抄録
The periglacial phenomena in Kitami District, NE-Hokkaido, is classified into three groups ; (a) those above 1700m Si. accompanying sorted polygons, etc., (b) those above 300m with severe frost-shattering, and (c) those below 300m, where verved clay and its involutions are observed. The ice-shove ridges along the beach of Okhotsk Sea is different characteristically from inland phenomena, but here it is included in the (c) group.
Hirayama (1775m) is located at the back-bone mountain, east of Daisetsu Mountain mass. The summit is occupied by a wide altiplanation terrace, and the lee-side gentle slope from westerlies shows nivation niches, and sorted circles. It is above the coniferous forest line, and locally known with its alpine flower gardens.
The ice-shove ridges along Okhotsk beach are formed by the sea-ice pushed up on the sandy beach by the drag force of surface wind during the winter season, and remain there for about four months. The sand bulldozered by the front of sea ice from the coastal sea bottom contains more grains of well polished, rounded agate, opal, chalcedony, and jasper than the normal beach sand.
The above two phenomena are directly connected with the climatological condition which is governed by the prevailing cold westerlies in winter, while the frost-shattering etc. of group (b) are controlled by the combination of complex microclimatological and microgeomorphological conditions.
