The floor of the volcano's caldera (the bowl where lava erupts) is deflating, causing stress at the volcano's base. They expect similar and possibly stronger explosions to occur from the summit crater.
Hawaiian Volcano Observatory and Hawaii National Park staff members were evacuated ahead of the eruption, according to the USGS.
The highway is the main thoroughfare for residents living in Volcano and Kau.
Earthquakes continue to shake the Big Island, with the most severe at around 8:30 a.m. producing a 4.4 magnitude quake.
"We are leaving Highway 11 open at this time, but will close it if it becomes unsafe for motorists", said Chief Ranger John Broward.
"We're all safe, and I wish they'd open the park back up, but they have to keep it safe for everybody", said Ken McGilvray, an area resident.
Hawaii Gov. David Ige says 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. There was no tsunami alert.
"Protect yourself from ash fallout", it said.
The eruption could not only enshroud large areas of the Big Island in volcanic ash and smog but other Hawaiian Islands and potentially distant areas if the plume reaches up into the stratosphere and ash is carried by winds.
An explosive eruption at Hawaii's Kilauea volcano has sent ash thousands of metres into the sky.
The explosion came at about 6 a.m. after two weeks of volcanic activity and the opening of more than a dozen fissures east of the crater that spewed lava into neighborhoods, said Mike Poland, a geophysicist with the U.S. Geological Survey.
About two hours later, Poland said the webcam view showed a dusty plume rising from the summit.
Instead, they will operate from a backup command center at the University of Hawaii at Hilo. Geologists have warned that the summit could have a separate explosive steam eruption that would hurl huge rocks and ash miles into the sky.
In this Tuesday, May 15, 2018 photo provided by the U.S. Geological Survey, highly viscous lava oozes from the edge of a flow spreading slowly from fissure 17 at Kilauea Volcano, in Hawaii.