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 :

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.


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انظر أيضاً

الهامش

  1. ^ Richard S. Williams, Jr. (1987). "Annals of Glaciology, v.9" (PDF). International Glaciological Society. p. 255. Retrieved 7 February 2011.
  2. ^ أ ب Mahapatra, G.B. (1994). Text book of Physical Geology. Nazia printers, Delhi. p. 269. ISBN  81-239-0110-0 .

المراجع

وصلات خارجية