011. That said, MODVOLC thermal alerts occurred regularly at Nyamuragira through 2 February 2010 and then ceased until early November 2011. We discuss the longer-term MODVOLC data at the end of the main body of this report.
Nyamuragira began to erupt again on its flanks at 1755 on 6 November 2011, according to GORISK, after two days of unspecified "intense seismic activity." GORISK inferred that the eruption lasted through April 2012. This report conveys information from a variety of sources credited below, but largely from Dario Tedesco and the GORISK Scientific Network. GORISK was an initiative of both the National Museum of Natural History (Luxembourg) and the Royal Museum for Central Africa (Belgium).
An early synopsis of the eruption that began on 6 November 2011 came from the Virunga National Park. The eruption was visible at Park headquarters. Park staff described the 6 November eruption as coming from a fissure on the volcano's NE flank. It produced slow-moving lava flows that advanced into unpopulated areas to the N. Park staff also took a (1080p) video of fountaining at night. On 7 November the Park uploaded 39 seconds of their footage on Youtube.
During the first week of the eruption the Park staff hiked cross country through the bush, in places having to cut vegetation, crossing young forest and irregular lichen-covered volcanic topography on a 4 hour hike that enabled them to take a closer view. This also established a narrow access route for later use.
The hikers described airfall scoria covering the landscape as they approached closer. Their log said that the ". . . eruption finally came into view, along with the roar of intensely spewing fire and lava, as well as lightning and thunder." The Park noted that the vent area was located 12 km ENE of the crater, close to one of the 1989 eruptive sites. The first fissure was oriented E-W, perpendicular to the rift, and emitted lava fountains up to 300 m high. The eruption site was described as a flat area cut by a 500- to 1,000-m-long fissure. Figure 39 shows a photo from around this time but a topographic high of new material had already grown. NASA Earth Observatory reported that lava flows had advanced as far as 11.5 km by 12 November 2011 (figure 40). On 12 November, the lava flow front was located 5 km from the Kelengera-Tongo road.
For about a month, the park allowed overnight treks to the eruption site. A video featured on Youtube ) by Piet Schutter contains footage taken on 12 November. Some scenes are at close range (looking up towards the eruption). That (720p) video shows both daylight and night scenes, features sound, and has people in the foreground, which helps establish scale.
The GORISK Scientific Team reported that satellite radar (InSAR) images acquired on 11 November 2011 revealed major ground deformation features associated with the eruption—the largest deformation detected by that method (InSAR) since the early 1990s at Nyamuragira. Preliminary estimation of the observed deformation signal suggested an affected area spreading over 250 km2. Pressure from the ascending magma caused the ground to rise more than 50 cm at the eruptive site where a spatter cone developed. Another 15 cm deformation was detected within the Nyamuragira caldera, which was accompanied by deflation observed on the flanks.
An elongated spatter-and-scoria cone, referred to by scientists as the western cone and by locals as "Umoja," formed along the first fissure (figure 41). In early December 2011, a new cone formed on a new eruptive fracture to the E; this cone was referred to by scientists as the eastern cone and by locals as "Tuungane" (figure 41). During the next few days, the eruptive activity migrated to this new edifice. Satellite images acquired on 3 January 2012 showed fresh lava flowing to the N-NE (figures 42 and 43).
|Figure 41. Panoramic view of Nyamuragira and the two new cones of the November 2011-April 2012 eruption. Date of photo unknown (sometime between November 2011 and early June 2012). Photo courtesy Benoit Smets, GORISK Scientific Network.|
According to scientists from the Afar Consortium Project visiting the 2011 fissure eruption, activity continued on 8 January 2012. The initial scoria cone appeared inactive and second cone formed to the N of the first cone. Both cones were about 300 m high. The second cone was extremely active for the duration of the observations (about 15 hours) with fire fountains over twice the height of the cone; lava flowed N. The observers, about 1.5 km away, felt the heat from the eruption and noted lapilli fall.
