Report on Nyamulagira (DR Congo) — September 2003
Bulletin of the Global Volcanism Network, vol. 28, no. 9 (September 2003)
Managing Editor: Edward Venzke.
Nyamulagira (DR Congo) Long-period earthquakes and swarms in July 2003
Please cite this report as:
Global Volcanism Program, 2003. Report on Nyamulagira (DR Congo) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200309-223020
1.408°S, 29.2°E; summit elev. 3058 m
All times are local (unless otherwise noted)
The last eruption at Nyamuragira occurred during 25 July-27 September 2002 (BGVN 27:07, 27:10, and 28:01). Tectonic and magmatic seismicity continued through June 2003, but there has been no confirmed eruptive activity. This report covers activity from early July to the beginning of August 2003. Seismicity generally consisted of long-period (LP) earthquakes on the NE side of the volcano. In addition, earthquake swarms were occasionally observed.
Between 6 and 12 July, seismicity was dominated by LP earthquakes NE of the volcano and SE along the fracture zone between Nyamuragira and Nyiragongo. Two large swarms occurred on 7 and 8 July, with 161 LP earthquakes and 10 short-period earthquakes. The earthquakes at Nyamuragira have been deep, between 15 and 20 km.
During 13-19 July 2003, LP earthquakes NE of the volcano again dominated seismicity. Compared to the previous week, activity was low, with no swarms and only one high-frequency earthquake. The following week, between 20 and 26 July, LP earthquakes continued in the NE and to a lesser extent along the SE fracture zone. Between 19 and 21 July new sequences of earthquakes occurred, with LP events followed by short-period earthquakes, coupled with high-amplitude tremor episodes.
Between 27 July and 2 August, LP earthquakes continued to dominate seismicity NE of the volcano as well as along the SE fracture zone. Seismicity increased from the previous week, with sequences of LP earthquakes coupled with volcanic tremor episodes between 28 and 31 July. Average seismicity doubled to 200 earthquakes with hypocenters between 3 and 20 km deep.
Geological Summary. Africa's most active volcano, Nyamulagira (also known as Nyamuragira), is a massive high-potassium basaltic shield about 25 km N of Lake Kivu and 15 km NE of the steep-sided Nyiragongo volcano. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Documented eruptions have occurred within the summit caldera, as well as from the numerous flank fissures and cinder cones. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Recent lava flows extend down the flanks more than 30 km from the summit as far as Lake Kivu; extensive lava flows from this volcano have covered 1,500 km2 of the western branch of the East African Rift.
Information Contacts: Goma Volcano Observatory, Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo.