Abstract
At Oosima Volcano, Izu, various geomagnetic studies have been continued since its great eruption of 1950-51. And also the results of geophysical and geological investiga-tions of the structure of Oosima Volcano have been accumulated. In 1957, the present author discussed the anomalous change in geomagnetic field observed in the 1953-54 eruption. In the present paper the author would revise this discussion reflecting upon the results of 10 years' observation of magnetic declination and the accumulated re-sults of the subsurface structure of the volcano. The conclusion is that the observed anomalous changes are interpretable by the possible thermal processes beneath the volcano. Its quantitative results on heat supply to the volcano may lend a sugges-tion as to energetics of volcanisms.
