New observations show that the July 1986 eruption vent was located 4.5 km S of the caldera's edge at the S foot of Kitazungurwa in Mashiga (figure 6) rather than... 3.5 km SW of the caldera's edge.

Figure 6. Map of the Nyamuragira/Nyiragongo area by N. Zana (1984), appended with vents and flows through 1988. The heavy dashed line indicates the approximate path of the 1989 flow.

Geological Summary. Africa's most active volcano, Nyamulagira (also known as Nyamuragira), is a massive high-potassium basaltic shield about 25 km N of Lake Kivu and 13 km NNW of the steep-sided Nyiragongo volcano. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Documented eruptions have occurred within the summit caldera, as well as from the numerous flank fissures and cinder cones. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Recent lava flows extend down the flanks more than 30 km from the summit as far as Lake Kivu; extensive lava flows from this volcano have covered 1,500 km2 of the western branch of the East African Rift.

Information Contacts: B. Louant, GEOVAR, Kigali, Rwanda.