Samstag, 7. November 2009

Continental drift

Nov, 1880 - Nov, 1930

"The presence of those seeking the truth is infinitely to be preferred to those who think they´ve found it."
T. PRATCHETT (2003): Monstrous Regiment.

Illustration from Thomas Burnet´s book "The Sacred Theory of the Earth", published in 1684, where he tries to explain the shape of the earth by the biblical flood. Parts of the crust of earth broke up (first drawing), releasing water from the underground. This water covers the entire planet (second drawing), and finally flowing back in the fissures, leaves back a shattered crust that now forms islands and continents (last drawing).

Already after the first maps of the American continent were published (1507 and after) and become public, the similarity between the coast of Africa and America intrigued geographers and naturalists, and this fascination continued in the following centuries.
In 1620 the E
nglish philosopher Francis Bacon noted the jigsaw form in his "Novum Organum" and claimed that "it's more then a curiosity", and 38 years later the munch Francois Placet published "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 sin flood beaked them apart.

The great naturalist Alexander von Humboldt explored South America from 1799 until 1804, and observed that the similarities between the two coastlines were not only restricted to the morphological pattern, but also geological features: mountain chains that seemed to end on the one continent, continued on the other , the Brazilian highland remembers the landscape of Congo, the Amazonian basin has it's counterpart in the lowlands of Guinea, and the mountain ranges of North America are - geologically - very similar to the old European mountains.
But still the flood argument was a strong one, and so he argued that the Ocean represents a large, ancient river bed, flooded by the biblical catastrophe. The French zoologist Jean-
Baptiste Lamarck (1744-1829) developed a theory by itself, explaining the discovery of fossil marine animals on the dry land, he proposed that the continents "move" slowly, but irresistible, around the globe. The east coastlines of the single continents were eroded by the sea, but in the same rate new sediments were deposited on the west coast, so doing, the land were "flooded" many times by the oceans. Unfortunately, also for the lack of evidence for his theory, Lamarck was not capable to find a publisher for his "Hydrogéologie", and printed in 1802 on his own behalf 1025 copies, but only a small number of books could be sold.
The new century saw the birth a new therory to explain the shape of Earth, formulated by the American geologist James Dwigth Dana (1813-1895) - mountains and continets were products of the cooling, and shrinking earth.

After the theory of Dana, the modern continents represent remnants of the former earth crust, or the first parts of earth that solidified after the formation of the planet. The Austrian Geologist Eduard Sueß published in "Das Antlitz der Erde (1883-1909)" this hand coloured map, showing the primordial continents "cores", today separated by younger, during the contraction of Earth formed, and today water filled basins.

But this therory, explaining some aspects, couldn´t explain the irregular distribution of mountain ranges on erath, and why eras with strong tectonic movements alternate with "quie
t" eras.

George Darwin, the son of Charles R. Darwin, explained the formations of the continents as result of the detachment of the moon from earth 57 million years ago. The American geologist Frank Taylor in contrary tried to prove that the moon was captured by earth some 100 million years ago, and the resulting tide waves rip apart the single continent on the planet.

Antonio Snider, an American scientist living in Paris, was the first in 1858 to publish a schematic representation of America and Africa forming a single continent. But he also explained the break up of the two landmasses by the strength of the great flood. Still no mechanism was known to explain if, and how, continents could move over the planet´s crust.

This 1858 drawing represents one of the first schematic maps to explain the drift of continents. In contrary to other naturalist, and later geologists, Antonio Snider-Pellegrini assumed a sudden, and very fast movement, caused presumably by the biblical flood.

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