Plate Tectonics - Continental Drift

From circa 1911 Alfred Wegener, after being influenced by a scientific paper he had come across that listed fossils of identical plants and animals found on opposite sides of the Atlantic, began proposing a then most controversial theory which held that the continents of the earth had once been joined together but had drifted apart through a process that he explicitly, by circa 1915 - with the publication of the first edition of The Origin of Continents and Oceans, a book outlining Wegener's theory, - seems to have referred to as Continental Drift (actually - in his own mother tongue - as Kontinentalverschiebung or die Verschiebung der Kontinente).

As he later wrote: "A conviction of the fundamental soundness of the idea took root in my mind."

Beyond speculating that thermal currents in the Earth's mantle may have provided the driving force Alfred Wegener was unable to propose a thoroughly plausible mechanism for his notion of continental drift which seems as much as anything else to have been based on the circumstantial evidence that the present-day continental outlines (including submerged edges near shore) - if individually "cut out" from the map - could be placed together fairly completely in a vast earlier continent that Alfred Wegener hypothesised and which he referred to as Pangaea.

Alfred Wegener's hypotesis of continental drift envisioned a vast early continent he refeered to as Pangaea
Alfred Wegener's vision of Pangaea.

Alfred Wegener was not the first person to "speculate" in this way - Abraham Ortelius (1597), Francis Bacon (1625), Benjamin Franklin, Antonio Snider-Pellegrini (1858), are just some of the more prominent persons who had noted earlier that the shapes of continents on opposite sides of the Atlantic Ocean seem to fit together.
The scientific establishment of the day - in so far as it even gave Wegener's view a hearing - closed ranks against the very idea of such an "impossible" process as Continental Drift.

It was only in the early 1950s with the emergence of the new science of paleomagnetism that Alfred Wegener's theory of began to be taken seriously by anything like mainstream geologists and other scientists.

By the 1960s science accepted a theory of Plate Tectonics where there are "solid plates" - be they continents or ocean floor - comprising a so-called Lithosphere which effectively "floats" on an underlying fluid-like (visco-elastic solid) Asthenosphere. The underlying "rock" that is the Asthenosphere is present under such high pressure and high temperature conditions as to permit slight flows of movement that over geological timescales have had a cumulative effect that has distinctly shaped our planet.
The fact that ocean floor as well as continental expanses seem to be solid plates has tended to discredit the term - continental drift - and to establish the alternative term - plate tectonics.

The Earth's main Tectonic Plates
their boundaries and boundary types

Charles Darwin biography

Alfred Russel Wallace biography

Thomas Malthus
Essay on Population

Darwin quotes
his beliefs about God

Thomas Henry Huxley
Darwin's Bulldog

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