Analiza rzeźby okolic wsi Woszczele z zastosowaniem zdjęć lotniczych

When investigating the young glacial relief of the western fragment of the Ełk Lake District mezoregion and analysing accessible cartographic and geologic material with the use of a photomap (1: 10 000) and of panchromatic photos (1: 16 400) the authors’ attention was drawn by the surroundings of the Woszczelskie and the Sawinda Wielka lakes. Wast surfaces stretch here, gently sloping toward the lake basins, cut by long valleys. On the East and the West they are bordered by distinct slopes, at the foot of which there lies a varying area with a large number of small hills separated from one another by peaty depressions. Those areas are well noticeable on the photomap because of varying ways of land exploitation and because of a different disposition of phototones. According to J. Kondracki (1978) and M. Bogacki (1976) they are outwash routes connected with the seventh marginal zone and functioning during the whole time of recession of the Pomeranian phase of the Baltic glaciation. A. Ber (1975 a, b) has reckoned a part of those surfaces among outwash and some fragments-among marginal plains. The deposits which form the surface and bear the features of typical fluvioglacial-ablational cones, display lithological differentiation. Their highest fragments along a steep ridge, attaining 136-140 m above sea level, are built of gravels and shingle among which there occur streaks of silty sand. These forms appear on panchromatic air photos as large surfaces with a striped disposition of fields. Slight phototone differences among the particular plots indicate a similar type of land exploitation. In the foreland of those cones, in the immediate neighbourhood of the lakes, came terraces are stretching. Also eskers and cames occur here. On panchromatic air photos they appear as fragments of land of a light, almost white, phototone. The fact that they are so well visible on photos is due to the proximity of the peaty plain having a very dark phototone. The network of dry little valleys in the vicinity of the lakes has a parallel run or it approaches this direction. They begin near the steep slopes of the ice contact and descend concentrically toward the axis of the through of the Woszczelskie and Sawinda Wielka lakes. The good visibility of the fluvioglacial-ablation cones observed on air photos is due to a different type of relief of the adjoining areas. There the prevailing grounds have a dark phototone and an amorphous structure, which corresponds with the depressions filled with organogenetic deposits. Here lies a strongly differentiated ground moraine with numerous dead-ice hollows. The spatial situation of the dead-ice hollows and of small-radius convex forms as well as the geological structure indicate an areal and slow decay of the ice-sheet in this part of the Ełk Lake District. The process probably consisted in the formation of thawing spots around culminations of the ground while depressions were still filled with ice. The slope of fluvioglacial-ablation cones toward the lake trough leads to the conclusions that on the slopes of large-radius ground culminations near the investigated area there was still dead ice. Instead, the depression along the present-day lakes: Woszczelskie and Sawinda Wielka was already clear of ice. Only the trough was then filled with dead ice. The above considerations show how complex the process of deglaciation was in North-East Poland and permit to reconstruct certain mechanisms of degradation of the ice cover. It is generally assumed that along with progressing areal deglaciation lower and lower parts of the land were getting free. It appears that there existed situations when the dead ice remained on the slopes longer than in the bottoms of depressions. It may then be spoken of local inversion in the order of degradation of the ice-sheet.