This study established tephrostratigraphy and clarified the eruption history of Niijima volcano (Izu Islands, Japan) after the Miyatsukayama event (12.8-8.5calka) through geological survey around the central and northern parts of Niijima island, and Shikinejima and Jinaijima islands. Detailed explanation is summarized below. The Miyatsukayama eruptive event started at the north of Akazakinomine lava dome (central part of Niijima island) at 12.8calka. The series of eruptions formed Miyatsukayama lava dome, and produced Nj-MtG tephra (12.8-8.5calka) and K tephra (ca. 8.5calka). In particular, the first pyroclastic density current covered the Akazakinomine lava dome thickly, accompanying fallout deposits (Nj-Mt tephra) which were widely distributed in the northern part of Izu Islands. Subsequently, the Shikinejima event ejecting Nj-Sk tephra occurred at ca. 8calka. At ca. 7.5calka, H(s) tephra was produced by the eruption near Shikinejima island, and H(n) tephra was produced by the Niijimayama event. During the Miyatsukayama-nanbu event (ca. 5.5calka) producing Nj-Mt(s) tephra, pyroclastic density currents erupted from the southern part of Miyatsukayama lava dome, buried depressions on the Miyatsukayakma lava dome and formed horizontal and flat surface. The erupted pyroclastic material covered the Akazakinomine lava dome widely and formed pyroclastic cones and lava domes near the source. After that, the Wakago event (Ni-Wg tephra), the D tephra event and the Kudamaki-Atchiyama event (Nj-KdAt) erupted basaltic magma at ca. 3.6calka, ca. 1.6calka and AD 856-857, respectively. Several decades after the Kudamaki-Atchiyama event, the Mukaiyama event (Nj-My) occurred at the southern part of Niijima island in AD 886-887. The Mukaiyama event is the largest eruption during the last 12.8 kys. At Niijima Volcano, eruptions with the magnitude equivalent to the Mukaiyama event (>0.1DREkm3) have occurred every thousand years since the Miyatsukayama event, and the large area of the island was covered with pyroclastic density currents at each eruption.
