MANILA: The Taal Volcano, which burst into life on Sunday, could remain restive for months or even years, warned a volcanology expert.
Thousands of people living on the volcano island fled their homes as the volcano sent a 1km-high column of ash into the sky.
Winds carried the ash north, as far as Metro Manila.
The Manila Times reported that the province of Batangas had declared a state of calamity.
Antonia Bornas, the Volcano Monitoring and Eruption Prediction Division chief of the Philippine Institute of Volcanology and Seismology (Phivolcs), said this could just be the start of a long seismic episode for Taal.
She said the activity could last months or years.
The volcano is at Alert Level 4 of a five-stage alert ladder, meaning a “hazardous explosive eruption is possible within hours to days”.
In 1911, the volcano’s eruption lasted only three days, while in 1754, it lasted seven months.
Phivolcs supervising science research specialist Winchelle Sevilla said the seismic activity could intensify and become a volcanic tsunami.
A tsunami could occur when water is displaced by deformations on the lake floor caused by rising magma.
On Monday, a “weak” lava fountain gushed from the volcano for an hour and a half.
Phivolcs director Renato Solidum said the fountain indicated that lava had reached the volcano’s crater.
“However, it does not mean the volcano has entered the hazardous explosive eruption (phase).”