The explosion from the Overlook vent within Halemaumau crater at Kilauea Volcano's summit produced a volcanic cloud that reached as high as 30,000 feet (about 9,100 meters) above sea level and drifted northeast, according to HVO.
"This is the sort of explosive activity that was anticipated", said USGS geophysicist Mike Poland, who was based at Kīlauea from 2005 to 2015.
"I think it's going to be a series of explosions similar to the one that happened this morning, and that's based on what happened in 1924, which is really our only analog", he said of the almost century old event, which lasted 2-1/2 weeks and killed one person who was hit by a "ballistic block".
US Geological Survey geologist Michelle Coombs described the event as "energetic, but short-lived" and said most of the debris ejected from the crater likely fell near the explosion site.
Thursday's eruption lasted only a few minutes, said Coombs who called it "a big event that got people's attention, but did not have widespread impact".
Time lapse images taken from a camera at the Gemini Telescope on the Big Island captured the eruption plume just before sunrise. Pahala is the closest town west of the summit crater.
"Ash fall was pretty localised to volcano village area and volcano national park".
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Thursday's event was, if not the big one, then certainly a big one, researchers said.
This increases the risk of steam-powered explosions as the magma meets underground water. But this is not Kilauea's first massive eruption.
This is because Kilauea is a so-called shield volcano, which is typically broader in shape and has lava that is relatively fluid.
PAHOA, HI - MAY 16: Eruptive activity from the Kilauea volcano continues in the vicinity of fissure 17 with cooling lava (center and center left) on Hawaii's Big Island on May 16, 2018 in Pahoa, Hawaii.
Other than phreatic eruptions can still pose a deadly threat to anyone near the eruptive vent - which is somehow extremely hard to forecast, Poland stated. More than 1,000 people have been evacuated so far.
In another news conference Thursday, the deputy scientist in charge of the Hawaii Volcano Observatory, Steve Brantley, said the lava flows in the east rift zone have slowed in recent days.
Phreatic eruptions are "much more random", Poland said.