Plate Tectonics

In 1912, Alfred Wegener took the scientific community by surprise in postulating that the present continents had once been united in a mega- continent named Pangea that broke up about 200 million years ago into smaller fragments — the present continents—, which drifted apart and still do so today. This went against all contemporary scientific belief of the permanence of ocean basins and continents. A fundamental argument was the very good morphological and structural fit of South America and Africa and many other geological similarities between the southern continents. Wegener’s revolutionary vision of a mobile dynamic Earth continued to be opposed by most scientists for almost fifty years. His ideas were dramatically revived during the 1960s. The hypothesis of continental drift was then greatly expanded and superseded by the models of seafloor spreading and plate tectonics, both of which have come to revolutionize all of Earth sciences. This new view of a dynamic planet also heralded a new phase in our understanding of the location and origin of volcanoes. The striking difference in their eruptive behavior could now be related to different magma sources, processes of magma generation and thus magma compositions. The time was passed to view volcanoes such as Surtsey or Mauna Loa as isolated local phenomena.