The Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday, Jan. 21, observed an increase in volcanic activity of Kanlaon Volcano in Negros Island.

In an advisory issued at 10:30 a.m., Phivolcs said 18 volcanic earthquakes were recorded within the last 24 hours by the Kanlaon Volcano Network.

"These included four very shallow tornillo signals that are associated with magmatic gas movement along fractures within the upper volcanic slopes," it said.

Meanwhile, it noted that degassing activity from the crater has been "very weak to moderate" and "low" steam-laden plumes that rose only 200 meters were last observed on Jan. 16.

In addition, Phivolcs said that ground deformation data from continuous GPS measurements indicate short-term slight inflation of the edifice since mid-October 2021.

"The increased seismic activity and short-term ground deformation are likely caused by shallow hydrothermal processes beneath the edifice that could generate phreatic or steam-driven eruptions from the summit crater," it explained.

Phivolcs reminded the public that Kanlaon Volcano remains under Alert Level 1, which means that it is at an "abnormal" condition.

"The local government units and the public are strongly reminded that entry into the four-kilometer radius permanent danger zone must be strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions," Phivolcs said.

"Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ejecta from any sudden phreatic eruption can be hazardous to aircraft," it added.