2018 Volume 69 Issue 3 Pages 153-163
Azuma Volcano, located in Yamagata and Fukushima prefectures, is a large composite Quaternary volcano group. K–Ar ages by the isotope dilution method were determined for 38 lava samples. The volcano consists mainly of lava flows which have mostly similar petrographic characteristics. According to the determined age data, the volcanic edifice was divided into 12 units including Holocene Jododaira Volcano. The volcanic activity of Azuma Volcano began at ca. 1200 ka from the east and migrated to the west, and at ca. 700 ka, reversely migrated to the east. The latest activity is occurring at Jododaira Volcano. There is no long dormancy during the activity of Azuma Volcano from ca. 1200 ka to the present.