Plate tectonic theory

Alfred Wegner, widely regarded to be a pioneer in this area of earth sciences, presented a paper on the theory of continental drift in the 1920s. It was based on evidence from the distribution of fossil organisms found on different land masses and now separated by vast distances across oceans. He theorised that this was evidence of a large supercontinent, called Pangea, which allowed these species to live together before the continents broke up and drifted apart.

In the 1950s, geologists examining the direction and strength of the Earth’s magnetic field, as recorded in a specific mineral (magnetite) found in rock on the ocean bed, observed that there were variations in the directions of the magnetic fields that had been preserved in these minerals over time. By linking the location of these rocks with Wagner’s continental drift theory, it showed that the hypothesised pathways of these rocks had been very similar, therefore, supporting the theory of continental drift even further. In addition, the work of Marie Tharp in the 1970s helped map the oceans to reveal a network of ridges and trenches along the ocean floor. This, together with the jigsaw fit of continents, heat flow measurements and the age of the ocean floor, provided evidence for the theory of Plate Tectonics.