Mount Nyiragongo is a volcano, one of eight in the Virunga Mountains chain, in the Albertine (western) branch of 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 metres deep and 2 kilometres wide. Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa's historical volcanic eruptions. This picture shows the lava lake at the bottom of the main crater, which forms a glow visible more then 50 kilometres away and releases large quantities of gas.