Phivolcs observed a “light grayish steam and ash column” that reached an approximate height of 600 meters above the crater rim at 8:11 a.m. on Saturday.

Due to the current activity of the volcano, Phivolcs raised Bulusan Volcano's status from Alert Level 0 to Alert Level 1, which is described as “abnormal.”

“The ash ejection was reflected as an explosion-type earthquake with a duration of 57 seconds,” it said.

The agency's seismic records before the event showed four volcanic earthquakes.

Field investigation by volcanologists disclosed that areas six to 10 kilometers (km) northwest of the crater were adversely affected by traces of ash.

These are barangays Rangas, Aniog, Cogon, and Juban Proper, all in Juban town, and Casiguran Proper and San Antonio, both in Casiguran town.

Phivolcs said that Alert Level 1 status indicates that the volcano's current activity may be a sign of hydrothermal disturbance under the volcano, which may lead to more steam and ash ejections.

Phivolcs Director Renato Solidum Jr. warned the public against entering the four-kilometer permanent danger zone from the volcano.

Phivolcs said Bulusan is one of the country’s active volcanoes that has already erupted 15 times.

Its latest major eruption occurred from November, 1994 to January, 1995.

Its earliest recorded eruption occurred in 1852, followed by 1886, 1892, and 1894. It took a lull for 22 years before rumbling anew on January 16, 1916, spewing mud and ash for five straight days, triggering landslides. More volcanic activities followed until December 25, 1933.

From that time, Bulusan rested for 45 years until it ejected ash clouds on June 28, 1978. More volcanic activities followed later.

Quakes rock Bicol, Batanes

Meanwhile, an earthquake measuring 5.8-magnitude on the Richter scale and at least two aftershocks jolted Bicol Region on Saturday.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said another moderate 5.2-magnitude earthquake also jolted Batanes before dawn on Saturday.

The tremor, which was felt at 1:43 a.m., had its epicenter located at 310 kilometers (km) southeast of Basco, Batanes.

The East Luzon trench is being looked on as the possible origin of the earthquake.

Phivolcs said there was no report to damage to property or loss of lives due to the earthquake in Batanes.

Meanwhile, the tremor in Bicol Region was felt at 12.41 a.m. with the epicenter 24 km southeast of San Pascual town located in Burias Island in Masbate province.

Phivolcs said the earthquake was of tectonic in origin.

Intensity V was recorded in Lignon Hill in Legazpi City; Intensity IV in Masbate City, Sorsogon City, Irosin in Sorsogon and Sto. Domingo in Albay; and Intensity II in Cebu City.

Before Phivolcs recorded the 5.8-magnitude earthquake in San Pascual, two tremors measuring 4.4 and 3.7 were already documented at 10:04 p.m. and 10:40 p.m. respectively on Friday.

A magnitude 4.1 aftershock was felt at 1:45 a.m. on Saturday with the epicenter at 39 km southeast of San Pascual town in Burias Island.

Another aftershock measuring 3.6 was recorded at 2:25 a.m. on Saturday with the epicenter at 23 km southwest of San Pascual.

Last Thursday, a 5.2-magnitude quake already hit San Pascual town in Burias Island.

Phivolcs said all the tremors were of tectonic in origin.

Ellalyn de Vera, Manila Bulletin