The Taal Volcano near the Philippine capital of Manila spewed fountains of lava 800 metres into the air on Tuesday, trembling with earthquakes continuously as tens of thousands of people flee villages blanketed by heavy ashfall.
Experts believe a more perilous eruption is due, and several new fissures cracking the ground nearby likely means magma is rising, the Philippine Institute of Volcanology and Seismology said.
The alert level since eruptions began on Sunday has been at four, indicating a hazardous eruption is possible in hours to days. About 50 volcanic earthquakes were detected over eight hours on Tuesday, the institute said.
“The speed in the rise of magma is important (in determining) when the volcano will have a strong eruption and if it will slow down and freeze," said Renato Solidum, who heads the institute.
"As of now, we don't see activities slowing down and the earthquakes still continue.”
The scenic volcano in the middle of a lake in Batangas province ,south of Manila, rumbled to life on Sunday in a powerful explosion that blasted a 15-kilometre column of ash, steam and pebbles into the sky. Clouds of volcanic ash blowing over Manila, 65 kilometers to the north, closed the country’s main airport on Sunday and into Monday.
More than 500 international and domestic flights were cancelled or delayed, affecting about 80,000 passengers.
Government work was suspended and schools were closed in a wide swath of towns and cities, including Manila, because of the health risks from the ash.
The small island where the 311m volcano lies has long been designated a “permanent danger zone,” though fishing villages have long existed there.
Those villages were all evacuated, though volcanology officials have called for a total evacuation of endangered communities within a 14km radius of Taal.
The volcano's last disastrous eruption, in 1965, killed hundreds of people.
It is the second-most restive of about two dozen active volcanoes in the Philippines, which lies along the Pacific “Ring of Fire."
A long-dormant volcano, Mount Pinatubo, erupted north of Manila in 1991, killing hundreds of people.