A team from Volcano Discovery observed the ongoing fissure eruption during 22-25 January 2012 from the newly formed cinder cones near the fissure. They reported three coalescent cones, the largest cradling a small lava lake. The lake ejected spatter every few seconds, rising as high as 200 m above the summit. Some bombs reached the base of the cone. Lava flows from the vent extended several kilometers N. Numerous small breakouts formed secondary flows, and a large breakout ~2 km N of the cone fed a large lava flow ~20 m wide. Burning forests were reported to the NNE.
A lava lake was present within the eastern cone during February 2012 through the end of the eruption in April 2012. Lava flows were fed through lava tubes, with fresh lava mainly visible at night.
Preliminary estimates by the GORISK Scientific Team for the 2011-2012 eruption indicated a volume of emitted lavas of at least 81.5 x 106 m3. The lava flows did not reach inhabited areas and only affected vegetation in Virunga National Park. The 2011-2012 eruption was the biggest event at Nyamuragira since the 1991-1993 eruption, which lasted nearly 1.5 years and emitted an estimated ~131 x 106 m3 of lava (Smets and others, 2010).
Beginning in late February 2012 through at least June 2012, degassing occurred in the Nyamuragira's caldera. The emission site was located inside the pit crater, but degassing occurred from all fractures inside the caldera. On several occasions, meteorological conditions caused sulfur odors to reach the city of Goma (~30 km S from Nyamuragira's crater).
A report by Dario Tedesco stated that in March 2012, a series of explosion earthquakes were recorded by the seismic network of the Goma Volcano Observatory. Following this activity, the fissure eruptions suddenly stopped. Also in March 2012, the morphology of the pit crater began to change (figures 44 and 45).
|Figure 44. View of Nyamuragira's pit crater on 20 January 2012. Direction unknown. Courtesy Dario Tedesco, International Organization of Migrants and Second University of Naples.|
|Figure 45. View of Nyamuragira's pit crater on 16 April 2012. Direction unknown. Courtesy Dario Tedesco, International Organization of Migrants and Second University of Naples.|
MODVOLC thermal alerts were accessed online in late July 2014. The alerts had waned at the fissure area in late March 2012 suggesting the end of the fissure eruption in that time frame. The last alerts around the summit area had occurred on 2 February 2010. The next alerts in the summit area appeared on the NE rim on 5 March 2014 and again on 30 May 2014. A sequence of several alerts took place in the same spot during 22-29 June and on 12 and on 28 July 2014.
References. Kervyn, F, d'Oreye, N, van Overbeke, A-C, 2010, GORISK: The combined use of Ground-Based and Remote Sensing techniques as a tool for volcanic risk and health impact assessment for the Goma region (North Kivu, Democratic Republic of Congo). Final Report. [Project SR/00/113] (URL: http://www.ecgs.lu/gorisk/wp-content/uploads/2010/11/GORISK_Final_Report_DISSEMINATION.pdf )
Smets, B., Wauthier, C., d'Oreye, N. (2010). A new map of the lava flow field of Nyamulagira (D.R. Congo) from satellite imagery. Journal of African Earth Sciences, 58 (5), 778-786. DOI:10.1016/j.jafrearsci.2010.07.005
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: Dario Tedesco, International Organization of Migrants (I.O.M.), Goma, DRC, and Second University of Naples, DISTABIF, Caserta, Italy; GORISK Scientific Team [an International scientific team for the study and monitoring of active volcanoes and their corresponding hazards in the Virunga Volcanic Province] (URL: http://terra.ecgs.lu/rnvt/); Virunga National Park, Democratic Republic of Congo (URL: http://virunga.org/); Jesse Allen and Robert Simmon, NASA Earth Observatory (URL: http://earthobservatory.nasa.gov); Volcano Discovery (URL: http://www.volcanodiscovery.com/); and Afar Consortium Project (URL: http://www.see.leeds.ac.uk/afar/).