GEOLOGIC HISTORY
Nyamuragira is a massive basaltic shield volcano with a
small summit caldera. It is located north of Lake Kivu and
NW of Nyiragongo volcano, along the border between Rwanda
and the Democratic Republic of Congo (formerly Zaire). The
summit caldera is 2 x 2.3 km wide with walls up to about 100
m high. Historical eruptions have occurred within the summit
caldera and from numerous flank fissures and cinder cones.
Twentieth century flank lava flows extend >30 km from the
summit. Most active of volcanoes in the Virunga chain of the
African Rift.
Historic Activity:
- Eruptions in 1882, 1894, 1896, 1899, 1901, 1902,
1904-1907, 1912, 1920-1940, 1947-1948, 1951-1952, 1954,
1956-1958, 1967, 1971, 1977, 1980, and1982.
- Historic eruptions have occurred in the caldera and
on the flanks.
- Lava lake activity in caldera from 1921 to 1938.
- Flank radial fissure activity has been common in the
30 eruptions known since 1882.
- Twentieth century flank lava flows extend >30 km
from the summit reaching as far as Lake Kivu
Recent Activity:
- During February and March 1984 a fissure on the NW
flank fed a 20 km long lava flow.
- During July and August 1986 a fissure on the S flank
fed a 17 km long lava flow and built an elongate cinder
cone 150 meters high with a breach crater.
- From December 30, 1987 to January 3, 1988 an eruption
fed a lava flow 500 meters in width which extended 2.5
kilometers and built a cone 60 meters high.
- An eruption began on April 23, 1989 with lava
fountains built a cone and were feeding a flow at least 6
km long. Continuous eruption ended on May 24, when
intermittent activity began.
- An eruption began on September 20, 1991, from a
fissure about 15 km NE of the summit caldera. An
earthquake swarm began about a week before the eruption
but gradually declined between Sept. 16 and eruption's
onset. Eruption formed cinder cone (Mikombe) at north end
of fissure and fed two lava flows.
- Vigorous lava production continued through Sept. 1992
at Nyamuragira, where a fissure eruption began on Sept.
20, 1991. The eruption has built 21 cinder cones along a
2.5 km zone that trends generally NE, about 15 km NE of
Nyamuragira caldera. The eruption's early phases produced
substantial lava flows, but since Nov. 20, 1991 activity
has been characterized by vigorous ejection of bombs,
lava fragments, and ash, with lava flows of only limited
extent.
- A new vent on the west flank became active late on
July 4, 1994, but remaind active for only 4-5 days. Lava
flows generally moved west and activity continued until
July 27.
- Seismicity began to increase in August 1996 and an
eruption was reported to be in progress on Dec. 1,
1996.
- Eruptive activity occurred at Nyamuragira volcano
beginning on Oct. 17, 1998. During the following week
several Strombolian explosions and effusive activity were
reported.
- Eruptive activity occurred at Nyamuragira volcano
beginning on January 27, 2000. Details difficult to come
by due to rebel army units presences in the area.
Ejection of bombs, cinders, and ash from a crater SE of
the summit. Also a lava flow to the west.
- Lava flow eruptive activity began on Feb 6, 2001 and
continued until at least early March.
Data Sources
- Smithsonian's SEAN Bulletin (V. 1, No. 15 to V. 14,
No. 9)
- Global Volcanism Network (V. 16, No. 9 to V. 26 , No.
3).
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