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タイトルヨミ
ウンゼンダケ 1991ネン 5ガツ 28ニチ ノ カサイリュウ ニトモナッテ コウカ シタ カザン マメイシ ノ ブンプ ニツイテ
タイトル別表記
Distribution of accretionary lapilli fan accompanied with the pyroclastic flow at Mt.Unzen, Japan, 28 May, 1991
ファイル
言語
日本語
著者
三宅 康幸
藤井 純邦
Al Jailani Ashraf Saiyed
福元 和孝
藤木 淳司
内容記述(抄録等)
Pyroclastic flow was formed at about am 9:40 28th May, 1991, when a part of growing lava dome near the peak of Mt. Fugendake, Unzen volcano, was gravitationally collapsed and fragments of broken lava fell down through the steep slope of the eastem frank of Mt. Unzen. Although the wind near the surface blew from north, the direction of wind at the height of more than about 600 meters was from south to north, therefore the ash cloud was blown norhthward. At am 11 28th, fall-out ash with abundant accretionary lapilli was found to have covered the downwlnd area. As it was cloudy and the base of the cloud was about 1,000 meters high, most of the ash moved through the cloud. The accretionary lapilli were dry and fragile being easily disintegrated on small impact, and all lapilli got out of the shape after the light rain in the moming on 29th May.
The accretionary lapilli were distributed with in the fan-shaped area with 3km radius, the apex of which is located about 3km to the north of the crater. Accretionary lapilli ranged from 3-4mm to less than 0.5mm diameter, and the largest lapilli were found near the apex of the fan-shaped area, the maximum diameter of lapilli being gradually reduced outward.
The location of the apex of the accretionary lapilli distribution is not concordant with that of the generation of the pyroclastic flow. This discrepancy is probably attributed to that the accretionary lapilli had progressively grown during ash cloUd was moving northward, and that accretionary lapilli could not start to fall until they grew so large that their terminal fall velocity exceeded the upward current of air caused by hot pyroclastic flow and by the upward wind along the slope of the north flank of Mt. Fugendake.
掲載誌名
島根大学地質学研究報告
10
開始ページ
25
終了ページ
29
ISSN
0287816X
発行日
1991-07-30
NCID
AN00054980
出版者
島根大学理学部地質学教室
出版者別表記
Department of Geology, Faculty of Science, Shimane University
資料タイプ
紀要論文
部局
総合理工学部
備考
1-11 / 1982-1992
島田�郎教授退官記念論誌集