伊豆大島火山カルデラ形成以降の噴火史

• 小山 真人

  静岡大学教育学部地学教室

• 早川 由紀夫

  群馬大学教育学部地学教室

書誌事項

タイトル別名

• Syn- and Post-caldera Eruptive History of Izu Oshima Volcano based on Tephra and Loess Stratigraphy
• イズ オオシマ カザン カルデラ ケイセイ イコウ ノ フンカシ

抄録

We reveal the detailed syn-and post-caldera eruptive history of Izu Oshima Volcano, Japan, by tephra and loess stratigraphy. Twenty-four tephra layers, which overlie the slope outside the caldera, show that 24 eruptions occurred since the formation of the caldera (about 1, 450 years ago). These eruptions are separated by 10-200 years clear dormant periods, which can be identified by eolian dust (loess) interbedded with tephra layers. The 24 eruptions can be classified into three types : 1) eruption with scoria and ash falls (12 eruptions), 2) eruption only with scoria falls (7 eruptions), and 3) eruption only with ash falls (5 eruptions). While tephra discharge mass of the type 1 is generally large (1.5×10¹⁰ to 7×10¹¹ kg), that of the type 2 or 3 is small (0.6 ×10⁹ to 1 ×10¹¹ kg). The 1986 eruption is classified into the type 2. Debris avalanches, which occurred just before the caldera formation and covered almost all of the Izu Oshima island, demonstrate that the present caldera wall was formed by slope failure of an old edifice. The tephra-discharge stepdiagram, which shows a relationship between time and cumulative discharge volume / mass of magma, shows : 1) the average tephra-discharge rate is constant (92 kg/ s before the N1.0 eruption and 25 kg/s after the N1.0 eruption), showing an abrupt decrease of the rate at about the time of the N1.0 eruption, which occurred about 900 years ago and was the most voluminous eruption for the past 1, 450 years, 2) both before and after the N1.0 eruption, the type 1 eruption shows volume-predictability, that is, the discharge volume / mass of a next type 1 eruption can be predicted, 3) a type 1 eruption should occur sometime in the future again, and when it occurs, the discharge mass of tephra should attain to as much as 2×10¹¹ kg or more.

収録刊行物

• 地学雑誌

  地学雑誌 105 (2), 133-162, 1996

  公益社団法人 東京地学協会

キーワード

• 伊豆大島火山
• テフラ層序
• 噴火史
• レス
• 噴出量
• 史料

詳細情報

• CRID: 1390282679206250240
• NII論文ID: 10003774556
• NII論文ID: 10003562823
• NII書誌ID: AN00322536
• DOI: 10.5026/jgeography.105.2_133
• ISSN: 18840884
• ISSN: 0022135X
• NDL書誌ID: 3953607
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I3953607
• データソース種別:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可