鹿児島県トカラ諸島諏訪之瀬島御岳火山の1960年活動について

抄録

The new crater of On-take Volcano, Suwanose Island, opened in Autumn, 1960. The inlanders found this new crater in January, 1961. But, this fact was not reported due to an out-of-the-way island. The present writer visited this island in August, 1963, surveyed this new crater and got some new specimens of ejectas. The new crater which is about 50m. in diameter, opened on the northeastern wall of the old beautiful cinder cone. The bottom of the new crater is filled with the black ejectas, and the eastern part, about 1m. in diameter, is seen red colour. The ejectas about 0.1m. diameter are thrown as far as 400m. All these rocks olivine augite hypersthene andesite. All past ejectas and lavas from On-take have no phenocrystic olivine. This problem should be thought not only from the crystallization of magma, but from the structure of the underground. Their chemical compositions are shown in Table 1.