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ICEBERG (from ice and See also: sheet
.
The word is sometimes, but rarely, applied to the See also: arch of an Arctic glacier viewed from the See also: sea
.
It is more commonly used to describe huge floating masses of ice that See also: drift from polar regions into navigable See also: waters
.
They are occasionally encountered far beyond the polar regions, rising into beautiful forms with breakers roaring into their caves and streams of See also: water pouring from their pinnacles in the warmer air
.
When, however, they rest in comparatively warm water, melting takes place, most rapidly at the See also: base and they frequently overturn
.
Only one-ninth of the mass of ice is seen above water
.
When a glacier descends to the sea, as in See also: Alaska, and " advances into water, the See also: depth of which approaches its thickness, the ends are broken off and the detached masses float away as icebergs
.
Many of the bergs are overturned, or at least tilted, as they set See also: sail
.
If this does not happen at once it is likely to occur later as the result of the See also: wave-cutting and melting which disturb their equilibrium" (T
.
C
.
Chamberlin and R
.
D
.
See also: Salisbury, Geology: Processes and their Results, 1905)
.
These bergs carry a load of debris from the glacier and gradually strew their load upon the sea floor
.
They do not travel far before losing all stony and earthy debris, but glacial material found in dredgings shows that icebergs occasionally carry their load far from See also: land
.
The structure of the iceberg varies with its origin and is always that of the glacier or ice-sheet from which it was broken
.
The breaking off of the ice-sheet from a See also: Greenland glacier is called locally the " calving " of the glacier
.
The constantly renewed material from which the icebergs are formed is brought down by the motion of the glacier
.
The ice-sheet cracks at the end, and masses break off, owing to the upward pressure of the water upon the lighter ice which is pushed into it
.
This is accomplished with considerable 'iolence
.
The disintegration of an Arctic ice-sheet is a simpler See also: matter, as the ice is already floating
.
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