In this study the author attempts to discuss slow mass-movement processes caused by freezing and thawing in relation to the compositions of slope materials and fluctuations of ground temperature, in Spitsbergen and in the Japanese high mountains. Study sites in Spitsbergen are located in Adventdalen and Reindalen, Nordensiöldland, central Spitsbergen (Fig. 1). These sites are debris slopes with gradients ranging from 6° to 32°, mainly covered with Jurassic, Cretaceous, and Tertiary shale fragments. The rates and deformation patterns of downslope movement of surface rubble are measured by eighteen painted stone-lines. Many grass fibre-tubes, furthermore, were inserted vertically into the ground in order to detect downslope movement in the active layer. Year-round ground temperature measurement was achieved at a flat surface (480 m a.s.l.) of the Adventdalen site using data logged at 3-hour intervals in 1988-1989. Sensors were installed at 5, 15, 30, 50 and 80 cm depths. Studies to slow mass-movement in the Japanese high mountains were performed in Mt. Shirouma, the Kitakami Mountains, and Mt. Hoh-o. Long-term ground temperature records were observed on the Kitakami Mountains, Mt. Hoh-o and Mt. Akaishi. The results of this study can be summarized as follows. The average movement rate of painted stones from 1988 to 1990 was 3.3 cm/yr. in Spitsbergen (Fig. 2). Deformation features of all painted stone-lines showed patterns parallel to the basement lines independently of the compositions of slope materials (Figs. 3. 4. 5. 6). The movement rates at the tops of grass fibre-tubes were similar to the rate of movement measured by painted stone-lines (Fig. 8). These imply that deformations of painted stone-lines and grass fibre-tubes occurred by the same processes, that is, frost creep and gelifluction. Furthermore, movement of slope materials by diurnal freeze-thaw cycles is negligible in Spitsbergen, because of the very low frequency of this cycle (Fig. 10; Table 3). Therefore it is considered that annual freeze-thaw cycles mostly contribute to the movement of the slope materials in this area. Average movement rates of painted stones measured in the Japanese high mountains are 26.1 cm/yr. in Mt. Shirouma, 21.7 cm/yr. in the Kitakami Mountains, and 39.7 cm/yr. in Mt. Hoh-o (Fig. 2). These rates are one figure faster than those of Spitsbergen. Deformation features of painted stone-lines are classified mostly into two patterns, one a festoon type and the other a parallel type (Fig. 7). The parallel type occurs on slopes mantled with thick surface rubble of coarse size. The festoon type is recognized on slopes mantled with thin surface rubble and fine materials. The vertical profiles of many flexible tubes from the above-mentioned mountains on which they were inserted to become almost negligible at about 30-40 cm in depth (Fig. 8). This depth is about one half as shallow as that of Spitsbergen. Freeze-thaw cycles in the Japanese high mountains overlap with diurnal ones and annual ones, especially those occurring in very high frequency (Fig. 9; Table 3). Movements on the slopes covered with thin rubble and fine materials are caused by diurnal and annual cycles. On these slopes deformations of painted stone-lines show the festoon pattern, and the movement rates are faster than those on slopes consisting of coarse rubble, which almost all move in annualfreeze-thaw cycles. Considering the above mentioned results, in Spitsbergen differences incompositions of slope materials do not reflect movement processes and the rate of movement, because movement of slope materials occurs in almost annual freeze-thaw cycles. On the other hand, in the Japanese high mountains movement of slope materials occurs in two different freeze-thaw cycles, which are annual and diurnal ones.
