The active surface flow from PuÊ»u ʻŌʻō is still advancing slowly downslope and was 4.4 km (2.7 miles) long when mapped today. Averaged over the past six days, the flow has been advancing at a rate of about 200 m (220 yards) per day. At that rate, it will take about 10 days to reach the top of PÅ«lama pali, which is in the middle distance about 2 km (1.2 miles) farther downslope. The coastal plain and ocean are in the far distance. The active flow is creeping across some of the last-exposed Ê»Aʻā flows erupted from PuÊ»u ʻŌʻō in the 1980’s. Photo taken Thursday, June 16, 2016 courtesy of USGS/HVO

This view is of the front of the active lava flow, looking upslope. Puʻu ʻŌʻō is partly obscured in the clouds at upper left. Most surface activity on the advancing flow is actually where the flow widens, upslope of the flow front. Photo taken Thursday, June 16, 2016 courtesy of USGS/HVO

The uppermost part of the nascent lava tube has several skylights, which reveal the lava stream within the flow, like capillaries beneath the skin. This is the uppermost skylight, just downstream from where the lava broke out from the east flank of Puʻu ʻŌʻō on May 24. Photo taken Thursday, June 16, 2016 courtesy of USGS/HVO

The lava stream was flowing toward the photographer in this photo. Higher lava levels are preserved in the shelf-like protrusions on the darker orange wall to the left. Photo taken Thursday, June 16, 2016 courtesy of USGS/HVO

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

Early on the morning of May 24, 2016, USGS Hawaiian Volcano Observatory scientists were alerted by text message that a tiltmeter on the Puʻu ʻŌʻō cone on Kīlauea 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 Puʻu ʻŌʻō. Tiltmeter data showed that the breakout likely began at 6:50 a.m., HST, resulting in a rapid deflation of the cone as magma burst forth from new vents.

HVO geologists were soon 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 Puʻu ʻŌʻō. Both lobes traveled atop older Puʻu ʻŌʻō lava flows, forming shimmering deltas of pāhoehoe channels, fingers, and toes. At the time, the two flows were about 1 km (3,300 yds) 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 27th” lava flow field remained active in scattered areas within about 5–6 km (3–4 mi) 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 Puʻu ʻŌʻō 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 Puʻu ʻŌʻō. This is most likely because the 61g vent is at a lower elevation on the flank of Puʻu ʻŌʻō compared to the 61f vent and the older June 27th 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 Puʻu ʻŌʻō 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 Kīlauea’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 Puʻu ʻŌʻō 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 Puʻu ʻŌʻō 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 ‘Ō‘ō.

Meanwhile, Kīlauea’s summit magma reservoirs have also 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 Kīlauea’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 KÄ«lauea respond to this pressurization.

For now, the recent activity at Puʻu ʻŌʻō is just the latest chapter in what long-time volcano watchers have observed for decades: Kīlauea’s complex and long-lived East Rift Zone eruption site is dynamic and always changing.

This small-scale map shows Kīlauea’s active East Rift Zone lava flow field in relation to the southeastern part of the Island of Hawaiʻi. The area of the active flow field on June 10 is shown in pink, while widening and advancement of the active flow field as mapped on June 16 is shown in red. The area covered by the inactive June 27th flow is shown in orange. The Puʻu ʻŌʻō lava flows erupted prior to June 27, 2014, are shown in gray.
The blue lines over the PuÊ»u ʻŌʻō flow field are steepest-descent paths calculated from a 2013 digital elevation model (DEM), while the blue lines on the rest of the map are steepest-descent paths calculated from a 1983 DEM (for calculation details, see http://pubs.usgs.gov/of/2007/1264/). Steepest-descent path analysis is based on the assumption that the DEM perfectly represents the earth’s surface. DEMs, however, are not perfect, so the blue lines on this map can be used to infer only approximate flow paths. The base map is a partly transparent 1:24,000-scale USGS digital topographic map draped over a 1983 10-m digital elevation model (DEM).

This map shows recent changes to Kīlauea’s active East Rift Zone lava flow field. The areas covered by the recent breakouts at Puʻu ʻŌʻō as of June 10 are shown in pink, while widening and advancement of the active flow as mapped on June 16 is shown in red. The inactive June 27th flow is shown in orange. Puʻu ʻŌʻō lava flows erupted prior to June 27, 2014, are shown in gray.

https://youtu.be/Sj7aoch5JYI
Time-lapse movie from a camera positioned on the southeast flank of Puʻu ʻŌʻō, looking toward the active flow advancing to the southeast. The breakout point is at the left edge of the image, and the mid-field skyline at the right is roughly coincident with the top of the pali. June 9-16, 2016%. Images courtesy of USGS/HVO

https://youtu.be/G94VMd2Pqes
Time-lapse movie of Pu’u ‘O’o Crater East Flank. June 9-16, 2016. Images courtesy of USGS/HVO