北海道駒ケ岳火山は1694年に噴火したか? : 北海道における17〜18世紀の噴火年代の再検討

概要

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Some major plinian eruptions have been documented in Hokkaido Komagatake since 1640. The Ko-c2 is one of such major plinian pyroclastic fall deposits. Katsui and Ishikawa (1981a) inferred that the Ko-c2 is a product of 1694 eruption. Tokui (1989) supported them by means of tephra stratigraphy. However, Hayakawa (1991) claimed that time interval between Ko-c2 and 1640 Ko-d eruptions was less than 10 years because of the thickness of interbedded humic soil. The volcanic ash soil between Ko-d and Ko-c2, which includes plant opals, flne grained quartz particles, and crystalline clay minerals, is recognized at a proximal exposure of the Komagatake. Then the Ko-d and Ko-c2 eruptions occurred with an intercalated dormant period. The Ko-c2 layer was also detected as a thin fine ash layer, which intercalated within 1667 Ta-b and 1739 Ta-a ash both from Tarumai volcano at the distal exposures 120-250 km away from the Komagatake. These three distal ash layers were chemically correlated with those of proximal juvenile ejecta. Historical documents describe the eruption of Komagatake around 1694 which can exclusively satisfy the geological constraints. We comprehensively support that Komagatake has erupted and discharged Ko-c2 in 1694.
特定非営利活動法人日本火山学会の論文
1997-08-31