Lava from Hawaii's Kilauea volcano is oozing toward a main road. With the flow threatening to isolate about 8,500 people—many of whom rely on the highway to reach their jobs—everyone wants to know when the lava will halt its advance.
Geologists studying the situation have no answer, because there's no way to know how much lava will seep out.
Lava from Kilauea usually flows south, toward the ocean, so it was startling when on June 27 a newly opened fissure started sending lava in the opposite direction, toward the Kaohe Homesteads subdivision.
"It's sending flows in directions that haven't been threatened in a very long time," says Matthew Patrick, a geologist with the U.S. Geological Survey's Hawaiian Volcano Observatory on the rim of the Kilauea caldera.
The outflow from Kilauea—which has been erupting since 1983, making it one of the world's most active volcanoes—is defying about a half century of tradition. Other recent outbursts, such as the ones that buried the town of Kalapana in 1990 and again in 2010, tended to head southward toward the ocean.
This one has been traveling to the north, riding for some distance in a crack that kept the lava insulated after it emerged in late June from a fissure in the Puu Oo crater.
Predicting a Slow Threat
Using on-the-ground measurements, Patrick and his colleagues can forecast the potential paths that will be taken by the flow, which is about 10 miles (17 kilometers) long and moving 270 yards (250 meters) per day at the latest estimate. Satellites and planes have mapped the rocky terrain of the area in detail.
Using this topographic information, computer simulations have been generating continually updated maps over recent months showing probable routes of flow. But even these predictions could be thrown off by an unnoticed crack that channels the lava, or by a sudden surge of particularly runny flow.
The big unknown is how much material will ultimately emerge from the earth. Instruments can help scientists determine the rate of outflow at any given moment: One device charges lava with electricity, measuring how the electrically conductive lava interferes with radio waves to reveal the flow's cross section. Meanwhile, a radar gun aimed down a lava tube clocks its speed. But the discharge can speed up or slow down with little notice.
"The volcano in the past has repeatedly changed its mind," says Michael Garcia, a geologist at the University of Hawaii at Manoa. During a 1997 eruption, the underground lava tubes seized up, stopping the flow suddenly.
Subterranean swells detected by measuring the tilt of the ground near the summit, where the main magma chamber that feeds an eruption lies, provide at most only a few days of warning.
Preparing for Lava
With the full extent of the destruction impossible to predict, communities in the line of fire have been preparing. Diverting the lava isn't an option, says Kevin Dayton, executive assistant to the County of Hawaii mayor. "It creates at least as many problems at it solves. There haven't really been any examples of successful diversions, and there are cultural concerns as well."
No evacuations have been ordered for the dozens of homes in the Kaohe Homesteads area, which was grazed by the flow Monday. The 284 acres of empty property in the community are expected to provide a buffer zone.
The next community in potential danger is Pahoa, just over three miles (4.8 kilometers) from the current lava front. Businesses there have been holding "fire sales" to lighten their inventories.
To provide an alternate route for traffic, bulldozers and earth movers that broke ground on a $22.3 million park in Pahoa have been redirected to renovate two smaller roads located downhill from the main highway. This may prove to be merely a temporary fix; if lava overruns these roads, a more permanent but expensive solution being considered by officials is to rebuild a larger road buried by an eruption decades ago.