The Washiba-Kumonotaira volcano group consists of a cluster of small shield volcanoes with possible lava domes in a remote area in Chubu Sangaku National Park in the heart of the Northern Japan Alps. Iwagokekodani, an older Kumonotaira volcano was active from about 1-0.9 million years (Ma) . The younger Kumonotaira volcano was active about 0.3-0.1 Ma. Washiba-ike volcano is younger than 0.12 Ma (Nakano et al., 2001-). Hayakawa (2009 pers. comm.) indicated that the Washiba-ike explosion crater was formed in an area that post-dates the latest Pleistocene glaciation, and produced a tephra layer consisting of accretionary lapilli and fresh volcanic bombs.