Human Remains in O-sima Volcano, Izu, and the History of Volcanic Activity

Abstract

Human remains of Middle Zyomon (Jomon) age (about 4500 years old) have been found between a tuff layer and a lava flow exposed at Tatunokuti on the western coast of O-sima, Izu, south-southwest of Tokyo. These rocks were formed during the period of pre-caldera or Somma lava activity. As the surface of the tuff layer had been subjected to weathering and stream erosion before the remains were laid down, the volcano appears to have been dormant or at least weakly active for some time before the pre-historic men lived at this place. The time interval between this stage and the close of the Somma lava activity is estimated as at least 1000 years, and probably about 2000 years . Therefore the formation of the summit caldera may be dated as 3000 or 2000 years old.