|
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 down ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyramidal Peak
A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are often examples of nunataks. Formation Glaciers, typically forming in drainages on the sides of a mountain, develop bowl-shaped basins called cirques (sometimes called ‘corries’ - from Scottish Gaelic ʰəɾə(a bowl) - or s). Cirque glaciers have rotational sliding that abrades the floor of the basin more than walls and that causes the bowl shape to form. As cirques are formed by glaciation in an alpine environment, the headwall and ridges between parallel glaciers called arêtes become more steep and defined. This occurs due to freeze/thaw and mass wasting beneath the ice surface. It is widely held that a common cause for headwall steepening and extension headward is the crevasses known as bergschrund that occur between the moving ice and the he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarn (lake)
A tarn (or corrie loch) is a Proglacial lake, proglacial mountain lake, pond or pool, formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn. Etymology The word is toponymy, derived from the Old Norse word ''tjörn'' ("a small mountain lake without tributaries") meaning pond. In parts of Northern England - predominantly Cumbria but also areas of North Lancashire and North Yorkshire - 'tarn' is widely used as the name for small lakes or ponds, regardless of their location and origin (e.g. Talkin Tarn, Urswick Tarn, Malham Tarn). Similarly, in Scandinavian languages, a ''tjern'' or ''tjørn'' (both Norwegian) or ''tjärn'' or ''tärn'' (both Swedish) is a small natural lake, often in a forest or with vegetation closely surrounding it or growing into the tarn. The specific technical use for a body of water in a glacial corrie comes from high number of tarns found in corries in the Lake District, an upland area in Cumbria. Nonetheless, there are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires distinguishing features, such as Crevasse, crevasses and Serac, seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand. Between lati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bergschrund
A bergschrund (from the German for ''mountain cleft'') or rimaye (from French; ) is a crevasse that forms where moving glacier ice separates from the stagnant ice or firn above. It is often a serious obstacle for mountaineers, who sometimes abbreviate "bergschrund" to "schrund". Bergschrunds extend to the bedrock and can have a depth of well over . The bergschrund is distinct from the randkluft (also called ''rimaye''), which is the crevasse of which one face is the rock, back wall of the corrie. The randkluft arises in part from the melting of the ice due to the presence of the warmer rock face. However, the randkluft is sometimes called a bergschrund. The French word ''rimaye'' covers both notions of randkluft and bergschrund. In a corrie or cirque, the bergschrund is positioned at the rear, parallel to the back wall of the corrie. It is caused by the rotational movement of the glacier. In a longitudinal glacier, the bergschrund is at the top end of the glacier at a right angl ... [...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] |
Cliff
In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs. An escarpment (or scarp) is a type of cliff formed by the movement of a geologic fault, a landslide, or sometimes by rock slides or falling rocks which change the differential erosion of the rock layers. Most cliffs have some form of scree slope at their base. In arid areas or under high cliffs, they are generally exposed jumbles of fallen rock. In areas of higher moisture, a soil slope may obscure the talus. Many cliffs also fea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Headwall
In physical geography and geology the headwall of a glacial cirque is its highest cliff. The term has been more broadly used to describe similar geomorphic features of non-glacial origin consisting of a concave depression with convergent slopes typically of 65 percent or greater forming the upper end of a drainage valley. In civil engineering, a headwall is a small retaining wall placed at the inlet or outlet of a stormwater pipe or culvert A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom .... In medicine, a headwall is the wall at the head end of a hospital bedspace. The bed abuts this headwall perpendicularly, which is furnished with equipment such as regulators for supplemental oxygen, regulators for suction, suction canisters, connections for the call bell system, lighting, elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nivation
Nivation is the set of geomorphic processes associated with snow patches. The primary processes are mass wasting and the freeze and thaw cycle, in which fallen snow gets compacted into firn or névé. The importance of the processes covered by the term ''nivation'' with regard to the development of periglacial landscapes has been questioned by scholars, and the use of the term is discouraged. ''Nivation'' has come to include various subprocesses related to snow patches which may be immobile or semi-permanent. These sub-processes include erosion (if any) or initiation of erosion, weathering, and meltwater flow from beneath the snow patch. Weathered particles are moved downslope by creep, solifluction Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to it ... and rill wash. Over time, thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Segregation
Ice segregation is the geological phenomenon produced by the formation of ice lenses, which induce erosion when moisture, diffused within soil or rock, accumulates in a localized zone. The ice initially accumulates within small collocated pores or pre-existing cracks, and, as long as the conditions remain favorable, continues to collect in the ice layer or ice lens, wedging the soil or rock apart. Ice lenses grow parallel to the surface and several centimeters to several decimeters (inches to feet) deep in the soil or rock. Studies between 1990 and present have demonstrated that rock fracture by ice segregation (i.e., the fracture of intact rock by ice lenses that grow by drawing water from their surroundings during periods of sustained subfreezing temperatures) is a more effective weathering process than the freeze-thaw process which older texts proposed."Periglacial weathering and headwall erosion in cirque glacier bergschrunds"; Johnny W. Sanders, Kurt M. Cuffey, Jeffrey R. Moo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abrasion (geology)
Abrasion is a process of erosion which occurs when material being transported wears away at a surface over time. It is the process of friction caused by scuffing, scratching, wearing down, marring, and rubbing away of materials. The intensity of abrasion depends on the hardness, concentration, velocity and mass of the moving particles. Abrasion generally occurs in four ways: glaciation slowly grinds rocks picked up by ice against rock surfaces; solid objects transported in river channels make abrasive surface contact with the bed and walls; objects transported in waves breaking on coastlines; and by wind transporting sand or small stones against surface rocks. Abrasion, under its strictest definition, is commonly confused with attrition and sometimes hydraulic action however, the latter less commonly so. Both abrasion and attrition refers to the wearing down of an object. Abrasion occurs as a result of two surfaces rubbing against each other, resulting in the wearing down of one o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Abrasion (geology)")