"We're beginning to see the cycle of clogging and pressure building and then the blast", Klemetti said.
Kilauea's falling lava lake has likely descended to a level at or below the water table, allowing water to run on to the top of its lava column and create steam-driven blasts, they said.
Driving conditions in the area may be risky and drivers are advised to pull off the road until visibility improves, according to Hawaii County Civil Defense. "Shelter in place if you are in the path of the ash plume".
"It's just time to go - it really, really is", she said, preparing to leave town.
But by 1:30 p.m. (7:30 p.m. EDT) reported ashfall was limited to only light, wet deposits about 3-4 miles (5-6 km) northwest of the summit, as rain over the volcano curbed the spread of ash.
Staffs for the Hawaiian Volcano Observatory and Hawaii Volcanoes National Park had previously evacuated Kilauea summit.
Such eruptions, last seen almost a century ago, have been a looming threat since Kilauea, one of the world's most active volcanoes, erupted almost two weeks ago.
Hawaii Volcanoes National Park officials said the caldera - the depression at the center of the volcano - dropped more than three feet (900 cm) overnight, triggering frequent earthquakes that have cracked highways in the area. He has gas masks to protect himself from the toxic fumes and ash.
Dramatic photos show lava pouring into residential neighborhoods around a series of volcanic fissures that have opened. The threat was significant enough, reports CBS News correspondent David Begnaud, that some first responders were pulled back from their positions on Thursday to safer areas.
Geologists say boulders the size of cows could be hurled from the summit if the explosions continue to strengthen.
Toby Hazel, who lives in Pahoa, near the mountain, said she heard "a lot of booming sounds". Several schools closed because of the risk of elevated levels of sulfur dioxide, a volcanic gas.
Coincidentally, Thursday's explosive event comes one day before the 94th anniversary of that death and on the 38th anniversary of the 1980 eruption of Mount St. Helens in Washington state.
More than 2,000 residents of the Big Island remain under mandatory evacuation as Kilauea continues to threaten nearby communities.