VOLCANO WATCH: ‘Leaky’ lava tubes

During the past four months, the June 27 lava flow, named for the date in 2014 that it began erupting from Puʻu ʻŌʻō on Kilauea Volcano’s East Rift Zone, has consisted of small surface pāhoehoe flows scattered across a broad area within 8 km (5 mi) of Puʻu ʻŌʻō.

These flows are fed by countless leaks, or lava “breakouts,” from the main lava tube. All of the leaks start within about 6 km (4 mi) of Puʻu ʻŌʻō; the tube beyond this distance became completely inactive in March 2015.

Some surface flows are also being fed from a second, much shorter tube that began forming when the original tube ruptured near its source on Puʻu ʻŌʻō, sending a lobe of lava toward the northeast on February 21. This younger lobe advanced across older parts of the June 27 flow and even over the main tube.

The location of the main tube is relatively well known based on thermal (infrared) imagery acquired during many helicopter overflights during the past year, but the path of the second tube is complex and difficult to locate. The many overlapping breakouts immediately north of Puʻu ʻŌʻō have obscured its thermal “signature” in the images.

By spawning so many short-lived flows over a large area, the leaky nature of the tubes means that no single flow has been able to capture the volume of lava needed to develop into a sustained, rapidly advancing flow similar to the June 27 flow late last year.

At any one time since late March, the combined surface area of the active flows—leaks from the tubes—has varied between about 3.6 and 5.3 hectares (9 and 13 acres)! Total surface areas of the active flows are calculated using a thermal (infrared) camera and specialized software to stitch together the images and total the hottest areas. The “active” flows are assumed to have surface temperatures greater than about 200 degrees Celsius (390 degrees Fahrenheit). Earlier thermal studies of pāhoehoe lava flows erupted from Puʻu ʻŌʻō indicate that this temperature threshold represents lava flows that were emplaced within the previous five hours.

This pattern of activity continues to be good news for the Puna District of the Island of Hawai‘i. There is no immediate (weeks) or short-term (months) threat of inundation of residential areas from the current series of flows. The breakouts, especially the one that began February 21, were the main reason the lower part of the June 27 flow became completely inactive in March.

Currently active lava flows are far upslope from the tips of the June 27 flow that reached as far as 23 km (14.3 mi) from Puʻu ʻŌʻō and repeatedly threatened to inundate residential areas, businesses, electric and communication utilities, and Highway 130. For now, the breakouts are mostly filling in low areas on the June 27 flow and only slowly widening and thickening the flow field.

How long might this pattern last?

Veteran volcano watchers accustomed to more than 32 years of changes at Puʻu ʻŌʻō know well that the current pattern of lava-flow activity will not last. When and how the activity will evolve is, of course, not known at this time, but a change in the erupting vent on Puʻu ʻŌʻō—its geometry or location—would likely result in a change in the flow activity or direction.

Kilauea Activity Update

Kīlauea’s summit lava lake level remained fairly steady at 51 m (167 ft) below the vent rim until July 21, when the level dropped in response to summit deflation to about 65 m (210 ft), where it remained as of July 23.

Kilauea’s East Rift Zone lava flow continues to feed widespread breakouts northeast of Puʻu ʻŌʻō.  Active flows are slowly covering and widening the flow field, but remain within about 8 km (5 mi) of Puʻu ʻŌʻō.

One earthquake was reported felt on the Island of Hawai‘i this past week. On Friday, July 17 at 7:38 p.m., a magnitude-2.6 earthquake occurred 6.4 km (3.9 mi) south of Mauna Loa Summit at a depth of 2.6 km.

Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey`s Hawaiian Volcano Observatory.