Volcano Watch — "Leaky" lava tubes spread flows only short distances from Pu‘u ‘Ō‘ō

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 Pu‘u ‘Ō‘ō; 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 Pu‘u ‘Ō‘ō and sending a lobe of lava toward the northeast on February 21. This younger lobe advanced across older parts of the June 27th 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 Pu‘u ‘Ō‘ō 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 27th 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 Pu‘u ‘Ō‘ō indicate that this temperature threshold represents lava flows that were emplaced within about the previous 5 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 27th flow became completely inactive in March.

Currently active lava flows are far upslope from the tips of the June 27th flow that reached as far as 23 km (14.3 mi) from Pu‘u ‘Ō‘ō 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 27th 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 Pu‘u ‘Ō‘ō 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 Pu‘u ‘Ō‘ō—its geometry or location—would likely result in a change in the flow activity or direction.

In the meantime, keep up to date with the activity at Pu‘u ‘Ō‘ō and Kīlauea's summit on the USGS Hawaiian Volcano Observatory (HVO) website, where updates are posted each morning at http://hvo.wr.usgs.gov/activity/kilaueastatus.php. This update is linked to maps and photographs that are posted following each overflight made by HVO scientists to assess the current activity.

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Volcano 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.

Kīlauea's East Rift Zone lava flow continues to feed widespread breakouts northeast of Pu‘u ‘Ō‘ō. Active flows are slowly covering and widening the flow field, but remain within about 8 km (5 mi) of Pu‘u ‘Ō‘ō.

One earthquake was reported felt on the Island of Hawai‘i this past week. On Friday, July 17, 2015, at 7:38 p.m., HST, a magnitude-2.6 earthquake occurred 6.4 km (3.9 mi) south of Mauna Loa Summit at a depth of 2.6 km.