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Mount Nyiragongo

2007 Schools Wikipedia Selection. Related subjects: African Geography

                 Mount Nyiragongo
   Lava lake in the crater of Mount Nyiragongo
   Elevation     3,470 metres (11,384 feet)
   Location      Democratic Republic of the Congo
   Range         Virunga Mountains
   Coordinates   1°31′0″S, 29°15′0″E
   Type          Stratovolcano
   Last eruption 2006 (continuing)

   Mount Nyiragongo is a volcano in the Virunga Mountains associated with
   the Great Rift Valley. It is located in the Democratic Republic of the
   Congo, about 19 km north of the town of Goma and the Lake Kivu and just
   west of the border with Rwanda. The main crater is 250 m deep, two km
   wide and sometimes contains a lava lake. Nyiragongo and nearby
   Nyamuragira are together responsible for 40% of Africa's historical
   volcanic eruptions.

Geology

   Not much is known about how long the volcano has been erupting, but
   since 1882, it has erupted at least 34 times, including many periods
   where activity was continuous for years at a time, often in the form of
   a churning lava lake in the crater. The volcano partly overlaps with
   two older volcanoes, Baratu and Shaheru, and is also surrounded by
   hundreds of small volcanic cinder cones from flank eruptions.

   Volcanism at Nyiragongo is caused by the rifting of the Earth's crust
   where two parts of the African Plate are breaking apart. A hot spot is
   probably also partly responsible for the great activity at Nyiragongo
   and Nyamuragira.

   The lava emitted in eruptions at Nyiragongo is often unusually fluid.
   Nyiragongo's lavas are made of melilite nephelinite, an alkali-rich
   type of volcanic rock whose unusual chemical composition may be a
   factor in the unusual fluidity of the lavas there. Whereas most lava
   flows move rather slowly and rarely pose a danger to human life,
   Nyiragongo's lava flows may race downhill at up to 60 miles per hour
   (97 km/h). This is because of the extremely low silica content (the
   lava is mafic). Hawaiian volcanic eruptions are also characterised by
   lavas with low silica content, but the Hawaiian volcanoes are broad,
   shallow-sloped shield volcanoes in contrast to the steep-sided cone of
   Nyiragongo, and the silica content is high enough to slow most flows to
   walking pace.

1977 eruption

   Between 1894 and 1977 the crater contained an active lava lake. On 10
   January 1977, the crater walls fractured, and the lava lake drained in
   less than an hour. The lava flowed down the flanks of the volcano at
   speeds of up to 60 miles per hour on the upper slopes, overwhelming
   villages and killing at least 70 people. Some reports quote much higher
   figures of up to several thousand people. The hazards posed by
   eruptions like this are unique to Nyiragongo. Nowhere else in the world
   does such a steep-sided stratovolcano contain a lava lake containing
   such fluid lavas. Nyiragongo's proximity to heavily populated areas
   increases its potential for causing natural disasters. The 1977
   eruption raised awareness of the unique dangers posed by Nyiragongo,
   and because of this it was designated a Decade Volcano, worthy of
   particular study, in 1991.

   The 1977 eruption was preceded by the creation of a new small volcano,
   Murara, a short distance away on the slopes of Mount Nyamuragira.

2002 eruption

   Satellite image of the eruption plume from Nyiragongo in July 2004
   Enlarge
   Satellite image of the eruption plume from Nyiragongo in July 2004

   Lava lakes reformed in the crater in eruptions in 1982- 1983 and 1994.
   Another major eruption of the volcano began on January 17, 2002, after
   several months of increased seismic and fumarolic activity. An 18 km
   fissure opened in the south flank of the volcano, spreading in a few
   hours from 2800 m to 1550 m elevation.

   The fissure emitted three streams of lava, one of which flowed through
   the city of Goma. 400,000 people were evacuated from the city during
   the eruption. Lava also destroyed Goma Airport, and reached nearby Lake
   Kivu. This raised fears that the lava might cause gas-saturated waters
   deep in the lake to suddenly rise to the surface, releasing lethally
   large amounts of carbon dioxide and methane - a similar event to the
   disaster at Lake Nyos in Cameroon in 1986. This did not happen, but
   volcanologists continue to monitor the area closely.

   About 45 people died in the eruption, and property damage was
   extensive. At least 15% of Goma was destroyed, leaving about 120,000
   people homeless. The eruption was the most destructive effusive
   eruption in modern history.

   Six months after the start of the 2002 eruption, Nyamuragira volcano
   also erupted. Activity at Nyiragongo is ongoing, but currently confined
   to the crater, where another lava lake has formed about 250 metres
   below the level of the 1994 lava lake.

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