3. Special observations
The high-altitude Suntar-Khayata Station was operating in the Suntar River basin in 1957-1959 under the program of the International Geophysical Year (Dodds et al., 2010). Glaciological, geomorphological, geocryological and hydrological observations were carried out (Grave et al., 1964). The Station was located at an altitude of 2067 m in a rocky talus (goltsy) landscape and the observations are unique for the high-mountain areas of Eastern Siberia and the North-East of Russia.
We systematized the observations from the Station, which included meteorological data, snow measurements, evaporation data, the descriptions of soils and landscapes, the data on typical active layer depth, ground temperature at various depths, etc. (Grave, 1959; Grave et al., 1964; Grave & Koreisha, 1957, 1960; Koreisha, 1963).
According to the results of the Station studies and descriptions, the high-altitude landscapes zoning of the Suntar River basin was elaborated:
The active layer depth within the study territory is very variable. Table 1 shows some data on maximum active layer depth, obtained in 1958. In the high mountainous area of the altitude 1700 m and above, the depth of thawing of rocky talus sediments ranges from zero under glaciers and perennial snowfields to 70-90 cm at the foot of the slopes at the alluvial cone, folded by gravelly loam. Observed values at the Suntar-Khayata Station reached 75 cm in 1958 and 90 cm in 1959 (Grave et al., 1964). On steep slopes with southern exposure, the depth of penetration of positive temperature into the ground is expected to be greater. In similar landscapes with the same conditions, large-scale crushed stone thaws up to 55-60 cm during the season, and crushed loam thaws up to 80-85 cm. Observations show that large-scale sediments at the time when the snow comes down are firmly cemented by ice, which fills all the pores between the material. The data indicates that the variation of active layer depth in the high-altitude area is significantly variable over individual years. The depth of the seasonal thaw layer is more stable in the mid-mountain region. The maximum depth of thawing is observed in coarse-grained rocks this region. In sand-gravel-pebble ground at an altitude of about 1400 m, the depth of seasonal thawing reaches 120-150 cm and in loam soils ranges from 25 to 30 cm, depending on the moisture content (Grave et al., 1964).