Lake Mafuru

Lake Mafuru showcases an elliptical shape, spanning approximately 600 yards in length and 100 yards in width. Adjacent to the lake crater’s western side, there exists an older, dry crater, separated by a narrow ridge about 70 feet in height. This older crater spans around 300 yards in length by 100 yards across, revealing an open southwestern end truncated by a marshy depression leading toward Lake Lujongo. Interestingly, the water surface within the lake crater sits lower than the floor of the dry crater.

During an initial visit at Lake Mafuru, Combe (1934, p. 66) described the southern wall of the older crater, towering approximately 400 feet high, primarily composed of tufts and agglomeratic rocks. He noted a lava sheet around halfway up the wall, visible for roughly 70 feet, potentially extending further but obscured at the base. Subsequent visits in 1938 revealed extensive clearing for banana cultivation. The lava sheet’s discovery expanded, stretching along the wall for at least 150 yards. Its exposed thickness increased from 6 feet near the eastern end to approximately 120 feet towards the western side. The upper section exhibited scoriaceous and slaggy characteristics, topped by 30 feet of tuff and agglomerate containing ejected blocks of diverse mafurite types, some up to 4 feet wide. A layer of black soil, about 20 feet thick, separated the highest lava exposure from the lowest tuft layer. Observations suggested a gradual decrease in the sheet’s height westward, hinting at its origination from a source in the direction of the lake crater.