Jigokudani Crater is located at the altitude of 2,100m a.s.l. in the subalpine zone of northern area of the Yatsugatake volcanic chain （Kita-Yatsugatake）. The relations between seasonal crater lake appearance and ground-ice development under the algific environment of talus slope in the crater were observed through 6 years from 2009 to 2014. The crater lake appeared during more than two months in early summer of 2010, 2012 and 2014 and ground-ice disappeared in autumn in each year except 2014. On the other hand, perennial ground-ice was formed in 2009, 2011, 2013 and maintained until next summer, and crater lake appeared. These periodic phenomena suggest that the appearance of crater lake depends on the frozen ground as an impermeable layer represented by ground-ice which was maintained from former year.
