At Glacier Bay icebergs are being born all the while.  Muir Glacier, the largest that dips into the bay, presents a front of 5000 feet.  It is 700 feet thick, five-sevenths of it being under water.  It extends back for miles and miles.

Each day the central part moves 70 feet into the sea, the discharge every twenty-four hours being 140,000,000 cubic feet of clear ice.  As this great quantity cracks into pieces from the glacier, the bergs of the North Pacific begin their life.  The separation from the larger mass and the plunge into the sea cause terrific noises.

The interior of Greenland is a solid mass of ice.  In fact, some people think that at about the central part of Greenland there is a high mountain, around whose sides there has grown through the centuries an enormous glacier, sending down in every direction branch glaciers that extend to the coast.  It is known that the only part of the land which is not covered completely by ice is a narrow belt around the shore.

Crossing this belt at hundreds of places are the glaciers.  Some are only a few hundred feet wide and 50 feet thick, while others are several miles wide and measure 1500 feet from surface to bottom.

All of these ice streams are making their way to the sea, and as their ends are forced out into the water by the pressure behind, they are broken off and set adrift as bergs.

Ensign Hugh Rodman, of the United States navy, in his report on the “ice and ice movements in the North Atlantic Ocean,” explains many interesting things about ice and bergs.

Once the glacier extends into deep water, pieces are broken off by their buoyancy, aided possibly by the currents and the brittleness of the ice.

The size of the pieces set adrift varies greatly, but a berg from 60 to 100 feet to the top of its walls, whose spires or pinnacles may reach from 200 to 250 feet in height and from 300 to 500 yards in length, is considered an average size berg in the Arctic.  These measurements apply to the part above the water, which is about one-eighth or one-ninth of the whole mass.

Many authors give the depth under water as being from eight to nine times the height above.  This is incorrect, and measurements above and below water should be referred to mass and not to height.

It is even possible to have a berg as high out of water as it is deep below the surface, for if we imagine a large, solid lump, of any regular shape, which has a very small, sharp, high pinnacle in the centre, the height above water can easily be equal to the depth below.  An authentic case on record is that of a berg grounded in the Strait of Belle Isle, in sixteen fathoms of water, that had a thin spire about one hundred feet in height.

Each glacier in Greenland, so far as any estimate has been made, is the parent each year of from ten to one hundred icebergs.  When these bergs have plunged into the Arctic Sea, they are picked up by the Arctic current and begin their journey to the North Atlantic.  But there are thousands of them afloat; they crowd and rub against each other and frequently they break into smaller masses.