Cwm Idwal Page 1 of 2  Students examining the features of glacial erosion at Cwm Idwal. Group of students sitting on a roche moutonée at Cwm Idwal, with a view of the Llyn and Glyders (the mountains in the background). The amphitheatre of the cwm was scooped out by ice thousands of years ago and is one of the best examples of a glacial cwm to be found in Wales. High crags, screes, rounded rocks and moraines found within the cwm are all evidence of glacial action. The Nant Ffrancon valley, which lies to the north west of the cwm, is a spectacular example of a U-shaped valley, formed by the erosion of glacier ice. Cwm Idwal covers an area of 398 hectares. Llyn Idwal occupies the floor of the cwm and is about 800m long by 300m wide. Two hanging, valleys - Cwm Clyd, on the western side; Cwm Cneifon, on the eastern side - open into Cwm Idwal. The scientific interest of Cwm Idwal ranges from its rocks and soils and their dependant plants and animals, to the evidence of past glaciation and the history of the landscape that can be interpreted from the topography and peat deposits in the cwm. | 1 | 2 | Page 1 of 2