ICEBERG. Under this name is understood a detached fragment or section of a glacier, whose terminal foot has reached a body of water, whether fresh or salt, and there broken (calved) off. Fresh-water bergs are those of lakes, and are of comparatively rare oecurrence, and never of large size. The oceanic bergs, on flue other hand, are frequently of very great size: they may measure even miles in length, as those of parts of the Antarctic waters and even of Mel ville Bay. off the west enact of Greenland; and they not infrequently rise 250 or even 300 feet above the surface of the sea. In the case of the flat-topped or even-formed bergs it can readily be inferred from the specific gravity of ice that they at times descend fully 1200 to 1500 feet, or more, into the abyss of the ocean; and it is a Common condition to find the larger bergs `stranded' or anchored at this depth to the floor of the sea. The pinnacled or fancy-shaped bergs are usually those which have undergone considerable weathering or beating up by the sea, and are thus necessarily of smaller size than those of even contour. It is a common statement that the Antarctic bergs differ from those of the Arctic uy their larger and more generally tabular form; but these differences are not fundamental, and are hardly more than comparative. But it may be questioned whether all the larger detached masses of ice in the Antarctic Ocean are, indeed, true glacial bergs; many of them might well be only accumulated sea-ice, formed by accretional growth, independent of any assisting land-mass.
The source of practically all the icebergs of Arctic and sub-Arctic waters is Greenland, from whose ice-cap and radiate off hundreds of glaciers, the vast majority of which—at least those of larger size—reach the sea, either di rectly or through the long fjords which extend 20 to 70 miles into the land. One or more of
the glaciers of :Melville Bay present ocean fronts of 25 or 30 miles, and there are a number of nearly equal size in Western, Southwestern, and Eastern Greenland.
Owing to the northward set of the West Green land current, the bergs of this side are carried first to the north, and it is only at about the 74th or 75th parallel that they begin to make their way westward to come down on the `...Itneri can side.'„ Alany of the East Greenland bergs follow in the trail of these, rounding the south ern apex of the great insular land-mass. The lowest point reached by the bergs in North-At lantic waters is about the western half of the basin; eastward, the zone of distribution, fol lowing largely in the course of Gulf-Stream drift, rises sharply northward, and entirely clears the coast of Scandinavia.
Icebergs are apt to carry much debrital ma terial with them, the remains or parts of the glacial moraines which were formed on land. These, on the melting of the ice, naturally find their way to the bottom of the sea, whether deep or shallow, and these help to build up a `bowlder clay deposit,' somewhat similar to the basal till of glaciers. The stranding of bergs on rock masses also tends to bring about grooving and polishing, again similar to what is produced by moving land-ice (glaciers). Consult Tyndall. The Forms of Water in Clouds and Rivers. Ice. and Glaciers (New York, 1972). See WATER; MELT ING-POINT ; FREEZING-POINT; GLACIER; REFRIGER ATION.