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Iriga erupted in 1628 and 1642. Asog is generally known for its phreatic explosions. It is one of the active volcanos in the Philippines, which are all part of the Pacific ring of fire.
The dominantly andesitic stratovolcano has satellitic cinder cones of basaltic composition. A large breached crater that opens to the SE was formed as a result of a major debris avalanche that buried several villages and formed a broad hummocky deposit that extends across the plain south of Lake Buhi. This catastrophic event was at one time considered to have occurred during 1628 AD, but later work has shown that the collapse and eruption occurred earlier at some unknown date during the Holocene. The avalanche was followed by phreatic explosions that created a small crater at the base of the scarp.
Collapse of the summit and flanks of volcanoes during major volcanic landslides creates large horseshoe-shaped depressions that open in the direction of the landslide. This 2.1 x 3.5 km horseshoe-shaped caldera at Iriga volcano in the Philippines was produced by a massive landslide during the Holocene. The resulting debris avalanche traveled more than 10 km to the SE and flowed into Lake Buhi at the upper right. This view is from the south, with the summit of Iriga at the extreme left.
Coordinates: 13°27′N 123°27′E
