Abraham Ortelius (1527-98) in his Thesaurus Geographicus (1587) suggested that the Americas were torn away from Europe and Africa by earthquakes and floods and that this is apparent from the outlines of the coasts of the three continents. In 1912 Alfred Lothar Wegener (1880-1930) hypothesised that the continents once formed a single landmass, broke up, and drifted to their present locations.
Support for the existence of continental drift is found in the fact that plant and animal fossils of the same age are found on different continental shores, which implies that those shores were once joined. The continuity of glaciers suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift.
One of the main problems with Wegener’s theory was that he believed that the continents ‘ploughed’ through the rocks of the ocean basins. Most geologists did not believe that this could be possible. In the 1960s Wegener’s idea for the cause of continental drift was replaced by the now accepted theory of plate tectonics which accommodates continental motion as the mechanism of seafloor spreading. Volcanism at the mid-ocean ridges that run north to south in both the Pacific and the Atlantic create a new crust that forces the existing crust to spread outwards.
Leave a Reply