Lava, ash, thunder and lightning spewed from the Taal Volcano in Philippines on Monday as thousands of residents fled the region along roads choked by cars and ominous darkness.
The Philippine Institute of Volcanology and Seismology warned that a "hazardous explosive eruption" was possible within hours to days.
President Rodrigo Duterte ordered families in nearby communities to evacuate to safer ground, a process made difficult by the poor visibility and, for many, a lack of transportation. Hundreds of thousands of people may ultimately flee the region, officials said.
"Taal Volcano entered a period of intense unrest," the volcano institute said in a statement. "This magmatic eruption is characterized by weak lava fountaining accompanied by thunder and flashes of lightning."
Philippine Defense Secretary Delfin Lorenzana warned that the "worst-case scenario" for Taal could be similar to the eruption of Mount Pinatubo, 90 miles to the north, that killed 800 people and rendered 200,000 homeless in 1991.
"Remember Pinatubo – the entire mountain collapsed during the eruption," Lorenzano said. "That's what we are fearing, that the eruption would cause the entire island to rise and scatter debris on the nearby areas."
Taal started acting up Sunday, spewing enough ash, steam and even smaller rocks nearly 10 miles into the air. The debris forced the airport in Manila, 65 miles away, to shut down for several hours. More than 500 flights were canceled, and authorities warned that the airport could again be closed if conditions worsen.
"We can never predict the actions of this volcano," Lorenzana said.
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Tracy Gregg, an associate professor of geology at University at Buffalo, agreed with the Philippine government's assessment. She said that nearby Lake Taal is actually a volcanic crater formed from at least four "cataclysmic" eruptions more than 500,000 years ago.
Taal Island, essentially the volcano, was formed from subsequent, smaller eruptions.
"The truth is that we have no good precedent for how such a large volcano gears up into a cataclysmic eruption," Gregg told USA TODAY. "We know that such eruptions occur ... but we don't know what specific advance signs such a gigantic eruption would give us because we've never witnessed one."
She said that could be what Taal is revving up for. But she said it also could simply be venting some extra pressure – "like a pot will boil over on the stove."
Taal is among two dozen active volcanoes in the Philippines. The country is part of the Pacific “Ring of Fire,” a seismically active region prone to earthquakes and volcanic eruptions.
At least 30,000 people had fled homes in Batangas and Cavite province by Monday, the nation's disaster response team said. More than 15,000 people had fled to emergency shelters Monday, the Philippine News Service reported.
Irene de Claro, a mother of four, worried about her father, who stayed in their village in Agoncillo town in Batangas while the rest of the family fled in panic.
“My father is missing. We don’t know too what happened to our house because the ash was up to our knees," she said. "It was very dark and the ground was constantly shaking when we left.
“Most likely there’s nothing for us to return to. We’re back to zero.”
In the town of Balete, Mayor Wilson Maralit said some panicked residents were more interested in saving the livestock that provides their livelihood as they were in saving themselves.
“We’re trying to stop them from returning," he told DZMM radio. "Ad warning that the volcano can explode again any time and hit them.”
Contributing: The Associated Press
This article originally appeared on USA TODAY: Taal volcano: 30,000 flee lava, ash in Philippines