Permafrost occurrence in Hokkaido and related effect of climatic changes

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Intensive field investigations on permafrost occurrence in Mt. Taisetsu were conducted by members of this project. Boring cores were taken from the frozen ground. Using bored holes temperature profiles of the ground were also measured for whole year round with newly developed devices. Continuous monitoring of temperature profiles gives mean annual temperature gradients in soil layers. The extra-polation of temperature gradient to the frozen layers indicates that the permafrost table is located at 550cm depth. Active frost cracks on the ground surface were observed on the flat summits. The increase of the width of frost cracks were recorded as 1cm in one winter. The palsas were formed at the area where considerable depth of peat was deposited.The existence of ground ice-body was reported by field survey around Mt. Taisetsu. The genesis of ice-body may related with the large scale land slides at early Holocene.