Exploration Insights Great Geos ebook | Page 85

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