In response to the USGS Hawaiian Volcano Observatory’s (HVO’s) Aug. 22 news release (http://hvo.wr.usgs.gov/pressreleases/view.php?id=111) that Kilauea’s June 27th lava flow could become a concern for communities downhill of the Pu‘u ‘O‘o vent, the Hawaii County Civil Defense Agency (HCCDA) quickly organized a series of informational meetings.
To date, four meetings have been held at the Pahoa Community Center to raise public awareness of the lava flow and to let potentially affected residents know how to stay informed about the flow’s progress. HCCDA also addressed the possible emergency-response measures that are being considered should the flow continue its northeastward advance.
During these meetings, HVO Scientist-in-Charge Jim Kauahikaua and Civil Defense Administrator Darryl Oliveira provided brief presentations about the lava flow activity and emergency planning efforts, respectively, before answering dozens of questions from attendees. When and where the lava flow might reach specific communities, roads and infrastructure were topmost among residents’ concerns, but are the most difficult questions to answer at this time.
While it’s true that lava flows travel downhill, their movement is more complex than might be expected. There are several critical factors that affect where lava actually flows and how quickly it advances.
For the June 27th lava flow, these include: (1) how much and how consistently lava is erupted from the Pu‘u ‘O‘o vent; (2) whether or not lava breaks out of the tube and creates new surface flows (and tubes) that “steal” lava from the current flow front; and (3) the topography (shape and features) of the ground over which the lava is flowing, including slope steepness and direction, depressions, ground cracks, fault cliffs, craters and cones.
During the past week, the most active part of the June 27th lava flow moved into extremely irregular topography with lots of cracks and depressions, which makes it futile — at this time —to forecast exactly which areas might be impacted.
The June 27th flow, named for when it began, is erupting from a vent located on the northeast flank of Pu‘u ‘O‘o. The lava remained close to the vent for two weeks, but on July 10, the flow began to advance to the northeast, with an average speed of about 250 meters per day (820 feet/day), but as fast as about 500 meters per day (1,600 feet/day). These relatively rapid advance rates were likely due to two factors: a steady lava supply and confinement of the flow to a narrow low area between older lava flows.
This low area funneled the flow into a section of Kilauea Volcano’s East Rift Zone that is marked by dozens of deep, discontinuous ground cracks and linear depressions that are hundreds to thousands of meters (yards) long. In mid-August, the lava flow disappeared into one of these cracks, creating uncertainty about if, when and where it would reappear at the surface.
Over the following days, a line of rising steam along the crack suggested that lava was continuing to advance. On Sunday, Aug. 24, the flow resurfaced about 1.3 kilometers (0.8 mile) farther down the rift zone, where, after forming a small pad of visible lava, the flow again cascaded into another crack and disappeared from view. As of Friday, a new line of steam progressing farther east along the crack indicated that lava continues to advance.
The irregular topography of the rift zone has kept the lava flow moving toward the northeast. But, as long as the lava continues to travel out of view within ground cracks, forecasting a precise flow path will remain difficult.
At the time of this writing on Friday, the June 27th lava flow did not pose an immediate threat to any residential area. However, HVO and HCCDA continue to closely track the flow with daily overflights of the area, which will continue as long as warranted.
We encourage you to stay informed about the flow. Daily eruption updates are posted on the HVO website (http://hvo.wr.usgs.gov) every morning, and maps and photographs of the flow are added after each HVO overflight.
Kilauea activity update
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 lake level was roughly 50-55 meters (165-180 feet) below the rim of the Overlook crater on Friday.
On the East Rift Zone of Kilauea Volcano, the June 27th flow from Pu‘u ‘O‘o remained active. The farthest point on the steaming ground crack was 11.9 kilometers (7.4 miles) from the vent and 2.6 kilometers (1.6 miles) from the east boundary of the Wao Kele o Puna Forest Reserve on Friday. Within the Pu‘u ‘O‘o crater, glow was visible above several outgassing openings in the crater floor.
There was one felt earthquake during the past week across the Hawaiian Islands. On the previous Friday, Aug. 22, at 2:37 a.m., a magnitude-4.2 earthquake occurred 55 kilometers (34 miles) southwest of Maunaloa, Molokai, at a depth of 6 kilometers (4 miles).
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 earthquake data, and more; call 967-8862 for a Kilauea summary; 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.