Halema'uma'u still fuming but may be simmering down
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The Kilauea summit eruption that began with a bang at Halema'uma'u Crater on March 19 stopped spewing rock particles in mid-December, but continues to vent a lot of sulfur dioxide gas.
The March-to-December eruption was Kilauea's longest summit eruption since 1924.
Whether it has truly ended or is "in repose" remains to be seen, say scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory on the Big Island.
"Several lines of evidence confirm a decrease in activity at the vent in Halema'uma'u Crater," scientist-in-charge Jim Kauahikaua wrote in an update two weeks ago. They are:
During its latest event, scientists estimate, the summit crater has so far ejected 2,540 cubic yards of tephra — rock, rock fragments and dust.
That's enough to cover a standard football field to a depth of just over 17 inches.
Volcanically speaking, that's a tiny amount, said Janet Babb, the observatory's public information geologist.
"For comparison, the volume of ash erupted from Mount St. Helens on May 18, 1980, would cover a football field to a depth of at least 150 miles," she said.
Eight explosive eruptions (March 19, April 9 and 16, Aug. 1 and 27, Sept. 2, and Oct. 12 and 14) accounted for more than 80 percent of the total volume of solids ejected from Halema'uma'u in 2008.
Sulfur dioxide levels have not yet dropped enough to safely reopen areas of Hawai'i Volcanoes National Park that have been closed since February, when unsafe emission levels started coming from Halema'uma'u, Babb said.
"Background" levels of 150 to 200 metric tons per day of sulfur dioxide have been measured at Kilauea's summit for years, Babb said. But last March, the crater was spewing 10 times that.
The most recent emission rate, measured Jan. 7, was 770 metric tons a day — still too high to allow anyone but experts with special masks and protective equipment to venture close to Halema'uma'u, officials say.
Halema'uma'u Overlook, several park trails and the portion of Crater Rim Drive between the Jaggar Museum and Chain of Craters Road also remain closed.
Sulfur dioxide, SO2, is an invisible gas that can aggravate pre-existing heart and breathing problems such as asthma, and at high levels can be dangerous to anyone.
Since the first written accounts of Halema'uma'u in 1823, the duration of its eruptions has ranged from over a century to less than a day, according to the observatory Web site.
One scientist described efforts to unravel the mystery of the summit vent as being "perched on Pele's roof, trying to understand what is going on inside the house by watching smoke rise from the chimney and listening very carefully to the sounds coming from within."
Meanwhile, up to 1,500 people a day are visiting Hawai'i County's viewing area (open 2 to 10 p.m. daily) outside the national park, on the Kalapana side of the volcano, said Quince Mento, the county civil defense administrator.
There, spectators can safely watch the glow of molten lava entering the ocean after dark, or see the steam plume by day.
