(ABOVE VIDEO) Frank Trusdell with the U.S. Geological Survey’s Hawaiian Volcano Observatory discusses the stall at the lava flow front during Thursday night’s public meeting in Pahoa.

NEWS BRIEF

• USGS Hawaiian Volcano Observatory geologist Frank Trusdell gave a presentation during Thursday night’s public meeting in Pahoa, detailing the current situation on the flow front. The distal tip of the lava has not advanced beyond where it stalled on October 30, in a residential area approximately 170 yards above Pāhoa Village Road.

PRIMARY SOURCE

Now is a good time to share this week’s Volcano Watch article entitled: How long will Kīlauea Volcano’s June 27th flow last? Volcano Watch is a weekly feature provided by scientists at the Hawaiian Volcano Observatory.

With the June 27th lava flow entering Pāhoa this past week, the USGS Hawaiian Volcano Observatory (HVO) and Hawaiʻi County Civil Defense have been providing updates to the media and the public each day. This short-term information is useful to gauge the immediate hazards that the flow might pose to nearby residences and infrastructure. But recently, a frequent inquiry has been, “When will this end?” To answer this question, we should first consider the June 27th flow as a whole and examine it over a longer time frame.

Whenever HVO geologists are asked about when the flow will stop, we remind people that the Puʻu ʻŌʻō eruption—Kīlauea Volcano’s ongoing East Rift Zone eruption and the source of the June 27th lava flow—has been going on for over 31 years. This sustained time period suggests that Puʻu ʻŌʻō could continue to erupt for years to come.

But how long the Puʻu ʻŌʻō eruption persists is only part of the story. For most of its 31 years, the eruption has sent lava flows south, towards the ocean. In recent years, these flows created only minor risks, because much of the area south of Puʻu ʻŌʻō was already covered by a broad lava flow field. The June 27th flow is unusual (but not unprecedented) in that the flow direction is towards the northeast.

What caused this shift in flow direction and change in hazard? The short answer is vent location.

The Puʻu ʻŌʻō eruption began in 1983 and has continued essentially nonstop ever since, but the vent location (the spot where lava comes out of the ground) has shifted many times. A vent can create its own lava flow field that covers areas downslope, and a given vent can remain active for days to several years before it shuts down.

Recent flows (those erupted 2013 to present), such as the Kahaualeʻa flows and the June 27th flow, have been directed towards the northeast, because their vents opened on the northeast part of the Puʻu ʻŌʻō cone. Because these vent locations are slightly north of the pre-2013 vents, lava has not been able to flow south of the East Rift Zone ridgeline. Instead, the East Rift Zone, with its older lava shields, lava ponds, and ground cracks, helped contain these more recent flows north of the ridgeline—sending them to the northeast.

There is no way of knowing how long the June 27th vent will persist, but for guidance, we can look at the duration of other recent vents on Kīlauea. The Kahaualeʻa and Kahaualeʻa 2 vents (2013–2014) lasted for 2.5 months and 13 months, respectively. The Peace Day vent (2011–2013) erupted for about two years. The Fissure D vent (2007–2011) lasted for nearly four years. This indicates that individual vents on Puʻu ʻŌʻō have the potential to remain active for several years.

If the June 27th vent remains active for several years, its lava flow activity will likely follow the same pattern exhibited by other recent vents and their flow fields. Routine fluctuations in lava supply to the pāhoehoe flow field will trigger new breakouts from the lava tube, which will slowly widen the flow. What begins as a narrow pioneer flow can gradually, over the course of months, widen with the addition of breakouts into a more expansive lava flow field. This lateral enlargement of the flow field can be the most destructive aspect of the activity.

So, how long will the June 27th lava flow last? All we can say with certainty is that, based on other recent activity, it has the potential to persist for months to years. But we cannot precisely forecast the flow’s duration. Should an abrupt change occur at Puʻu ʻŌʻō, the June 27th vent and its flow could end any day. Currently, there are signs that the eruption rate is varying but no signs that the vent is shutting down. We should be prepared for the flow to remain active for some time.

Puna residents are encouraged to stay informed about the June 27th lava flow’s status and progress through daily updates posted on HVO and Hawaiʻi County Civil Defense websites (http://hvo.wr.usgs.gov and http://www.hawaiicounty.gov/active-alerts/). You can also sign up to receive Volcano Activity Notices, distributed via the USGS Volcano Notification Service, at http://volcanoes.usgs.gov/vns/.USGS Hawaiian Volcano Observatory’s Volcano Watch on Nov. 6, 2014