Rungwe volcano, the largest in the Karonga basin NW of Lake Malawi (Lake Nyasa), is cut by a 4-km-wide caldera that is breached to the WSW. Hummocky terrain from a debris-avalanche deposit produced by collapse of the summit and western flank extends at least 20 km SW of the volcano. The trachytic caldera is largely filled by a series of youthful-looking uneroded and sparsely vegetated pumice cones, lava domes, and explosion craters. The latter are also found on the southern and northern flanks. A large area of basaltic cones and lava flows are found on the NW flank, and youthful-looking lava flows extend SW from vents inside the caldera. Explosive and effusive eruptions were produced during the Holocene; the largest explosive eruption took place about 4,000 years ago, and the most recent about 1,200 years ago.