Hiuchigatake volcano lies in Nikko National Park and erupted the 8 km3 Hiuchigatake-Nanairi tephra and pyroclastic flow deposit about 170,00-160,000 years ago. Two lava domes at the southern end of the summit overlook Ozenuma lake, a popular hiking destination in the national park. The southern of the two domes, Akanagure, produced a series of viscous lava flows about 3500 years ago that extend to the S and W flanks. The northern dome, Miike, was the source of a tephra layer correlated with a report of historical activity in 1544 (Hayakawa, 1994b).