Thick, dark columns of ash poured from Halemaumau Crater on Tuesday, extending up to 12,000 feet above sea level and dropping ash as far as 18 miles downwind.
But geologists stressed the "big one" — the series of explosive eruptions feared when lava hits the water table — hasn't happened yet.
"Over the last few days we've seen the waxing and waning," said Michelle Coombs, USGS geologist. "It seems like the system up at the summit has been what we call somewhat opened, relieving that pressure. And so it intensified today but it wasn't the big one, so to speak."
Dramatic images Tuesday showed large plumes looming over the Volcano Golf Course. In Pahala, residents reported heavy vog and significant ashfall.
An ashfall advisory was issued for the Big Island's Ka'u district, and residents were being warned to prepare for air quality issues throughout the day.
Winds carried the ash southwest of the crater to a number of towns, including Pahala, Wood Valley, Punaluu and Hawaiian Oceanview Estates.
Those with respiratory illnesses are being urged to remain indoors to avoid inhaling particles, the National Weather Service said. Anyone who goes outside should cover their mouth and nose with a cloth or mask.
The ash could also harm crops and animals.
The warnings come as authorities continue to closely watch Kilauea's summit crater for explosive, steam-induced eruptions that could happen if lava hits the water table.
Fears of an eruption at the summit prompted the Hawaii Volcanoes National Park to shut down indefinitely Friday.
Scientists say an eruption at the crater would be potentially disastrous, sending rocks "the size of cows" flying as far as a half a mile and dropping thick ash as far away as Hilo.
The plumes emitting from the crater aren't from an eruption, however. Geologists say they're likely being created by rockfalls in the crater and gas explosions, though there's no way to confirm that.
Residents are being urged residents to avoid "excessive exposure to ash," which can irritate eyes and can make breathing more difficult.
Summary of #HVO #Kilauea VAN/VONA: Ash eruption at summit has increased in intensity. NWS radar & pilot reports show top of the ash cloud is as high as 10,000-12,000 feet above sea level. Ashfall and vog has been reported in Pahala (18 mi downwind). #KilaueaErupts pic.twitter.com/ChzRdu0Ch7
— USGS Volcanoes?? (@USGSVolcanoes) May 15, 2018
On Monday, when the plume was much less intense, residents in Ka'u said the increased activity at the summit already had them feeling sick. Several residents have reported having headaches, sore throats, and watery eyes as a result of ashfall.
"I do have neighbors and friends and family and it has created more problems for them," said Jessie Marques, a Pahala resident. "Now they tend to stay indoors ... it has created a breathing problem for them."
Marques, who has asthma, says that the heightened sulfur dioxide levels and ash particles has complicated her health.
"I have asthma and (the volcanic activity) has exacerbated it, but I'm taking more of my medication and I'm taking care," Marques said.
Residents also reported ash coating their cars, decks and buildings as a result of recent volcanic activity.
County officials went door-to-door Monday to hand out information about the ashfall and ways for residents to protect themselves from hazardous fumes and ash.
"There was really a thick layer of dust on our cars, and on our decks, and such so you can see and feel it," Marques added. "It's like black, grimy soot."
This story will be updated.
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