What evidence did scientist use to support the plate tectonic theory?
Until the mid twentieth century, the evidence consisted mostly of fossil similarities in areas that were considered to have been joined geographically earlier in Earth’s history. No mechanism had been revealed, however, to explain why continents would move apart. In the 1950’s, a scientific expedition was made to map the ocean floor. The exploration revealed a more or less continuous seismically active ridge in the middle of the Atlantic Ocean. Later, it was discovered, with the use of a magnetometer mounted in an airplane, that rock on either side of the ridge was chronologically a mirror image of the rock on the other side. This was due to the magnetic orientation of the Earth, which can abruptly change, being recorded in the rock at the time of its formation. This creation of new crust at the mic-ocean ridges was the mechanism for plate movement that had previously been undiscovered, leading to the understanding of lithospheric plate tectonics that we know today.
