March 5, 2014, marked the third anniversary of the onset of Kilauea Volcano’s four-day-long Kamoamoa fissure eruption. This brief episode marked the end of the eruptive vent established east of Puu Oo in 2007 and presaged a return of activity to Puu Oo that continues today.
Months before the Kamoamoa eruption began, lava output from Kilauea’s long-lived east rift zone eruption, ongoing since 1983, had started to wane. This was coupled with uplift and increased seismicity at the volcano’s summit and at Puu Oo. Moreover, the lava lake within Halemaumau Crater, active at the summit since 2008, started to slowly rise. Lava flows also began to erupt within Puu Oo’s crater.
The sudden onset of seismic tremor and elevated earthquake activity along Kilauea’s east rift zone at 1:42 p.m., March 5, 2011, signaled the start of a magmatic intrusion uprift from Puu Oo. Rapid deflation started at Puu Oo at almost the same time and at Kilauea’s summit about 30 minutes later. Shortly afterward, most of the Puu Oo crater floor began to subside, dropping 371 feet in about four hours. Almost simultaneously, the lava lake at Kilauea’s summit began to drain, falling about 469 feet before stabilizing.
The Kamoamoa eruption began at 5:09 p.m., when lava reached the surface about 1.2 miles southwest of Puu Oo, forming a 0.6-mile-long eruptive fissure. A second 0.6-mile-long fissure opened early on March 6 farther to the southwest. Designated the “eastern” and “western” fissures, they were separated by 0.2 mile of heavily cracked ground.
The eruption was initially sporadic, and activity migrated from one spot to another along both fissures and repeatedly started and stopped. On March 8, however, the eruption became focused near the western end of the western fissure and began to feed a fast-moving channelized aa flow that bowled over ohia trees like matchsticks as it advanced downslope.
This activity continued unabated overnight, but late in the afternoon on March 9, the western fissure began to wane and finally shut down at about 10:30 p.m., marking the end of the Kamoamoa eruption. The channelized aa flow stalled soon afterward, having reached a total length of 2.1 miles.
Altogether, approximately 3.5 million cubic yards of lava erupted, and eruptive sulfur dioxide emissions averaged 8,500 tonnes/day — several times higher than Kilauea’s normal east rift zone output at that time. The summit of Kilauea dropped about 6 inches over the course of the eruption, and the east rift zone at the eruption site spread apart by about 10 feet.
The Kamoamoa eruption was probably a result of the gradual shutdown of the previous east rift zone vent — the episode 58 vent — with no slow-down in the amount of lava entering the rift zone. This led to the pressurization of Kilauea’s magma system, which was manifested as inflation at the summit and at Puu Oo, spreading of the east rift zone, increased seismicity along the upper east rift zone, and rising lava levels within both the summit vent and Puu Oo’s crater.
The pressurization culminated in the Kamoamoa fissure eruption, which diverted magma from beneath Puu Oo and Kilauea’s summit, thereby causing Puu Oo’s crater floor to collapse and the summit lava lake to drain, respectively. Once the excess pressure had dissipated, the pressure gradient between the summit and the east rift zone fissure was insufficient to sustain the eruption, and the Kamoamoa eruption stopped.
Afterward, the pressure climbed within Kilauea’s magma storage areas and transport pathways as the supply of magma to the volcano continued unchanged. This renewed pressure led to the reappearance of the summit lava lake and eventually restarted eruptive activity at Puu Oo, which remained the easiest pathway for magma to reach the surface.
Because of the excellent geological, geophysical and geochemical monitoring of Kilauea, progressions in eruptive activity, like those observed prior to the Kamoamoa eruption, can likely be recognized months in advance of any shifts in eruption style or location. At the moment, no such precursory activity is apparent.
Kilauea activity update
A lava lake within Halemaumau produced nighttime glow visible via HVO’s webcam during the past week. The lava level fluctuated with a deflation-inflation cycle and varied between 130 and 160 feet below the rim of the overlook vent.
On Kilauea’s east rift zone, the Kahaualea 2 flow continued to be active northeast of Puu Oo. After the flow front stalled in late January at a distance of 4.8 miles northeast of Puu Oo, surface flows have been active behind the stalled flow front. This week, the flows reached the stalled flow front, and are active about 4.8 miles northeast of Puu Oo. Webcam images indicate that small forest fires are continuing.
There were no earthquakes reported felt on Hawaii Island in the past week.
Visit hvo.wr.usgs.gov for current Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.