PAHOA, Hawaii—Hawaii's Kilauea volcano soon could send boulders and ash shooting out of its summit crater in the kind of explosive eruption last displayed nearly a century ago.
Scientists said yesterday the risks of an explosive summit eruption will rise in coming weeks as magma drains down the flank of the volcano toward the area where it began erupting lava in a residential neighbourhood last week.
A summit explosion also could release ash, steam, and sulfur dioxide emissions.
Kilauea has destroyed 36 structures, including 26 homes, since it began releasing lava from vents about 40 km east of the summit crater.
There are now 15 of the vents spread through Leilani Estates and neighbouring Lanipuna Gardens.
But in the weeks ahead, the summit crater could eject blocks up to 1.8 metres in diameter a little less than a mile away, the United States Geological Survey said.
It also may send pebbles shooting into the air several miles away, it noted.
Distant towns such as Hilo, about 50 km away, could get a dusting of ash.
The receding lava lake resembles conditions seen before a major summit eruption in 1924, said Tina Neal, scientist-in-charge at the USGS Hawaiian Volcanoes Observatory.
That explosion killed one person and sent rocks, ash, and dust into the air for 17 days.
This event could occur again when the summit lava lake drops so low that groundwater is able to flow into the conduit that feeds magma to the crater.
The magma would heat the water, sending steam into the air that would push any accumulated rocks out in an explosion.
Don Swanson, a geologist with the Hawaiian Volcano Observatory, said the magma likely is to drop below the water table around the middle of the month.
Scientists don't know how long after that it an explosion could occur.
“We suspect it's a rapid process. We really don't know for certain,” he told reporters on a conference call.
No one lives in the immediate area of the summit crater.
Hawaii Volcanoes National Park, which includes the crater and surrounding region, announced yesterday it will shut down tomorrow in anticipation of the possible explosive event.
“It seems pretty safe to me right now but they'd know best,” said Cindy Woodd, who was visiting from B.C.
“We don't know what's going on underground," she noted. "Life and safety is what's most important.”