Early on the morning of May 24, 2016, USGS Hawaiian Volcano Observatory scientists were alerted by text message that a tiltmeter on the Pu‘u ‘O‘o cone on Kilauea Volcano’s East Rift Zone had detected rapid change. Soon after, an HVO field crew reported that lava had broken out from the flanks of Pu‘u ‘O‘o. Tiltmeter data showed that the breakout likely began at 6:50 a.m., resulting in a rapid deflation of the cone as magma burst forth from new vents.
HVO geologists soon were in the air to investigate the sudden — although not entirely surprising — change in activity at this long-lived eruption site.
Once on scene, the geologists mapped and sampled two vigorous lobes of lava advancing from new vents on the north and east sides of Pu‘u ‘O‘o. Both lobes traveled atop older Pu‘u ‘O‘o lava flows, forming shimmering deltas of pahoehoe channels, fingers and toes. At the time, the two flows were about 1 km (3,300 yards) in length, too short to reach the forest on the north, but active enough to thrill tourists flying above the area.
Over the following days, activity continued from these breakouts — now called episodes 61f and 61g in the lexicon of HVO eruptive activity tracking. Each was developing nascent lava tubes and distributary channels that carried lava downslope, slowly extending their lengths and widths.
During this time, the “June 27” lava flow field remained active in scattered areas within about 5-6 km (3—4 miles) northeast of the vent, a continuation of the activity observed in the same general area for the past year. Apparently, the supply of lava from Pu‘u ‘O‘o to the lava tube feeding the June 27th flow was not immediately starved by the new breakouts.
Now, however, only the eastern breakout is active — no lava has been sighted in the northern breakout or on the June 27 flow field since June 6. Clearly, the eastern breakout — informally called the “61g flow” — has captured most, or all, of the outflow from Pu‘u ‘O‘o. This is most likely because the 61g vent is at a lower elevation on the flank of Pu‘u ‘O‘o compared to the 61f vent and the older June 27 lava flow tube.
As of June 16, the 61g flow is moving steadily southeast along, and just outside of, the Hawaii Volcanoes National Park boundary. The flow is contained within topography of older Pu‘u ‘O‘o lava flows and is headed for the northwestern corner of the long-abandoned Royal Gardens subdivision.
At its present advance rate, the flow could reach the Pulama pali (a steep, lava mantled fault scarp on Kilauea’s south flank) in days to weeks. If and when it reaches the coastal plain and then the ocean depends on the evolution of a tube system and constancy of lava supplied from the vent — variables that are difficult to forecast at this time.
This turn of events at Pu‘u ‘O‘o was not entirely unexpected. For weeks, an HVO tiltmeter on the north rim had shown steady outward tilting as magma accumulated in the subsurface reservoir system, pushing on the sides of the cone and the floor of the crater. Indeed, thermal webcam imagery showed the floor of Pu‘u ‘O‘o slowly lifting as the pressure increased from below and numerous small lava flows repeatedly erupted from vents within the crater.
The cone was clearly filling with magma, the crater floor responding like a piston and the flanks bulging outward. A new outbreak of lava was certainly possible, and, on May 24, it happened: flows 61f and 61g erupted from the flanks of Pu‘u ‘O‘o.
Meanwhile, Kilauea’s summit magma reservoirs also have been on a long run of inflation, punctuated by occasional DI (deflation-inflation) events. For some months now, we have considered the magmatic plumbing system of Kilauea’s summit and upper rift zones to be pressurized and full, a condition ripe for change as stresses increase on the walls of engorged magma reservoirs.
Time will tell if and how other parts of Kilauea respond to this pressurization.
For now, the recent activity at Pu‘u ‘O‘o is just the latest chapter in what longtime volcano watchers have observed for decades: Kilauea’s complex and long-lived East Rift Zone eruption site is dynamic and always changing.
Volcano
activity updates
Kilauea continues to erupt at its summit and East Rift Zone. During the past week, the summit lava lake level varied between about 30 and 37 m (100 and 120 feet) below the vent rim within Halema‘uma‘u Crater. On the East Rift Zone, the June 27 lava flow is inactive. The eastern Pu‘u ‘O‘o breakout remained active, producing a lava flow (informally called the 61g flow) that continued to advance to the southeast. As of June 16, the flow was about 4.4 km (2.7 miles) long. No lava flows were threatening nearby communities.
Mauna Loa is not erupting. Seismicity rates have decreased since the earthquake activity recorded in late May, but remain above background levels. Deformation related to inflation of a magma reservoir beneath the summit and upper Southwest Rift Zone continues, with inflation recently occurring mainly in the southwestern part of Mauna Loa’s magma storage complex.
No earthquakes were reported felt on the Island of Hawaii this past week.
Visit the HVO website (http://hvo.wr.usgs.gov) for past Volcano Watch articles, Kilauea daily eruption updates, Mauna Loa weekly updates, volcano photos, recent earthquakes info and more; call for summary updates at 967-8862 (Kilauea) or 967-8866 (Mauna Loa); email questions to askHVO@usgs.gov.
Volcano Watch (http://hvo.wr.usgs.gov/volcanowatch/) is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.
