With the June 27th lava flow entering Pahoa this past week, the USGS Hawaiian Volcano Observatory (HVO) and Hawaii 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 27 flow as a whole and examine it over a longer time frame.
With the June 27th lava flow entering Pahoa this past week, the USGS Hawaiian Volcano Observatory (HVO) and Hawaii 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 27 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 Pu‘u ‘O‘o eruption — Kilauea 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 Pu‘u ‘O‘o could continue to erupt for years to come.
But how long the Pu‘u ‘O‘o 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 Pu‘u ‘O‘o 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 Pu‘u ‘O‘o 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 Kahauale‘a flows and the June 27th flow, have been directed towards the northeast, because their vents opened on the northeast part of the Pu‘u ‘O‘o 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 Kilauea. The Kahauale‘a and Kahauale‘a 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 Pu‘u ‘O‘o 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 pahoehoe 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 Pu‘u ‘O‘o, 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 Hawaii 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/.
Kilauea activity update
The June 27th lava flow from Pu‘u ‘O‘o remained active on Kilauea Volcano’s East Rift Zone. Since Oct. 30, the leading edge of the flow has not moved and remains approximately 155 meters (170 yards) above Pahoa Village Road. Over the past week, the flow has widened due to breakouts along the flow margins. Breakouts are also occurring upslope, within about 3 kilometers (1.8 miles) of Cemetery Road/Apa‘a Street. At Pu‘u ‘O‘o, glow was visible above several small outgassing openings in the crater floor.
The summit lava lake within Halema‘uma‘u Crater produced nighttime glow that was visible via HVO’s webcam over the past week. The lava level dropped and then rose over the course of the past 10 days, matching the trend in ground tilt and reflecting the occurrence of the most recent DI (deflation-inflation) event.
As of this writing on Thursday, the lava lake was about 55 meters (180 feet) below the rim of the Overlook crater.
There were no earthquakes reported felt on the Island of Hawaii during the past week.
Visit the HVO website (http://hvo.wr.usgs.gov) for past Volcano Watch articles and current Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes, and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.