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64688
Cold Enviroments
Descripción
Geography-Food Supply Mapa Mental sobre Cold Enviroments, creado por hughwhitlock96 el 01/05/2013.
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geography-food supply
geography-food supply
Mapa Mental por
hughwhitlock96
, actualizado hace más de 1 año
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hughwhitlock96
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Resumen del Recurso
Cold Enviroments
Glaciers movement
Basal Slippage
this is a sliding effect of the glacier over the bedrock by either regelation slip or creep
regelation slip operates most effectively with smaller obstacles, while creep is the process that overcomes larger obstacles
on the upglacier side of an obstacle, the increasing pressure in the lower ice causes pressure metiling locally.
this meltwater permits slippage of the ice cover the obstacle but then refreezes in the lower pressure conditions of the downside of the obstacle.
internal flow/ internal deformation
this is the movement within the glacier ice resulting from the stresses applied by the force of gravity.
Where ice crystals orientate themselves in the direction of the glaciers overall movement, they may slide past eachother.
Such movements often result in the formation of crevasses within and at the surface of the ice
Landforms produced by glacial erosion
Aretes
these are formed when 2 or more ciques erode back towards each other from opposing sides, they produce a knife edge ridge between them called an arete
e.g. Striding Edge above Red Tarn, Lake District
Pyramid Peaks
where 3 or more cirques erode back towards each other, a pyramind peak may form.
e.g. the Matterhorn
Landforms
Roche moutonnes
masses of more resistant rock that have smooth, rounded upvalley slopes formed by abrasion. the downvalley sides are steep and jagged.
which reflects the plucking action that formed them
Abrasion on the upvalley side may have left striations as pieces of rock debris within the ice were dragged accross the surface under great pressure
Rock Drumlins
these are more streamlined bedrock and lack the jagged downhill slope.
Crag & Tail
this consists of a larger mass of resistant rock or crag and a gently sloping tail of less resistant rock/ or sediment on one side.
Striations
when glaciers move accross exposures of rock, angular debris embedded within the ice may leave paralell scratches and grooves called strations
Glacial Deposition
Till
all material deposited directly by the ice, largely unsorted in nature
Fluvioglacial material
sediments deposited by meltwater streams. these usually have been sorted with coarser material nearer the the original glacier snout.
finer particles carried further way by the meltwaters.
Moraines
Lateral Moraine
formed from debris fallen from the sides of the valley and transported along the edges of the glacier.
After glaciation it appears as elongated embankments of debris at the sides of the valley.
Medial Moraine
where 2 glaciers meet, the lateral moraine may combine to form a medial moraine towards the middle of the main glacier.
this may eventually form some deposition features once the glacier has retracted.
however the location of the medial moraine towards the middle of the valley may be destroyed by subsequent fluvioglacial action
Terminal Moraine
this is often a high mound or series of mounds of debris that extend across a valley, it marks the furthest extent of the glacier
Influences on the rate of movement
snow and ice masses do not generally move downslope until the thickness exceeds 60m
steep glaciers flow faster than gently graded ones and thus are usually thinner
the amount of precipitation and ablation are significant factors
the greatest velocity is usually at the firn line, as velocity is directly related to thickness
the centre of the glacier, where the ice is thickest, moves more rapidly than the margins, where friction plays a considerable role in reducing speed
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