Continental Drift: Not Even Wrong - Four Revolutions in the Earth Sciences - page 79

Continental Drift: Not Even Wrong
Powerful Currents in the Underworld
With the publication of his first scientific paper in 1911, Arthur Holmes started
on a path that would soon establish him as the leading authority on the age of the
Earth. 1 He would remain so well into the 1950s. But Holmes had an equally long-
standing interest in another aspect of radioactivity: heat production. Since the days
of his mentor Robert Strutt, geologists had known that radioactive elements were
widely distributed in the Earth's crust and that the heat they produce must have
played a role in the thermal evolution of the Earth. Holmes set out to uncover that
role.
In 1929, he published two articles that, had the oligarchy of geology taken them
seriously, might have saved the science four decades of wheel-spinning. One titled
“RadioactivityandEarthMovements,”appearinginthe Transactions of the Geolo-
gical Society of Glasgow ( TGSG ), was based on a lecture Holmes had given to the
society in January 1928. His thinking had evolved from regarding radioactive de-
cay as one of several factors in the Earth's thermal history to judging it capable
of generating earth currents that would move continents. 2 A companion three-part
article appeared in Mining Magazine , titled “A Review of the Continental Drift
Hypothesis.” 3
At forty-seven pages, the TGSG paper was a tour de force of scientific reason-
ing. It began by reviewing the various forces that geologists had thought might ex-
plain the Earth's major features: tidal pull from the Moon and the Sun, flight from
the poles, isostatic adjustments, condensation from planetesimals, contraction of
a cooling Earth, and so on. For a variety of reasons, Holmes judged each to have
failed, but even without those reasons the explanations would still have been sus-
pect because they did not take into account radioactive heat. “To ignore the cease-
less outpouring of energy that is everywhere occurring in terrestrial materials,”
Holmes wrote, “would be as wrong as to ignore the effects of gravitation.” 4
Holmes recognized that the planet must be able to discharge the inexorable
buildup of heat from radioactive decay. “To avoid permanent heating-up,” he
wrote, “some process such as continental drift is necessary to make possible the
discharge of heat.” 5 That process was convection in the mantle, which might also
be able to move continents. Thus Holmes arrived at the possibility of continental