Geology Reference
In-Depth Information
ten years later, and nearly twenty years since Wegener had first
proposed his ideas, the controversy was in full flood.
As we have seen, geologists are frequently not very receptive
to new ideas. Years later, at the age of eighty, Doris Reynolds
succinctly summed up the situation:
Geology is always like this, very slow moving. When a new geologi-
cal discovery or suggestion is made it is quite quick if it is noticed in 20
years, and may take 50 to 100 or more. Then dogmas form obstructions .
Indeed, for fifty years dogma formed obstructions to con-
tinental drift, and only a few enlightened individuals recog-
nised early on that it was the only way so many geological
phenomena could be explained. Arthur Holmes had long been
part of that small group.
While work on the uranium-lead dating techniques was in
abeyance, Holmes was looking for some other problem to get
his teeth into. With his profound understanding of radioactivity
- the amount of heat it generated within the Earth, and the
enormous time it bestowed on geology for infinitely slow
processes - he found himself placed in a unique position to for-
mulate a mechanism for continental drift. So as soon as he had
established his teaching routine at Durham he seriously started
to formulate his ideas, and in December 1927 he read a ground-
breaking paper to the Edinburgh Geological Society. In it he
proposed that di¬erential heating of the Earth's interior,
generated by the decay of uranium and other radioactive
elements, caused convection in the substratum, on which the
continents floated, rather like icebergs in the sea. Although the
substratum was essentially considered to be solid, Holmes
believed that given enough time, and of all people Holmes knew
that there was enough time, it actually behaved like a very thick
liquid. (Roman glass, for example, today shows evidence of hav-
ing 'flowed' during the last 2000 years.) The di¬erential heat-
ing caused convection cells to form, rising in some places and
descending in others, behaving in much the same way as trea-
cle would if heated in a saucepan on the stove. As hot material
 
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