Mount Iriga is a small stratovolcano that rises to 1196 m immediately SW of Lake Buhi. 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.