Nearly 1,500 residents have been ordered to evacuate their homes after Hawaii's Kilauea Volcano erupted, sending molten lava through forests and bubbling up on paved streets.
Officials could not predict how long Thursday's eruption may last, prompting Hawaii's governor to activate the National Guard to help with evacuations and provide security to about 770 structures left empty.
There were no immediate reports of injuries.
Hawaii County officials said steam and lava poured out of a crack in the community of Leilani Estates near the town of Pahoa on the Big Island.
Footage shown on local television showed lava spurting into the sky from a crack in a road. Drone footage showed a line of lava snaking through a forest.
Resident Jeremiah Osuna captured drone footage of the lava burning through the trees, a scene he described as a "curtain of fire".
"It sounded like if you were to put a bunch of rocks into a dryer and turn it on as high as you could. You could just smell sulfur and burning trees and underbrush and stuff," he told Honolulu television station KHON.
Asta Miklius, a geophysicist with the USGS Hawaiian Volcano Observatory, said there is no way to know exactly how long the eruption will continue.
"One of the parameters is going to be whether the summit magma reservoir starts to drain in response to this event, and that has not happened yet," he said.
"There is quite a bit of magma in the system. It won't be just an hours-long eruption probably, but how long it will last will depend on whether the summit magma reservoir gets involved. And so we are watching that very, very closely."
County, state and federal officials had been warning residents all week that they should be prepared to evacuate, as an eruption would give little warning.
Officials at the US Geological Survey raised the volcano alert level to warning status, the highest possible.
More than 100 people were staying the night at two shelters after the eruption, with many more at the homes of relatives and friends.
Henry Calio says he noticed cracks in the driveway of his retirement home in Leilani Estates. His wife Stella then took a call from an official who told them to get out immediately.
The two feared that they might lose their home.
"This is our retirement home, this is our retirement dream," Mr Calio said.
American Red Cross disaster services director Debbie Weeks said 100 people were staying in one shelter with about 20 more outside it in their cars. Seven more people were at another shelter.
The US Geological Survey said new ground cracks were reported on Thursday afternoon. Hot vapour emerged from a crack and spattering lava began to erupt.
Scientists said areas downslope of the erupting vent were at risk of being covered by lava.
Leilani Estates appeared to be at greatest risk, but scientists said new vents and outbreaks could occur and it is not possible to say where.
The eruption comes after days of earthquakes rattled the area's Puna district. A school was closed and several roads cracked under the strain.
A magnitude 5.0 earthquake was recorded hours before the eruption began.
The Puu Oo crater floor began to collapse on Monday, triggering a series of earthquakes and pushing the lava into new underground chambers.
The collapse caused magma to push more than 16km downslope toward the populated south east coastline of the island.
USGS geologist Janet Babb said the magma crossed under Highway 130, which leads to a popular volcano access point, on Tuesday.
Hawaii County Civil Defence Agency closed the area to visitors on Tuesday and ordered private tour companies to stop taking people into the region.