Meetings held on lava flow advancing on Pahoa

September 1, 2014 8:39 pm 0 comments

In response to the USGS Hawaiian Volcano Observatory’s news release that Kīlauea’s June 27th lava flow could become a concern for communities downhill of the Pu‘u ‘Ō‘ō vent, the Hawaii County Civil Defense Agency (HCCDA) quickly organized a series of informational meetings.

To date, four meetings have been held at the Pāhoa 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’s Scientist-in-Charge, Jim Kauahikaua, and HCCDA’s Director, 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 ‘Ō‘ō 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 ‘Ō‘ō. 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 ft/day), but as fast as about 500 meters per day (1,600 ft/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 Kīlauea 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 August 24, the flow resurfaced about 1.3 km (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 August 29, 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 (August 29), 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 every morning, and maps and photographs of the flow are added after each HVO overflight.

This photograph (left) and thermal image (right) of the June 27th lava flow were taken at the same time on August 28, 2014. Distant plumes of blue smoke mark the farthest active surface lava, which is also shown as small hot spots in the thermal image. The bright yellow patch in the center of the thermal image shows the pad of still-hot, but inactive, lava that emerged from a ground crack earlier this week. East of this lava pad, new steaming (shown by arrows) suggests that lava is continuing to advance below the surface along a ground crack. Direct views into the crack were not possible due to thick vegetation, but thermal images of the steaming areas revealed temperatures up to 190 degrees Celsius (370 degrees Fahrenheit), further evidence of lava moving through the crack. The most recent map of the June 27th flow is posted at http://hvo.wr.usgs.gov/maps/.  USGS images.

This photograph (left) and thermal image (right) of the June 27th lava flow were taken at the same time on August 28, 2014. Distant plumes of blue smoke mark the farthest active surface lava, which is also shown as small hot spots in the thermal image. The bright yellow patch in the center of the thermal image shows the pad of still-hot, but inactive, lava that emerged from a ground crack earlier this week. East of this lava pad, new steaming (shown by arrows) suggests that lava is continuing to advance below the surface along a ground crack. Direct views into the crack were not possible due to thick vegetation, but thermal images of the steaming areas revealed temperatures up to 190 degrees Celsius (370 degrees Fahrenheit), further evidence of lava moving through the crack. The most recent map of the June 27th flow is posted at http://hvo.wr.usgs.gov/maps/. USGS images.

Kīlauea activity update

The summit lava lake within Halemaʻumaʻu Crater produced nighttime glow that was visible via HVO’s webcam over the past week. The lava lake level was roughly 50‒55 m (165‒180 ft) below the rim of the Overlook crater on Friday, August 29.

On the East Rift Zone of Kīlauea Volcano, the June 27th flow from Puʻu ʻŌʻō remained active. The farthest point on the steaming ground crack was 11.9 km (7.4 mi) from the vent and 2.6 km (1.6 mi) from the east boundary of the Wao Kele o Puna Forest Reserve on August 29. Within the Puʻu ʻŌʻō 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 Friday August 22, 2014, at 2:37 a.m., HST, a magnitude-4.2 earthquake occurred 55 km (34 mi) southwest of Maunaloa, Moloka`i, at a depth of 6 km (4 mi).

Visit the HVO website for past Volcano Watch articles and current Kīlauea, Mauna Loa, and Hualālai activity updates, recent volcano photos, recent earthquake data, and more; call (808) 967-8862 for a Kīlauea summary; email questions to askHVO@usgs.gov.

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

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