The Earth's Shifting Crust by Charles Hapgood - wire of information

170
EARTH'S SHIFTING CRUST
see that the icecap has accumulated nonetheless, and that it
is now accumulating. Thus we can safely conclude that these
anticyclonic winds have not prevented, and can never prevent,
the continuing growth of the ice sheet.
One other factor may limit the accumulation of ice. Ice-
bergs break off from the icecap every year in great numbers,
and it has even been suggested that they may amount to
roughly the entire annual deposition of snow upon the conti-
nent. How far this is from representing the true state of
affairs can be determined from the following considerations.
In the first place, the icebergs form, it is generally agreed,
because the ice sheet is flowing slowly outward from the pole
in all directions, by the effect of gravity. The ice has accumu-
lated in the central area of the continent to a great but as yet
unknown depth, and from this central area the surface of the
ice sheet slopes gently downward toward the coasts. It is
recognized
that what sets the ice sheet in motion is not the
slant of the land it lies on (it would move even if the land
were all flat) but the angle of the slope of its own surface:
the gradient (87:46). This being the case, two factors govern
the speed of movement: the more gradual the gradient, the
slower the ice flows, while the colder the ice, the greater its
viscosity and its resistance to movement. Now, in Antarctica
it has been observed that the gradient is only one third of the
gradient in Greenland, where, despite a more rapid movement
of the ice, the glacier still maintains itself approxi-
mately in a static condition. The Antarctic, in addition, is
much colder, and therefore its ice is more viscous, more rigid,
more resistant to motion. What the temperatures deep in the
icecap are is at present unknown, but they are probably considerably
lower than those in the northern glaciers. Coleman
notes how much slower is the movement of ice in Antarctica
than it is in Greenland (87:44). (See n. i, p. 192.)
Brown has correctly pointed out that a large production of
icebergs, such as we note in Antarctica, is a sign of an expanding
glacier, while a dwindling supply of icebergs is evidence
of an icecap in decline (54). Einstein was of the opinion that