Manila: While communities around the Taal Volcano must stay vigilant, the head of the Philippine Institute of Volcanology and Seismology (Phivolcs) said Tuesday they have nothing to worry about. "They just have to stay vigilant and refrain from entering the permanent danger zone which is the whole Taal Volcano Island," Phivolcs Director Teresito Bacolcol told the Philippine News Agency in an interview.

According to Philippines News Agency, based on the 24-hour observation from 12 a.m. Monday to 12 a.m. Tuesday, there is an ongoing volcanic tremor in Taal since 3:37 a.m. Sunday. Bacolcol said continuous volcanic tremor may last for several days. "There were instances in the past when Taal Volcano had volcanic tremor for several days," he added.

Bacolcol explained that volcanic tremor is triggered by the continuous flow of magma or gas inside a volcano. This is different from volcanic earthquake, which usually happens when rocks inside the volcano break or crack. Moreover, volcanic earthquake's duration usually lasts for seconds.

Meanwhile, Taal Volcano is still under alert Level 1 (low-level unrest) and Bacolcol said "the possibility of a phreatic eruption is still there." Sulfur dioxide emission measured 377 tonnes on July 4. For the past 24 hours, weak emission of plume reaching 900 meters high was observed. Pilots are advised to avoid flying close to Taal Volcano, as airborne ash and ballistic fragments from sudden explosions may pose hazards to aircraft.