Great Geologists | 85
and South America, especially at the
“Urkontinent”, or Pangea. Had the
edge of their respective continental
continents once been conjoined
shelves. Reading a paper by Erich
then their geology should match at
Krenkel in July 1911 that mentioned
the edges “it is just as if we were to
the similarities of the Cretaceous
refit the torn pieces of a newspaper
geology between Brazil and Africa
by matching their edges and check
further piqued his interest, as did
whether the lines of print run smoothly
a paper on the “Former ice ages
across” he wrote. “If they do, there is
of Earth” by Konrad Keilhack
nothing left but to conclude that the
that outlined the similarities in
pieces were in fact joined in this way”.
Carboniferous geology of the
For Wegener, one of the most obvious
Southern Hemisphere continents.
examples of this was the distribution
In rapid time he assimilated a good
of late Paleozoic glacial deposits. Two
deal of geological data such that
examples of paleontological matching
by January 6th, 1912, he was able
across continents were cited. First were
to give a lecture on his developing
fossils of the small Permian reptile,
theory to the German Geological
Mesosaurus, found in identical rocks
Association in Frankfurt, followed by
in south-eastern Brazil and south-
an article in the journal Petermanns
western Africa. Second was the fossil
Geographischen Mitteilungen.
fern Glossopteris, found across the
Despite serving in the German
Southern Hemisphere. To Wegener
Army in the First World War, (and
their distribution suggested continental
being twice wounded) by 1915 he
juxtaposition.
had prepared a first version of his
As well as gathering empirical
Professor Alfred Wegener Circa 1924. Photographer
book summarizing his theory on
unknown.
evidence to support his theory
The Origins of the Continents and
of moving continents he also
Oceans. Four editions would appear,
understood that isostasy implies
the last in 1929, and the 1922 edition, translated into several
a different nature of oceanic and continental crust and that
languages, would open up an often heated and vigorous debate
this crust must lie on a material that has fluid properties.
within the geological community on the validity of the theories
Therefore “if…the continental blocks really do float on a fluid…
expressed within it.
there is clearly no reason why their movements should only
Wegener was not the first to notice the apparent fit of the
occur vertically and not also horizontally”. He supposed that
continents if moved from their present day position, nor was
the driving mechanisms might be the centrifugal force of the
he the first to suggest that the continents had indeed moved.
Earth’s rotation (“Polflucht”) or astronomical precession, but
Abraham Ortelius, compiler of the first global atlas, noted in
with some degree of foresight noted that “it is probable….that
1596 that the Americas had been “torn away from Europe and
the complete solution of the driving forces will still be a long
Africa….by earthquakes and floods”. In 1910 the American
time coming”.
geologist Frank Taylor proposed that tidal forces generated by
To say that the geoscience community of the 1920’s was
the capture of a comet that is now the moon caused continents
skeptical about the idea of continental drift would be an
to slide from the poles towards the equator. Unlikely as this
understatement. Land bridges across oceans were invoked
theory is, he did correctly suggest that the Himalayas originate
to explain paleofaunal and paleofloral similarities between
from collision between India and Asia and noted the importance
continents, or faunal and geological similarities were simply
of the mid-Atlantic ridge as suggestive of progressive separation
denied to exist. Geophysical arguments were presented to
of Africa and South America.
deny the possibility of crustal movement.
Wegener’s critical contribution was to bring together all the
Most telling was that the theory that Wegener suggested
evidence that suggested that the continents could have
for continental movement was (rightly) deemed impossible.
been conjoined around 300 million years ago into an original
Consequently the observations that Wegener had summarized