View is from innermost southeast rim of caldera (lower left) toward the northwest. Uwekahuna Bluff is in upper right, and Mauna Loa is in background.
These small spatter cones and ramparts formed along an eruptive fissure that broke across the southern caldera floor on July 19-22, 1974. A pahoehoe flow in the foreground spilled from the fissure. The fissure also fed a much more extensive pahoehoe flow that flooded the eastern caldera floor to the base of the north caldera wall (see geologic map). The eruption started a few hours earlier from several fissures within and near Keanakako`i Crater, following several hours of intense seismicity and sharp deflation of the summit area.
This brief summit eruption coincided with the end of a prolonged eruption on the east rift zone at Mauna Ulu, and it represents the beginning of a period of renewed summit activity and intrusions into both the southwest and east rift zones. After the July 1974 eruption in the caldera, no molten lava was observed at Mauna Ulu, and volcanic tremor associated with Mauna Ulu's activity ceased.