Corrie basins in the Lake District

One striking feature of corrie basins is the way in which the majority have a north or northeast aspectThings to do in Windermere
. There are obvious exceptions like those which serrate the southern slopes of Blencathra, but taken as a whole a northeast orientation is dominant. It is this preferential development which gives many 66 of the ridges their asymmetrical appearance. No greater contrast of landforms exists than on the opposing sides of Helvellyn or the internally ridge separating Ennerdale and Buttermere.

On the one side are smooth even slopes broken occasionally by rock crags and low precipices while on the other glacial erosion has bitten deeply and successfully to create what has been called 'biscuit topo¬graphy'.

With rock type not exerting any great influence, other explanations have to be sought to account for the preferential northeast aspect. As early as 1917 Enquist noted that the aorries tended to lie on the lee side of a mountain range, that is in relation to the dominant snow bearing wind. More recently Manley has shown that in this situation the wind which blows over the ridge top the helm wind considerably aids snow accumulation on the upper part of the lee slope through the development of a back eddy. The presence of the eddy can often be detected on the waters of a tarn where wavelets move towards the back¬wall of the corrie basin. During the Ice Age thick snow would be likely to accumulate in any hollow on the lee slope, and through the addition of successive layers be ultimately transformed into ice.

In time this ice would gouge out a deeper hollow and ultimately a true corrie basin. Having reached this stage, the rapid build up of snow and ice would bring about increased erosion of the floor of the hollow. Due to the effect of the helm wind, the greatest amount of snow would accumulate on the upper part of the corrie glacier just below the bare upper part of the backwall. Differential loading on the upper surface of the corrie glacier would tend to cause the ice to move in a rotatory manner. With continuous additions at the head and constant depletion at the snout through melting, the rotatory movement could be instrumental in scooping out the floor of the corrie .

Other processes like frost shattering of the bare rocks of the upper part of the backwall and the grinding action of rock debris within the glacier would also contribute to the enlargement of the corrie basin. It follows that if the prevailing snowbearing wind was from the southwest then the northeast facing lee slopes would become the most suitable sites for corrie development. This northeast aspect also happens to be one of minimum isolation so that snow and ice would persist longer here. When the snow had long since disappeared from the upland peaks and plateau tops, some of the deep shadowy hollows would retain their active glaciers. Even today snow patches last until late Mayor early June in situations like the steep northfacing buttress of Great End.

Wordsworth, in his poem Fidelity, mentioned the persistence of snow under the lee of Helvellyn which he had noticed on a walk across to Patterdale in early June. The ice which was so prominent in fashioning the landscape of the central high part of the Lake District also left its mark in the peripheral lowland, though to different effect. Here various ice streams jostled for occupation of the low ground. In addition to the local glaciers fanning out from the mountainous core, a great wall of ice moved in from the Irish Sea and impinged on the western coasts. Passing over the softer rocks of the lowlands, the ice was able to incor¬porate great quantities of sands, clays and rocks which it subsequently deposited on melting. In contrast to the highland area, the glacial landforms of the margins 68 are nearly all associated with deposition rather than erosion.