Since 1945, the volcanic activity of the Kurile Islands has been isolated from the Japanese volcanologists and the related scientists. In this paper, the activity is resumed from G.S. Gorshkov’s transactions. Among these activity, three volcanoes carried out a characteristic eruption, Mt. Kuroishi (Krenitzyn Peak), Mt. Berg and Midoriko Caldera (Zavaritzky Caldera), are described in detail. The description is partly added by the writer’s observation performed thirty years ago.

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The volumes and geologic ages of the lavas and ejecta of the Kaimon-dake volcano were studied from the standpoint of volano-ecology. The Kaimon-dake proper is a double volcano composed of stratovolcano and lava dome. According to the archaeological identification, the ¹⁴C age determination, and the study on the thickness of the weathering products (soils), it is concluded that the first eruption of the Kaimon-dake occurred ca. 4000 years ago and the last one ca. 1000 years ago. The thermal energy transported with the solid materials is 10²²～10²⁵ erg in a single eruptive cycle and ca. 1×10²⁶ erg in total through ca. 3000 years. Some notable facts are summarized as follows : 1) Volcanic products were rich in lithic ashes in the early stage, while rich in scoria lapilli in the later. 2) Outflows of lavas with scoria falls took place at least in four stages. 3) Eruptions occurred more frequently in the later stage than in the earlier stage. 4) Lava dome was built up and then gas explosion took place finally. These facts seem to show the possible ascending of the Kaimon-dake magma reservoir through growth.

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Among 47 active volcanoes in Japan which have historical records of eruption, 17 volcanoes are under continuous instrumental observations by Japan Meteorological Agency and several Universities. The remnant active volcanoes, namely, 30 in number, being left from continuous volcanological observation. Several of them have been studied on some occassions in short period from geophysical point of view, however, scarcity of quantitative observation for most of these volcanoes makes it impossible to estimate the future volcanic risk. For instance, Volcano Huzi which made violent volcanic eruptions in historic time has still possibility to have future volcanic activity. Volcano Huzi is located near densely populated cities, where inhabitants are thus exposed to likely future volcanic violence. However, we have no detailed data of the present seismic activity there. Thus, we came to choose Volcano Huzi for precise seismic observation in order to know the present seismic activity of Huzi itself. Six seismic stations were set up during Oct. 3∿13, 1965 by the research group of five universities. High magnification seismographs at each station recorded several small shocks originating from Huzi. Epicenters of these earthquakes were determined as located at southern flank of the volcano with the focal depth less than 10 km. Beside these earthquakes, seismic stations at the southern flank of the volcano recorded small shocks of volcanic origin which were not observed at other stations. From these observational facts, we concluded that 1) present seismic activity of Volcano Huzi is quite low compared with other active volcanoes in Japan, and 2) seismic activity of volcanic origin seems to be concentrated at the southern flank of the volcano.

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