Lava erupting from Pu‘u ‘O‘o since mid-March has slowly spread and irregularly across three areas located within about 7 km (4 mi) from the vent on Kilauea Volcano’s East Rift Zone. These active lava flows are not presently posing an immediate threat to any community in the Puna District.
The currently active flows are reminiscent of the slow-moving Kahauale‘a flows that were active in 2013–14, before the new vent opened on the north flank of Pu‘u ‘O‘o on June 27, and sent flows toward Pahoa. The Kahauale‘a flows spread gradually north and northeast from Pu‘u ‘O‘o in fits and starts, intermittently advancing a short distance before stopping as the supply of lava changed.
The current activity is a welcomed relief from the long, tube-fed June 27 lava flow that spread 22 km (14 miles) eastward from Pu‘u ‘O‘o and repeatedly threatened the Pahoa area. That flow entered Pahoa in late October, nearly cutting Pahoa Village Road, before becoming inactive in mid-November.
Days later, a new breakout upslope developed into a second flow lobe that reached to within 500 m (550 yd) of the Pahoa Marketplace just before Christmas. This lobe stopped advancing, but continued to spread laterally just upslope from the Marketplace during the next few months. Because these breakouts, and others farther upslope, were widely dispersed, no single flow lobe became focused, which limited the advance of the flow front.
Lava was further diverted from the June 27 flow front on Feb. 21 when a series of flows broke out of the lava tube near its source on the north flank of Pu‘u ‘O‘o. This breakout was followed by another large breakout March 9 near Pu‘u Kahauale‘a — an old, nearly buried cone about 2 km (1.2 mi) northeast of Pu‘u ‘O‘o. Together, these two breakouts captured the entire supply of lava from the tube, effectively starving the June 27 flow front, and, by March 13 surface flows near the Pahoa Marketplace no longer were active.
Even as the flows near Pahoa were dying out, lava slowly reoccupied the tube below Pu‘u Kahauale‘a. This culminated in a third area of breakouts about 6 km (4 mi) northeast of Pu‘u ‘O‘o. Lava has not reoccupied the tube below this breakout.
All three of these breakouts remained active last week. The USGS Hawaiian Volcano Observatory (HVO) currently is monitoring the breakouts with biweekly overflights, after which maps and photos of the activity are posted on the HVO website (http://hvo.wr.usgs.gov/). HVO scientists also are using other methods to track the status of Kilauea’s ongoing eruption, including webcam images, satellite imagery, sulfur dioxide gas emission measurements and continuous recording of earthquake and ground deformation by instruments on the volcano.
The lava flows of the past eight months have demonstrated the complex factors that affect the ways in which lava moves across the ground. The intertwining conditions that enabled lava to advance right to Pahoa’s doorstep were remarkable.
For example, older lava flows and large ground cracks along the East Rift Zone kept the June 27 flow narrow, facilitating its advance and promoting development of a robust lava tube system.
The constant uncertainties in estimating if the June 27 lava flow would continue moving downslope, what path it would take, how fast it would advance and whether lava would cover Pahoa Village Road, Pahoa Marketplace, Highway 130 and other vital infrastructure, made this a somewhat harrowing experience. With lava flow advance rates varying from a few meters (yards) to more than 500 m (550 yards) per day, flow forecasts were imperfect at best.
Fortunately, the June 27 flow stopped before completing what seemed to be a certain path to significant destruction in Pahoa.
The Puna District can breathe more freely for the moment, but the activity during the past eight months has demonstrated that the area is not immune to Kilauea’s lava flows. While the currently active flows do not represent an immediate hazard to communities, they eventually could. We must all remember that unpredictable changes at Pu‘u ‘O‘o can quickly change the hazard prognosis.
Kilauea activity update
Kilauea’s East Rift Zone lava flow continues to feed three areas of breakouts northeast of Pu‘u ‘O‘o. The front of the breakout farthest downslope was 7.4 km (4.6 mi) from Pu‘u ‘O‘o on Thursday based on satellite imagery.
There have been no major changes at Kilauea’s summit vent, which continues to host an active lava lake. The lava lake level fluctuated between about 30 and 40 m (100–130 ft) below the rim of the Overlook crater during the week.
No earthquakes were reported felt in Hawaii during the past week.
Visit the HVO website (http://hvo.wr.usgs.gov) for past Volcano Watch articles, Kilauea daily eruption updates and other volcano status reports, current volcano photos, recent earthquakes and more; call (808) 967-8862 for a Kilauea summary update; email questions to askHVO@usgs.gov.
Volcano Watch (http://hvo.wr.usgs.gov/volcanowatch/) is a weekly article and activity update written by scientists at the U.S. Geological Survey`s Hawaiian Volcano Observatory.
