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The Pu'u 'O??'o??'-Ku??paianaha eruption on the east rift zone of Ki??lauea began in January 1983. The first 9 years of the eruption were divided between the Pu'u 'O??'o?? (1983-1986) and Ku??paianaha (1986-1992) vents, each characterized by regular, predictable patterns of activity that endured for years. In 1990 a series of pauses in the activity disturbed the equilibrium of the eruption, and in 1991, the output from Ku??paianaha steadily declined and a short-lived fissure eruption broke out between Ku??paianaha and Pu'u 'O??'o??. In February 1992 the Ku??paianaha vent died, and, 10 days later, eruptive episode 50 began as a fissure opened on the uprift flank of the Pu'u 'O??'o?? cone. For the next year, the eruption was marked by instability as more vents opened on the flank of the cone and the activity was repeatedly interrupted by brief pauses in magma supply to the vents. Episodes 50-53 constructed a lava shield 60m high and 1.3km in diameter against the steep slope of the Pu'u 'O??'o?? cone. By 1993 the shield was pockmarked by collapse pits as vents and lava tubes downcut as much as 29 m through the thick deposit of scoria and spatter that veneered the cone. As the vents progressively lowered, the level of the Pu'u 'O??'o?? pond also dropped, demonstrating the hydraulic connection between the two. The downcutting helped to undermine the prominent Pu'u 'O??'o?? cone, which has diminished in size both by collapse, as a large pit crater formed over the conduit, and by burial of its flanks. Intervals of eruptive instability, such as that of 1991-1993, accelerate lateral expansion of the subaerial flow field both by producing widely spaced vents and by promoting surface flow activity as lava tubes collapse and become blocked during pauses.
Additional Publication Details
The character of long-term eruptions: Inferences from episodes 50-53 of the Pu'u 'O??'o??-Ku??paianaha eruption of Ki??lauea volcano