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

CONTINENTS AND OCEAN BASINS 157
It is not quite clear, however, why such opposed movements should
have occurred in areas of almost equal extent. Nor is it clear why
these movements should have occurred in such a way that the sea-
level remained comparatively stable. . . . (430:235-36).
But a displacement of the crustor several displacements
would fulfill all these requirements. In a displacement two
quarters of the surface, opposite each other, must move toward
the poles, while the other two quarters must move toward
the equator. Whatever forces tend to produce uplift in
the poleward-moving areas will be balanced by equal forces
producing subsidence in the quarters moving equatorward.
And the sea level would be stable, except for very minor
fluctuations.
Barrell himself suggests that subsidence of continental
areas would be aided by liquid intrusions, "the weight of
magmas of high specific gravity rising widely and in enormous
volume from a deep core of greater density into these
portions of an originally lighter crust. . . ." (430:235-36).
Barrell's suggestion points to the chief weakness of the
geophysical argument in favoi of the permanence of the con-
tinents. As I have already pointed out, geophysicists seem,
too often, to take as the frame of reference only the outermost
ten miles or so of the crust. Theoretically they base
calculations on the full depth of the crust, but practically
this assumption is cancelled out by the assumption that the
crust is arranged in layers of equal density, so that significant
are excluded. But if the real
changes of density in depth
possibilities of changes of average density in the full depth
of the crust are taken into account, the difficulties in the
face of the subsidence and elevation of continents vanish.