2002 年 47 巻 4 号 p. 217-225
Nekoma Volcano, situated between Bandai Volcano and the Aizu Basin in northeast Japan, is a composite volcano of andesite to dacite with a total eruption volume of 16 km3. A horseshoe-shaped caldera a few km in radius was formed at the top of the volcano, and the volcanic activity is divisible into the Old Nekoma Volcano established before the caldera forming event from ca. 1 Ma to 0.6 Ma and the New Nekoma Volcano established after the caldera forming event after ca. 0.5 Ma. Old Nekoma Volcano is subdivided into Oguninuma north lava, Hayama lavas, Hagidaira pyroclastic flow (block and ash flow) deposit, Main cone lavas, Oguniyama lavas and Ougigamine lavas, in ascending stratigraphic order. They formed a flat cone-shaped volcano. All but the Ougigamine lavas were produced by summit eruptions and the Ougigamine lavas formed monogenetic volcanoes from several vents on the western flank. New Nekoma Volcano, erupted after Oshizawa debris avalanche deposit, which related to the caldera forming event, is composed of Nekomagatake lavas and 1349 m lavas occurred at the horseshoe-shaped caldera margin.