MANILA, Philippines – The Philippine Institute of Volcanology and Seismology (Phivolcs) confirmed at midnight on Thursday, June 6, that thunderstorms over Negros Island’s Kanlaon Volcano generated volcanic sediment flows or lahars, as seen in various social media posts.

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Moderate to heavy rain from the thunderstorms mixed with debris from the volcano early Wednesday afternoon, June 5, producing lahars on Kanlaon’s southern slopes.

“These lahars began approximately around 1 pm and lasted 25 minutes based on the seismic record,” Phivolcs said in an advisory.

The lahars then deposited “gray cohesive mud, plant debris, and gravel” in at least four waterways:

• Tamburong Creek, which courses through Biak-na-Bato and Calapnagan, La Castellana, Negros Occidental
• Intiguiwan River in Guinpanaan and upstream Baji-Baji Falls in Cabacungan, La Castellana, Negros Occidental
• Padudusan Falls, Masulog, Canlaon City, Negros Oriental
• Binalbagan River, which drains the southern flank of Kanlaon Volcano

“The lahars were generally channel-confined, but flows along Tamburong Creek overflowed and dumped a few centimeters of deposit on a stretch of the main road in Biak-na-Bato, rendering this impassable to motorists,” added the agency.

More rain, lahars

Citing a forecast of the Philippine Atmospheric, Geophysical, and Astronomical Services Administration, Phivolcs said more thunderstorms might bring heavy rain to Negros Island on Thursday.

The rain “could generate lahars, muddy streamflows, or muddy run-off in the abovementioned [waterways] and other rivers draining the southern Kanlaon edifice.”

“Phivolcs thus strongly recommends increased vigilance and readiness of communities along rivers draining southern Kanlaon,” the agency said.

“These communities and local government units are advised to continually monitor weather conditions and take preemptive response measures for their safety from potential lahars.”

Kanlaon Volcano erupted last Monday, June 3, its first eruption in nearly six and a half years. This prompted Phivolcs to place the volcano under Alert Level 2, which means there is “increasing unrest” and “further explosive eruptions” are possible. – Rappler.com