ICEBERGS.
When glaciers advance into water, the depth of which approaches their thickness, their ends are broken off ([Fig. 284]), and the detached masses float away as icebergs ([Fig. 285]). Many of the bergs are overturned, or at least tilted, as they set sail. If this does not happen at the outset, it is likely to occur later as the result of the melting and wave-cutting which disturb their equilibrium. The great majority of bergs do not travel far before losing all trace of stony and earthy débris, but the finding of glacial material in dredgings far south of all glaciers shows that they occasionally carry stones far from land.
Fig. 284.—End of Muir glacier, Alaska. (Reid.)