There is no record of such an event at Lake Kivu in the past. However, in 1986, Lake Nyos in Cameroon released a cloud of gas, which killed more than 1,700 people.
Nyiragongo, and nearby Nyamuragira, are the two active volcanoes among the eight volcanoes in Rwanda, the Democratic Republic of Congo and Uganda.
Both are in the Virunga mountain range, which straddles the border with Rwanda. The pair is responsible for nearly two-fifths of Africa's historical eruptions.
Nyamuragira erupted early last year. It caused no casualties but cultivated land was burnt out by ash, trees were destroyed and some water supplies were polluted.
Fracture faults
Scientists understand the geology of the area relatively well. Physical stretching of the continent gives rise to large fractures that allow volcanic magmas to rise up through the Earth's crust.
Eugene O'Connor, regional geologist for Africa at the British Geological Survey, said: "The volcano is located in part of the East African Rift Valley system, which is a chain of major fracture faults running along the eastern half of Africa."
Dr O'Connor said he was not aware of any local monitoring of volcanic activity, although several academic institutions in the United States carried out remote monitoring using seismographic records.
"The important thing now is to ensure that the local population is moved to safer ground," he told BBC News Online.
"That is the first consideration. The second one is to set up some sort of closer monitoring observatory," he added.
According to wildlife experts, many wild animals in the forests surrounding Congo's Nyiragongo volcano will likely be harmed by the torrent of lava, ash, and sulphurous gas pouring from the crater. Nyiragongo is one of eight volcanoes on the borders of Rwanda, the Democratic Republic of Congo and Uganda, which is dense with tropical forests and home to rare mountain gorillas.
But the gorillas only inhabit the slopes of the six dormant volcanoes, and experts said they should be safe from direct impact from the destruction inflicted by Nyiragongo on the town of Goma and nearby forest. "It is unlikely that the forest the gorillas inhabit will be affected greatly," said Annette Lanjouw, head of the International Gorilla Conservation Programme in a statement. "However, chimpanzees and other wildlife in the forest around Nyiragongo will probably be devastated."
Nyiragongo last erupted in 1977, killing many people and gutting the town. After that incident, there were reports of elephants being found in the rubble alongside the human debris of cars and houses. According to the east African representative for the world-wide Fund for Nature, Sam Kanyamibwa, the recent eruption would affect every level of the mountain's ecosystem, from worms to primates.
"The problem is the physical destruction of habitat, and of course the sulphur gases over the area," he told Reuters in Nairobi. "Obviously some animals have some possibility of moving to other places, snakes for example, but some will be trapped in the area...The impact is enormous."
Although the mountain gorillas are too far from Nyiragongo to fear immediate harm, the long-term effects from the volcano's eruption could be more severe. "The ecological integration in the whole region is going to be affected one way or another," Kanyamibwa said. "Also the movement of the population, refugees, may lead to some instability in the region. This may lead to some problems for gorillas."
About 650 mountain gorillas are all that remain in the world, and more than half that inhabits the slopes of the six dormant Virunga volcanoes. These are ranked as critically endangered by international wildlife conventions. There are also fears that the lava pouring into Lake Kivu beside Goma will severely contaminate the water and may even cause explosions, due to the lake's unusual accumulation of carbon dioxide in the lower strata of its basin.
