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.