MANILA -- It was a typical Sunday for most Filipinos on January 12 when the Taal Volcano in Batangas province began spewing ashes in the afternoon.
Alert Level 3 was raised only about two hours after Alert Level 2 was announced. By 7:30 p.m., authorities raised the Alert Level 4 status, meaning hazardous explosive eruption is possible within hours to days, over the volcano.
Many people were caught off guard. "Why so sudden?" some asked.
But for geologist Carlos Arcilla, director of the Philippine Nuclear Research Institute (PNRI), the volcanic eruption was not sudden.
"There was gas surge, base surge (pyroclastic surge). This is too fast, and if it hits someone in the danger zone, he or she would die," Arcilla told the Philippine News Agency (PNA) in an interview.
It has been a week since Taal Volcano's eruption, and the Philippine Institute of Volcanology and Seismology (Philvolcs) recorded fewer sulfur dioxide (SO2) emissions and volcanic earthquakes for the past 24 hours.
This is good news but Arcilla noted that this does not signify the volcano would calm down anytime soon.
Nobody could predict when a volcanic eruption would happen, Arcilla said, adding that things might escalate today and subside tomorrow.
He said that in the 1754 Taal eruption, the volcano was erupting for six months.
"There's no timetable," he said, noting that even if the eruption subsides for one month, it is not an assurance that there would be any hazardous eruption after.
As long as there are sulfur dioxide emissions, Arcilla said there is always risk for earthquakes, and volcanic inflammation.
Arcilla also refuted claims that Taal Volcano would only erupt after 55 years.
Seeing a record of low sulfur dioxide emission and few volcanic earthquakes is good news, but this has to be consistent, he added.
"There is a lot of data that need to be studied. It's hard to predict. Even if you see low SO2 emissions and few earthquakes for a week, the volcano would not calm in the near future," he said.
Arcilla said a volcanic eruption is still very dangerous even if the volcano does not reach the Alert Level 5 (hazardous eruption in progress).
"It's because (we're talking about) phreatic eruption. One cannot run away from gas. An N95 mask could not save him or her, since this mask is only used (to protect oneself) from the ashes," he said.
Arcilla cited as an example the Mount Pelee eruption in 1902, which had left thousands dead in a matter of minutes.
"They (people around Mount Pelee) saw the ash cloud. Everybody, except one, died," he said.
"You can compare a base surge to shaking a bottle of (soda). Gas would explode if you shake the soda bottle. You multiply that (impact) to one million times, and it would shock you," Arcilla said.
Arcilla noted that people could run from the lava flow but they could not run away from toxic gases.
"Look at the ash plume in Mount Pinatubo eruption. The plume reached 40 kilometers in height. The plume was emitted vertically. If it was emitted across or vertically, then that would be a problem as it would directly hit the people," Arcilla said.
He said people must understand the nature of eruption, adding that they should not think that the possibility of explosions would take much longer time.
Arcilla noted that even if it rains hard, for instance, this would not reduce the risk of big explosions.
The rain, he said, would only reach the surface, and would only be good to clean or wipe away the ashes.
"Understand also that there are at least 40 craters around Taal. There are craters beneath the lake," he said.
Phivolcs, he said, has the instruments vital to studying volcanic activities, and so the public should listen to it.
"If they (Phivolcs) would not warn the public and something happens, they would be blamed. If they warn the public and nothing happens, people would still blame them," Arcilla said.
"They must heed Phivolcs' advice, stay away from the 14-kilometer radius from Taal crater. They have the tools. They coordinate with international experts or scientists before issuing advisories. People should listen to them," he said. (PNA)