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The Ephemeral Volcanic Island in the Iwojima Group
http://hdl.handle.net/2261/16440
http://hdl.handle.net/2261/164402f8e2e06-4241-4f37-bb72-4a691055dea2
名前 / ファイル | ライセンス | アクション |
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KJ00004857105.pdf (3.7 MB)
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Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
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公開日 | 2010-07-14 | |||||
タイトル | ||||||
タイトル | The Ephemeral Volcanic Island in the Iwojima Group | |||||
言語 | ||||||
言語 | eng | |||||
資源タイプ | ||||||
資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
資源タイプ | departmental bulletin paper | |||||
著者 |
Wakimizu, T.
× Wakimizu, T. |
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著者所属 | ||||||
値 | Geology in the Coll. of Agriculture, Tokyo Imp. Univ. | |||||
抄録 | ||||||
内容記述タイプ | Abstract | |||||
内容記述 | 1. Considering both its geographic position and the nature of its ejecta, it is clear that the New Island was a volcano belonging to the same volcanic line as the other three principal volcanic islands of the Iwojima group. 2. The eruption was no doubt explosive, and ejected, most of all, the fine debris of pumice at the first stage of eruption, but afterwards vitrophyric lava composed half of obsidian and half of pumice. And though it is certain that other substances composed the body of the island, it remains doubtful whether they were subaerial ashes loosely accumulated or tuffs previously consolidated at the sea-bottom before the eruption ; the latter being the case with Motoyama in Iwojima. Pumice fragments transformed from lava came drifting to the shore of the island and formed a gravel-beach, 120 or 180 feet wide. 3. Petrographically the lava is of olivine-augite-andesite. It greatly resembles, as a whole, the glassy lava of Mt. Pipe in Iwojima. and widely differs from the agglomeratic lava in Kita-Iwojima. 4. In point of materials and structures, as Peel Island and Hills-borough Island in the Bonin group are of two different volcanic types, so the volcanic islands of the Iwojima group may be divided into two different types. To speak more concretely, Minami-Iwojima and Kita-Iwojima (San Augustino Is. and San Alessandro Is. respectively) which became inactive long ago, are composed of the same kind of agglomeratic rock of Hillsborough Island type, are very similar in mountain shapes, and seem to belong to one volcanic type peculiarly their own. On the contrary, Mt. Pipe, Motoyama, the New Island and the submarine volcano in the neighborhood of Kita-Iwojima, which are all still active and explosive, eject chiefly glassy ashes and rarely vitrophyric lavas, but never to such an extent as to augment themselves. Mt. Pipe alone, however, poured forth a comparatively great quantity of lava, so as to assume a conic shape. These four volcanoes ara of the other type. 5. On the 1st of February 1905, the New Island was 3 miles in circumference, 200 acres in area, and about 480 feet in height ; but, on the 16th of June of the same year, that is, only 136 days after the above-given date, it was reduced to a low reef, only 1500 feet long and less than 10 feet high. The causes of its subsidence remain uncertain, but the chief of them seems to be the encroaching action of the waves. But what brought its submergence so soon? That is the question. It may be that the aforesaid agency was accompanied by a depression of the crater rim. | |||||
書誌情報 |
Publications of the Earthquake Investigation Committee in foreign languages 巻 22/3, p. 1-33, 発行日 1908-03-29 |
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書誌レコードID | ||||||
収録物識別子タイプ | NCID | |||||
収録物識別子 | AA00360012 | |||||
日本十進分類法 | ||||||
主題Scheme | NDC | |||||
主題 | 453 | |||||
出版者 | ||||||
出版者 | 震災豫防調査會 |