江戸市内に降下し保存されていた富士宝永噴火初日の火山灰

概要

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Archived ash fall sample with description of the first day ash from 1707 eruption of Mount Fuji was found at an old household material at a city near Nara. The sampling site of the archived ash locates downtown of the City of Yedo (Tokyo). The sample is mostly dense dacitic ash. Major element compositional variation of the ash sample supports the interpretation given by Miyaji (1984, 1993) that fall unit I was ejected during the first day of the eruption. The sampling site was locating at the north side from principal fallout axis. The grain-size distribution of the sample is enriched in finer-grained portion. Such grain-size distribution supports also the interpretation given by Miyaji (1984) that lower terminal velocity particles were selectively enriched at down wind direction of lower atmosphere.
2002-07-10