Glaciers

Question	Answer
Factors affecting the snow line?	quantity of snow fall, steepness of slope, exposure of an area to sun + prevailing wind, type + velocity of wind, presence/ absence of large bodies of water, distance from equator
How glaciers form...	Zone of accumulation- snow added Zone of ablation- snow removed
First stage of glacier formation	snow falls as flakes with a feathery structure that traps air
Second stage...	snow accumulates and becomes more compressed from layers above. Gradually turns into a more compact form of snow called 'neve' or 'firn'
Third stage...	continuos melting and refreezing fills gaps in the snow
Alpine glacier/ warm glacier?	Smallest type, retreats in summer and advances in winter due to temps, glacier moves quickly due to meltwater, they erode, transport and deposit
Polar glacier/ cold	• Found in areas below 0 degrees so little melting/ movement • Ice sheets also smaller ice caps/ ice fields • Movement is slower as they are frozen to beds and move internally Less erosion, transportation and deposition
Valley glacier	large mass of ice flows down a previously smaller valley in periglacial area
Piedmont glacier	larges lobes of ice which forms where valleys ice spreads out as it reaches lower areas
Niche glacier	small patches of glacier ice on upland slopes
Ice caps	huge flattened dome shaped ice that form on high plateaus, similar to ice sheets but smaller than 50,000km2, more than that =ice sheets
ice shelf	extension of an ice sheet that reach out over sea, can be up to 1000km thick
Why does a glacier move at different speeds?	Different parts of glacier move at different speeds due to different degrees of friction, because of this the top (brittle + cracks) forms crevasses
Main factors affecting ice movement?	Friction, ice temp, mass, meltwater and gravity
type and rate of movement in a glacier	compressional flow, internal flow, basal flow, rotational flow, extensional flow, crevasses
why does the bottom layer of glacial ice turn blue/ green?	due to no air
how do glaciers move?	weight of ice due to gravity, temp, melt water, mouldable lower layer (ductile zone), removes obstacles by becoming attached to constant freezing & thawing outer layers
Basal flow/ sliding?	large blocks of ice move in short jerks, melt water lubricates base formed by pressure of weight (pressure melting), it reduces friction, where obstacle meltwater allows glacier to flow over and then refreezes
Internal flow/ internal deformation	slow movement within glacier, ice crystals slip + slide over each other(gravity), surface ice moves faster= crevasses, takes place in all glaciers
Creep	stress builds due to obstacle in path, flows around it and erodes sides
Surges	excessive melt water under glacier= rapid movement (250-300 m per day)
extended flow	valley becomes steeper, ice flows faster + becomes thinner as it stretches,= crevasses and less erosion
Compressing flow	valley becomes less steep, ice slows + thickens then piles up. Crevasses may close and lots of erosion
Rotational flow	curved movement back and forth, important in formation of corrie
INPUTS	snow + rain, avalanches along valley side, eroded sediment picked up by ice
TRANSFERS STORED PROCESSES	Ice flow Ice Erosion, transportation & deposition
OUTPUTS	water vapour, melt water, sediment deposited, calving (ice bergs breaking off)
Zone of accumulation	occurs in upper reaches of glacier where yearly additions of snow exceeding losses due to melting + evaporation. Surface zone covered in snow. INPUTS EXCEED OUTPUTS.
Zone of ablation	losses of snow + ice from melting, evaporation + sublimation are greater than the additions. OUTPUTS EXCEED INPUTS- NET LOSS OF ICE

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	Created by Alice Kimpton over 8 years ago