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

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EARTH'S SHIFTING CRUST
ber of consultants have been in doubt on this point because
of their knowledge that the crust is, from certain points of
view, very weak. It has little tensile strength, and as a conse-
quence cannot bear heavy loads without fracturing or giving
way by plastic flow. However, tensile strength and crushing
strength are two very different things. A bar made of a brittle
but hard substance will have little tensile strength, but con-
siderable force may be required
to crush it. The rocks com-
posing the earth's crust are highly rigid, and therefore, despite
the fact that they have little tensile strength, such as
would be required to contain vertical stresses, they have
enormous strength to resist horizontally applied compressive
stresses. They simply cannot be compressed to any extent,
and only an enormous force will produce plastic flow. The
rocks of the crust are so rigid (despite the fact that they do,
of course, possess a certain small degree of elasticity) that the
penetration of the crust by fractures does not seriously mod-
ify its power to transmit horizontal or tangential stresses.
There is geological evidence in the mountain systems, in the
planetary fracture systems, in the great globe-encircling canyon
system recently discovered by Ewing, that stresses have
been applied to the earth's crust as a whole, and various geol-
ogists, including Hobbs and Umbgrove, have made statements
to that effect.
A proper understanding of this question requires that the
magnitude of the stress and its mode of application should
be considered. An enormous pressure per square inch, especially
if applied all at once, might cause local deformation of
the crust by bringing about rock flow, as it has been sug-
gested by Bridgman (p. 189), but the stresses that we suppose
to derive from the icecap are not of this order, nor do they
reach their maximum intensity until after a period of gradual
growth during which they could be transmitted to the crust
as a whole. The icecap produces a gentle pressure, slowly
growing and steadily applied over a considerable length of
time, incapable of radically deforming the crust adjacent to