It is located inside Virunga National Park, in the Democratic Republic of the Congo, about 20 km (12 mi) north of the town of Goma and Lake Kivu and just west of the border with Rwanda. The main crater is about two kilometres wide and usually contains a lava lake. The crater presently has two distinct cooled lava benches within the crater walls - one at about 3,175 m (10,417 ft) and a lower one at about 2,975 m (9,760 ft). Nyiragongo's lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably. A maximum elevation of the lava lake was recorded at about 3,250 m (10,660 ft) prior to the January 1977 eruption - a lake depth of about 600 m (2,000 ft). A recent very low elevation of the lava lake was recorded at about 2,700 m (8,900 ft). Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa's historical volcanic eruptions.