Fig. 5

a Distribution of pyroclastic flow deposits and air-fall ash. b, c, d, f, g with small arrows show the direction or location where b, c, d, f, g were taken, respectively. b The Jigokudani valley viewed from the southwest on September 28. c Distribution axis of air-fall ash extending to the north-northeast, viewed from above the Ninoike cone on September 28. d Close-up of the depositional area of the pyroclastic flow on September 28. e Air-fall ash deposited on a leaf, taken on the evening of September 27 (120 m east-northeast of Shikano-yu ropeway station). f Impact craters and sun cracks (representative cracks are suggested by arrows) that developed on the ash deposits in Ichinoike on September 28. g Impact craters on the inner wall of the Ichinoike cone, most of which contained water at the bottom and appear to be glistening white because of reflected sunlight. The topographic base map was produced using a GSI map issued by the Geospatial Information Authority of Japan