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.
Many go aground in the Arctic basin; others get to the shores of Labrador, where from one end to the other they continually ground and float. Some disappear there, while others get safely past and reach the Grand Banks.
According to Ensign Rodman, the ice of bergs, although very hard, is at the same time extremely brittle. A blow of an axe will at times split them, and the report of a gun, by concussion, will accomplish the same end.