Going with the flow

While the 1-year-old June 27 lava flow hasn’t threatened populated areas since March, geologists at the Hawaiian Volcano Observatory continue to study samples that might help fine-tune projections if it sends another 2,000-degree river of molten rock toward homes in lower Puna.

That is no simple task.

Frank Trusdell, HVO geologist, said it requires analyzing thousands of slides and counting crystals “one by one.”

“We got all the samples, sent them in for chemical analysis, and now we’re doing the nitty-gritty science,” he said.

But the analysis could help researchers determine if there were temperature and chemical changes in the flow as it advanced downslope and why it continued to stall about 14 miles from Kilauea’s Pu‘u ‘O‘o vent, just shy of major roads, homes and businesses.

Such changes could increase the lava’s viscosity and make its advance more sluggish.

Trusdell, who is conducting the research with HVO geologist Tim Orr, said they could have some solid results in the fall. A scientific paper might take another year to publish.

That data is important since the flow that started June 27, 2014, was the Pu‘u ‘O‘o eruption’s first to stretch more than a few miles without being impeded by the ocean.

The vent has been erupting for 32 years, with flows heading primarily to the south where it covered the communities of Kalapana and Royal Gardens in the 1980s and ’90s. The June 27 flow remains active about five miles from the vent and continues to flow to the northeast.

When it started, researchers didn’t know how far it could go, but understanding changes in the flow as it advances could explain why — to the benefit of thousands — it struggled to advance farther and whether that could be replicated again.

“We could sample in real time and look at the crystallinity and make some judgments of how viscous is this lava, which would then provide some information as to how far the lava goes,” Trusdell said. “It’s still premature for us to actually go there.”

Temperature and gas content are just a few of the factors that determine how a lava flow behaves. There’s also eruption output, leaks in the lava tube, and a flow’s own alterations to the landscape that can determine whether a community stays safe or is inundated by hot molten rock.

If any of those factors were different, the flow could still have reached Highway 130, geologists cautioned.

“There’s not an invisible wall there that kept the flows from advancing downslope,” said Steve Brantley, HVO deputy scientist-in-charge.

When the flow was advancing toward Pahoa, geologists also had success in predicting pathways for the flow, even if it remained unknown how far it would go.

That’s because for the first time they combined topographical data, infrared images, and a computer code developed by HVO geologist Matt Patrick to assess which direction the flow could be pulled and which path of steepest descent it will follow.

“We were trying to simulate the dynamic nature of the flow,” Patrick said, “(and) show the full potential or the possibility of different flow paths from any starting point.”

Unlike a‘a flows, pahoehoe events tend to break out behind its leading edge, making its path harder to predict.

Jim Kauahikaua, HVO geophysicist, said that has always made it difficult to create simulations for these type of flows.

“There’s nothing that really simulates pahoehoe flows at this point,” he said.

Kauahikaua was responsible for developing maps showing the many steepest paths of descent that the flow for the most part followed.

“I think it served pretty well for our purpose here,” he said. “It caused dismay for a fewer number of people at any one time, I think.”

But, with the flow already having carved a path downslope, some of those steepest descent lines are already filled in.

Geologists say that would have an impact on flow’s path if it again found its way downslope.

That could be a good thing for Pahoa. If lava travels to the north of the earlier flow, the hardened lava could act initially as a bit of a buffer.

But lava also could travel along the south margin of the earlier flow and make its way back to town.

For now, it’s a matter of wait and see.

Geologists say the flow is active in multiple areas near the vent, allowing it to mostly spread out and cover the same terrain without advancing too far forward.

The flow also has filled in low points that channeled it initially toward Pahoa.

For the time being, Orr said the flow is behaving similarly to the Kahaualea 2 flow that the June 27, 2014, event ended.

Until the flow becomes more focused, this activity could remain near the vent for awhile, geologists say. How long, though, is unclear.

“These flows can be active in this area potentially for years,” Orr said. “We don’t know.”

“Nothing is imminent right now for sure,” he said.

Email Tom Callis at tcallis@hawaiitribune-herald.com.