The importance of topography in the occurrence of glacial valleys in Belarus

The relief of the ice-sheet bed predetermines the location of the valleys both in vast regions and in local, relatively limited areas. The influence of the relief in a large region on the formation of valleys occurs in lowland, more dissected northern and western regions of Belarus. Here, the bedrock relief plays a key role in appearance the hollow-like Vidzovsky, Polotsk and Surazh glacial erosion depressions and in isolation of the elevations separating them. The distribution of these largest forms of glacial erosion is associated with the regional picture of the glacial ice flow in topographic depressions, increased erosion of the ice bed, which developed under the glacial streams and lobes of the Scandinavian ice sheet. The degree and character of the relief dissection, the size, surface slope and orientation of the depressions, river paleo-valleys, elevations, and escarps had a leading role in the location of valleys in local, relatively limited areas. Their significance for the formation of valleys was to determine the local picture of the glacial flow and the areas where stresses were concentrated at the bed and glacial erosion intensified. The formation of tunnel valleys was possible in depressions and in the dissected relief of the glacial bed, which contributed to the accumulation of meltwater, the formation of subglacial lakes, as well as the concentration of meltwater in the subglacial channels.