白河火砕流を噴出したマグマ供給系の進化 1. 噴出様式の時間変化 Evolution of magma plumbing system of the Shirakawa pyroclastic flow deposits 1. Temporal variation of mode of eruption
The Shirakawa pyroclastic flows consist of four pyroclastic flow deposits erupted about 1.3-1.0 Ma in the southern part of Tohoku-Honshu arc. These eruptions are characterized by two different modes of eruption. The eruptions of the older two deposits, the Kumado and Ashino pyroclastic flows, were followed by many numbers of intermittent Plinian eruptions, which persisted for about a few ten thousand years. It is thought that the mode of volcanic eruption corresponds to that of a polygenetic volcano. In contrast, the eruptions of the younger two deposits, the Nishigo and Ten-ei pyroclastic flows, were both single eruption event and no subsequent Plinian eruption was associated. The mode of eruption is similar to that of a monogenetic volcano. The duration of repose between each eruption of pyroclastic flow deposits exceeded a few ten thousand years and is nearly comparable with that of the Aso volcano and longer than that of the Towada volcano (10 or 20 thousand years). The estimated whole life span of the volcanic activity of the Shirakawa pyroclastic flows is about 250 thousand years. It seems to be rather shorter than that of a ordinary Quaternary stratovolcano.
- 岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology
岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology 91(5), 177-184, 1996-05-05
Japan Association of Mineralogical Sciences