Plate tectonics is the theory that explains the structure and motion of the Earth’s lithosphere. The theory states that the Earth’s crust is split into large sections called tectonic plates, and these move relative to one another creating boundaries at which plates converge, diverge and move past each other. Alfred Wegener pioneered the theory of continental drift in the early 1900s which he supported with multiple pieces of evidence. Perhaps the earliest indicator of the theory was the apparent fit of some of the Earth’s continents; analysis of these coastlines, notably the eastern edge of South America and the western edge of Africa, has shown that they are very similar geologically suggesting that at some point in the Earth’s history the landmasses were joined together. Another indicator that the continents were once distributed differently was geological evidence of glaciation in India – it is unlikely that glaciers could ever reach such low latitudes, but this problem can easily be explained by continental drift. Fossil distribution also provided some of the earliest evidence for plate tectonics – certain land-dwelling fossil species have been found in areas that are now separated by ocean which indicates that those areas were at some point joined together. However at the time of Wegner’s work many of the geophysical tools that are used today did not exist making the theory much more difficult to support.
Paleomagnetism is one of the strongest pieces of evidence for plate tectonic theory and was developed in the 1950s which managed to convince scientists of the validity of the theory. When new crust is formed certain minerals align themselves with the Earth’s magnetic field. Analysis of the Mid-Atlantic Ridge has shown that as you move outwards from the ridge, the polarity of the sea floor alternates and the age of the sea floor increases; the magnetic field