Anatomy and behaviour of a post-eruptive rain lahar triggered by a typhoon on Mayon volcano, Philippines

Abstract

Mayon Volcano in the Philippines, one the world's most active, is situated in a moist, tropical-maritime climate with frequent typhoons. A third of Mayon's eruptions generate destructive lahars (volcanic debris flows and hyperconcentrated streamflows). Lahars also occur during quiescent periods when monsoons and typhoons deliver rains of appropriate intensity and duration to the loose debris on the volcano slopes. Both eruption- and post-eruptive lahars occur most frequently during the typhoon-prone October–December season of the Northeast Monsoon. Post-eruptive lahars, the most poorly documented, are exemplified by a debris-flow event triggered by Saling, a typhoon of only moderate intensity, that occurred in Mabinit Channel on the southeast Mayon flank on October 17–18, 1985, one year after the last Mayon eruption.