K-Ar ages of the Oshidomari lava from the Rishiri Volcano, off northern Hokkaido, Japan: Insight into the incipient stage of volcanic activity

Abstract

Two K-Ar ages (0.30±0.19 Ma and 0.39±0.17 Ma) were obtained from the Oshidomari lava from the Rishiri Volcano, off north Hokkaido, Japan. The age data indicate the lava was erupted in the Middle Pleistocene. We newly propose an incipient stage of volcanic activity followed by the initial stage.