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

THE ICE AGES 55
tween 6,000 and 4,000 years ago; since then (again with minor fluctua-
tions) it has become cooler and more moist down to the present time.
Apparently as recently as 500 B.C. the climate was still slightly warmer
than it is today. The warm, relatively dry interval of 2000 years' dura-
tion has been called the Climatic Optimum. It is the outstanding
fact of the so-called post-glacial climatic history (156:487).
Dr. Hough attempts to identify the last warm period in
Antarctica with this Climatic Optimum, but we have seen
that, according to his own core, the last temperate period in
Antarctica apparently began 15,000 years ago, and ended
6,000 years ago, thus enduring for some 9,000 years, while
the Climatic Optimum began 6,000 years ago, when the temperate
age was drawing to a close in Antarctica, and endured
for only 2,000 years. It seems to me, therefore, that there is
no good reason to identify the two.
For some time attempts were made to attack the reliability
of the ionium method. I raised the question of these attacks
in a conversation with Einstein and received assurance that
in his opinion the method was reliable. Ericson and Wollin
have recently shown that the results obtained by the ionium
method agree very well with results achieved by other relia-
ble means (Chapter IX). We shall have occasion to cite the
work of Soviet scientists who appear to have used the ionium
method successfully in the Arctic Ocean, and to have ob-
tained results in good agreement with other methods of dat-
ing. We shall see that they have found a warm period for the
Arctic to correspond with the warm period indicated for Ant-
arctica, and at about the same time, just as we should expect
if both areas lay outside of the polar circles when the last
North American icecap was centered at Hudson Bay.
Volchok and Kulp have recently published the results of
a study by which some sources of errors in the use of the ionium
method for dating have been identified. Their results
suggest that in some cases errors in dating may result from
the use of cores that have not been continuously deposited,
or that have been disturbed since their original deposition.
However, in the cases^of the Ross Sea cores cited above we