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

THE MOUNTAINS 87
ing. Joly attempted to prove that the accumulation of radioactive
heat in the earth resulted in mountain building at
intervals of 30,000,000 years (244; 235:153). Gutenberg, how-
ever, says that details of Joly's theory have been disproved
(194:158) and, moreover, that the theory includes no mechanism
to account for the 3o,ooo,ooo-year intervals (194:188).
It is impossible to see that the resulting upheaval of the
surface could produce mountain ranges of the patterns that
exist. Joly's theory does postulate a growing earth, but
whether the crust bursts occasionally or is continually col-
it all amounts to the same
lapsing because of shrinking,
thing: neither theory meets the requirements. Attempts have
also been made to explain periodicity as the result of longrange
astronomical cycles, but they have been unsuccessful
(430:281-82). It is obviously difficult to explain mountain
building by astronomical cycles.
For some years, geologists have been looking for a mountain-folding
force below the earth's crust. They have been
investigating the possibility of the existence of currents in
the semiliquid layers under the crust, and speculating on the
possible effects of such currents, if they exist, on the crust
itself. It has been suggested that such currents, rising under
the crust, or sinking, might fold the crust. A sinking current,
for example, would have the effect of drawing the crust to-
gether over it, and pulling it down, forming wrinkles, in
long narrow patterns, like the mountain ranges. Calculations
have been made of the forces that could be brought to bear
upon the crust in this way. Vening Meinesz prefers this way
of accounting for mountain building:
If we examine the pattern of great geosynclines over the earth's
surface, we cannot doubt that their cause must have a world-wide
character. The geology in these belts points to horizontal compression
in the crust, at least during the later stages of their development. The
two main hypotheses suggested to explain these great phenomena are
(i) the thermal-contraction hypothesis, and (2) the hypothesis of subcrustal
current systems of such large horizontal dimensions that, ver-
tically, they must involve at least a great part of the thickness of the
mantle and probably the whole mantle (349:319).