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The Nature and Impact of Glaciation and Deglaciation
The French Alpes are an excellent place which illustrate the impact of glaciation and deglaciation. The areas
of Glacier Blanc and Glacier Noir have been chosen as examples to show the characteristics of such processes and
the resulting Impact on the geomorphology of the area as a whole, namely erosion and deposits.
Glaciation: process of growth and spreading ice sheets and glaciers to cover a major portion of the Earth's
land (approx. 30% during height of Pleistocene glaciations).
The Glacial System
A glacier, a slow-moving river of ice, academically considered having a system, where two processes work over the
periods of summer and winter. The positive process of the winter months, akin to a production line of ice and debris,
this is namely accumulation, which has the building mechanism for the spreading of the glacier. Input of snow to
the glacier head, which becomes ice due to gravitational pressure, is fed in through the glacier, gravity takes
its toll and the glacier gives, creating movement and the mode to transport. Transporting itself, the glacier and
debris from under the glacier and above via rock fall.
Obviously if the accumulation process is in excess the head of the glacier would become steep thus giving the
glacier a greater velocity with flow. When this occurs, advancement of the ice river pushes further down the valley.
(Clowes and Comfort, 1994)
So, glaciation is where precipitation in the form of snow has covered an area and has eventually been converted
into ice by force of gravity and pressure. Accumulation of such ice would be found on mountains or near the poles.
As the ice gathers and layers itself, gravity forces it down thus creating a slowly moving mass, a river of ice,
a glacier. During the colder seasons, the glacier will advance downward. Gravitational pressures are created as
more snow and ice accumulates in the highlands. During this process the land begins to be carved, moulded and shaped
by the glaciers erosional capacity.
Deglaciation: is the opposite, the shrinking of ice Aeets and glaciers to uncover land areas; the world
is presently in an interglaciation in which roughly 10% of the land is ice covered'.
During the summer months at the other end of the glacier an adverse process is in play, the negative. This is called
ablation, rather than an input to the glacier this process acts as the output, output of glacial melt water and
moraine which are continuously flushed from the glacial system. So, during summer the glacier begins to melt and
releases its melt water and debris carried within the glaciers storage system. As it slowly recedes it deposits
such debris, pushing large amounts to its sides and front. Stone stored within the glacier is deposited along the
valley after a period of time, resulting in mounds such as drumlins, erratics, eskers, and moraines.
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(Waugh, 1990)
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There are different types of glacier that can be seen here as well as the evidence of receded glaciers, for instance:
CIRQUE GLACIERS
A deep bowl-shaped hollow at the head of a valley or on a mountainside, created by an accumulation of ice in
a shaded or sheltered hollow is what is namely a cirque glacier. Gravity and weathering enlarges the hollow to
such a deep, circular shape. The action is similar to that of a front-end loader or an ice cream scooper. These
glaciers are usually quite short in length and are confined to the hollowed-out area. If the cirque has a large
enough accumulation of snow and ice they feed a valley glacier.
VALLEY GLACIERS
Due to its name the valley glacier is contained between valley walls, often enroute to a preglacial river valley
which is deepened by erosion of ice. The valley glacier is a river of ice moving from highland, where ice accumulates
over time.
PIEDMONT GLACIERS
These are magnificent features where valley glaciers come together. Ice of each of the valley glaciers amalgamate
and form a roundish and flattish projecting glacier which extends over the mountain ranges, the piedmont variety
of glacier is then formed.
ICE-CAPS
A sight to be found along the mountaintops and mountain plateaux, where ice accumulates and flows outwards usually
to meet and feed valley glaciers.
Nick Catahan
Bibliography
Glossary of ice terms. www.academic.emporia.edu/aberjame/ice/gloss.htm (September 1999). U.S.A.
Clowes, A. and Comfort, P. (2nd ed.)(1994). Process and Landform Conceptual frameworks in Geography.
Oliver & Boyd, London.
Nagle, G. and Spencer, K. (1997). Advanced geography. Oxford University Press, Oxford.
Waugh, D. (1990). Geography an integrated approach. Thomas Nelson & Sons Ltd. U.K.
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