ビリーミチェル火山

Billy Mitchell, a small pyroclastic shield immediately NE of Bagana volcano, has produced some of the largest Holocene eruptions in Papua New Guinea. The andesitic-to-dacitic volcano is truncated by a 2-km-wide caldera containing a shallow lake with a small island near its S shore. Two major explosive eruptions, one about 900 years ago and the other about 370 years ago, produced dacitic pyroclastic-fall deposits that cover most of the northern half of Bougainville Island. The younger eruption may have been responsible for formation of the nearly vertical, steep-walled summit caldera. Pyroclastic-flow and -surge deposits extend 25 km to the E coast of Bougainville Island.