Study on rock glaciers in the Japanese Islands and their palaeoenvironmental significance

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1. More than 30 rock glaciers were found and mapped by aerial photo-interpretation of the present study, and a preliminary inventory of rock glaciers was completed. Most of the rock glaciers are located in the Hida Mountains, central Japan, and a few in the Akaishi Mountains, central Japan, and the Hida Mountains and Taisetsu Volcanic Massif, Hokkaido.2. The inventory contains 22 large-scale contour maps of typical rock glaciers compiled by using stereo-plotting of air photographs.3. The internal structures of rock glaciers has been approached by indirect geophysical soundings such as the year-round monitoring of ground temperature besides the snow-depth measurements and geoelectrical measurements. In Kuranosuke Rock Glacier a frozen layer was observed beneath the surface debris layer in October, 1999.Field researches of active rock glaciers were carried out outside Japan, in the Nepal and Bhutan Himalayas, the Swiss Alps, and Antarctica.The periglacial model attributes a slow rock glacier movement to permafrost creep.Rock glaciers in the Japanese high mountains were classified into the following three types and periods: (1) Fossil rock glaciers formed during the Late Glacial period around 10000 years ago, (2) Fossil rock glaciers formed during the Neoglacial and Little Ice Age periods between a few million years and a few hundred years ago, (3) Inactive rock glaciers formed during the Little Ice Age between a few hundred years ago and 150 years ago. The mountain permafrost belt must have been wide enough to form a number of rock glaciers during the above mentioned cold periods. Subsequent permafrost melting would have fossilized these rock glaciers, some of which may have been misinterpreted as moraine ridges or protalus ramparts.