Helvellyn, Lake District - Local Flashcards
Explain how the ribbon lakes Ullswater and Windermere were formed.
The Pleistocene glaciation period, modifying and deepening the pre-glacial drainage system.
They occupy corries because of snow accumulation at high altitudes - creating glaciers. The glaciers deepened the original hollows and when the ice melted they were filled with meltwater to form small lakes. This has created over 150 glacial corries in the Lake district.
Why are most of the corries in Helvellyn facing east?
Because this was the orientation most conductive to snow accumulation, which subsequently lead to intensified corries from erosion as glaciers expanded within them.
Describe the glacial trough in Grisedale valley.
The head of Grisedale contained the largest glacier in the range.
Fed ice from at least four corries, and the glacier extended down valley with an altitude of 215m.
Above this altitude are moraines marking the position of the glacial snout.
Ice in latter stages was not as extensive and moraines from earlier glacial periods are not as well formed due to post-glacial erosion.
Describe the topography of Grisedale.
Deep rock basins filled with meltwater as a ribbon lake - Ullswater.
Bands of hard rock are more resistent to glacial erosion and the basin has an irregular profile.
One of the points between the smaller rock basins, is a roche moutonnee forming an island in the lake
