地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
燧ヶ缶火山の噴火史
早川 由紀夫新井 房夫北爪 智啓
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キーワード: 燧ケ岳, 噴火史, 尾瀬
ジャーナル フリー

1997 年 106 巻 5 号 p. 660-664

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The Edifice of Hiuchi Volcano was founded on the Mokake ignimbrite plateau which is directly underlain by the Nanairi pumice. They erupted from near the present summit successively about 350ka. On the plateau, the Ozorizawa cone was first established about 100 ka. Next, the Shibayasugura cone having twin peaks, Shibayasugura (2, 356 m) and Manaitagura (2, 346 m), was built shifting slightly southeast. At 19ka, the Jubeike lava flow and Kumazawa Tashiro lava dome were issued from the northeastern flanks. The latter was accompanied by a devastating blast. Southward-opening horseshoe depression is source of the Nushiri debris avalanche, which dammed up the Nushiri River and formed the Oze marsh about 8ka. The Akanagure lava dome and flows immediately occupied the depression. The youngest volcanic feature at Hiuchi is the Miike lava dome, 300m south of the Manaitagura peak. It emplaced during the 16th century, just before the Shirohikemizu flood descended the Hinoemata River on July 28, 1544. Hiuchi Volcano has erupted 17 × 1012 kg of magma since its birth, 350 thousand years ago. Average discharge rate is 4.9 × 1010 kg per thousand years, an order of magnitude smaller than that of the most active Japanese volcanoes.

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