Zusammenfassung der Ressource
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