The location of vents for lava flows erupted by Mauna Loa in the past 10,000 years may vary between the summit caldera and rift zones in a systematic way (Lockwood, 1995). Below are excerpts from Lockwood's paper, Mauna Loa Eruptive History - The Preliminary Radiocarbon Record, in which he proposes a cyclic model to explain the long-term eruptive behavior of Mauna Loa of the past several thousand years. New geologic research and radiocarbon ages for additional lava flows may result in other models or a refinement of Lockwood's cyclic model.
Aerial view of lava fissure and flows from northeast rift of Mauna Loa on March 25, 1984 Photograph by J.P. Lockwood on March 25, 1984.
Eruptive fissure high on the northeast rift zone of Mauna Loa about 10 hours after the eruption started in Moku`aweoweo Caldera (top left). Although historical eruptions of Mauna Loa have occurred from both the summit and the volcano's two rift zones, geologic mapping shows that the focus of activity alternates between the rift zones and summit area over a time span of about 2,000 years. Overview
Radiocarbon dating of Mauna Loa lava flows has provided one of the most refined eruptive chronologies of any volcano on Earth. An analysis of 170 well-dated prehistoric lava flows reveals variations in eruptive frequency not explicable by random sampling but instead reflecting systematic changes in time and place of eruptive activity. Pronounced decreases in eruptive activity on Mauna Loa's rift zones correlate with periods of increased lava-lake activity and shield-building at the volcano's summit. Voluminous eruptions of olivine-rich lavas low on the rift zones may have heralded the cessation of summit overflows and the resumption of increased rift zone activity. These picrites (i.e. olivine-rich lava) were possibly erupted at a time when picritic melts had risen higher than normal into shallow supply conduits [Rhodes, 1995], and their eruption low on Mauna Loa's flanks may...