Giant rocks spewing from Hawaii volcano summit

Ash emissions from the summit at Hawaii's Kilauea volcano decreased, prompting the cancellation of an ash fall advisory.

There are occasional bursts of ash coming from the crater causing ash to fall downwind to several communities, though there are only trace amounts, said the Hawaiian Volcano Observatory. Ash plumes on Tuesday had spouted as high as 12,000 feet (3,657 metres) into the air, scientists said.

These plumes are separate from the lava eruptions happening about 40 kilometres away from the summit, where about 20 lava fissures have destroyed more than two dozen homes and forced the evacuation of about 2000 residents.

Dense, large rocks roughly 60cm in diameter were found in a parking lot a few hundred metres away from Kilauea's summit crater, which reflect the "most energetic explosions yet observed and could reflect the onset of steam-driven explosive activity," the Hawaiian Volcano Observatory said in a statement, and continues to monitor activity.

This image by the US Geological Survey shows sulphur dioxide plumes rising from the fissures viewed from the Hawaiian Volcano Observatory overflight. Photo / AP

Earthquakes continue to shake the Big Island, with the most severe at around 8.30am producing a 4.4 magnitude quake. The Pacific Tsunami Warning Center says there is no tsunami alert at this time.

Scientists say earthquakes may shake loose rocks underground and open up new tunnels for lava to flow.

Hawaii Governor David Ige said the state is forming a joint task force that could handle mass evacuations of the Big Island's Puna district if lava from Kilauea volcano covers major roads and isolates the area. The troops may be needed for emergency evacuations, search and rescue, clearing debris and other duties.

On Tuesday, the volcano discharged ash because of rocks falling into the summit, US Geological Survey geophysicist Mike Poland said.

"There is very little wind at the summit," he said. "The plume, it's not near as ashy as it was yesterday, and it's rising more or less vertically over the summit region."

Because of the ash, USGS scientists operated from a backup command centre at the University of Hawaii at Hilo.

Poland did not have an immediate height on the plume on Wednesday since scientists were not staffing the observatory at the summit. They will have to rely on remote observations, he said.

"Things seem to be progressing largely as they have been, except for a shift in wind and less ash," Poland said.

Scientists remained on alert for more violent activity. Geologists have warned that the summit could have a separate explosive steam eruption that would hurl huge rocks and ash miles into the sky. But it's not certain when or if that might happen.

For those on the ground near the lava vents, health warnings were issued because of dangerous volcanic gases.

An air-quality alert was in effect for an area near the Lanipuna Gardens subdivision. That area was evacuated shortly after the eruption began May 3. Most fissures are in that subdivision or the adjoining Leilani Estates neighborhood.

Several fissures remained active Wednesday, producing lava spatter. Lava from one fissure that had been clearing a path toward the ocean, about 2 miles (3 kilometers) away, had not advanced in the last 24 hours.

- AP