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.
Can you identify a corrie, pyramid peak, hanging valley, terminal moraine, corrie lip, arete, glacial trough? In summary….
- 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)
<ul><li>small tributary valley above the floor of the main valley (due to differential erosion) (e.g. Cwm Dyli, N Wales) </li></ul>- steep-sided valley with flat-floor (e.g. Nant Ffrancon, N Wales) - steep, rocky section of the side of a trough where the tips of pre-glacial interlocking spurs have been removed by glacial erosion (nr trough end in Nant Ffrancon Valley) - resistant rock outcrop with gentle sloping smooth up-valley side and jagged lee-ward side. (e.g. in Nant Ffrancon Valley, N Wales) Hanging Valley U-shaped valley (trough) Truncated spur Roche Moutonnée
Glacial Landscapes <ul><li>1 is a Pyramidal Peak because it has steep, triangular faces divided by sharp ridges or arêtes. </li></ul><ul><li>2 is an Arête , because it is a sharp ridge between corries. </li></ul><ul><li>3 is a Corrie or Cirque , because it is an armchair shaped hollow with steep back and sides. </li></ul><ul><li>4 is a Corrie Lochan or Tarn , because water has gathered in the hollow in the floor of the corrie. </li></ul><ul><li>5 is an Alluvial Fan , because it is a fan shaped pile of rock remains (alluvium) washed down by the stream and piled up where the steep valley side meets the valley floor. </li></ul><ul><li>6 is a Ribbon Lake , because it is a long narrow lake in a part of the valley cut deeper by the glacier. </li></ul><ul><li>7 is a Truncated Spur , because the ridge has been cut off sharply by the ice that flowed down the main valley. </li></ul><ul><li>8 is a Misfit Stream , because it is far too small to have cut the valley. </li></ul><ul><li>9 is a Hanging Valley , because the valley floor is much higher than the floor of the main valley. </li></ul><ul><li>10 is a 'U' Shaped Valley , because it has steep sides and a nearly flat floor. (The other side of the valley is missing in this cut-away diagram. </li></ul>