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:
- Goltsy (or rocky-talus, completely
bare landscape) is located in the altitude range 1900 to 2700 m a.s.l.
(average height is 2040 m), its share accounts for 7% of the Suntar
river basin. Ground profile consists of argillite broken stone with
admixed loam materials, cemented together with ice and the layers of
clean ice up to 2 m depth. Vegetation is absent. Despite significant
amount of precipitation and its irregular distribution, the upper
layer of diluvia is characterized by low moisture content and its
barely visible variations during the warm season. It is explained by
the high permeability of broken rocks. Unevaporated water easily
infiltrates deep down and flows along the frozen bedrock. The
unsuccessful experience of experimental runoff site construction had
shown that the bedrock has deep splits and hollows, and even though
their temperature is below zero, they are not fully filled with ice
(Grave, 1959).
- Mountain tundra is located within the altitudes of 1450-1900 m a.s.l.
(1630 m on average) and takes 37 % of the Suntar River basin. It has
tight and depressed layer of grass and moss with bushes under which
there is rock formation with some ice with admixtures.
- Sparse larch forest (1100-1450 m a.s.l., 1310 m on average) consists
of sparse growth of larch forest at north slopes and larch forest at
south slopes, and covers 42% of the basin.
- Swampy sparse larch forest is spread within the river valleys and
floodplains (828-1100 m a.s.l., 1060 m on average) and covers 14% of
the basin.
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).