ABSTRACT. A glacier at the summit of Ushkovsky volcano, Kamchatka peninsula, Russia, was studied in order to obtain information about the physical characteristics of a glacier that fills a volcanic crater. The glacier has a gentle surface and a concave basal profile with a maximum measured depth of 240 m at site K2. The annual accumulation rate was 0.54 m a^1w.e., and the 10 m depth temperature was^15.8³C. A 211.70 m long ice core drilled at K2 indicates that (1) the site is categorized as a percolation zone, (2) the stress field in the glacier changes at 180 m depth from vertical and longitudinal compression with transversal extension, which is divergent flow, to a shear-dominated stress field, and (3) the frequent occurrence of ash layers can be a good tool for dating the ice core.The borehole temperature profiles were considered to be non-stationary, but the linear profile made it possible to estimate the basal temperature and the geothermal heat flux at K2. Assuming constant surface and the basal boundary conditions, we constructed two depth^age relationships at K2. These predicted that the bottom ages of the ice core were about 511 or 603 years.

Unique boreal forest, consisting mainly of sparse larch (Larix cajanderii), creeping pine (Pinus pumila) and birch forest (Betula ermanii), occurs above the lower elevational limit of discontinuous permafrost of about 500 m above sea level in the area around Esso, central Kamchatka ($568N). Permafrost is present beneath surfaces covered by Sphagnum or creeping pine, but is absent beneath birch forest. Thermal conductivities in mid-September are low in Sphagnum (0.07-0.19 W/(mÁK)) and in the thick (13-20 cm) litter layer beneath creeping pine-covered areas (0.06-0.09 W/(mÁK)). Seasonal changes in the subsurface ground temperatures beneath creeping pine show that the surface litter prevents ground temperature increases at depth in summer, resulting in a thin active layer (several decimetres). The surface organic layer appears to be the most important factor controlling the presence or absence of permafrost in this area.

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