Glacial landforms arelandforms created by the action ofglaciers. Most of today's glacial landforms were created by the movement of largeice sheets during theQuaternary glaciations. Some areas, likeFennoscandia and the southernAndes, have extensive occurrences of glacial landforms; other areas, such as theSahara, display rare and very old fossil glacial landforms.
Striations: grooves and indentations in rock outcrops, formed by the scraping of small sediments on the bottom of a glacier across the Earth's surface. The direction of striations display the direction the glacier was moving.
Cirque: Starting location for mountain glaciers, leaving behind a bowl shaped indentation in the mountain side once the small glacier has melted.(add geology book citation already in the article)[1]
U-shaped, or trough, valley: U-shaped valleys are created by mountain glaciers. When filled with ocean water so as to create aninlet, these valleys are calledfjords.
Arête: spiky high land between two glaciers. If the glacial action erodes through, a spillway (orcol) forms
Horn: a sharp peak connecting multiple glacier intersections, made up of multiple arêtes.
Valley step: an abrupt change in the longitudinal slope of a glacial valley
Hanging Valleys: Formed by glacial meltwater eroding the land partially, often accompanied by a waterfall.[2]
Later, when the glaciers retreated leaving behind their freight of crushed rock and sand (glacial drift), they created characteristicdepositional landforms. Depositional landforms are often made of glacialtill, which is composed of unsorted sediments (some quite large, others small) that were eroded, carried, and deposited by the glacier some distance away from their original rock source.[1][3] Examples include glacialmoraines,eskers, andkames.Drumlins andribbed moraines are also landforms left behind by retreating glaciers. Many depositional landforms result from sediment deposited or reshaped by meltwater and are referred to asfluvioglacial landforms. Fluvioglacial deposits differ from glacial till in that they were deposited by means of water, rather than the glacial itself, and the sediments are thus also more size sorted than glacial till is. The stone walls ofNew England contain manyglacial erratics, rocks that were dragged by a glacier many miles from their bedrock origin.
Esker: Built up bed of asubglacial stream, forming small, string-like mounds left behind as a glacier retreats.[1][3]
Kame: Irregularly shaped mound of sediments previously deposited by falling into an opening of glacial ice.
Moraine: Built up mound of glacial till along a spot on the glacier. Feature can be terminal (at the end of a glacier, showing how far the glacier extended), lateral (along the sides of a glacier), or medial (formed by the merger of lateral moraines from contributory glaciers). Types:Pulju,Rogen,Sevetti,terminal,Veiki
Outwash fan: Braided stream flowing from the front end of a glacier into a more flat, lower elevation plain of sediments.[1]
Lakes and ponds may also be caused by glacial movement.Kettle lakes form when a retreating glacier leaves behind an underground or surface chunk of ice that later melts to form a depression containing water.Moraine-dammed lakes occur when glacial debris dam a stream (or snow runoff).Jackson Lake andJenny Lake inGrand Teton National Park are examples of moraine-dammed lakes, though Jackson Lake is enhanced by a man-made dam.
Kettle lake: Depression, formed by a block of ice separated from the main glacier, in which the lake forms
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
Apart from the landforms left behind by glaciers, glaciers themselves are striking features of the terrain, particularly in thepolar regions of Earth.Notable examples includevalley glaciers where glacial flow is restricted by the valley walls,crevasses in the upper section of glacial ice, andicefalls—the ice equivalent ofwaterfalls.
The glacial origin of some landforms has been questioned:
Erling Lindström has advanced the thesis thatroches moutonnées may not be entirely glacial landforms, and may have already had most of their shapebefore glaciation.Jointing that contributes to their shape typically predates glaciation, and roche moutonnée-like forms can be found in tropical areas such asEast Africa andAustralia. Further, atIvö Lake in Sweden, rock surfaces exposed bykaolin mining and then weathered resemble roche moutonnée.[4]
The idea of elevatedflat surfaces being shaped by glaciation—theglacial buzzsaw effect—has been rejected by various scholars. In the case of Norway the elevatedpaleic 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 surfaces consist of a series of steps at different levels.[5] Glacialcirques, that in the buzzsaw hypothesis contribute to leveling the landscape, are not associated with any paleosurface levels of the composite paleic surface, nor does the modernequilibrium line altitude (ELA) or theLast Glacial Maximum ELA match any given level of the paleic surface.[6] Theelevated plains ofWest Greenland are also unrelated to any glacial buzzsaw effect.[5]
^Hall, Adrian M.; Ebert, Karin; Kleman, Johan; Nesje, Atle; Ottesen, Dag (2013). "Selective glacial erosion on the Norwegian passive margin".Geology.41 (12):1203–1206.Bibcode:2013Geo....41.1203H.doi:10.1130/g34806.1.
