which the lake forms Tarn: A lake formed in a cirque by overdeepening Paternoster lake: A series of lakes in a glacial valley, formed when a stream is dammed by successive recessional moraines left by an advancing or retreating glacier Glacial lake: A lake that formed between the front of a glacier and the last recessional moraine Ice features Apart from the landforms left behind by glaciers, glaciers themselves may be striking features of the terrain, particularly in the polar regions of Earth. Notable examples include valley glaciers where glacial flow is restricted by the valley walls, crevasses in the upper section of glacial ice, and icefalls—the ice equivalent of waterfalls. Disputed origin The glacial origin of some landforms has been questioned. Erling Lindström has advanced the thesis that roches moutonnées may not be entirely glacial landforms taking most of their shape before glaciation. Jointing that contribute to the shape typically predate glaciation and roche moutonnée-like forms can be found in tropical areas such as East Africa and Australia. Further at Ivö Lake in Sweden weathered rock surfaces exposed by kaolin mining resemble roche moutonnée. The idea of elevated flat surfaces being shaped by glaciation—the glacial buzzsaw effect—has been rejected by various scholars. In the case of Norway the elevated paleic surface has been proposed to have been shaped by the glacial buzzsaw effect. However, this proposal is difficult to reconcile with the fact that the paleic surface consist of a series of steps at different levels. Further glacial cirques, that in the buzzsaw hypothesis contribute to belevel the landscape, are not associated to any paleosurface levels of the composite paleic surface, nor does the modern equilibrium line altitude (ELA) or the Last Glacial Maximum ELA match any given level of the paleic surface. The elevated plains of West Greenland are also unrelated to any glacial buzzsaw effect. The Gulf of Bothnia and Hudson Bay, two large depressions at the centre of former ice sheets, are known to be more the result of tectonics than of any weak glacial erosion. See also Fluvioglacial Landforms Glaciofluvial deposits References External links Illustrated glossary of alpine glacial landforms Landforms of glaciation Diagram illustrating mechanisms of glacial landforms in The Ice Melts: Deposition on page 6 of "Pennsylvania and the Ice Age" published 1999 by PA DCNR Bureau of Topographic and Geologic Survey