ICEBERG, a mass of floating ice, usually detached from the front of a glacier, though the term is also applied to floe ice that has frozen on the surface of the ocean and then broken up. The fronts of many Alaskan and Greenland glaciers are discharging icebergs al most continuously. The ice masses may break away from the glacier as a result of under mining by waves, as a result of large blocks shearing away from the ice cliffs due to their weight and the great height of the cliff (300 to 500 feet in some cases), or as a result of the buoyant effect of the deep water into which they flow.
Ice in the north Atlantic occurs in three forms: slab ice, ice fields and icebergs. Slab ice is sea-ice formed in the river mouths, as in Labrador, occurring in sheet or circular masses. Ice fields are caused by the freezing of the sea itself and come usually from Labra dor, though occasionally from Greenland. These two forms are not particularly danger ous to mariners, but may become so by mass ing or freezing to an unusual thickness. Ice bergs, however, which are always freshwater ice, are never anything but dangerous, and constitute the deadliest menace to navigation that ships have to face.
All the icebergs that are so perilous to travel in the transatlantic routes come from Green land, in the neighborhool of Melville Bay, or outlying islands. Greenland is itself a huge, dome-shaped island covered with an ice-cap in places probably more than a mile in thickness. The western slope is far more extensive and it is on this side that most of the icebergs are formed; those that are made on the east coast are smaller, fewer in number, and, being quickly broken up by the open Atlantic waves, melt before they float far south.
The immense glaciers on the West Greenland side are constantly descending and push out to sea in enormous qtongues,° as they find their way down the ice-covered mountains. These °tongues° form icebergs in three ways. Masses of ice may simply break off of their own weight; the sea waves may undermine the °tongue° until the weight of overhanging ice causes it to fall into the sea — a process called °calving°; or the ground swell of the ocean may dislodge large blocks of ice from the base of the glaciers. This glacier ice is unlike any other, having become exceedingly hard and flintlike from the enormous pressure; and, mingled with it, on the underside, are often boulders, stones, soil and other detritus. This is the birth of the iceberg — masses of ice of all shapes and sizes, launched into the sea every day of the year, but most generously in the short Arctic summer and contributed to by every mile of coast from Cape Farewell to Disco Bay, tributary to 120,000 square miles of ice cap. There is a single glacier that furnishes 200,000,000,000 cubic feet annually in icebergs.
These icebergs, as released, drift across the entrance of Baffin's Bay and Davis Strait to the Labrador coast. Here they catch the Labra dor current and drift slowly southward on a journey of weeks or months — that is, for those that manage to escape to the open. The great
majority of them become grounded or are immeshed by the numerous islands and bays that mercifully line the Labrador coast and protect the Atlantic in large measure from the iceberg menace. Those that finally make their way through—and they are countless in num ber—divide into two streams, one passing through the Strait of Belle Isle into the Gulf of Saint Lawrence, and the other, much the larger, going to sea by the way of the Grand Banks of Newfoundland. The aBanks,° it is interesting to note, have been formed, it is thought, by the detritus brought down from Greenland by icebergs through unnumbered ages and dropped here,• as the icebergs disin tegrated, to become the breeding ground of cod, herring and other fish used by man.
When icebergs reach this point, they seem of every size, shape and contour, some of them rising to a hundred or more feet in height, with spires of crests or °minarets° 200 to 300 feet above the base, which may be hundreds of yards in length. From one-eighth to one-ninth of the mass— not necessarily height — lies above water. It must be remembered that mass and height are very different qualities. It is quite possible that an iceberg is disintegrating in such a way that it is as high out of the water as it is deep below the surface.
Icebergs reach the transatlantic routes in greatest numbers in April, May and June, but may be met with earlier and later. During the months named a more southern route is chosen by the ocean steamships. The place of most frequent contact with icebergs is at latitude 42° 45' and longitude 47° 52', where the Labra dor current meets the Gulf Stream. It was at about this point that the Titanic met her fate in April 1912. The iceberg peril is lessened by the issuance of monthly "pilot charts" through the United States Hydrographic Office, which locate ice fields observed the previous month. Little reliance can be placed on the various devices invented to detect the vicinity of icebergs in foggy weather, though an "echo recorder" has been invented which is some times of service. But in spite of all precautions icebergs may creep upon a mariner unawares, and, with fog, are his deadliest peril.
Icebergs disintegrate very rapidly, beginning almost as soon as they are afloat. This is due in part to the fact that there is so marked a difference between the tension of the exterior and interior portions of such a mass of ice. The water that melts on an iceberg during the day works its way into crevices, and then, freezing at night, expands and splits the ice, often violently. After the icebergs get out of the Labrador current, disintegration goes on naturally and much more rapidly. They finally disappear about 400 miles south of Nova Scotia, the 'Graveyard of the Iceberg," a point which they have to travel over 2,000 miles to reach.