A week after the Bulusan Volcano erupted, the Philippine Institute of Volcanology and Seismology (Phivolcs) on Sunday morning recorded another phreatic eruption due to shallow hydrothermal activity.

The latest phreatic eruption at 3:37 a.m. lasted 18 minutes, but Phivolcs said the eruption plume was not visible in the camera monitors.

As a result, the Manila International Airport Authority recorded at least eight domestic flights that were canceled due to Bulusan's activity.

The affected flights were Cebu Pacific (5J) 325/326, Manila-Legazpi-Manila; CebGo (DG) 6111/6112, Manila-Naga-Manila; and PAL Express (2P) 2923/2924 and 2P 2919/2920, Manila-Legazpi-Manila.

Phivolcs earlier warned that the increased seismic activity or number of volcanic quakes observed may indicate that a phreatic eruption could occur.

For the past 24 hours, 136 volcanic earthquakes caused by movements or eruptions of magma from the volcano were recorded. Plumes reaching 150 meters high have also been observed for the past 24 hours.

A weaker eruption is based on the height of the plume coming out of the crater.

Sulfur dioxide flux was 613 tonnes on June 10, according to Phivolcs.

Alert Level 1 (low level unrest) remains.

Entry into the 4-kilometer radius permanent danger zone must be strictly prohibited and vigilance in the 2-kilometer extended danger zone on the southeast sector must be exercised due to the increased possibilities of sudden and hazardous phreatic eruptions.

Pilots are advised to avoid flying close to the volcano’s summit as ash from sudden phreatic eruption can be hazardous to aircrafts.

Phivolcs likewise urged those living within valleys and along river or stream channels, especially on the southeast, southwest and northwest sector of the edifice, to be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should phreatic eruption occur. (PNA)