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

CONCLUSION 381
sized by Brown, that the present Antarctic icecap is larger
than the last North American icecap. If Campbell's calcula-
tions are close to the truth, it seems that the bursting stresses
in the crust may now be close to the critical point, from this
source alone. Yet there is also a possibility that the centrifu-
gal effect of the Antarctic icecap may at the present time be
supplemented by another significant centrifugal effect cre-
ated by the icecap in Greenland. It is true that the Greenland
cap is much smaller than the one in Antarctica, but, on the
other hand, its center is much farther from the pole. For
this reason it could conceivably have an important centrifu-
gal effect. Its position on the meridian is such that any un-
mass would add to rather than counteract the
compensated
effect of the Antarctic cap; the two icecaps are, so to speak,
in tandem.
In recent years a French polar expedition has taken many
gravity readings across the top of the Greenland icecap. The
purpose of these readings was to assemble data for a determination
of the state of isostatic adjustment of the Greenland
cap. The results of this piece of research are instructive for
the whole subject of isostasy. They can be read two ways. On
the one hand, the gravity data when reduced according to
one of the formulas in common use the Faye-Bouguer -
showed an enormous excess of mass in Greenland (441:60-
61); on the other hand, the same data, when reinterpreted
differently, resulted in a finding of good isostatic adjustment.
It is important to realize that the different methods
of reducing gravity data are based on varying assumptions
regarding the deeper structure of the earth's crust, and that
these assumptions are not subject to direct confirmation.
Daly at one time remarked that he did not believe that any
of the different methods of evaluating gravity data came very
near the actual truth. It is reasonable to think that the se-
lection of assumptions in this field may be influenced by a gen-
eral belief in the soundness of isostasy, and that this general
belief will lead to a preference for those assumptions that
result in findings of close isostatic adjustment. It is perhaps