HILO — Geologists reassured Volcano residents Thursday it is highly unlikely that seismic activity at the summit of Kilauea will escalate to catastrophic levels.
“A 1 percent chance,” said Mayor Harry Kim, quoting Tina Neal, U.S. Geological Survey scientist-in-charge.
Volcano-area residents attending a Thursday night community meeting at Cooper Center remained fixated on that 1 percent, however.
Although Neal emphasized she predicts the pattern of seismic activity at Kilauea will continue as it has for the past two months, many residents pressed USGS representatives about what they should do if the worst should happen.
After lava broke out in lower Puna on May 3, the lava lake at Kilauea receded, causing ground subsidence and collapses around Halema‘uma‘u crater, which has more than doubled in size since the eruption began. The recession of the crater floor is accompanied by periodic tremors that release energy equivalent to a magnitude-5 earthquake, while hundreds of smaller quakes occur each day.
Hawaii County Civil Defense Administrator Talmadge Magno praised residents’ caution because the purpose of Thursday’s meeting was partly to get them thinking about their own emergency plans.
Magno said Volcano residents — particularly those in more isolated areas — should devise plans to leave the area quickly should disaster strike. Evacuation plans should include any required medications, financial information and pets and should be tailored for residents’ homes and workplaces.
One resident asked where the safest direction to go would be in the event of a disaster. Hawaiian Volcano Observatory geologist Don Swanson responded, saying north would probably be safer.
In the unlikely event that increased seismic activity produces pyroclastic surges — extremely hot and fast masses of gas and debris generated by volcanic eruptions — they are likely to follow terrain to the south and southwest, although they could still flow northward.
Pyroclastic surges were one of the potential — but very unlikely — hazards that USGS is monitoring for.
Swanson said there also is historical precedent for a greater collapse of the summit caldera, affecting areas outside the caldera’s radius.
“Twenty-two hundred years ago, we know the caldera was much bigger than it is now,” Swanson said.
HVO research geophysicist Kyle Anderson said Kilauea is a “long way from a massive collapse,” however.
While long-term predictions about the volcano’s activities are difficult, Anderson said USGS and HVO are watching for signs of increased seismic activity: primarily, increased frequency and intensity of quakes, as well as patterns of terrain deformation. Anderson said that, so far, no change in activity has been observed.
“We’ll know it when we see it,” Neal said.
Even without catastrophic activity, Kilauea’s murmurings have caused considerable damage to the area. Neal said the HVO building, located near the edge of Halema‘uma‘u, has become unusable, with sizable cracks through the building’s floors and fallen ceiling tiles.
Residents also brought up a sinkhole measuring about 5 feet in diameter and up to 30 feet deep that formed Thursday under Highway 11 near the 30-mile marker shortly before the meeting began.
Ben Hayes, chief of interpretation for Hawaii Volcanoes National Park, said park rangers cordoned off the sinkhole and controlled traffic around where it formed, near the Volcano Golf &Country Club. Traffic was reduced to one lane from late Thursday through Friday as crews worked on the hole.
The sinkhole was not connected to Kilauea’s internal magma tunnels, but was simply caused by subsidence brought about by the near-constant tremors at the summit. The subsidence eventually formed a void, which caused the road’s surface to collapse, Hayes said.
Magno said Civil Defense is having active discussions about alternate routes in case other roads become impassable due to road surface damage.
While many of the residents’ concerns were about what to do should the worst happen, one resident asked what to do should lava return to the summit crater.
Neal said that, although she does miss the glow of the lava lake, the return of lava to the summit would possibly be accompanied by potentially dangerous steam explosions.
“The return of lava may not be a good thing,” Neal said.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.