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"What are they?
Creations of mind?- The mind can make Substance,
and people planets of its own
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With beings brighter than have been, and give
A breath to forms which can outlive all flesh."
"The Dream", Lord Bryon (1788-1824)
Already when the first maps of the American continents were published (1507 and after), the similitude between the western coast of Africa and the eastern coast of South America intrigued geographers and naturalists and this fascination continued in the following centuries. In 1620 the English philosopher Francis Bacon noted the jigsaw shape in his "Novum Organum" and claimed that "it's more then a curiosity". In 1658 the munch Francois Placet published a small booklet entitled "The break up of large and small world's, as being demonstrated that America was connected before the flood with the other parts of the world." He argued that the two continents were once connected by the lost continent of "Atlantis" and the flood of the bible separated them.
The idea of the biblical flood to explain the shape of continents will remain very popular for the next 250 years.
Fig.1. Illustration from Thomas Burnet´s book "The Sacred Theory of the Earth", published in 1684, where he tries to explain the shapes of the continents by the biblical flood. The homogenous primordial crust of earth is shattered (first drawing) releasing water from the underground. This water covers the entire planet (second drawing) and finally flows back in the fissures, leaving behind fragments of the crust that now forms the modern islands and continents (last drawing) (image in public domain).
The great French palaeontologist Buffon in his "Les Epoques de la Nature" (1717) not only addresses the age of earth, but also speculates about a former land bridge connecting Ireland and America to explain the distribution of fossil shells found on both sides of the Atlantic Ocean.
The American president (of the Academy and College of Philadelphia) and naturalist Benjamin Franklin explained marine fossils found on the summits of mountains in a letter to French geologist Abbé J. L. Giraud-Soulavie in 1782 as follows:
"Such changes in the superficial parts of the globe seemed to me unlikely to happen if the earth were solid to the center. I therefore imagined that the internal parts might be a fluid more dense, and of greater specific gravity than any of the solids we are acquainted with, which therefore might swim in or upon that fluid. Thus the surface of the earth would be a shell, capable of being broken and disordered by the violent movements of the fluid on which it rested."
The great German naturalist and geographer Alexander von Humboldt explored South America from 1799 until 1804 and observed that the similitude between the two coastlines were not only restricted to a morphological pattern, but also to the geological features: mountain ranges that seemed to end on one continent continued on the other, the Brazilian highland is similar to the landscape of the Congo, the Amazonian basin has it's counterpart in the lowlands of Guinea, the mountain ranges of North America are - geologically - very similar to the old European mountains and rocks in Mexico resemble those found in Ireland.
Fig.2. Columnar Jointing in the basalts of Regla, Mexico, as depicted in Alexander von Humboldts (1810) "Pittoreske Ansichten der Cordilleren und Monumente amerikanischer Völker." (image in public domain), the accompanying text explains:
"The basalts of Regla, which are presented on this copper plate, are an incontrovertible proof of this identity of forms, which is noted on the rocks of different climates. Travelled mineralogist need only to look at this drawing to recognize the basalt forms in Vivarais, in the Euganean Mountains or in the foothills of Antrim, in Ireland. The smallest coincidences observed in the European rock-pillars are also found in this group of Mexican basalts. Such a great analogy let us assume a similar principle of formation acting under all climates in various temporal epochs, the basalts covered by compact limestone and clay-slate must be of different age than those who are resting on layers of coal and boulders."
But even Humboldt still argued that the Atlantic Ocean represents a large and ancient river bed, flooded subsequently by the biblical catastrophe.
The French zoologist Jean-Baptiste Lamarck developed a surprisingly new hypothesis. To explain the discovery of fossil marine animals on dry land he proposed that the continents "move" slowly around the globe in a very peculiar manner. The eastern coastlines of the single continents are eroded by the sea, but in the same time new sediments were deposited on the western coasts, so the continents apparently move around the globe and the sea becomes land.
Unfortunately, also for the lack of evidence for his theory, Lamarck was not able to find a publisher for his "Hydrogéologie" and printed in 1802 on his own behalf 1.025 copies, but only a small number of books were sold.
In the early 19th century another hypothesis was proposed to explain the shape of Earth: the Contracting Earth theory formulated by the American geologist James Dwigth Dana explained mountains and continents as products of a cooling and subsequently shrinking earth. Like an old and dry apple the shrinking surface of earth would develop fissures (basins) and wrinkles (mountains).
Austrian Geologist Eduard Suess published in his multi-volume work "Das Antlitz der Erde" (1883-1909) this hand coloured map, showing the supposed remains of the primordial continents - preserved "cores of crust" surrounded by younger basins today filled with oceans. Curiously he suggested also that the deep-sea trenches, found along the borders of the Pacific, are zones where the ocean floor was pushed under the continents (!).
Fig.3. Hand coloured map showing the primordial continent -"cores" according to the Austrian geologist Eduard Suess, published in "Das Antlitz der Erde" (The Face of the Earth) 1883 to 1909 (image in public domain).
But the Contracting Earth theory couldn't explain the irregular distribution of mountain ranges on earth and why there are regions with strong tectonic movements and earthquakes and "quiet" areas. According to this theory, such features and events should to be distributed randomly on the surface of a homogenous cooling and shrinking planet.
Already in 1858 the French naturalist Antonio Snider-Pellegrini (1802–1885) published a reconstruction of America and Africa forming a single continent on a planet with fixed volume. But Snider-Pellegrini couldn't propose a convincing mechanism, apart the great flood, an obsolete idea even in those times, to explain the forces needed to move entire continents.
Fig.4. This 1858 reconstruction by Antonio Snider-Pellegrini represents one of the first maps showing a former supercontinent (image in public domain).
The idea of ancient supercontinents forming by individual movements will be neglected until the early 20th century, when an atlas will capture again the imagination of a man.
Bibliography:
FRISCH, W.; MESCHEDE, M. & BLAKEY, R. (2011): Plate Tectonics - Continental Drift and Mountain Building. Springer-Publisher: 212
MILLER, R. & ATWATER, T. (1983): Continents in Collision. Time-life books, Amsterdam: 176