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mistakenly to believe that pressure could reset a rock's magnetization, which
would invalidate the method. As reasons to doubt the paleomagnetic results, Munk
and MacDonald cited this potential flaw, as well as the possibility that the Earth's
magnetic field might not always have been dipolar. But the paleomagnetists had
already debunked those arguments. As for continental drift, Munk and MacDonald
brushed it aside: “The question concerning the reality of such a drift we can, fortu-
nately, avoid.” 5
In his 1962 review of a topic titled Continental Drift , edited by Runcorn,
MacDonald doubled down. 6 Frankel judges that “as far as general nastiness goes,
it rivals anything found in the proceedings of the 1928 American Association of
PetroleumGeologists(AAPG)symposium.” 7 Inalookbackatplatetectonicsfrom
2001, MacDonald had a chance to show that he had reconsidered his earlier opin-
ion. But neither his mind nor his rhetorical style had changed. 8
And what of Harold Jeffreys, whom we met in part 1 attending a 1922 discus-
sion of continental drift? He went on to write a famous textbook, The Earth , and
in the 1959 fourth edition said,
When I last did a magnetic experiment (about 1909) we were warned against careless handling
of permanent magnets, and the magnetism was liable to change without much carelessness
[ sic ]. In studying the magnetism of rocks the specimen has to be broken off with a geological
hammer andthen carried tothe laboratory.Itissupposedthat inthe process its magnetism does
not change to any important extent, and though I have often asked how this comes to be the
case I have never received any answer. 9
This statement insulted the intelligence of paleomagnetists, suggesting that they
lacked theintelligence torecognize that their method isfatally flawed inawaythat
even a third-grader could understand. Of course, paleomagnetists had long been
awareoftheproblemthatJeffreyscalledoutandhadmadetestsshowingthatstrik-
ing a rock with a hammer did not change its magnetism.
Unambiguous, Decisive Proof
Two meetings, one in 1963 and one in 1964, capture in midstream the reversal of
opinion over continental drift. The first focused on ancient climates, the second on
geophysics and the new findings from the ocean basins.
Wegener was much more a climatologist than a geologist, having devoted a
chapter in The Origin of Continents and Oceans to paleoclimatology and also hav-
ing written an important textbook with his father-in-law. The paleomagnetists real-
ized that for independent evidence to corroborate their findings of past latitudes,
they could turn to ancient climates.
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