Abstract
The dirt cone-formed deposition as shown in Photos 13 (size : 230 m in length, 20 m in width and 46 m in height) was observed on 26 July 1970 in a channel of Shiretoko Peninsula (Fig. 1), eastern Hokkaido.
Within the dirt cone, natural, probably drifted, snow accumulation could be found. Only the surface layer, about 1015 cm in thickness, was composed of volcanic pyroclastic rocks and clods (Fig. 2).
The rocks are about 40 cm in maximum diameter and the volume of the dirt surface is estimated to be about 1, 000m3.
These angular rocks and clods seemed to have been transported by the snow-rock avalanches.
The process of formation of the dirt cone configuration is shown in Fig. 3.
This type of avalanching action appears to be an important clue to the analysis of mass movement in the cold, snowy mountain areas, which are made up of eroded volcanic formations in Hokkaido.
