The Kilauea volcano is the youngest and most active on the island of Hawaii, and has been erupting almost continuously since 1983, according to the US Geological Survey. It's in the Hawaii Volcanoes National Park, a major tourist attraction.
Aerial shots show the Puu Oo volcanic vent southeast of Kilauea's caldera churning smoke after the eruption.
"The summit crater hosts an active lava pond and a vigorous gas plume," the USGS says. "Kīlauea ranks among the world's most active volcanoes and may even top the list."
Kilauea lava flows have threatened communities numerous times. "From 1983, when the Puu Oo eruption began ... residential areas were threatened and homes were lost," said Janet Babb of the USGS Hawaiian Volcano Observatory.
"Any time lava poses a threat to residents, it's a big deal."
There are 770 structures and 1,700 people in the area under mandatory evacuation, said Cindy McMillan, a spokeswoman for Gov. David Ige.