Everything about Mount Nyiragongo totally explained
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 20 km north of the town of
Goma and
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 (up to 100 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 Hawaiian flows to walking pace.
Nyiragongo is most famous for its semi permanent lava lake, which was discovered by French vulcanologist
Haroun Tazieff. The last known eruption was in 2007.
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 that contains such fluid lavas. Nyiragongo's proximity to heavily populated areas increases its potential for causing a
natural disaster. 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.
Latest 2002 eruption
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. A 13 km
fissure opened in the south flank of the volcano, spreading in a few hours from 2800 m to 1550 m elevation, reaching the outskirts of the city of
Goma the provincial capital on the northern shore of
Lake Kivu. Lava streamed from three spatter cones at the end of the fissure and flowed in a stream 200 to 1000 m wide and up to 2 m deep through Goma. Warnings had been given and 400,000 people were evacuated from the city across the
Rwandan border into neighbouring
Gisenyi during the eruption. Lava covered the northern end of the runway at
Goma International Airport, leaving the southern two-thirds usable, and reached
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 didn't happen, but
volcanologists continue to monitor the area closely.
About 45 people died in the eruption from
asphyxiation by
carbon dioxide and buildings collapsing due to the lava and earthquakes. She landed on a small ledge and apparently survived the fall, but was dead by the time three rescue workers (from a team of Indian peacekeepers and two vulcanologists) could reach her early the following day. An initial rescue attempt using a UN helicopter failed when the victim couldn't be found due to poor visibility.
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