1. Glacial Erosion features (3) Objectives: To understand the formation of the following glacial erosion features: Ribbon lakes To know the terms: truncated spurs, alluvial fan
3. - grooves on rock created by abrasion due to debris embedded in base of glacier - Sharp, pointed hilltop between three or more corries (e.g. Snowdon, N Wales) - large armchair shaped hollow enlarged as ice moves in a rotational movement under gravity (e.g. Cwm Idwal, Glaslyn, North Wales) - Knife shaped ridge between two corries (e.g. Grib Goch, N Wales) Striations Corrie (Cirque) Arête Pyramidal Peak Ribbon Lake - long narrow lake occupying an area of the trough floor which has been overdeepened (e.g. Llyn Ogwen, Snowdonia)
6. Ribbon Lakes Many glacial troughs contain long, anwrro ribbon lakes. They may be the result of: (i) sreioon when a reicalg over-deepens part of its alylev in an area of softer okcr . (ii) a glacier over deepening its valley due to increased erosive power after being joined by a ibuttarry glacier (iii) deposition of aeimnor across the main valley forming a dam. When the glacier retreats, the deepened sections fill with melt water and become lakes. These lakes remain after glaciation, supplied by rainfall, streams and rivers. There are a number of examples of ribbon lakes to be found in the Lake District.