The colossal collapse of the Iriga Volcano
For today’s Bulkan Ng Bikol series, we head to Camarines Sur to learn about one of the rarest volcanic hazards in the region’s history!
The Philippine Institute of Volcanology and Seismology (PHIVOLCS) has listed Mt. Iriga as an active volcano, with its latest eruption dating back to 4 January 1642.
Mt. Iriga or Mt. Sumagang is a small andesitic stratovolcano rising to 1,143 meters immediately west of Lake Buhi. Locals also call this volcano Mt. Asog, its older name mentioned in the 1800’s Bikol folk epic Ibalong as a large mountain that sunk and created a lake.
There are various scientific studies confirming the massive collapse of the Iriga Volcano. These studies referred to this collapse as a debris avalanche that occurred during the Holocene (about 11,700 years ago – present) epoch.
Debris avalanche or sector collapse is the mass failure of the volcano flanks due to edifice instability. The triggering mechanism could be either a volcanic event, extreme rainfall, or tectonic movement. In the case of Mt. Iriga, a non-volcanic trigger caused the collapse of its summit and southern flanks. The collapse resulted in two primary debris avalanche deposits, one on the southwest side (Iriga debris avalanche) and the other southeast (Buhi debris avalanche) side of the mountain.
The Iriga volcano’s massive collapse is an indication that it may also occur to other volcanoes. This geological event is a more compelling reason to educate ourselves about the nature of the place we live in and appreciate nature’s process.
Discover more about geology and volcanoes in our upcoming exhibition when your National Museum PH in Bicol re-opens
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