The authors discuss the development of block fields and sorted polygons on the flat surfaces at the summits of fells (monadnocks; tunturi in Finnish) in Finnish Lapland in relation to the retreat of the ice sheet during the last glaciation. There are many fells in the study area (Fig. 1) with their summits elevated several hundred meters; the highest peak is 806 m. Block fields and inactive sorted polygons with erratic boulders in their forming materials were developed on the flat surfaces at the summits of fells above about 600 m. Only block fields with erratics were developed on the summits between about 500 m and 600 m in elevation. Furthermore, on the summits below about 500 m, neither block fields nor sorted polygons were developed but glacial striaes and erratics existed. All of the summits in the study area were covered with ice sheet during the late glaciation. However, because the higher summits with block fields appeared above the ice sheet like nunatak forms in the early stages of deglaciation, it was cold enough to produce block field-forming materials. On the other hand, the lower summits without block fields were covered with ice sheet for a longer period than the higher ones. It was not cold enough to produce block field-forming materials on the lower summits (Fig. 3, Table 1). Therefore, in the present study area, the authors define a boundary zone, which is a transitive zone of freeze-thaw weathering with an altitudinal range below the linear weathering limit (Nesje et al., 1987). Inactive sorted polygons are commonly developed on the summits of fells higher than 600 m in their elevation. On the other hand, active sorted polygons are developed on the river floors and lower river terraces at the bottoms of the shallow valleys, mostly about 100 m in elevation (Fig. 2). Very severe temperature inversion was observed at Kevo (Fig. 1) in one of the valleys where active sorted polygons were developed. This is a very common phenomenon in Finnish Lapland. The values for freezing index, thawing index, and freeze-thaw days and cycles (Fig. 4, Table 2) show that valley bottoms have a more suitable climatic environment for periglacial processes than mountain tops. The authors think that severe temperature inversion is one of the important factors for active sorted polygon forms.
Three-dimensional fabric analysis was done in order to characterize the fabric of slope deposits gathered from various sources. Although the distribution of periglacial slope deposits on a logarithmic ratio plot partly overlaps those of nonperiglacial deposits such as soil creep, sediment flow plots, debris flow plots, talus, outwash and stratified slopes (in openwork beds) indicate low values of both C and K compared with those of periglacial slope deposits (Fig. 1, Table 1). This result leads to the conclusion that (1) the periglacial slope deposits have higher C and K values than non-periglacial deposits except for glacial ones; (2) the periglacial slope deposits are plotted in a zone with C ranging over 2.5, K ranging over 0.5 on the logarithmic ratio plot; and (3) it is, therefore, possible to distinguish the periglacial slope deposits from the non-periglacial ones by means of logarithmic ratio plots. Three-dimensional fabric analysis of 2, 350 clasts in the site located on the fossil periglacial slope deposits in the Hidaka Mountains has been done to evaluate the relations of macro fabrics to both length of a-axis (Table 2) and clast shape (Table 3). The main results are that (1) clasts with a longer a-axis have macro fabrics with little deviation from mean orientation (Figs. 2 and 3); and (2) clast shape has little effect on fabric in the longer a-axis range (Fig. 4, Table 4). Taking these results into consideration, azimuths and dips of clasts with longer a-axis have to be measured in order to gain fabrics with little deviation from mean orientation in periglacial slope deposits.
The authors conducted a field survey related to the genesis and occurrence of permafrost in James Ross Island and Seymour Island, Antarctic Peninsula region, during the 1989-1990 Antarctic summer season. Mean annual air temperature in both islands is estimated at about-10°C. Seymour Island is located in the Weddell Sea. There was no ice-sheet over the island during or since the last glaciation period. Marine terraces of three different levels are distributed in the is-land: an upper terrace at Meseta (about 200 m a. s. 1.), a middle terrace at Sub-Meseta (about 50 m a. s. 1.) and a lower terrace at Larsen (about 5 m a. s. 1.). In order to estimate the thickness of permafrost, geo-electric resistivities were surveyed on these terraces. In the lower terrace at Larsen, long-term monitoring of ground temperature profiles was carried out for two years. The annual mean ground temperature and the temperature gradient indicate that the permafrost base is 34 m deep. This coincides with the depth obtained by geo-electric resistivity measurements. In James Ross Island, about 90% of the ground surface is covered with an ice sheet or glaciar. Ice-free ground spreads to the northwestern part of the island. Coastal terraces of three different levels develop around Santa Marta Point along Croft Bay: upper terrace(21-24 m, 32-35 m a. s. 1.), middle terrace (10-17 m a. s. 1.) and lower terrace (3-5 m a. s. 1.). The group of upper terraces is composed of glacial till or fluvio-glacial deposits. Shell samples were collected from the deltaic deposit which composes the middle terrace, and from marine sands and gravels which cover the surface of the lower terrace. Then 14C dating was done with the results of about 25, 000 y. B. P. and 3, 000 y. B. P. respectively. According to geo-electric resistivity measurements, the depths of permafrost bases on the upper and lower terraces are estimated at 40 m and 3-5 m, respectively. It is considered that permafrost on the upper terrace occurred prior to the last glacial maximum age. The comparison between Antarctic and Arctic permafrost suggests that the permafrost in Antarctic regions is shallower than that in Arctic regions under similar annual mean temperatures at the present time.