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Glacier Erosion
Glacial landforms are landforms created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display rare and very old fossil glacial landforms. Erosional landforms As the glaciers expand, due to their accumulating weight of snow and ice they crush and abrade and scour surfaces such as rocks and bedrock. The resulting erosional landforms include striations, cirques, glacial horns, arêtes, trim lines, U-shaped valleys, roches moutonnées, overdeepenings and hanging valleys. * Cirque: Starting location for mountain glaciers * Cirque stairway: a sequence of cirques * U-shaped, or trough, valley: U-shaped valleys are created by mountain glaciers. When filled with ocean water so as to create an inlet, these valleys are called fjords. * Arête: spik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cirque
A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform arising from fluvial erosion. The concave shape of a glacial cirque is open on the downhill side, while the cupped section is generally steep. Cliff-like slopes, down which ice and glaciated debris combine and converge, form the three or more higher sides. The floor of the cirque ends up bowl-shaped, as it is the complex convergence zone of combining ice flows from multiple directions and their accompanying rock burdens. Hence, it experiences somewhat greater erosion forces and is most often overdeepened below the level of the cirque's low-side outlet (stage) and its down-slope (backstage) valley. If the cirque is subject to seasonal melting, the floor of the cirque most often forms a tarn (small lake) behind a dam, which marks the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valley Step
A valley step (german: Talstufe or ''Talschwelle'') is a prominent change in the longitudinal slope of a valley, mainly in trough valleys formed by glaciers. Typically, a valley formed by glaciers has a series of basins with intervening steps formed by the locally varying erosion depths of valley glaciers. After the ice melts, this initially becomes a sequence of lakes with intermediate rapids or waterfalls. The transportation of gravels, erosion and sedimentation processes in the streams lead to the formation of sequences of flat valley bottoms and gorges. Such basin forms, with an abrupt beginning, often appear as marked steps, which may separate the flatter sections of the valley. Large steps were often formed where the erosion forces of the glacier that once filled the valley were suddenly increased, for instance, when large glaciers merged. They are then referred to as confluence steps. Similar steps are formed when moving sheets of ice merge into glacial streams, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arête
An arête ( ) is a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequently this results in a saddle-shaped pass, called a col. The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arête steepened through mass wasting events and the erosion of exposed, unstable rock. The word ''arête'' () is actually French for "edge" or "ridge"; similar features in the Alps are often described with the German equivalent term ''Grat''. Where three or more cirques meet, a pyramidal peak is created. Cleaver A ''cleaver'' is a type of arête that separates a unified flow of glacial ice from its uphill side into two glaciers flanking, and flowing parallel to, the ridge. ''Cleaver'' gets its name from the way it resembles a meat cleaver slicing meat into two parts. A cleaver may be tho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fjord
In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Förden and East Jutland Fjorde, Germany, Greenland, the Faroe Islands, Iceland, Ireland, Kamchatka, the Kerguelen Islands, Labrador, Newfoundland (island), Newfoundland, New Zealand, Norway, Novaya Zemlya, Nunavut, Quebec, the Patagonia region of Argentina and Chile, Russia, South Georgia Island, Tasmania, United Kingdom, and Washington (state), Washington state. Norwegian coastline, Norway's coastline is estimated to be long with its nearly 1,200 fjords, but only long coastline paradox, excluding the fjords. Formation A true fjord is formed when a glacier cuts a U-shaped valley by ice segregation and Abrasion (geology), abrasion of the surrounding bedrock. According to the standard model, glaciers formed in pre-glacial valleys with a gently sloping valley floor. The work o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inlet
An inlet is a (usually long and narrow) indentation of a shoreline, such as a small arm, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In marine geography, the term "inlet" usually refers to either the actual channel between an enclosed bay and the open ocean and is often called an "entrance", or a significant recession in the shore of a sea, lake or large river. A certain kind of inlet created by past glaciation is a fjord, typically but not always in mountainous coastlines and also in montane lakes. Multi-arm complexes of large inlets or fjords may be called sounds, e.g., Puget Sound, Howe Sound, Karmsund (''sund'' is Scandinavian for "sound"). Some fjord-type inlets are called canals, e.g., Portland Canal, Lynn Canal, Hood Canal, and some are channels, e.g., Dean Channel and Douglas Channel Douglas Channel is one of the principal inlets of the British C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
U-shaped Valley
U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight sides and a flat or rounded bottom (by contrast, valleys carved by rivers tend to be V-shaped in cross-section). Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice, called glacial till or glacial erratic. Examples of U-shaped valleys are found in mountainous regions throughout the world including the Andes, Alps, Caucasus Mountains, Himalaya, Rocky Mountains, New Zealand and the Scandinavian Mountains. They are found also in other major European mountains including the Carpathian Mountains, the Pyrenees, the Rila and Pirin mountains in Bulgaria, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cirque Stairway
A cirque stairway or sequence of cirque steps is a stepped succession of glacially eroded rock basins.Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, p. 95. . Their individual formation is that of a cirque. These steps are arranged one above and behind the other at different heights in the terrain and caused by the same geomorphodynamic processes, albeit resulting in different landform shapes depending on the type of rock and the depositional circumstances involved. The lower step often lacks the steep headwalls typical of cirques.Leser, Hartmut, ed. (2005). ''Wörterbuch Allgemeine Geographie'', 13th ed., dtv, Munich, p. 915 (''Stufenkar''). . A well-known example is the Zastler Loch below the summit of the Feldberg, the highest mountain of the Black Forest in Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overdeepening
Overdeepening is a characteristic of basins and valleys eroded by glaciers. An overdeepened valley profile is often eroded to depths which are hundreds of metres below the deepest continuous line (the thalweg) along a valley or watercourse. This phenomenon is observed under modern day glaciers, in salt-water fjords and fresh-water lakes remaining after glaciers melt, as well as in tunnel valleys which are partially or totally filled with sediment. When the channel produced by a glacier is filled with debris, the subsurface geomorphic structure is found to be erosionally cut into bedrock and subsequently filled by sediments. These overdeepened cuts into bedrock structures can reach a depth of several hundred metres below the valley floor. Overdeepened fjords and lakes have significant economic value as harbours and fisheries. Overdeepened basins and valleys filled with sediment (termed tunnel valleys) are of particular interest to engineers, petroleum geologists, and hydrologists; ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roche Moutonnée
In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock and plucking on the "lee" (downstream) side. These erosional features are seen on scales of less than a metre to several hundred metres.Douglas Benn and David Evans, ''Glaciers & Glaciation,'' Arnold, London, 1st ed. 1998 Etymology The 18th-century Alpine explorer Horace-Bénédict de Saussure coined the term ''Roches moutonnées'' in 1786. He saw in these rocks a resemblance to the wigs that were fashionable amongst French gentry in his era and which were smoothed over with mutton fat (hence ''moutonnée'') so as to keep the hair in place. The French term is often incorrectly interpreted as meaning "sheep rock". Description The contrasting appearance of the erosional stoss and lee aspects is very defined on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valley
A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas. At lower latitudes and altitudes, these glacially formed valleys may have been created or enlarged during ice ages but now are ice-free and occupied by streams or rivers. In desert areas, valleys may be entirely dry or carry a watercourse only rarely. In areas of limestone bedrock, dry valleys may also result from drainage now taking place underground rather than at the surface. Rift valleys arise principally from earth movements, rather than erosion. Many different types of valleys are described by geographers, using terms that may be global in use or else applied only locally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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