علم الجليد

Lateral moraine on a glacier joining the مثلجة گورنر، زرمات، الألپ السويسرية. The moraine is the high bank of debris في الربع العلوي الأيسر من الصورة.

عالمة الجليد إرن پتيت في أنتارتيكا، 2016

علم الجليد (Glaciology من اللاتينية: glacies، "frost, ice", and Ancient Greek: λόγος, logos, "subject matter"; literally "study of ice") is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.

علم الجليد is an interdisciplinary Earth science that integrates geophysics, الجيولوجيا, physical geography, geomorphology, climatology, meteorology, hydrology, biology, and ecology. The impact of glaciers on people includes the fields of human geography and anthropology. The discoveries of water ice on the القمر والمريخ وأوروپا وپلوتو add an extraterrestrial component to the field, which is referred to as "astroglaciology".^[1]

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استعراض

A glacier is an extended mass of ice formed from snow falling and accumulating over a long period of time; glaciers move very slowly, either descending from high mountains, as in valley glaciers, or moving outward from centers of accumulation, كما في المثالج القارية.

مصطلحات جليدية

Ablation: Wastage of the glacier through sublimation, ice melting and iceberg calving.
Ablation zone: Area of a glacier in which the annual loss of ice through ablation exceeds the annual gain from precipitation.
Arête: an acute ridge of rock where two cirques meet.
Bergschrund: Crevasse formed near the head of a glacier, where the mass of ice has rotated, sheared and torn itself apart in the manner of a geological fault.
Cirque, Corrie or cwm: Bowl shaped depression excavated by the source of a glacier.
Creep: Adjustment to stress at a molecular level.
Flow: Movement (of ice) in a constant direction.
Fracture: Brittle failure (breaking of ice) under the stress raised when movement is too rapid to be accommodated by creep. It happens for example, as the central part of a glacier moves faster than the edges.
Horn: Spire of rock, also known as a pyramidal peak, formed by the headward erosion of three or more cirques around a single mountain. It is an extreme case of an arête.
Plucking/Quarrying: Where the adhesion of the ice to the rock is stronger than the cohesion of the rock, part of the rock leaves with the flowing ice.
Tarn: A post-glacial lake in a cirque.
Tunnel valley: The tunnel that is formed by hydraulic erosion of ice and rock below an ice sheet margin. The tunnel valley is what remains of it in the underlying rock when the ice sheet has melted.

معدل الحركة

Movement of the glacier is very slow. Its velocity varies from a few centimeters per day to a few meters per day. The rate of movement depends upon the numbers of factors which are listed below :

Temperature of the ice
Gradient of the slope
Thickness of the glacier^[2]
Subglacial water dynamics

الترسيبات الجليدية^[2]

A kettle pond in Hossa, Suomussalmi municipality, Finland

الطبقي

Outwash sand/gravel: from front of glaciers, found on a plain
Kettles: block of stagnant ice leaves a depression or pit
Eskers: steep sided ridges of gravel/sand, possibly caused by streams running under stagnant ice
Kames: stratified drift builds up low steep hills
Varves: alternating thin sedimentary beds (coarse and fine) of a proglacial lake. Summer conditions deposit more and coarser material and those of the winter, less and finer.

غير الطبقي

Drowned drumlin in Clew Bay, Ireland

Till-unsorted: (glacial flour to boulders) deposited by receding/advancing glaciers, forming moraines, and drumlins
Moraines: (Terminal) material deposited at the end; (Ground) material deposited as glacier melts; (lateral) material deposited along the sides.
Drumlins: smooth elongated hills composed of till.
Ribbed moraines: large subglacial elongated hills transverse to former ice flow.

انظر أيضاً

الهامش

^ Richard S. Williams, Jr. (1987). "Annals of Glaciology, v.9" (PDF). International Glaciological Society. p. 255. Retrieved 7 February 2011.
^ ^أ ^ب Mahapatra, G.B. (1994). Text book of Physical Geology. Nazia printers, Delhi. p. 269. ISBN 81-239-0110-0.{{cite book}}: CS1 maint: location missing publisher (link)

المراجع

Benn, Douglas I. and David J. A. Evans. Glaciers and Glaciation. London; Arnold, 1998. ISBN 0-340-58431-9
Greve, Ralf and Heinz Blatter. Dynamics of Ice Sheets and Glaciers. Berlin etc.; Springer, 2009. ISBN 978-3-642-03414-5
Hambrey, Michael and Jürg Alean. Glaciers. 2nd ed. Cambridge and New York; Cambridge University Press, 2004. ISBN 0-521-82808-2
Hooke, Roger LeB. Principles of Glacier Mechanics. 2nd ed. Cambridge and New York; Cambridge University Press, 2005. ISBN 0-521-54416-5
Paterson, W. Stanley B. The Physics of Glaciers. 3rd ed. Oxford etc.; Pergamon Press, 1994. ISBN 0-08-037944-3
van der Veen, Cornelis J. Fundamentals of Glacier Dynamics. Rotterdam; A. A. Balkema, 1999. ISBN 90-5410-471-6

وصلات خارجية

[1] Richard S. Williams, Jr. (1987). "Annals of Glaciology, v.9" (PDF). International Glaciological Society. p. 255. Retrieved 7 February 2011.

[:0-2] أ ^ب Mahapatra, G.B. (1994). Text book of Physical Geology. Nazia printers, Delhi. p. 269. ISBN 81-239-0110-0.{{cite book}}: CS1 maint: location missing publisher (link)

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